(C) S Chand And Company Limited Limited - SoftWiz

Lakhmir Singh’s Science

Teacher’s Resource Kit

LAKHMIR SINGH

MANJIT KAUR

7

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Branches :

Ahmedabad : Ph: 27541965, 27542369, [email protected]

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© 2017, Lakhmir Singh and Manjit Kaur

All rights reserved. No part of this publication may be reproduced or copied in any material form (including photocopying or storing it in any medium in form of graphics, electronic or mechanical means and whether or not transient or incidental to some other use of this publication) without written permission of the publisher. Any breach of this will entail legal action and prosecution without further notice.Jurisdiction : All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, Tribunals and Forums of New Delhi, India only.

First Published in 2017

Code: 10SE000073

PRINTED IN INDIA

By Vikas Publishing House Pvt. Ltd., Plot 20/4, Site-IV, Industrial Area Sahibabad, Ghaziabad-201010 and Published by S. Chand And Company Limited, 7361, Ram Nagar, New Delhi -110 055.

S. CHAND SCHOOL BOOKS(An imprint of S. Chand Publishing)A Division of S. Chand And Company Limited(An ISO 9001 : 2008 Company)7361, Ram Nagar, Qutab Road, New Delhi-110055Phone: 23672080-81-82, 9899107446, 9911310888; Fax: 91-11-23677446www.schandpublishing.com; e-mail : [email protected]

Lakhmir Singh Science Teachers Resource Kit 07

(C) Jurisdiction :

(C) Jurisdiction : All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, Tribunals and Forums of New

(C) All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, Tribunals and Forums of New

Delhi, India only.

(C) Delhi, India only.

(C)

First Published in 2017(C)

First Published in 2017

S All rights reserved. No part of this publication may be reproduced or copied in any material form (including photocopying or storing it in any

S All rights reserved. No part of this publication may be reproduced or copied in any material form (including photocopying or storing it in any medium in form of graphics, electronic or mechanical means and whether or not transient or incidental to some other use of this publication) S medium in form of graphics, electronic or mechanical means and whether or not transient or incidental to some other use of this publication) S without written permission of the publisher. Any breach of this will entail legal action and prosecution without further notice.S without written permission of the publisher. Any breach of this will entail legal action and prosecution without further notice.

All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, Tribunals and Forums of New S All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, Tribunals and Forums of New

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Ph: 2443142, [email protected] (Marketing Office)

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© 2017, Lakhmir Singh and Manjit KaurChand

© 2017, Lakhmir Singh and Manjit Kaur

All rights reserved. No part of this publication may be reproduced or copied in any material form (including photocopying or storing it in any Chand

All rights reserved. No part of this publication may be reproduced or copied in any material form (including photocopying or storing it in any medium in form of graphics, electronic or mechanical means and whether or not transient or incidental to some other use of this publication) Cha

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Taking into consideration the ever-growing advancements in the field of education; the concept of teaching goes beyond the conventional chalk and talk method. It evolves into the new-age learning where rote learning is replaced by the concept of activity-based learning and imparting knowledge. Illustrations and experimental pedagogy aid to imbibe the scientific concepts with a better understanding of the subj ect.

The Lakhmir Singh’s Science series enhances the overall learning experience of a child. Learning science is made fun through numerous experiments, activities, proj ects, assignments and assessments. This not only proves to be engaging for the pupils but also helps the teachers to customize teaching and add an innovation to their classes.

In the new age of technology; these books bring to you a variety of performance-based assessments that will enable the learners to inculcate knowledge of concepts and provide an insight within. This will help the students to develop a scientific and rational attitude towards the concept and work upon the challenges with zeal and confidence. Holistic development of the students will be successfully achieved by:

rational approach

execution of learnt concepts

developed inquisitiveness

critical mindset

research and study beyond the books

Lakhmir Singh’s Science Teacher’s Resource Kit is tailor-made for the teachers who use the course book. The resource kit will serve as a medium to support the classroom lessons and renovate them with activities and tasks mentioned in it. It will serve as an effective tool to the teachers' classroom lessons.

Salient features

Detailed lesson plan: This is a briefing of the entire chapter. It includes key points to be highlighted, suggested number of periods for each subtopic, aim of learning and supporting tasks.

Warm-up activities: This focuses on some brainstorming activities that will help in initiating the chapter and create a suitable environment for learning.

V ocabulary: It helps the students to learn new terminologies.

Expected learning outcomes: Distinct introspection and the ability to comprehend the chapter should be enabled by the students at the end of the chapter.

Proj ects, discussions and activities: This helps in continuous and comprehensive learning of the concepts by the students.

Answers to the questions mentioned in the course book alongwith the Higher Order Thinking Skills ( HOTS) answers.

Worksheets after every chapter will help the teacher to conduct surprise test or assessments to realize the understanding level of the students.

IntroductionIntroduction

(C)

concepts by the students.

(C)

concepts by the students.

(C) Answers to the questions mentioned in the course book alongwith the Higher Order Thinking Skills

(C) Answers to the questions mentioned in the course book alongwith the Higher Order Thinking Skills

( HOTS) answers.

(C) ( HOTS) answers.

(C)

Worksheets after every chapter will help the teacher to conduct surprise test or assessments to (C)

Worksheets after every chapter will help the teacher to conduct surprise test or assessments to realize the understanding level of the students.(C)

realize the understanding level of the students.

S Proj ects, discussions and activities: This helps in continuous and comprehensive learning of the

S Proj ects, discussions and activities: This helps in continuous and comprehensive learning of the concepts by the students.S concepts by the students.

Answers to the questions mentioned in the course book alongwith the Higher Order Thinking Skills S Answers to the questions mentioned in the course book alongwith the Higher Order Thinking Skills

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suggested number of periods for each subtopic, aim of learning and supporting tasks.

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Warm-up activities: This focuses on some brainstorming activities that will help in initiating the

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Warm-up activities: This focuses on some brainstorming activities that will help in initiating the chapter and create a suitable environment for learning.

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chapter and create a suitable environment for learning.


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Expected learning outcomes: Distinct introspection and the ability to comprehend the chapter

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Expected learning outcomes: Distinct introspection and the ability to comprehend the chapter should be enabled by the students at the end of the chapter.Cha

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should be enabled by the students at the end of the chapter.

Proj ects, discussions and activities: This helps in continuous and comprehensive learning of the Chand

Proj ects, discussions and activities: This helps in continuous and comprehensive learning of the

And The resource kit will serve as a medium to support the classroom lessons and renovate them with activities

And The resource kit will serve as a medium to support the classroom lessons and renovate them with activities

and tasks mentioned in it. It will serve as an effective tool to the teachers' classroom lessons.

And and tasks mentioned in it. It will serve as an effective tool to the teachers' classroom lessons.

Detailed lesson plan: This is a briefing of the entire chapter. It includes key points to be highlighted, And

Detailed lesson plan: This is a briefing of the entire chapter. It includes key points to be highlighted, suggested number of periods for each subtopic, aim of learning and supporting tasks.And


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ny that will enable the learners to inculcate knowledge of concepts and provide an insight within. This will help

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with zeal and confidence. Holistic development of the students will be successfully achieved by:

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Lakhmir Singh’s Science Teacher’s Resource Kit is tailor-made for the teachers who use the course book. Compa

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Lakhmir Singh’s Science Teacher’s Resource Kit is tailor-made for the teachers who use the course book. The resource kit will serve as a medium to support the classroom lessons and renovate them with activities Com

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dand experimental pedagogy aid to imbibe the scientific concepts with a better understanding of the subj ect.

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dand experimental pedagogy aid to imbibe the scientific concepts with a better understanding of the subj ect.

The Lakhmir Singh’s Science series enhances the overall learning experience of a child. Learning science

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dThe Lakhmir Singh’s Science series enhances the overall learning experience of a child. Learning science is made fun through numerous experiments, activities, proj ects, assignments and assessments. This not only

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dis made fun through numerous experiments, activities, proj ects, assignments and assessments. This not only proves to be engaging for the pupils but also helps the teachers to customize teaching and add an innovation

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dproves to be engaging for the pupils but also helps the teachers to customize teaching and add an innovation

In the new age of technology; these books bring to you a variety of performance-based assessments

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that will enable the learners to inculcate knowledge of concepts and provide an insight within. This will help Limite

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the students to develop a scientific and rational attitude towards the concept and work upon the challenges

Chapter 1: Nutrition In Plants 5

Chapter 2: Nutrition In Animals 16

Chapter 3: Fibre To Fabric 27

Chapter 4: Heat 36

Chapter 5: Acids, Bases And Salts 48

Chapter 6: Physical And Chemical Changes 58

Chapter 7: Weather, Climate And Adaptations of Animals To Climate 67

Chapter 8: Winds, Storms And Cyclones 80

Chapter 9: Soil 93

Chapter 10: Respiration in Organisms 106

Chapter 11: Transport in Animals and Plants 118

Chapter 12: Reproduction in Plants 130

Chapter 13: Motion And Time 143

Chapter 14: Electric Current And Its Effects 152

Chapter 15: Light 162

Chapter 16: Water: A Precious Resource 174

Chapter 17: Forests: Our Lifeline 183

Chapter 18: Wastewater Story 191

ContentsContents

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Chapter 18:

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Electric Current And Its E

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Water: A Precious Resource

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Motion And Time And

Motion And Time

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SCIENCE 7 TEXT BOOK

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1

Lesson Plan

Expected Learning Outcomes

The present chapter will help the students to imbibe the following concepts. He/She will be able to learn:

• The autotrophic and heterotrophic modes of nutrition.

• The food making process in plants- Photosynthesis.

• Conditions necessary for photosynthesis.

• The other modes of nutrition.

• How nutrients are replenished in the soil.

• Cell and its structure.

Textbook: Refer to pages 1 to 16

Periods allocated: 10 periods

VOCABULARY

Nutrition, autotrophs, autotrophic nutrition, heterotrophs, heterotrophic nutrition, chlorophyll, photosynthesis, glucose, algae, parasite, host, saprophytes, insectivorous plants, symbiosis, leguminous plants, cells, cytoplasm, cell membrane, nucleus, mitochondria, vacuoles.

ACTIVITIES FOR PERIOD 1

Modes of nutrition (Page 1)

Learning Tools

Interactive warm up exercise: Discussing with the students the importance of eating food would be a good start for the topic. Students should realize that human beings and animals depend on plants for their food requirements, directly or indirectly.

Nutrition in Plants Nutrition in Plants

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(C) Modes of nutrition (Page 1) (C) Modes of nutrition (Page 1)

Learning Tools (C)

Learning Tools

S S leguminous plants, cells, cytoplasm, cell membrane, nucleus, mitochondria, vacuoles.

S leguminous plants, cells, cytoplasm, cell membrane, nucleus, mitochondria, vacuoles. Chand

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Nutrition, autotrophs, autotrophic nutrition, heterotrophs, heterotrophic nutrition, chlorophyll,

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Nutrition, autotrophs, autotrophic nutrition, heterotrophs, heterotrophic nutrition, chlorophyll,

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photosynthesis, glucose, algae, parasite, host, saprophytes, insectivorous plants, symbiosis, Cha

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photosynthesis, glucose, algae, parasite, host, saprophytes, insectivorous plants, symbiosis, leguminous plants, cells, cytoplasm, cell membrane, nucleus, mitochondria, vacuoles. Cha

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leguminous plants, cells, cytoplasm, cell membrane, nucleus, mitochondria, vacuoles.

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The autotrophic and heterotrophic modes of nutrition.

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The autotrophic and heterotrophic modes of nutrition.

The food making process in plants- Photosynthesis.

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The food making process in plants- Photosynthesis.

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How nutrients are replenished in the soil.

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The present chapter will help the students to imbibe the following concepts. He/She will be

SCIENCE 7 TEXT BOOK

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Chapter opening exercise: Students should be asked how plants prepare food from raw materials obtained from the environment. Ask them the difference between producers and consumers. Ask them to classify consumers on the basis of their food habits as herbivores, carnivores and omnivores.

Teacher guided discussion

Discuss with the students that nutrition is the process of taking food by an organism as well as its utilization by the organisms. Students should know that the organisms which can make food themselves from simple substances by the process of photosynthesis are called autotrophs ( green plants) . Students should be able to define autotrophic mode of nutrition. Explain that heterotrophs are organisms which cannot make food themselves by the process of photosynthesis and take food from green plants or animals and their mode of nutrition is called heterotrophic mode of nutrition.

Suggested home assignment

Make a list of autotrophs and heterotrophs and paste their pictures in your copy.

ACTIVITIES FOR PERIOD 2 AND 3

Photosynthesis (Page 2)


Discuss with them that the green plants make their own food from simple inorganic substances like carbon dioxide and water by using sunlight in the presence of green colored pigment chlorophyll present in leaves is called photosynthesis. Students should be able to express the process of photosynthesis in the form of a word equation and draw a neat diagram. They should be familiarized with the essential conditions of photosynthesis like carbon dioxide, water, chlorophyll and sunlight. They should be aware of the role of chlorophyll ( to trap sunlight) and sunlight ( to provide energy) . Students should know that leaves having colour other than green also undergo photosynthesis. Tell them about the photosynthesis by plant parts other than leaves. Students should be made to understand that besides glucose, plants also produce oils, proteins and vitamins.

Using resources

Students may run the video for the given topic using the QR Code given at the end of the chapter on the Study Gear app.


Write a word equation and draw a neat and well-labeled diagram to show the process of photosynthesis.

ACTIVITIES FOR PERIOD 4 AND 5

Other modes of nutrition in plants (Page 7)


Explain them that depending on the mode of nutrition of those plants which do not have chlorophyll

(C)


(C)


(C)

(C) Write a word equation and draw a neat and well-labeled diagram to show the process of

(C) Write a word equation and draw a neat and well-labeled diagram to show the process of

photosynthesis. (C) photosynthesis.

S on the Study Gear app.


Suggested home assignmentS Suggested home assignmentCha

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understand that besides glucose, plants also produce oils, proteins and vitamins.

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understand that besides glucose, plants also produce oils, proteins and vitamins.

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Students may run the video for the given topic using the QR Code given at the end of the chapter on the Study Gear app. Cha

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on the Study Gear app.

And present in leaves is called photosynthesis. Students should be able to express the process of

And present in leaves is called photosynthesis. Students should be able to express the process of

photosynthesis in the form of a word equation and draw a neat diagram. They should be familiarized

And photosynthesis in the form of a word equation and draw a neat diagram. They should be familiarized

with the essential conditions of photosynthesis like carbon dioxide, water, chlorophyll and sunlight.

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They should be aware of the role of chlorophyll ( to trap sunlight) and sunlight ( to provide energy) . Students should know that leaves having colour other than green also undergo photosynthesis. And

Students should know that leaves having colour other than green also undergo photosynthesis. Tell them about the photosynthesis by plant parts other than leaves. Students should be made to And

Tell them about the photosynthesis by plant parts other than leaves. Students should be made to

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Discuss with them that the green plants make their own food from simple inorganic substances like

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dthemselves from simple substances by the process of photosynthesis are called autotrophs ( green

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dthemselves from simple substances by the process of photosynthesis are called autotrophs ( green plants) . Students should be able to define autotrophic mode of nutrition. Explain that heterotrophs

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dare organisms which cannot make food themselves by the process of photosynthesis and take food from green plants or animals and their mode of nutrition is called heterotrophic mode of nutrition.

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dfrom green plants or animals and their mode of nutrition is called heterotrophic mode of nutrition.

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SCIENCE 7 TEXT BOOK

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and thus, cannot carry out the process of photosynthesis, all heterotrophic plants can be classified as parasites and saprophytes. Students should be able to define the terms parasite and host and give their respective examples. Explain that saprophytes like fungi obtain their food from the dead and decaying organic matter. Insectivorous plants feed on insects to obtain nitrogen compounds. They should be made to realize that plants can live together and help each other to survive forming a symbiotic relationship.

Using resources

• Students may run the video for the given topic using the R Code given at the end of the chapter on the Study Gear app.

• se a chart showing the process of photosynthesis to explain in detail.


What do you understand by th term symbiotic relationship? Give examples of plants showing symbiotic relationship.


How nutrients are replenished in the soil (Page 10)


Discuss with them that the main nutrients required by the plants are nitrogen, phosphorus and potassium. Although they are present in the soil but they can be replenished in the soil by adding fertilizers and manures. Make the students realize the importance of leguminous plants which have Rhizobium bacteria in their root nodules that can convert nitrogen gas of air into nitrogen compounds. Students should realize that by growing leguminous plants, farmers need not put nitrogen fertilizer in the fields.


How can plant nutrients or minerals be replenished in the soil? What is NPK?


Cells (Page 11)


Explain them that a cell is the smallest unit of life. Students should know they are the building blocks of plants and animals. Students should be familiarized with the classification of cells as plant cells and animal cells. They should be aware of the terms-cell membrane, cell wall, cytoplasm, nucleus, chloroplast, mitochondria, vacuole which form the structure of the cells. Students should be able to distinguish between plant cell and animal cell and draw their respective diagrams.

(C) Teacher guided discussion


Explain them that a cell is the smallest unit of life. Students should know they are the building blocks (C) Explain them that a cell is the smallest unit of life. Students should know they are the building blocks (C)

of plants and animals. Students should be familiarized with the classification of cells as plant cells (C)

of plants and animals. Students should be familiarized with the classification of cells as plant cells and animal cells. They should be aware of the terms-cell membrane, cell wall, cytoplasm, nucleus, (C

) and animal cells. They should be aware of the terms-cell membrane, cell wall, cytoplasm, nucleus,

S Cells (Page 11)

S Cells (Page 11)

Teacher guided discussionS Teacher guided discussion

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And fertilizers and manures. Make the students realize the importance of leguminous plants which

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SCIENCE 7 TEXT BOOK

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Using resources

se a chart showing the structure of plant cell and animal cell and explain their structures to the students.


Draw neat and well-labeled diagrams of plant cell and animal cell in your copy.


Revise all the topics covered in the previous lessons.

Using resources

Refer to the corresponding chapter in the CD given in the book.


Discuss the exercises given at the end of the chapter.


Assessment of understanding of the chapter could be done with the help of the given worksheet for the chapter.

TEXT BOOK ANSWERS

A. Very Short Answer Type Questions

1. Stomata

2. Photosynthesis

3. The process by which green plants can make their own food from simple substances like carbon dioxide and water by using sunlight ( in the presence of chlorophyll) is called photosynthesis.

4. ( a) False ( b) True ( c) True ( d) False ( e) False

5 . Pea plant

6 . Algae

7 . It contains green colored pigment called chlorophyll.

8 . ( a) Carbon dioxide ( b) Oxygen

9 . ( a) Autotrophs ( b) Heterotrophs

10 . Symbiotic relationship

11. Symbiotic relationship

12. Leaves

13. Because they contain green colored pigment called chlorophyll.

14. Chlorophyll

(C) It contains green colored pigment called chlorophyll.

(C) It contains green colored pigment called chlorophyll.

8 .

(C) 8 . ( a) Carbon dioxide ( b) Oxygen

(C) ( a) Carbon dioxide ( b) Oxygen

9 .(C)

9 . ( a) Autotrophs ( b) Heterotrophs (C)

( a) Autotrophs ( b) Heterotrophs

10 .(C)

10 . Symbiotic relationship (C)

Symbiotic relationship

S Algae S Algae

It contains green colored pigment called chlorophyll. S It contains green colored pigment called chlorophyll.

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like carbon dioxide and water by using sunlight ( in the presence of chlorophyll) is called photosynthesis.

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photosynthesis.

( a) False ( b) True ( c) True ( d) False ( e) False

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( a) False ( b) True ( c) True ( d) False ( e) False

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SCIENCE 7 TEXT BOOK

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15 . Nitrogen, Phosphorus, Potassium

16 . R h iz o biu m

17 . Leguminous plants

18 . Peas, beans

19 . Algae and mushroom

20 . Cuscuta

21. Pitcher plant

22. Cactus plant; stem

23. Starch, Oils ( or Fats) , Proteins and V itamins

24. Parasites and saprophytes

25 . (a) mushroom yeast (b) solution (c) air (d) alga (e) fungus (f) starch (g) chlorophyll ( h) carbon dioxide; oxygen ( i) oxygen ( j ) glucose ( k) proteins ( l) cells

B. Short Answer Type Questions

26 . ( i) d ( ii) a ( iii) e ( iv) b ( v) c

27 . The presence of starch in leaves can be tested as follows :

( i) Pluck a green leaf from a plant.

( ii) Boil the leaf in alcohol to remove the green pigment chlorophyll from it.

( iii) Wash the decolourised leaf with water to remove any chlorophyll sticking to it.

( iv) Pour dilute iodine solution from a dropper over the decolourised leaf.

( v) Appearance of blue-black colour in leaf shows the presence of starch in it.

28 . Chlorophyll is a green pigment present in the leaves of plants which helps them to trap sunlight for the formation of food.

29 . Sunlight and chlorophyll

30 . ( a) Grass ( b) Mushroom ( c) Lichen ( d) Pitcher plant ( e) Cuscuta

31. The organisms need to take food ( i) to obtain energy ( ii) to obtain materials for growth, and ( iii) to obtain materials for the repair of damaged parts of the body. The two modes of nutrition in organisms are autotrophic mode and heterotrophic mode.

32. Those organisms which can make food themselves from simple substances ( like carbon dioxide and water) by the process of photosynthesis are called autotrophs. All the green plants are autotrophs.

33. Those organisms which cannot make food themselves by the process of photosynthesis and take food from green plants or animals are called heterotrophs. All the non-green plants and animals ( including human beings) are heterotrophs.

34. All the animals ( including human beings) are categorised as heterotrophs because they cannot make their own food, they depend on plants or other animals for obtaining their food.

35 . Those green plants which obtain their food partly from insects are called insectivorous plants. Example: Pitcher plant.

(C) plants are autotrophs.

(C) plants are autotrophs.

33.

(C) 33. Those organisms which cannot make food themselves by the process of photosynthesis and

(C) Those organisms which cannot make food themselves by the process of photosynthesis and

take food from green plants or animals are called heterotrophs. All the non-green plants (C)

take food from green plants or animals are called heterotrophs. All the non-green plants and animals ( including human beings) are heterotrophs. (C)

and animals ( including human beings) are heterotrophs.

S Those organisms which can make food themselves from simple substances ( like carbon

S Those organisms which can make food themselves from simple substances ( like carbon

S dioxide and water) by the process of photosynthesis are called autotrophs. All the green S dioxide and water) by the process of photosynthesis are called autotrophs. All the green plants are autotrophs. S plants are autotrophs.

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sunlight for the formation of food.

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Sunlight and chlorophyll

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Sunlight and chlorophyll

( a) Grass ( b) Mushroom ( c) Lichen ( d) Pitcher plant ( e) Cuscuta

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( a) Grass ( b) Mushroom ( c) Lichen ( d) Pitcher plant ( e) Cuscuta

The organisms need to take food ( i) to obtain energy ( ii) to obtain materials for growth,

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The organisms need to take food ( i) to obtain energy ( ii) to obtain materials for growth, and ( iii) to obtain materials for the repair of damaged parts of the body. The two modes

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of nutrition in organisms are autotrophic mode and heterotrophic mode.

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Those organisms which can make food themselves from simple substances ( like carbon

And om a dropper over the decolourised leaf.

And om a dropper over the decolourised leaf.

Appearance of blue-black colour in lea

And Appearance of blue-black colour in lea

Chlorophyll is a green pigment present in the leaves of plants which helps them to trap

And

Chlorophyll is a green pigment present in the leaves of plants which helps them to trap sunlight for the formation of food. And


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The presence of starch in leaves can be tested as follows :

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The presence of starch in leaves can be tested as follows :

o remove the green pigment chlorophyll from it.

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f shows the presence of starch in it.

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d(a) mushroom yeast (b) solution (c) air (d) alga (e) fungus (f) starch (g) chlorophyll

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( h) carbon dioxide; oxygen ( i) oxygen ( j ) glucose ( k) proteins ( l) cells

SCIENCE 7 TEXT BOOK

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36 . Fertilisers and manures contain plant nutrients (or minerals) such as nitrogen, phosphorus and potassium, etc. So, when fertilisers and manures are added to the soil in the fields, then the soil gets enriched with nutrients like nitrogen, phosphorus and potassium, etc. The crop plants can then grow well in this soil. Thus, plant nutrients are added in the cultivated fields in the form of fertilisers and manures so as to get good crops.

37 . A plant ( or animal) which lives on or inside another organism ( called host) and derives the food from it, is called a parasite. An example of parasite plant is Cuscuta.

38 . Those non-green plants which obtain their food (or nutrition) from dead and decaying organic matter are called saprophytes. The fungi such as mushrooms, bread mould and yeast are saprophytes.

39 . The plants cannot absorb nitrogen gas for their needs ( like making proteins) . Now, the soil has certain bacteria which convert nitrogen gas of air into nitrogen compounds ( like nitrates) and release them into soil. Nitrates are the water soluble nitrogen compounds which are absorbed by the plants from the soil along with water. In this way, the plants fulfil their requirement of nitrogen. The plants also obtain nitrogen from the nitrogenous fertilisers which the farmers add to the soil in the fields from time to time.

40 . (a) Nucleus ( b) Cytoplasm ( c) Cell membrane ( d) Cell wall, vacuoles

C. Long Answer Type Questions

41. The process by which green plants make their own food ( like glucose) from carbon dioxide and water by using sunlight energy ( in the presence of chlorophyll) is called photosynthesis. Chlorophyll is present in the green leaves. So, the process of photosynthesis takes place in the leaves of a plant. Oxygen gas is produced during photosynthesis. This oxygen goes into the air. The oxygen gas released in photosynthesis is utilised by all the living organisms for their survival. The process of photosynthesis first produces a simple carbohydrate called ‘ glucose’ as food. The glucose carbohydrate then gets converted into a complex carbohydrate called ‘ starch’. This starch gets stored as food in the various parts of plant including leaves. Chlorophyll is a green substance which is present in the leaves of plants. Chlorophyll absorbs light energy from the sun and supplies this energy to the leaves to enable them to carry out photosynthesis for making food.

42. (a) The plants take carbon dioxide gas needed for photosynthesis from the air. The plants take carbon dioxide gas from air through the tiny pores called stomata ( singular: stoma) present on the surface of leaves. Actually, there are a large number of tiny pores called stomata on the the surface of leaves of plants. Each pore ( or stoma) is surrounded by a pair of guard cells. The opening and closing of stomatal pores in the leaves is controlled by the guard cells. The carbon dioxide gas present in air enters the leaves of a plant through the stomatal pores present on their surface and utilised in photosynthesis. The oxygen gas produced in the leaves during photosynthesis goes out into air through the same stomatal pores.The stomatal pores of leaves open only when carbon dioxide is to be taken in or oxygen is to be released otherwise they remain closed.

( b) The plants take water needed for photosynthesis from the soil. Soil always contains some water in it. Water present in the soil is absorbed by the roots of a plant and then

(C) leaves is controlled by the guard cells. The carbon dioxide gas present in air enters

(C) leaves is controlled by the guard cells. The carbon dioxide gas present in air enters

the leaves of a plant through the stomatal pores present on their surface and utilised (C)

the leaves of a plant through the stomatal pores present on their surface and utilised

S stoma) present on the surface of leaves. Actually, there are a large number of tiny

S stoma) present on the surface of leaves. Actually, there are a large number of tiny pores called stomata on the the surface of leaves of plants. Each pore ( or stoma) is S pores called stomata on the the surface of leaves of plants. Each pore ( or stoma) is surrounded by a pair of guard cells. The opening and closing of stomatal pores in the S surrounded by a pair of guard cells. The opening and closing of stomatal pores in the

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called ‘ starch’. This starch gets stored as food in the various parts of plant including leaves.

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called ‘ starch’. This starch gets stored as food in the various parts of plant including leaves. Chlorophyll is a green substance which is present in the leaves of plants. Chlorophyll absorbs

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Chlorophyll is a green substance which is present in the leaves of plants. Chlorophyll absorbs light energy from the sun and supplies this energy to the leaves to enable them to carry

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light energy from the sun and supplies this energy to the leaves to enable them to carry out photosynthesis for making food.

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out photosynthesis for making food.

The plants tak

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stoma) present on the surface of leaves. Actually, there are a large number of tiny

And the leaves of a plant. Oxygen gas is produced during photosynthesis. This oxygen goes into

And the leaves of a plant. Oxygen gas is produced during photosynthesis. This oxygen goes into

the air. The oxygen gas released in photosynthesis is utilised by all the living organisms for

And the air. The oxygen gas released in photosynthesis is utilised by all the living organisms for

their survival. The process of photosynthesis first produces a simple carbohydrate called

And

their survival. The process of photosynthesis first produces a simple carbohydrate called ‘ glucose’ as food. The glucose carbohydrate then gets converted into a complex carbohydrate And

‘ glucose’ as food. The glucose carbohydrate then gets converted into a complex carbohydrate And

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( c) Cell membrane

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( c) Cell membrane

The process by which green plants make their own food ( like glucose) from carbon dioxide

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The process by which green plants make their own food ( like glucose) from carbon dioxide and water by using sunlight energy ( in the presence of chlorophyll) is called photosynthesis.

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dThose non-green plants which obtain their food (or nutrition) from dead and decaying

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dThose non-green plants which obtain their food (or nutrition) from dead and decaying organic matter are called saprophytes. The fungi such as mushrooms, bread mould and

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dorganic matter are called saprophytes. The fungi such as mushrooms, bread mould and

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SCIENCE 7 TEXT BOOK

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transported to the leaves through the vessels which run like inter-connected pipes throughout the roots, stem, branches and leaves. The tiny, pipe-like vessels which transport water from the roots of a plant to its leaves are called xylem. The plants also need minerals to make foods other than carbohydrates. For example, plants need nitrogen mineral to make proteins. The minerals are present in the soil ( and have to be transported to the leaves) . The minerals dissolve in water present in the soil and get transported with it.

43. The plant nutrients ( or minerals) are replenished ( or put back) in the soil in the following two ways 1. utrients are Replenished in the Soil by Adding Fertilisers and Manures- Fertilisers and manures contain plant nutrients (or minerals) such as nitrogen, phosphorus and potassium, etc. So, when fertilisers and manures are added to the soil in the fields, then the soil gets enriched with nutrients like nitrogen, phosphorus and potassium, etc. The crop plants can then grow well in this soil. Thus, plant nutrients are added in the cultivated fields in the form of fertilisers and manures so as to get good crops. 2. itrogen can be replenished in the Soil by Growing Leguminous Crops-Though a lot of nitrogen gas is present in the air but the plants cannot use nitrogen in gaseous form. The plants need nitrogen in the form of water soluble compounds ( such as nitrates) . The plants such as gram ( chana) , peas, pulses ( moong, etc.) and beans are called leguminous plants ( or legumes) . The leguminous plants have root nodules in them which contain Rhizobium bacteria. Rhizobium bacteria can convert nitrogen gas of air into nitrogen compounds ( like nitrates) .

44. (a) The leaves having colours other than green also have chlorophyll in them. Actually, the large amount of red, violet, brown or other pigments in such leaves masks the green colour of chlorophyll. So, photosynthesis also takes place in leaves having colour other than green.

( b) Photosynthesis is important for the existence of life on this earth. In the absence of photosynthesis, life would be impossible on this earth. This is due to the following reasons: ( i) Photosynthesis by plants provide food to animals ( including human beings) . So, the survival of animals ( including human beings) depends on the food made by plants by photosynthesis. In the absence of photosynthesis, there would be no plants on this earth and hence no animals will survive. ( ii) The process of photosynthesis by plants puts oxygen gas into the air. It is this oxygen gas which the animals ( including human beings) use for breathing and respiration. In the absence of photosynthesis, there would be no oxygen in air and hence no animals could exist on this earth.

45. (a) There are two modes of nutrition in plants: autotrophic mode and heterotrophic mode of nutrition. Those organisms which can make food themselves from simple substances ( like carbon dioxide and water) by the process of photosynthesis are called autotrophs. All the green plants are autotrophs. Those organisms which cannot make food themselves by the process of photosynthesis and take food from green plants or animals are called heterotrophs. All the non-green plants and animals ( including human beings) are heterotrophs.

( b) The living together of two different species of plants as if they are parts of the same plant and help each other in obtaining food is called symbiosis ( and such plants are

(C) substances ( like carbon dioxide and water) by the process of photosynthesis are called

(C) substances ( like carbon dioxide and water) by the process of photosynthesis are called

autotrophs. All the green plants are autotrophs. Those organisms which cannot make (C)

autotrophs. All the green plants are autotrophs. Those organisms which cannot make

S there would be no oxygen in air and hence no animals could exist on this earth.

S there would be no oxygen in air and hence no animals could exist on this earth.

There are two modes of nutrition in plants: autotrophic mode and heterotrophic S There are two modes of nutrition in plants: autotrophic mode and heterotrophic mode of nutrition. Those organisms which can make food themselves from simple S mode of nutrition. Those organisms which can make food themselves from simple

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So, the survival of animals ( including human beings) depends on the food made by plants by photosynthesis. In the absence of photosynthesis, there would be no plants

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plants by photosynthesis. In the absence of photosynthesis, there would be no plants on this earth and hence no animals will survive. ( ii) The process of photosynthesis by

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on this earth and hence no animals will survive. ( ii) The process of photosynthesis by plants puts oxygen gas into the air.

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there would be no oxygen in air and hence no animals could exist on this earth. Chand

there would be no oxygen in air and hence no animals could exist on this earth.

And green colour of chlorophyll. So, photosynthesis also takes place in leaves having colour

And green colour of chlorophyll. So, photosynthesis also takes place in leaves having colour

And

thesis is important for the existence of life on this earth. In the absence of

And

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ny in the Soil by Growing Leguminous Crops-Though a lot of nitrogen gas is present in the air

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plants have root nodules in them which contain Rhizobium bacteria. Rhizobium bacteria can convert nitrogen gas of air into nitrogen compounds ( like nitrates) .

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can convert nitrogen gas of air into nitrogen compounds ( like nitrates) .

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dThe plant nutrients ( or minerals) are replenished ( or put back) in the soil in the following

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dThe plant nutrients ( or minerals) are replenished ( or put back) in the soil in the following two ways 1. utrients are Replenished in the Soil by Adding Fertilisers and Manures-

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dtwo ways 1. utrients are Replenished in the Soil by Adding Fertilisers and Manures- Fertilisers and manures contain plant nutrients (or minerals) such as nitrogen, phosphorus

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dFertilisers and manures contain plant nutrients (or minerals) such as nitrogen, phosphorus and potassium, etc. So, when fertilisers and manures are added to the soil in the fields, then

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dand potassium, etc. So, when fertilisers and manures are added to the soil in the fields, then the soil gets enriched with nutrients like nitrogen, phosphorus and potassium, etc. The crop

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dthe soil gets enriched with nutrients like nitrogen, phosphorus and potassium, etc. The crop plants can then grow well in this soil. Thus, plant nutrients are added in the cultivated fields

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in the Soil by Growing Leguminous Crops-Though a lot of nitrogen gas is present in the air

SCIENCE 7 TEXT BOOK

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known as symbiotic plants) . In lichens, the green coloured plant called ‘ alga’ ( autotroph) and non-green plant ‘ fungus’ ( saprophyte) live together. The fungus holds the alga cells in its mat of web-like hyphae ( thin filaments) . The fungus plant absorbs the water and mineral salts from the surroundings and supplies them to alga. The alga plant being green, prepares the food by photosynthesis and shares it with fungus. Thus, both alga and fungus gain mutually from one another by living together. This is an example of symbiosis. The plants which exhibit symbiosis are called symbiotic plants.

D. Multiple Choice Questions

46 . ( b) 47 . ( d) 48 . ( b) 49 . ( c) 5 0 . ( c)

5 1. ( d) 5 2. ( c) 5 3. ( c) 5 4. ( d) 5 5 . ( c)

5 6 . ( b) 5 7 . ( b) 5 8 . ( d) 5 9 . ( b) 6 0 . ( b)

6 1. ( c) 6 2. ( c) 6 3. ( c) 6 4. ( a) 6 5 . ( b)

6 6 . ( c) 6 7 . ( d) 6 8 . ( d) 6 9 . ( c) 7 0 . ( c)

E. Questions Based on Higher Order Thinking Skills

71. ( a) ( i) Carbon dioxide ( ii) Water ( b) ( i) Glucose ( ii) Starch ( c) Photosynthesis ( d) Food E ( e) Chlorophyll 72. ( a) Cactus plant ( b) Stem and Branches ( c) The photosynthesis in this desert plant is carried out by its green stem and branches whereas the photosynthesis in ordinary garden plants is carried out by their green leaves ( d) Green

7 3. A : Leaves ; B : Stomata ; C : Guard cells ; D : Carbon dioxide ; E : Photosynthesis ; F : Oxygen

7 4. (a) Pitcher plant (b) Insect (c) Proteins (d) Amino acids (e) Insectivorous plants

7 5 . (a) (i) Alga (ii) Fungus (iii) ichen (b) is green in colour (c) Symbiotic relationship (d) Rhizobium bacteria and Leguminous plants.

(C) S

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nd And

(a) Pitcher plant (b) Insect (c) Proteins (d) Amino acids (e) Insectivorous plants

And (a) Pitcher plant (b) Insect (c) Proteins (d) Amino acids (e) Insectivorous plants

(a) (i) Alga (ii) Fungus (iii) ichen (b) is green in colour (c) Symbiotic relationship (d)

And (a) (i) Alga (ii) Fungus (iii) ichen (b) is green in colour (c) Symbiotic relationship (d)

And

Rhizobium bacteria and Leguminous plants.

And

Rhizobium bacteria and Leguminous plants.

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xide ( ii) Water ( b) ( i) Glucose ( ii) Starch ( c) Photosynthesis ( d) Food E

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( e) Chlorophyll 72. ( a) Cactus plant ( b) Stem and Branches ( c) The photosynthesis in this

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( e) Chlorophyll 72. ( a) Cactus plant ( b) Stem and Branches ( c) The photosynthesis in this desert plant is carried out by its green stem and branches whereas the photosynthesis

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desert plant is carried out by its green stem and branches whereas the photosynthesis in ordinary garden plants is carried out by their green leaves ( d) Green

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in ordinary garden plants is carried out by their green leaves ( d) Green

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SCIENCE 7 TEXT BOOK

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WORKSHEET

Name: ............................................................... Class: ......................... Date: ...........................

A. Objective Type Questions

1. Name the following:

( a) The gas absorbed from the air which is required for the process of photosynthesis.

( b) The bacteria which can convert the nitrogen gas of air into nitrogen compounds.

( c) A plant where photosynthesis occurs in plant parts other than leaves.

( d) The green pigment present in the leaves of the plants.

2. Fill in the blanks:

( a) A parasitic plant with yellow, slender and tubular stem is .… … … … … ............ .

( b) A plant which can prepare food by both autotrophic and heterotrophic modes of nutrition is.… … … … … ............ .

( c) The j elly like material which fills the cell is .… … … … … ............ .

( d) Rhizobium bacteria live in the .… … … … … ............ nodules of the leguminous plants.

3. Write true or false:

( a) The solar energy is converted into chemical energy during the process of photosynthesis.

( b) Y east is an example of autotroph.

( c) The mineral needed by plants to form proteins is nitrogen.

( d) Grass can make its own food.

4. entionthefunctionofthefollowing:

( a) Stomata ( b) Chlorophyll ( c) Stem of cactus plant ( d) Cell membrane

B. Subjective Type Questions

5. Answerthefollowingquestionsinshort:

( a) Differentiate between autotrophs and heterotrophs.

( b) What are saprophytes? Give an example.

( c) How do plants obtain nitrogen for making proteins?

( d) What are insectivorous plants? (C) ( b)

(C) ( b)

( c)

(C) ( c) How do plants ob

(C) How do plants ob

( d)(C)

( d)

S 5. Answer

S 5. Answer

DifferS Differentiate between autotrophs and heterotrophs. S entiate between autotrophs and heterotrophs.

What are saprS What are sapr

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function

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entiate between autotrophs and heterotrophs. Chand

entiate between autotrophs and heterotrophs.

And nergy is converted into chemical energy during the process of photosynthesis.

And nergy is converted into chemical energy during the process of photosynthesis.

xample of autotroph.

And

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The mineral needed by planAnd

The mineral needed by plants to form proteins is nitrogen. And

ts to form proteins is nitrogen.

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ellow, slender and tubular stem is .… … … … … ............ .

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ellow, slender and tubular stem is .… … … … … ............ .

t which can prepare food by both autotrophic and heterotrophic modes of

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t which can prepare food by both autotrophic and heterotrophic modes of

erial which fills the cell is .… … … … … ............ .

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erial which fills the cell is .… … … … … ............ .

e in the .… … … … … ............ nodules of the leguminous plants.

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e in the .… … … … … ............ nodules of the leguminous plants.

nergy is converted into chemical energy during the process of photosynthesis. Compa

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nergy is converted into chemical energy during the process of photosynthesis.

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dom the air which is required for the process of photosynthesis.

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dom the air which is required for the process of photosynthesis.

onvert the nitrogen gas of air into nitrogen compounds.

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donvert the nitrogen gas of air into nitrogen compounds.

osynthesis occurs in plant parts other than leaves. Limite

dosynthesis occurs in plant parts other than leaves.

SCIENCE 7 TEXT BOOK

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SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) A parasitic plant.

( b) A non-green heterotrophic plant.

( c) Autotrophic organisms which grow as slimy green patches in ponds or other stagnant water bodies.

( d) A plant that has both autotrophic and heterotrophic mode of nutrition.

( e) Gas released during the process of photosynthesis.

2. Write True or False:

( a) The chemical used to test starch in plants is dilute iodine solution.

( b) A saprophyte derives its nutrition in solution form from soil organisms.

( c) A m ar be l is an example of host plant.

( d) The carbohydrates produced during photosynthesis are stored in plants as starch.

( e) Mushroom is a heterotroph.


( a) The .… … … … … ............ is the ultimate source of energy for all organisms.

( b) The mode of taking in food by an organism for utilization by the body is called .… … … … … ............ .

( c) Fertilizers and manure are rich in plant nutrients like .… … … … … ............, .… … … … … ............ and .… … … … … ............ .

4. Correct the following statements:

( a) The simplest food produced during photosynthesis is cellulose.

( b) Fungi are autotrophs.

( c) Spines of a cactus plant carry out the process of photosynthesis.

( d) Chloroplasts are present in animal cells.

( e) Symbiotic relationship is beneficial to only one partner.



( a) Differentiate between parasitic plants and saprotrophic plants.

( b) Give the functions of: Chlorophyll and Stomata.

(C)

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SCIENCE 7 TEXT BOOK

15

( c) Give the word equation describing the process of photosynthesis.

( d) Why do pickles, leather clothes, etc. get spoilt during rainy season?

( e) Why farmers do not add fertilizers to the soil in which leguminous plants are grown?

6. Answerthefollowingquestionsindetail:

( a) List the various modes of nutrition in plants. Give examples.

( b) Explain the term symbiosis. Give two examples to support your answer.

( c) How do insectivorous plants derive their nutrition? Give examples.

( d) Explain the structure of animal cell and plant cell with the help of a neat diagram.

( e) How are nutrients replenished in the soil?

C. Multiple Choice Questions

1. Which of the following plants is an example of autotroph?

( a) Mushroom ( b) Y east ( c) Bread mould ( d) Mimosa 2. The green insectivorous plants trap insects, kill them digest them to obtain mainly

( a) Glucose ( b) Starch ( c) Nitrogen ( d) Oxygen. 3. Which of the following shows symbiosis?

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( a) Phosphorus ( b) Iodine ( c) Nitrogen ( d) Calcium 5. Whichpartofaplantiscalledits itchen ?

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SCIENCE 7 TEXT BOOK

16

2

Lesson Plan



• The types and modes of nutrition in human beings.

• The digestive system in human beings.

• About the teeth and their structure.

• About the tongue.

• What is diarrhoea

• igestion in ruminants and amoeba.



VOCABULARY

Ingestion, digestion, absorption, assimilation, egestion, alimentary canal, trachea, diarrhoea, cud, ruminants.


Animal nutrition (Page 17)

Learning Tools

Interactive warm up exercise: iscussing the various food items students eat would be a good start for the topic. Ask them which nutrients they derive from these food items.

Chapter opening exercise: Ask the students the importance of having food and the various organs that help in the breaking down of this food inside the body.

Nutrition In AnimalsNutrition In Animals

(C) Animal nutrition (Page 17)

(C) Animal nutrition (Page 17)

Learning Tools (C)

Learning Tools

Interactive warm up exercise: (C)

Interactive warm up exercise:

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SCIENCE 7 TEXT BOOK

17


iscuss with them that the process of taking in food by an animal and its utilization in the body is called animal nutrition. Students should be familiarized with the steps in which animal nutrition takes place Ingestion, digestion, absorption, assimilation and egestion. Students should be able to define these terms. iscuss the method of ingestion in insects, hydra and starfish. xplain that digestion is the process in which the food containing large, insoluble substances is broken down into small, water soluble substances which can be absorbed by our body. Students should know that the alimentary canal is the digestive tract and food moves forward in it by peristalsis.


Mention the mechanism of ingestion in Butterfly, ydra and Starfish.

ACTIVITIES FOR PERIOD 2 TO 4

Human digestive system (Page 19)


iscuss that the human digestive system consists of the alimentary canal and its associated glands. Students should be aware of the main organs of the digestive system Mouth (Buccal cavity),

esophagus, Stomach, Small intestine, arge intestine, Rectum and Anus. The associated glands are the Salivary glands, iver and the Pancreas. Students should be familiarized with the digestive process when it passes through the various parts of the alimentary canal along with the role of secretions of digestive glands. The topic could be made interesting by explaining the reason for getting hiccups.

Using resources

• se a chart showing the human digestive system. xplain the role of various organs and the digestive glands through this chart.

• Conduct the activity given on Page no. 21 of the book to study the effect of saliva present in food.


raw a neat and well-labeled diagram to show the human digestive system (Fig.2).


Teeth (Page 22)


xplain to the students that food can be used by the body, only when it is broken down into small pieces, which is done by the teeth. Students should know that there are four types of teeth Incisors, Canines, Premolars and Molars. Students should know the positions of these teeth inside our mouth

(C)

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Teeth (Page 22) (C)

Teeth (Page 22)

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SCIENCE 7 TEXT BOOK

18

and their respective functions. Students should be able to differentiate between milk teeth and permanent teeth. They should know how the formation of cavities takes place in teeth and thus, how important oral care is, for our mouth.

Using resources

• se a chart to show the position of different types of teeth in our mouth.



ist the different ways by which you can prevent tooth decay.


Tongue (Page 24)


iscuss the structure and functions of tongue with students. Ask them the types of tastes they have experienced with different food materials. Familiarize them with the terms taste buds and their positions on the tongue.


raw the tongue and mention the different functions of it.


Diarrhoea (Page 24)


xplain them that the condition in which a person passes out watery stools frequently is called diarrhoea. Students should know that diarrhoea may lead to dehydration which can be prevented by ral Rehydration Solution ( RS).


Buy an RS packet from the chemist and list its ingredients in your copy. Try to find the role of these ingredients in controlling dehydration.


Grass eating animals (Page 25)


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SCIENCE 7 TEXT BOOK

19

xplain that the herbivorous animals eat grass which is rich in a carbohydrate called cellulose. So these animals have a special stomach to digest this carbohydrate. xplain the process of rumination in these animals like cow. Students should be able to answer why these animals are called ruminants.


Can human beings digest cellulose Why


Amoeba (Page 26)


iscuss that Amoeba is a microscopic organism which consists of a single cell, has no fixed shape and is the simplest animal. xplain the mechanism of feeding and digestion in Amoeba to the students. Students should be aware of the terms Pseudopodia and Vacuole.

Using resources

Students may run the video for the given topic using the R Code given at the end of the chapter on the Study Gear app.


raw the different stages in the feeding and digestion in Amoeba.



Using resources

Refer to the corresponding chapter in the C given in the book.


iscuss the exercises given at the end of the chapter.



TEXT BOOK ANSWERS


1. Ingestion 2. Saliva

3. Peristalsis 4. (a) arge intestine (b) Small intestine

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SCIENCE 7 TEXT BOOK

20

5. Oesophagus 6. Acid

7. a. Premolars b. Canines c. Incisors . a. Milk teeth b. Permanent teeth

9. Milk teeth 1 . and years

11. Tongue 12. Sweet and salty tastes

13. a. Sour b. Bitter 14. Ruminants

15. Cellulose digesting bacteria 1 . Amoeba

1 . Amoeba 1 . Pseudopodia

1 . Pseudopodia 2 . iarrhoea

21. iarrhoea 22. ral Rehydration Solution

23. nergy is produced 24. (a) True (b) False (c) True (d) True

25. (a) liver (b) digestive (c) villi (d) glucose amino acids fatty acids glycerol (e) digestive (f) milk (g) acid (h) cud (i) cow (j) pseudopodia (k) food vacuole


2 . (a) Mucus protects the lining of stomach (from its own secretions of hydrochloric acid). ydrochloric acid kills any bacteria which may enter the stomach with food.

(b) ydrochloric acid also makes the medium in the stomach acidic (which is necessary for the proper action of digestive juices on proteins in the stomach).

2 . A long tube running from mouth to anus of a human being (or other animals) in which digestion and absorption of food takes place is called alimentary canal. The human digestive system consists of the alimentary canal and its associated glands. The various organs of the human digestive system in sequence are Mouth (Buccal cavity), esophagus (or Food pipe), Stomach, Small intestine, arge intestine, Rectum and Anus. The glands which are associated with human digestive system and form a part of human digestive system are Salivary glands, iver and Pancreas.

2 . (i) b (ii) c (iii) a

2 . Saliva is a digestive juice which helps to digest the starch present in the food partially.

3 . a. Small intestine b. Buccal cavity (teeth) c. Stomach d. Small intestine e. arge intestine

31. iver secretes a liquid called bile (which is stored temporarily in the sac called gall bladder). The bile plays an important part in the digestion of fats.

32. The food of butterfly is nectar ( ectar is a sugary liquid present inside the flowers). The butterfly uses its long feeding tube to suck nectar from flowers of plants.

33. Frog is an animal which eats flying insects as food. Snakes are flesh eaters. They eat animals like rats, etc. Both male and female mosquitoes feed by sucking nectar from flowers. The female mosquitoes also suck blood from other animals (including human beings). ice feed by sucking blood from the skin of scalp. ouseflies feed on filth and refuse. They take in only liquid food by sucking. ouseflies spit out saliva on solid food to convert it into a liquid and then suck this liquid. Ants feed on plant material and other animals by biting and chewing. Snails feed on algae by scraping it from rocks.

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SCIENCE 7 TEXT BOOK

21

34. (i) c (ii) d (iii) a (iv) b (v) e (vi) f (vii) g

35. The inner surface of the small intestine has millions of tiny, finger-like outgrowths called villi. The presence of villi gives the inner walls of the small intestine a very large surface area (which helps in the rapid absorption of food). Thus, the role of villi in the small intestine is to increase the surface area for the rapid absorption of digested food.

36. iver secretes a liquid called bile (which is stored temporarily in the sac called gall bladder). The bile plays an important part in the digestion of fats.

37. Glucose is a kind of pre-digested food (so it has not to go through the slow digestive process in our body). Glucose solution is immediately absorbed by our body. The absorbed glucose then combines with oxygen to give us quick energy (or instant energy).

3 . Amoeba is a microscopic organism (very small organism) which consists of a single cell. Amoeba lives in pond water. A similarity between the nutrition in Amoeba and human beings is that in both the cases digestive juices break down the complex food particles into simpler substances (which can be absorbed). A difference is that Amoeba has no mouth and no digestive system whereas a human being has a mouth and a digestive system made up of many organs.

39. Amoeba takes in food (or ingests food) by using pseudopodia. When a considerable amount of undigested food collects inside Amoeba, then its cell membrane suddenly ruptures at any place and the undigested food is thrown out (or egested) from the body of Amoeba

4 . There are four types of teeth in our mouth. These are (i) Incisors, (ii) Canines, (iii) Premolars, and (iv) Molars. The incisors are for biting and cu ng the food. The canines are for piercing and tearing the food. The premolars and molars are for chewing and grinding the food.

41. Most of the adult men and women have a total of 32 teeth. f these, 1 are in the upper jaw and 1 are in the lower jaw. The 1 teeth of each jaw consist of 4 incisors, 2 canines, 4 premolars and molars. The teeth of upper jaw match with the teeth of lower jaw.

42. We can distinguish between ice and ice cream (even with our eyes closed) from their taste. A piece of ice kept on the tongue will appear to be tasteless whereas a piece of ice cream will give a sweet taste.

43. The various functions of the tongue are as follows 1.The tongue helps in mixing saliva with food during chewing (which is essential for the digestion of food). 2. The tongue helps in swallowing the food into the food pipe. 3. The tongue helps in ge ng the taste of food. 4. The tongue is essential for talking (or speaking). There are four types of tastes: sweet, salt sourand i er.

44. We (human beings) cannot survive by eating only grass (or raw leafy vegetables) because these foods contain mainly cellulose (carbohydrate) and our body does not have bacteria which can digest cellulose carbohydrate.

45. (i) Most taste buds at the front of the tongue detect sweet and salty tastes. The maximum effect of sweet taste is felt at the tip of the tongue whereas the maximum effect of salty taste is felt just behind the tip of the tongue. (ii) Most of the taste buds on the sides of the tongue detect sour taste. (iii) Most of the taste buds at the back of the tongue detect bitter taste.

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SCIENCE 7 TEXT BOOK

22


4 . The process in which the food containing large, insoluble substances is broken down into small, water soluble substances which can be absorbed by our body, is called digestion. The human digestive system consists of the alimentary canal and its associated glands. The various organs of the human digestive system in sequence are Mouth (Buccal cavity),

esophagus (or Food pipe), Stomach, Small intestine, arge intestine, Rectum and Anus. The glands which are associated with human digestive system and form a part of human digestive system are Salivary glands, iver and Pancreas. Refer to figure 2 for the diagram.

4 . xcessive use of sugar containing foods such as sweets, chocolates, toffees, ice cream and cold drinks, etc., are the major cause of tooth decay. Tooth decay can be prevented in the following ways 1. We should rinse the mouth thoroughly with clean water after every meal. 2. We should clean our teeth with a brush and toothpaste at least twice a day. 3. A dental floss should be used to take out food particles trapped between the teeth. ( ental floss is a soft thread used to clean between the teeth). 4. We should eat less of sugary foods such as sweets, chocolates, toffees, and ice cream, etc. Too many cold drinks should also be avoided (this is because sugar bacteria acid which eats up tooth).

4 . Refer to figure 11.

4 . The process by which the cud (partially digested food) is brought back from the stomach to the mouth of the animal and chewed again is called rumination (or chewing the cud). All the animals like cow and buffalo which chew the cud are called ruminants. (a) Cow, Sheep, Buffalo, eer, Goat, Giraffe (b) Cellulose The cellulose digesting bacteria are not present in the body of human beings due to which human beings cannot digest cellulose carbohydrate present in plant foods.

5 . The inner lining of stomach secretes mucus, hydrochloric acid and digestive juices. Mucus protects the lining of stomach (from its own secretions of hydrochloric acid). ydrochloric acid kills any bacteria which may enter the stomach with food. ydrochloric acid also makes the medium in the stomach acidic (which is necessary for the proper action of digestive juices on proteins in the stomach). The digestive juices secreted by the stomach lining break down the proteins present in our food into simpler substances (This happens in the acidic medium). The large intestine absorbs most of the water from the undigested food material.

51. There are four types of teeth in our mouth. These are (i) Incisors, (ii) Canines, (iii) Premolars, and (iv) Molars. The incisors are for biting and cu ng the food. The canines are for piercing and tearing the food. The premolars are for chewing and grinding the food. Molars are for chewing and grinding the food.

52. (a) Bitter. Most of the taste buds at the back of the tongue detect bitter taste. (b) Sour. Most of the taste buds on the sides of the tongue detect sour taste.

53. The process by which the cud (partially digested food) is brought back from the stomach to the mouth of the animal and chewed again is called rumination (or chewing the cud). All the animals like cow and buffalo which chew the cud are called ruminants. The animals called ruminants can survive on grass as food because they have certain bacteria in the

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SCIENCE 7 TEXT BOOK

23

rumen part of their stomach which can digest the cellulose carbohydrate present in grass (and other plant leaves). The cellulose digesting bacteria are not present in the body of human beings due to which human beings cannot digest cellulose carbohydrate present in plant foods.

54. The condition in which a person passes out watery stools frequently is called diarrhoea. iarrhoea may be caused by an infection (due to disease-causing microorganisms), food

poisoning or indigestion. iarrhoea leads to the loss of water and salts from the body of a person (through frequent watery stools). The loss of water from the body of a person through watery stools is called dehydration. The sudden loss of too much water (or dehydration) makes a person dangerously ill in a very short time. xcessive dehydration of body caused by diarrhoea can even lead to death. So, diarrhoea should never be neglected. In order to prevent dehydration, the person suffering from diarrohea should be given a solution of sugar and salt in clean water, many times a day. The solution of sugar and salt in water is called ral Rehydration Solution ( RS) (because it is given to the person orally, through mouth). We can make an oral rehydration solution ourselves by dissolving a teaspoonful of sugar and a pinch of salt in a glass of clean water. The water used for this purpose should be first boiled and then cooled (so as to make it germfree).

55. In order to prevent dehydration, the person suffering from diarrohea should be given a solution of sugar and salt in clean water, many times a day. The solution of sugar and salt in water is called ral Rehydration Solution ( RS) (because it is given to the person orally, through mouth). We can make an oral rehydration solution ourselves by dissolving a teaspoonful of sugar and a pinch of salt in a glass of clean water. The water used for this purpose should be first boiled and then cooled (so as to make it germfree).


56. (b) 5 . (c) 5 . (c) 5 . (d) . (b)

1. (b) 2. (b) 3. (c) 4. (c) 5. (b)

. (c) . (d) . (d) . (d) . (d)

1. (b) 2. (d) 3. (c) 4. (b) 5. (d)

. (b) . (c) . (b) . (d) . (a)


1. (a) (i) Salivary glands (ii) Saliva (iii) Starch (iv) esophagus (or Food pipe) (v) Stomach

(b) Proteins

2. (a) (i) Small intestine (ii) Bile (iii) Fatty acids (iv) Glycerol (v) Glucose (vi) Amino acids (b) Gall bladder

3. (a) (i) Villi (ii) arge intestine (iii) Rectum (iv) Anus (b) gestion

4. (a) (i) Bacteria (ii) Sugar (iii) Acid (iv) namel (v) entine (vi) Pulp cavity (b) Tooth decay

5. (a) (i) Starch (ii) A sugar (Maltose) (b) Saliva helps in digesting starch carbohydrate present in food.

(C) (b)

(C) (b)

2. (a)

(C) 2. (a) (i)

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SCIENCE 7 TEXT BOOK

24

WORKSHEET


1. amethefollowing:

(a) The substance which mixes with food in the mouth during chewing of food.

(b) The teeth in human beings which are replaced by permanent teeth.

(c) False feet of Amoeba.

(d) Form of carbohydrate digested by ruminants like cow.

2. illinthe lan s:

(a) The condition in which a person passes out watery stools is called . ...... .

(b) The digestive organ where water from the undigested food material is absorbed is . ...... .

(c) The process of taking in food into the body is . ..... .

(d) The process in which tooth becomes rotten due to formation of . ...... is called tooth decay.

. Writetrueorfalse:

(a) Butterfly sucks nectar from flowers.

(b) The gall bladder stores bile juice temporarily.

(c) We should eat excess sweets and do not care to brush our teeth.

(d) Canines are for biting and cutting of food.


(a) Incisors (b) Pseudopodia in Amoeba

(c) Tongue (d) Rumen in cow



(a) Give a point of similarity between the digestion in Amoeba and digestion in human beings.

(b) Why do we get hiccups

(c) Which is the largest gland of our body and mention its function

(d) ame the various components of the alimentary canal.

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SCIENCE 7 TEXT BOOK

25

SAMPLE PAPER

M.M. 5

ame ............................................................... Class ......................... ate ...........................


1. amethefollowing:

(a) The digestive gland which produces bile juice.

(b) The acid produced by the inner lining of the stomach.

(c) The organ in Amoeba which expels out the undigested food material.

(d) The false feet of Amoeba.

(e) The process by which digested food passes into the blood vessels in the walls of the small intestine.

2. Write rueor alse:

(a) Intake of food into the body of an organism is called egestion.

(b) The process of eliminating wastes from our body is called assimilation.

(c) The saliva is produced by the salivary glands.

(d) The pancreas is the largest organ of our body.

(e) Tongue helps us in talking.

. entiononefunctionofthefollowing:

(a) Pseudopodia in Amoeba (b) Vacuoles in Amoeba

(c) Gall bladder in human beings (d) Villi in small intestine

(e) ydrochloric acid in stomach

4. orrectthefollowingstatements:

(a) uring diarrhoea, we should not give water to the patient.

(b) uman beings are ruminants and can digest cellulose.

(c) The fats of food material are broken down in the stomach.

(d) Absorption of digested food takes place in the large intestine.

(e) The process in which the undigested food material is removed from the body is called digestion.



(a) ifferentiate between milk teeth and permanent teeth.

(b) What causes tooth decay

(C) (d) Absorption

(C) (d) Absorption

(e) The

(C) (e) The

B. Subjective Type Questions(C

) B. Subjective Type Questions

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SCIENCE 7 TEXT BOOK

26

(c) Briefly explain the role of liver in the human digestive system.

(d) Which mode of feeding is used by Starfish and ydra

(e) Which part of the alimentary canal is involved in illing of bacteria and the Formation of faeces


(a) ist the various stages in the process of nutrition.

(b) ow does digestion take place in a ruminant like cow

(c) ow does nutrition occur in Amoeba xplain with the help of a neat diagram.

(d) Write a short note on process of digestion in the small intestine.

(e) iscuss the different types of teeth, their position and functions in the mouth of a human being.


1. hemillionsoftin outgrowthsontheinnersurfaceofsmallintestinearecalled:

(a) Capillaries (b) Buds (c) Villi (d) Veins 2. helengthofsmallintestineinadulthuman eingsisa out:

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must contain mainly:

(a) Carbohydrates (b) Fats (c) Vitamins (d) Proteins 5. hedigestionofgroundnutoilpresentinfoodproduces:

(a) Amino acids (b) Glycerol (c) Alcohol (d) Fatty acids

(C) S

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SCIENCE 7 TEXT BOOK

27

3

Lesson Plan



• The concept of fibres and fabric and to know the differences between natural fibres and synthetic fibres.

• The method of production of wool and occupational hazard in wool industry.

• Discovery of silk, its sources and life history of silk moth.

• How to distinguish between natural silk and synthetic silk.



VOCABULARY

Fleece, selective breeding, shearing, scouring, sorting, dyeing, combing, spinning, anthrax, sericulture, cocoon, reeling.

ACTIVITIES FOR PERIODS 1 AND 2

Wool and its production (Page 32)

Learning Tools

Interactive warm up exercise: Discussing with the students with the students the differences between natural fibres and synthetic fibres would be a good start for the topic. Ask them the process of converting fibres into fabric. This will provide a good recapitulation of the topic covered in Class V I.

Chapter opening exercise: Students should be asked to list some of the important animal fibres. They should be asked the animals from which we yield these fibres. Y ou can use pictures of animals ( flash cards) and students may be asked to name the fibre which is obtained from that animal.

Fibre to FabricFibre to Fabric

(C) Learning Tools

(C) Learning Tools


Interactive warm up exercise: between natural fibres and synthetic fibres would be a good start for the topic. Ask them the process (C

) between natural fibres and synthetic fibres would be a good start for the topic. Ask them the process of converting fibres into fabric. This will provide a good recapitulation of the topic covered in Class V I.

(C)

of converting fibres into fabric. This will provide a good recapitulation of the topic covered in Class V I.

S Wool and its production (Page 32) S Wool and its production (Page 32)

Learning Tools S

Learning Tools

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Chand

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The method of production of wool and occupational hazard in wool industry.

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Discovery of silk, its sources and life history of silk moth.

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SCIENCE 7 TEXT BOOK

28


Discuss with the students that wool is the soft, wavy hair which covers the body of animals like sheep, goat, yak, camel, llama and alpaca. Students should be aware of the term selective breeding. Students should be explained the process of production of wool which involves the rearing and breeding of sheep, shearing of the fleece of sheep, scouring, sorting, dyeing, combing and spinning of fibres into thick yarn called wool. Students should be sensitized with the occupational hazards of the wool industry where the bacteria anthrax may cause a blood disease – Sorter’s disease.

Using resources



Paste pictures of different animals that provide us with wool in your copy.


Silk and its production (Page 35)


Discuss with them that silk is a fine, strong, soft and shining fibre produced by silkworms. Students should know the properties of silk. They should know that the rearing of silkworms for obtaining silk is called sericulture. They should be familiarized with the life history of silk moth and the process of production of silk. Students should be acquainted with the different types of silk. Y ou may discuss the story of discovery of silk to give the topic an interesting edge.

Using resources

• Conduct the activity given on Page no. 3 to distinguish between natural silk and artificial silk.



Make a collage with different types of pieces of silk.



Using resources


(C)

(C) Make a collage with different types of pieces of silk.

(C) Make a collage with different types of pieces of silk.

(C)

Revise all the topics covered in the previous lessons. (C)


S Suggested home assignment


Make a collage with different types of pieces of silk. S Make a collage with different types of pieces of silk.

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And is called sericulture. They should be familiarized with the life history of silk moth and the process of

And is called sericulture. They should be familiarized with the life history of silk moth and the process of

production of silk. Students should be acquainted with the different types of silk. Y ou may discuss

And production of silk. Students should be acquainted with the different types of silk. Y ou may discuss

the story of discovery of silk to give the topic an interesting edge.

And

the story of discovery of silk to give the topic an interesting edge.

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Discuss with them that silk is a fine, strong, soft and shining fibre produced by silkworms. Students

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SCIENCE 7 TEXT BOOK

29





TEXTBOOK ANSWERS


1. Wool and silk 2. Y ak wool

3. J ammu and Kashmir 4. Kashmiri goat

5. South America 6. Lohi and Rampur

7. erbivores . (a) Shearing (b) Scouring (c) Sorting

9. Bacteria called anthrax 10. Shearing

11. Silk 12. False

13. Mulberry

14. The natural colour of wool is generally creamy white though some breeds of sheep produce wool having brown and black colours.

15. Larva 16. Larva

17. Sericulture 1 . Wool and silk

19. Plant fibre

20. ( a) breeding ( b) goat ( c) wool ( d) herbivores ( e) sheep ( f) cocoon ( g) protein ( h) larvae ( or caterpillars) ( i) cocoon ( j ) reeling


21. Apart from grazing grass, the sheep are also fed mixture of pulses, corn, j owar, oil cakes ( oil cake is the material left after the extraction of oil from oil-seeds), and minerals. In winter, sheep are kept indoors and fed on leaves, grains and dry fodder.

22. Rearing of sheep means to look after the sheep by providing them feed (food), shelter and health care. Certain breeds of sheep have a thick coat of hair on their body which yields good quality wool in large quantities. These are called sheep of good breeds. Such sheep are ‘selectively bred’ by choosing at least one parent sheep of good breed. So, the breeding of sheep is done to obtain such breeds of sheep which yield good quality wool in large quantities.

23. Wool is obtained from the sheep by a long process which involves the following steps: Shearing, Scouring, Sorting, yeing, Combing and Spinning.

24. The wool-yielding animals have a thick coat of hair on their body to keep them warm during cold winter season. The hair ( or wool) traps a lot of air. Air is a poor conductor of heat. So,

(C) health care. Certain breeds of sheep have a thick coat of hair on their body which yields

(C) health care. Certain breeds of sheep have a thick coat of hair on their body which yields

good

(C) good quality

(C) quality

are(C)

are ‘selectively(C) ‘selectively

of sheep is done to obtain such breeds of sheep which yield good quality wool in large (C)

of sheep is done to obtain such breeds of sheep which yield good quality wool in large quantities.(C)

quantities.

S sheep are kept indoors and fed on leaves, grains and dry fodder.

S sheep are kept indoors and fed on leaves, grains and dry fodder.

RearingS Rearing ofS of sheepS sheephealth care. Certain breeds of sheep have a thick coat of hair on their body which yields S health care. Certain breeds of sheep have a thick coat of hair on their body which yields

Chand

( a) breeding ( b) goat ( c) wool ( d) herbivores ( e) sheep ( f) cocoon ( g) protein ( h) larvae ( or

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( a) breeding ( b) goat ( c) wool ( d) herbivores ( e) sheep ( f) cocoon ( g) protein ( h) larvae ( or caterpillars) ( i) cocoon ( j ) reeling

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caterpillars) ( i) cocoon ( j ) reeling


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Apart from grazing grass, the sheep are also fed mixture of pulses, corn, j owar, oil cakes ( oil

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the Chand

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sheep are kept indoors and fed on leaves, grains and dry fodder.

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Lohi and Rampur

SCIENCE 7 TEXT BOOK

30

the air trapped in hair ( or wool) of these animals prevents their body heat from being lost to cold surroundings and keeps them warm in winter.

25. Wool is a modified form of hair that grows with a waviness. Because of the waviness of wool, the woollen fabrics have a greater bulk (than cotton fabrics) and hence trap more air. Due to this, woollen fabrics keep us more warm during cold, winter days.

26. The risks faced by people working in any industry due to the ‘ nature of their work’ are called occupational hazards. Sorter’s disease is an occupational hazard.

27. The rearing of silkworms for obtaining silk is called sericulture.

2 . The most common silk moth is the mulberry silk moth. Silk is a fine, strong, soft and shining fibre produced by silkworms in making their cocoons.

29. Take a piece of natural silk fabric and another piece of artificial silk fabric, burn them separately and observe the smell produced :

( i) The fabric which burns giving a smell of burning hair will be natural silk ( or pure silk) .

( ii) The fabric which burns giving a smell of burning paper will be artificial silk ( or rayon) .

3 . The process of taking out silk fibres from the cocoons for use as silk is called reeling. Reeling is done in special machines which unwind the fibres of silk from cocoons.

31. ( i) e ( ii) c ( iii) b ( iv) a

32. Goat, sheep, yak, camel, alpaca yield wool. Wool comes mainly from sheep.

33. Some of the varieties of silk are Mulberry silk Tassar silk Mooga silk osa silk and ri silk. It is an animal fibre.

34. The silky covering spun by the silkworm ( or caterpillar) of silk moth is called cocoon.

35. Shearing, Scouring, Sorting, yeing, Combing, Spinning

B. Long Answer Questions

3 . (i) Shearing-The hair of sheep along with a thin layer of skin (called fleece) are removed from the body of sheep. The process of removing hair (or cu ng off hair) from the body of a sheep in the form of fleece is called shearing. (ii) The process of washing the fleece (cut hair of sheep) that removes dust, dirt, dried sweat and grease is called scouring. Scouring makes the fleece of sheep clean. The scoured fleece (or washed fleece) is then dried. (iii) The process of separating the fleece of a sheep into sections according to the quality of woollen fibres (such as fine, coarse, long, short, etc.) is called sorting. very section of wool obtained after sorting contains the same quality wool (or uniform wool). (iv) yeing. The natural fleece or hair of sheep (or goats) is white, brown or black in colour. The white woollen fibres obtained by sorting can be dyed in different colours. (v) Combing. Combing is a method to prepare woollen fibres for spinning the yarn. This is done by using combs having metal teeth. The process of combing straightens the entangled woollen fibres and also removes the small fluffy fibres (called ‘burrs’) which may be caught in them. (vi) Spinning. The long woollen fibres are spun (or twisted) into thick yarn called ‘wool’ (which is used for kni ng sweaters, etc.). The short woollen fibres are spun into fine yarn and then woven on a loom to make woollen cloth ( like shawls, etc.) .

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SCIENCE 7 TEXT BOOK

31

3 . The hair of sheep along with a thin layer of skin (called fleece) are removed from the body of sheep. The process of removing hair (or cu ng off hair) from the body of a sheep in the form of fleece is called shearing. The process of washing the fleece (cut hair of sheep) that removes dust, dirt, dried sweat and grease is called scouring. Scouring makes the fleece of sheep clean. The scoured fleece (or washed fleece) is then dried. ) The process of separating the fleece of a sheep into sections according to the quality of woollen fibres (such as fine, coarse, long, short, etc.) is called sorting. very section of wool obtained after sorting contains the same quality wool (or uniform wool).

3 . The life history of silk moth is as follows:

( i) The female silk moth lays eggs on the leaves of a tree ( such as mulberry tree) .

(ii) The eggs hatch to form worm-like larvae see Figure 4(b) . The larvae of silk moth are called ‘ caterpillars’ or ‘ silkworms’. The silkworms feed on the leaves of mulberry tree and grow bigger in size.

( iii) When the silkworm ( or caterpillar) is ready to enter the next stage of its development called pupa, it first weaves a net to hold itself. Then it swings its head from side to side in the form of figure of ‘eight’ ( ). uring these movements of head, the silkworm secretes silk in liquid form through the tiny opening in its head which solidifies on exposure to air and becomes a silk fibre ( or silk thread) . Soon the silkworm ( or caterpillar) covers itself completely by silk fibres. The silky covering spun by the silkworm ( or caterpillar) of silk moth is called cocoon. The cocoon is made by silkworm to protect its development as ‘ pupa’. Pupa is a stage in the life history of silk moth when the caterpillar ( or silkworm) becomes ‘encased’ in a hard shell of silk fibres called cocoon. The silkworm continues to develop in the form of pupa inside the cocoon to form the silk moth.

( iv) When the pupa ( encased in cocoon) develops fully to form an adult silk moth, then the cocoon splits up and a beautiful silk moth comes out. The adult female silk moth then lays more eggs. In this way, the life history of silk moth is completed. Refer to figure 4 for the diagram.

3 . (i) Rearing of Silkworms to btain Cocoons-A female silk moth lays hundreds of eggs at a time. The eggs of silk moths are stored carefully on paper strips (or cloth strips) and sold to silkworm farmers. The farmers keep these eggs at suitable temperature and humidity under hygienic conditions. The eggs are then warmed to a suitable temperature for hatching. When the eggs hatch, silkworms ( larvae or caterpillars) come out of eggs. The silkworms are fed cut-up mulberry leaves. The silkworms eat day and night and grow big in size. After about 25 to 3 days, the silkworms stop eating and get ready to spin cocoons. The silkworms climb the twigs placed near them and spin cocoons of silk fibres. The silkworms enclose themselves completely inside the silken cocoons in two or three days. (ii) Processing of Cocoons to btain Silk Fibres-All the cocoons are collected at one place. The pile of cocoons is placed in hot water. Hot water makes the silk fibres of cocoons to separate out. The long silk fibres are obtained by unwinding the threads from cocoons. The process of taking out silk fibres from the cocoons for use as silk is called reeling. Reeling is done in special machines which unwind the fibres of silk from cocoons. (iii) Converting Silk Fibres into Silk Cloth-Silk fibres obtained from

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SCIENCE 7 TEXT BOOK

32

cocoons are spun ( twisted) to form silk threads called ‘ silk yarn’. The silk yarn is then woven on looms into silk cloth by the weavers.

40. The shearing (cu ng the hair) of sheep is done in the hot weather of summer so that sheep may survive without their protective coat of hair. The hair of sheep grow again before the onset of winter and protect them in cold weather. Shearing does not hurt the sheep because the uppermost layer of the skin of sheep is ‘ dead’.


41. (d) 42. (c) 43. (b) 44. (c) 45. (a)

4 . (b) 4 . (a) 4 . (c) 4 . (d) 5 . (b)

51. (b) 52. (b) 53. (a) 54. (c) 55. (c)


56. ( a) ( i) Wool ( ii) Air ( b) Summer ( c) Sheep, Goat, Y ak, Camel

5 . (a) (i) Sheep (ii) Fleece (b) (i) Shearing (ii) Scouring (c) Wool (d) Making sweaters by kni ng

5 . P Wool Silk R Cotton S ute

59. ( a) Silk moth ( b) ( i) Larva ( ii) Caterpillar ( iii) Pupa ( iv) Silkworm ( c) Silk ( d) Mulberry tree

60. ( a) Silk moth ( b) ( i) Silkworm ( ii) Mulberry tree ( c) Silk ( d) Reeling

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SCIENCE 7 TEXT BOOK

33

WORKSHEET



( a) A breed of sheep found in India.

( b) Tree whose leaves provide food for the silkworms.

( c) A fibre made of proteins.

( d) The country in which discovery of silk was made.


( a) The fabric which burns to give a smell of burning hair is .… … … … … ...... silk.

( b) The silky covering spun by the silkworms of silk moth is called .… … … … … ..... .

( c) The process of removing hair from the body of sheep in the form of fleece is called .… … … … … ..... .

( d) .… … … … … ...... fibres are threads obtained from plants and animals.


( a) We obtain silk from alpaca.

( b) Shearing hurts the sheep.

( c) The process of washing the fleece that removes dust, dirt, dried sweat and grease is called scouring.

( d) Rearing of silkworms to obtain silk is called sericulture.

4. entiontheuseofthewoolo tainedfromthefollowing reedofsheep:

( a) Nali ( b) Bakharwal ( c) Patanwadi ( d) Lohi


5 . Answerthefollowingquestionsinshort:

( a) What is dyeing and why is it done on fabrics and wool?

( b) What is sorter’s disease and how is it caused?

( c) Name four varieties of silk.

( d) What do you observe when you burn a pure silk thread and an artificial silk thread?

(C) S

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SCIENCE 7 TEXT BOOK

34

SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) An animal which produces wool for making fine Pashmina shawls.

( b) A natural fibre obtained from insects.

( c) State of India where Angora goats are found.

( d) Threads obtained from plants and animals.

( e) The process of separating the fleece of a sheep into sections according to the quality of woolen fibres.


( a) Silk fibre is made up of carbohydrate.

( b) The rearing of silkworms for obtaining silk is called sericulture.

( c) The persons who look after the sheep are called shepherds.

( d) Rampur Bushair is commonly found in Uttar Pradesh.

( e) The most common variety of silk is Tussar silk.


( a) The discovery of silk was made in .… … … … … ..... .

( b) The fabric which burns giving a smell of burning paper is.… … … … … ...... silk.

( c) The process of taking out silk fibres from the cocoons for use as silk is .… … … … … ..... .

( d) The .… … … … … ...... silk moth lays eggs on the leaves of mulberry tree.

( e) The long, woolen yarns are twisted into thick yarn by the process of .… … … … … ..... .


( a) During shearing, the fleece of sheep is thoroughly cleaned.

( b) Sericulture means fish farming.

( c) Sorter’s disease is caused by a fungus.

( d) The fleece of sheep is cut into many pieces while shearing.

( e) Carpet wool is obtained from Lohi breed of sheep.



( a) Mention all the steps in correct order in which they are carried out during the production of woolen yarn from the sheep.

(C) ( b)

(C) ( b)

( c)

(C) ( c) Sorter’

(C) Sorter’

( d)(C)

( d)

( e)(C)

( e)

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SCIENCE 7 TEXT BOOK

35

( b) Name any four types of silk.

( c) Differentiate between shearing and scouring.

( d) Why does a woollen garment keep us warm during winters?

( e) Name an occupational hazard that may be caused during the production of wool. Give the name of its causative organism.


( a) Describe the life history of silk moth briefly.

( b) How will you differentiate between pure silk and synthetic silk?

( c) Name the animals which yield wool. What do you understand by selective breeding?

( d) Mention the steps involved in the production of silk in brief.

( e) Write a short note on the discovery of silk.


1. Whichofthefollowingdoesnot ieldwool:

( a) Alpaca ( b) Llama ( c) Goat ( d) Silkworm 2. Sorter sdiseaseiscaused :

( a) Bacteria ( b) V irus ( c) Fungus ( d) Protozoa . heprocessofta ingoutsil resfromthecocoonsiscalled:

( a) Reeling ( b) Combing ( c) Sorting ( d) Shearing 4. hewoolcoatofasheepthatiscuto alongwithathinla erofs inis:

( a) Fleece ( b) Grease ( c) Dried sweat ( d) Dirt 5. a harwalisa reedof:

( a) Goat ( b) Y ak ( c) Sheep ( d) Camel

(C) S

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SCIENCE 7 TEXT BOOK

36

4

Lesson Plan


The present chapter will help the students to imbibe the following concepts. He/She will be able to learn

• The meaning of the terms ‘ hot’ and ‘ cold’.

• About the clinical thermometer and laboratory thermometer.

• The different modes of transfer of heat.

• About conduction, good and poor conductors and their uses.

• About convection and formation of convection currents.

• About radiation and its effects on different colors.



VOCABULARY

Temperature, thermometer, kink, conduction, convection, land breeze, sea breeze, radiation.


Hot and cold (Page 42)

Learning Tools

Interactive warm up exercise: Discussing with the students the various obj ects that are hot and cold would be a good start for the topic. Ask students how the increase and decrease in temperature is related to heat.

Chapter opening exercise: Students should be asked how the doctor measures their body temperature when they fell ill / have high temperature.

HeatHeat

(C) Learning Tools

(C) Learning Tools

(C)

Interactive warm up exercise:(C)

Interactive warm up exercise:would(C

) would be(C

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SCIENCE 7 TEXT BOOK

37


iscuss that heat is a form of energy which makes a substance hotter. Students should know that a temperature is a reliable measure of hotness or coldness of an object. Students should realize the importance of thermometer which is used to measure the temperature. Perform the activity given on page no. 42 to find out that our sense of touch is not reliable in telling us whether an obj ect is really hot or cold.


When you finish your meal in a restaurant, a bowl of water is given to you to wash hands. Is it very hot, lukewarm or cold to touch


Temperature (Page 43)


Discuss with them that a hot obj ect has a high temperature whereas a cold obj ect has a low temperature. Students should be able to define the temperature of an obj ect. Students should be able to express the temperature of an obj ect in the unit of degree Celsius.

Using resources



What is the temperature of boiling water and ice in degree Celsius


Measuring temperature: Thermometers (Page 43)


Explain that a thermometer is a device for measuring the temperature of an obj ect. Students should be able to and draw a laboratory thermometer and describe its range as well as use. They should be acquainted with the precautions in using laboratory thermometer.

Using resources

• Students may be shown a laboratory thermometer.


(C) be able to and draw a laboratory thermometer and describe its range as well as use. They should

(C) be able to and draw a laboratory thermometer and describe its range as well as use. They should

be acquainted with the precautions in using laboratory thermometer.

(C) be acquainted with the precautions in using laboratory thermometer.

Using resources(C)

Using resources

• Students(C

) • Students

S Teacher guided discussion

S Teacher guided discussion

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SCIENCE 7 TEXT BOOK

38


Draw a neat and well-labeled diagram to show a laboratory thermometer.


Clinical Thermometer (Page 45)


iscuss with them the term kink constriction before starting the topic clinical thermometer. Students should be familiarized with the structure and range of the clinical thermometer. They should know that mercury is present in its glass bulb. They should know how to use it and precautions while handling it. Digital thermometers and maximum-and-minimum thermometers may also be discussed.

Using resources

Students may be shown a clinical thermometer to show its range.


Differentiate between a laboratory thermometer and a clinical thermometer.


Transfer of heat (Page 48)


xplain to the students that to carry heat from one part of an object to its other part, or from one object to another object, is called transfer of heat. Students should know that heat flows from a hot object to a cold object. They should know the different ways in which heat can be transferred- conduction in solids, convection in liquids and gases and radiation in vacuum.


What is transfer of heat


Conduction (Page 48)


Explain them that conduction is the transfer of heat from the hotter part of a material to its colder part without the movement of material as a whole. Students should be aware that it takes place only in solids. They should be able to differentiate between good conductors of heat and bad conductors of heat and cite their examples. Students should be acquainted with the uses of good conductors and bad conductors of heat.

(C)

(C)

(C) Conduction (Page 48)

(C) Conduction (Page 48)

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SCIENCE 7 TEXT BOOK

39

Using resources

• Conduct the activity given on Page no. 4 to show the conduction of heat. (Perform this activity under the supervision of an adult)

• Conduct the activity given on Page no. 5 to distinguish between good conductors and bad conductors of heat.


• Why is mercury metal used in making thermometers

• Why do we wear woolen clothes in winter


Convection in Water and Air (Page 52)


Discuss with the students that convection is the transfer of heat from the hotter parts of a liquid/ gas to its colder parts by the movement of the liquid itself. Students should be aware that convection takes place only in liquids and gases. Students should be made to realize that water transfers heat by convection because it is a poor conductor of heat. Explain that the circulatory movements of water in a beaker in which hot water rises and cold water sinks again and again are called convection currents. iscuss that since air is also a poor conductor of heat, it transfers heat from its hotter parts to colder parts by the process of convection. Air can transfer the heat of a source by convection only in the upward direction. Students should be familiarized with the blowing of land breeze and sea breeze in coastal areas due to convection currents in air.

Using resources

• Conduct the activity given on page no. 53 to show convection currents during heating of water.

• Conduct the activity given on page no. 54 to show the transfer of heat in air by convection.


xplain the blowing of sea breeze and land breeze with the help of diagrams.


Radiation (Page 56)


Explain them that radiation is the transfer of heat energy from a hot body to a cold body by means of heat rays, without any material medium between them. iscuss how the heat from the Sun reaches on the earth by the process of radiation. Students should know that objects having dark colors absorb more heat radiations than the objects having light colors. ot objects having dark colors emit more heat radiations than the hot obj ects having light colors. Students should be acquainted with the importance of color of obj ects in our everyday life.

(C) Radiation (Page 56)

(C) Radiation (Page 56)



Explain them that radiation is the transfer of heat energy from a hot body to a cold body by means of (C)

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SCIENCE 7 TEXT BOOK

40

Using resources

• Conduct the activity given on pages 5 and 5 .


List few examples to show that colors of the obj ects play an important role in the transfer of heat.



Using resources






TEXT BOOK ANSWERS


1. The temperature is expressed in the unit of ‘degree Celsius’ (which is written in short form as C).

2. The normal temperature of human body is 3 C (thirty seven degree Celsius). 3. The range of a laboratory thermometer is generally from, 1 C to 11 C. 4. Mercury 5. ink (or Constriction) 6. (a) aboratory thermometer (b) Clinical thermometer . A clinical thermometer has usually two temperature scales marked on its glass tube on

the two sides of the mercury thread: Celsius scale of temperature and Fahrenheit scale of temperature.

. The Fahrenheit scale of temperature marked on the clinical thermometer has a range of 4 F to 1 F ( F means degree Fahrenheit).

. The normal temperature of human body on Fahrenheit scale is . F. 1 . Digital thermometers 11. Maximum-and-minimum thermometer 12. eat can be transferred from a hot object to a cold object in three different ways (i) by

conduction, (ii) by convection, and (iii) by radiation (or heat rays). 13. Conduction

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SCIENCE 7 TEXT BOOK

41

14. Conduction 15. When temperature of both the objects becomes the same (or equal) 16. Insulators 1 . Convection 1 . Good convector of heat

1 . Convection

2 . (a) Convection (b) Convection 21. and breeze and sea breeze 22. Radiation 23. Radiation 24. (a) Radiation (b) Conduction (c) Convection 25. Radiation 26. By radiation 2 . Radiation 2 . Radiation 2 . (a) Shiny white surface Better reflector of heat (b) ull black surface Better absorber of

heat 3 . (a) conduction (b) conduction (c) plastic wood (d) poor good (e) air (f) temperature (g)

Celsius (h) clinical (i) radiation (j) convection


31. Metals are good conductors of heat while wood is not a good conductor of heat. 32. Wood is not a good conductor of heat. 33. A laboratory thermometer cannot be used to measure the human body temperature. This

is because as soon as we take out the bulb of the laboratory thermometer from our mouth, the level of mercury in its tube will start falling quickly (due to cooling of its bulb by air). This will give a wrong value of the body temperature.

34. The kink prevents the mercury level in the thermometer tube from falling on its own. So, even when the thermometer bulb is removed from the mouth of a patient, the mercury thread will keep standing at the maximum level reached.

35. Conduction is the transfer of heat from the hotter part of a material to its colder part (or from a hot material to a cold material in contact with it) without the movement of material as a whole. A cold metal spoon dipped in a hot cup of tea gets heated by conduction (In this case, hot tea acts only as a source of heat).

3 . Those materials which allow heat to pass through them easily are called good conductors of heat. For example, the metals such as silver, copper, aluminium, iron and mercury are all good conductors of heat.

3 . Those materials which do not allow heat to pass through them easily are called poor conductors of heat. The materials which are poor conductors of heat are called insulators. Some of the examples of poor conductors of heat (or insulators of heat) are plastic, wood, paper, cloth, leather, cotton, wool, thermocol, rubber, asbestos, clay, bricks, cork, cane, bamboo, straw, saw-dust, glass, fibreglass, water and air.

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SCIENCE 7 TEXT BOOK

42

3 . G ood cond uctors: Copper, stainless steel, aluminium Poor cond uctors: wood, plastic, air, paper, glass, thermocol, rubber

3 . (a) Conduction (b) Convection (c) Convection (d) Radiation 4 . Stainless steel is a good conductor of heat while thermocol is a poor conductor of heat. 41. The short range of a clinical thermometer is due to the fact that the temperature of human

body normally does not go below 35 C or above 42 C. 42. The kink prevents the mercury level in the thermometer tube from falling on its own. So,

even when the thermometer bulb is removed from the mouth of a patient, the mercury thread will keep standing at the maximum level reached. ue to this we can read the correct body temperature of the patient even after removing the thermometer bulb from his mouth.

43. The temperature of an object is the degree of hotness (or coldness) of the object. Temperature is measured by using a device (or instrument) called thermometer.

44. A similarity between clinical thermometer and laboratory thermometer is that both are mercury-in glass thermometers. The differences between a clinical thermometer and a laboratory thermometer are as follows (i) The clinical thermometer has a very short temperature range (35 C to 42 C) whereas a laboratory thermometer has a large temperature range (usually from, 1 C to 11 C). (ii) The clinical thermometer has a kink (or constriction) in its tube to prevent the back flow of mercury into the bulb whereas a laboratory thermometer has no kink. (iii) The clinical thermometer measures temperature more accurately (up to .1 C) than a laboratory thermometer (which usually measures up to 1 C).

45. eat from the sun cannot reach the earth by conduction or convection because both these processes require a material medium (like solid, liquid or gas) to transfer heat, they cannot take place in empty space (or vacuum).


46. Woollen clothes keep us warm during cold winter days. Wool is a poor conductor of heat due to which woollen clothes stop the flow of heat from our warm body to the cold surroundings. Moreover, there is air trapped in-between the fibres of the woollen clothes.

Air is a very poor conductor of heat. So, the air trapped in fibres of woollen clothes also stops the flow of heat from our warm body to the cold surroundings. Since our body does not lose its heat, we feel warm on wearing woollen clothes in winter. Wearing more layers of clothes keeps us warmer in winter than wearing just one thick piece of clothing. This is because more layers of clothes trap more air in them and air being a very poor conductor of heat, prevents our body heat from going away to cold surroundings.

4 . The thermometer used for measuring the temperature of human body is called clinical thermometer. A clinical thermometer has a very short range of temperature from 35 C to 42° C. A clinical thermometer cannot be used to measure high temperatures because it has been designed to measure only human body temperature which varies over a short range. If a clinical thermometer is used to measure high temperatures, it will get damaged.

4 . When a beaker containing water is kept over a burner, water at the bottom of beaker (near the flame) gets heated, expands and becomes lighter. This hot water (being lighter) rises upwards and carries heat along with it. The cold water from above (being denser) sinks downwards to take the place of hot rising water. This cold water then gets heated by

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42° C. A clinical thermometer cannot be used to measure high temperatures because it has been designed to measure only human body temperature which varies over a short range. (C)

been designed to measure only human body temperature which varies over a short range.

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SCIENCE 7 TEXT BOOK

43

the burner and also rises upwards carrying its heat upwards. And more cold water sinks downwards. This process of hot water rising upwards and cold water sinking downwards takes place again and again due to which the whole water in the beaker gets heated uniformly. The circulatory movements of water in the beaker in which hot water rises and cold water sinks again and again, are called convection currents. These convection currents transfer heat from water at the bottom of the beaker to the top of beaker rapidly. Refer to figure 11 for the diagram.

4 . In order to heat air in a room during winter, we keep the heater on the floor (usually in a corner of the room). ow, though the heater is placed on the floor at the bottom of the room but it still heats all the air in the room. Actually, when air is heated by the heater in one part of the room, it transfers heat by convection. When the heater kept on the floor in a room is switched on, the air near the heater gets heated, expands and become lighter. This hot air (being lighter) rises above the top of the heater and carries its heat alongwith it. The cold air from above (being denser) sinks downwards to the bottom of the heater to take the place of hot rising air. This cold air also gets heated by the heater and rises upwards carrying its heat upwards. And more cold air sinks downwards towards the heater. This process of hot air rising upwards and cold air sinking downwards takes place again and again due to which all the air in the room gets heated uniformly after some time. The circulatory movements of air in the room in which hot air rises and cold air sinks again and again are called convection currents. Thus, a room heater heats all the air in a room by se ng up convection currents in the air. Refer to figure 13 for the diagram.

5 . Refer to figure 15 and figure 1 and the text given on Page no. 55.

51. People prefer to wear white clothes (or light coloured clothes) in the hot summer days because white clothes (or light coloured clothes) absorb less heat from the sun. In fact, white clothes (or light coloured clothes) reflect most of the sun’s heat rays which fall on them and keep us cool and comfortable in hot weather. For example, in summer a white shirt reflects the sun’s heat rays and makes us stay cooler. People prefer to wear dark coloured clothes in the cold winter days. This is because dark coloured clothes absorb more heat rays from the sun and keep us warm in winter season. For example, a black shirt worn in winter absorbs the sun’s heat rays more e ciently and keeps us warm.

52. A thermometer is a device for measuring the temperature of an obj ect. A clinical thermometer is used to measure our body temperature by a doctor. A laboratory thermometer cannot be used to measure the human body temperature. This is because as soon as we take out the bulb of the laboratory thermometer from our mouth, the level of mercury in its tube will start falling quickly (due to cooling of its bulb by air). This will give a wrong value of the body temperature.

53. The box of solar cooker (and solar water heater) is painted black from inside. This is because a black surface is a very good absorber of heat and it will absorb maximum heat radiations coming from the sun. The houses in hot, sunny countries (like ours) are usually painted white or with light colours from outside. This is because a house painted white or with light colours absorbs very little sun’s heat rays, it reflects most of the sun’s heat rays. This keeps the house cool in the hot days of summer.

54. Convection is the transfer of heat from the hotter parts of a liquid (or gas) to its colder parts by the movement of the liquid (or gas) itself. In order to heat water, we keep the

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SCIENCE 7 TEXT BOOK

44

vessel containing water over a gas burner. ow, though the burner is kept at the bottom of the vessel, but it still heats all the water in the vessel. Actually, when water is heated in a vessel, it transfers heat from its hotter parts (just above the flame of burner) to its colder parts by the process of convection. The transfer of heat by convection cannot take place in solids because the particles in the solids are fixed at a place and hence cannot move about freely.

55. Radiation is the transfer of heat energy from a hot body to a cold body by means of heat rays, without any material medium between them. The best example of radiation is the transfer of heat energy of the sun to the earth. When we come out in the sunshine, we feel hot. This means that the heat from the sun is being transferred to us which makes us feel hot. When we stand next to a burning fire, we can feel the heat of the fire falling on our face. The heat is transferred from the fire to our face by the process of radiation.


5 . (b) 5 . (c) 5 . (d) 5 . (c) . (d)

1. (c) 2. (d) 3. (d) 4. (c) 5. (c)

. (c) . (d) . (d) . (c) . (b)

1. (c) 2. (d) 3. (d) 4. (b) 5. (d)


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. Steel spoon and divider (They are made of metals which are good conductors of heat).

. I would prefer to use two thin woollen blankets joined together to keep warm on a cold winter night. This is because the two thin blankets joined together will have a layer of air trapped in-between them. And this extra layer of trapped air (being a very poor conductor of heat) will prevent the body heat from going away more e ciently and hence keep me more warm.

. (a) The black shirt will make the person more comfortable in cold winter season. This is because the black coloured shirt will absorb more heat rays from the sun and keep him warm and comfortable in cold winter season (b) The white shirt will make the person more comfortable in the hot summer season. This is because the white coloured shirt will reflect most of the sun’s heat rays and keep him cool and comfortable in hot summer season.

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SCIENCE 7 TEXT BOOK

45

WORKSHEET



(a) The unit in which temperature is commonly measured.

(b) The liquid commonly used in making thermometers.

(c) Another term used for poor conductors of heat.

(d) Process of heat transfer involved when a utensil filled with hot water kept away from flame cools down by transferring heat to the surroundings.


(a) eat is transferred in solids by . ........... .

(b) Air and water are . ........... conductors of heat.

(c) The hotness or coldness of an object is determined by its . ........... .

(d) In liquids and gases, heat is transferred by the process of . ........... .


(a) very hot object emits invisible heat rays in only one direction.

(b) Air can transfer the heat of a source by convection only in the upward direction.

(c) Gentle wind is called breeze.

(d) Copper is a bad conductor of heat.

4. entionwhetherthefollowingaregoodconductororpoorconductorofheat:

(a) Steel (b) Thermocol (c) Clay (d) Aluminium



(a) ifferentiate between radiation and convection.

(b) What is the range of laboratory thermometer

(c) Why do we wear woollen clothes in winter

(d) Why do people generally prefer to wear light colored clothes in hot summer days

(C) S

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SCIENCE 7 TEXT BOOK

46

SAMPLE PAPER

M.M. 5

ame ............................................................... Class ......................... ate ...........................



(a) A narrow and sharp bend in the bore of a clinical thermometer tube.

(b) Transfer of heat from the hot material to a cold material which is in contact with it, without the movement of material as a whole.

(c) Materials which allow heat to pass through them easily.

(d) A poor conductor of heat.

(e) The breeze blowing from land towards the sea.


(a) The objects having dark colors absorb more heat radiations than the objects having light colors.

(b) Solar cooker is painted black because black color absorbs minimum heat radiations coming from the sun.

(c) eat is transferred from a glowing bulb to our hand by radiation.

(d) Gentle wind is called air.

(e) The clinical thermometer has a very short range of temperature.

3. G ive one example of:

(a) A good conductor of heat.

(b) A poor conductor of heat.

(c) A convector of heat.

(d) A color which absorbs more heat radiations.

(e) A color which emits less heat radiations.


(a) Weather reports on TV and newspapers are measured by digital thermometers.

(b) The normal temperature of a human body is 5 degree Celsius.

(c) Some stainless steel pans are provided with copper bottoms because copper is a poor conductor of heat.

(d) Water transfers heat by the process of conduction.

(e) The breeze blowing from the sea towards the land is called land breeze.

(C) Correct the follo

(C) Correct the follo

(a) Weather

(C) (a) Weather

(C)

(b) The(C)

(b) The

(c) Some(C)

(c) Some

S (e) A S (e) A S colorS color

Correct the folloS Correct the follo

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conductor

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SCIENCE 7 TEXT BOOK

47



(a) Mention any two precautions before using clinical thermometer.

(b) ifferentiate between conductors and insulators.

(c) State the direction of flow of heat.

(d) Why is mercury used in thermometers

(e) Why has the use of digital thermometer become so popular nowadays


(a) xplain the formation of land breeze with the help of a diagram.

(b) Why can the heat of the sun not reach us by conduction or convection

(c) ow can colors be related to the radiation in day to day life

(d) What precautions should be taken while using a laboratory thermometer

(e) What do you understand by convection xplain with the help of an example.


1. heconvectioncurrentsinairtransferheat:

(a) ownwards (b) pwards

(c) ownwards as well as upwards (d) Sideways

2. heinvisi lera swhichcantransferheat radiationarecalled:

(a) ltraviolet rays (b) ltrasonic rays

(c) Infrasonic rays (d) Infrared rays

3. The heat from the sun reaches us on the earth by the process of:

(a) Conduction (b) Radiation (c) Convection (d) one of these.

4. The process which can transfer heat through the vacuum as well as air is:

(a) Conduction (b) Convection (c) Irradiation (d) Radiation

5 . The normal temperature of a healthy person is thirty seven d egrees on:

(a) elvin scale (b) Fahrenheit scale (c) Celsius scale (d) one of the above

(C) S

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ansfer heat through the vacuum as well as air is:

(a) Conduction (b)

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The normal tempera

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SCIENCE 7 TEXT BOOK

48

5Lesson Plan



• The acids and bases.

• The indicators used to test acids and bases.

• About the neutralisation reactions.

• ses of neutralisation reactions in everyday life.

• About salts formed by the reaction of acids and bases.



VOCABULARY

Indicator, acid, acid rain, base, neutral substances, neutralisation, salt.


Indicators for testing acids and bases (Page 64)

Learning Tools

Interactive warm up exercise: iscussing the names of various acids and bases that students are already acquainted with, would be a good start for the topic. Ask students whether they know about substances that are neither acidic nor basic in nature.

Chapter opening exercise: Students should be asked to name the acid produced in the stomach that helps in the process of digestion.


iscuss with the students that indicators are special types of chemicals which are used to test whether a given substance is an acid or a base. Students should be acquainted with all types of

Acids, Bases and SaltsAcids, Bases and Salts

(C) Interactive warm up exercise:


(C) already acquainted with, would be a good start for the topic. Ask students whether they know

(C) already acquainted with, would be a good start for the topic. Ask students whether they know

about substances that are neither acidic nor basic in nature. (C)

about substances that are neither acidic nor basic in nature. (C)

Chapter opening exercise: (C)

Chapter opening exercise:

S Learning ToolsS Learning Tools

Interactive warm up exercise: S Interactive warm up exercise:

Chand

Chand


Chand



Chand


Indicators for testing acids and bases (Page 64) Chand

Indicators for testing acids and bases (Page 64)

And

And

And

And C

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About salts formed by the reaction of acids and bases.

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ny

About salts formed by the reaction of acids and bases.

Limite

d

Limite

d

Limite

d

Limite

d

Limite

dThe present chapter will help the students to imbibe the following concepts. He/She will be Lim

ited


SCIENCE 7 TEXT BOOK

49

indicators like itmus, China rose, Turmeric and Phenolphthalein and the color changes they produce with acids and bases.

Using resources

• Conduct the litmus paper test (given on page no. ) to differentiate between an acid and a base.



nder the guidance of your parents, conduct the activity given on page no. and use turmeric paper as an indicator to test acid (in orange juice) and base (in soap solution).


Acids (Pages 67)


Discuss that a substance which reacts with a base to form salt and water is called an acid. Students should know that acids turn blue litmus to red. They should be able to cite examples of common acids and differentiate between organic acids and mineral acids. They should be able to distinguish between strong and weak acids. Students should be sensitized about the harmful consequences of acid rain.


What are acids? Name the acids present in ant’s sting and curd.


Bases and neutral substances (Page 69)


xplain them that a substance which can neutralize an acid to form a salt and water is called a base. Students should know that bases turn red litmus to blue. A base soluble in water is termed as alkali. Students should be able to cite examples of different bases. They should be able to differentiate between strong and weak bases. They should be aware that not all substances are acidic or basic. Those substances which are neither acidic nor basic are called neutral substances.

Using resources

• Conduct the litmus paper test (activity on Page no. 1) to confirm the neutral nature of substances.


ifferentiate among acids, bases and neutral substances giving two examples of each.

(C) Students should be able to cite examples of different bases. They should be able to differentiate

(C) Students should be able to cite examples of different bases. They should be able to differentiate

between strong and weak bases. They should be aware that not all substances are acidic or basic.

(C) between strong and weak bases. They should be aware that not all substances are acidic or basic.

(C)

Those substances which are neither acidic nor basic are called neutral substances.(C)

Those substances which are neither acidic nor basic are called neutral substances.

Using resources(C

) Using resources

S xplain them that a substance which can neutralize an acid to form a salt and water is called a base.

S xplain them that a substance which can neutralize an acid to form a salt and water is called a base. Students should know that bases turn red litmus to blue. A base soluble in water is termed as alkali. S Students should know that bases turn red litmus to blue. A base soluble in water is termed as alkali. Students should be able to cite examples of different bases. They should be able to differentiate S Students should be able to cite examples of different bases. They should be able to differentiate

Chand

Chand


Chand



Chand




xplain them that a substance which can neutralize an acid to form a salt and water is called a base. Chand

xplain them that a substance which can neutralize an acid to form a salt and water is called a base.

And

And

What are acids? Name the acids present in ant’s sting and curd. And

What are acids? Name the acids present in ant’s sting and curd.

Compa

ny

Compa

ny

Discuss that a substance which reacts with a base to form salt and water is called an acid. Students

Compa

ny

Discuss that a substance which reacts with a base to form salt and water is called an acid. Students should know that acids turn blue litmus to red. They should be able to cite examples of common

Compa

ny

should know that acids turn blue litmus to red. They should be able to cite examples of common acids and differentiate between organic acids and mineral acids. They should be able to distinguish

Compa

ny

acids and differentiate between organic acids and mineral acids. They should be able to distinguish between strong and weak acids. Students should be sensitized about the harmful consequences Com

pany

between strong and weak acids. Students should be sensitized about the harmful consequences

Limite

d

Limite

dnder the guidance of your parents, conduct the activity given on page no. and use turmeric

Limite

dnder the guidance of your parents, conduct the activity given on page no. and use turmeric

paper as an indicator to test acid (in orange juice) and base (in soap solution).

Limite

dpaper as an indicator to test acid (in orange juice) and base (in soap solution).

SCIENCE 7 TEXT BOOK

50


Neutralisation (Page 72)


Discuss that the reaction in which an acid reacts with a base to form salt and water is called neutralisation reaction. eat is evolved during the reaction.

Using resources

• Conduct the activity given on page no. 2 to show the production of common salt (Sodium Chloride), when ydrochloric acid reacts with Sodium hydroxide.



Is sugar solution acidic, basic or neutral in nature ow will you test it


Neutralisation in everyday life (Page 73)


xplain them that neutralisation reactions involving acids and bases play a very important role in our everyday life. Students should know that remedy for indigestion, treatment of an ant’s sting, reducing the too acidic or too basic nature of soil and treatment of factory wastes, all involve neutralisation reactions.


Name the base used to treat indigestion and ant’s sting.


Salts (Page 74)


xplain them that a salt is a substance formed by the reaction of an acid with a base. Students should be able to classify salts as neutral salts, acidic salts and basic salts and cite their examples. They should be able to predict the name of the salt produced from its constituent acid and base.


ist the different types of salts and give two examples of each.



xplain them that a salt is a substance formed by the reaction of an acid with a base. Students (C)

xplain them that a salt is a substance formed by the reaction of an acid with a base. Students should be able to classify salts as neutral salts, acidic salts and basic salts and cite their examples. (C

) should be able to classify salts as neutral salts, acidic salts and basic salts and cite their examples. They should be able to predict the name of the salt produced from its constituent acid and base.

(C)

They should be able to predict the name of the salt produced from its constituent acid and base.

S Salts (Page 74) S Salts (Page 74)


Chand

Chand


Chand



Chand


And xplain them that neutralisation reactions involving acids and bases play a very important role in

And xplain them that neutralisation reactions involving acids and bases play a very important role in

our everyday life. Students should know that remedy for indigestion, treatment of an ant’s sting,

And

our everyday life. Students should know that remedy for indigestion, treatment of an ant’s sting, reducing the too acidic or too basic nature of soil and treatment of factory wastes, all involve And

reducing the too acidic or too basic nature of soil and treatment of factory wastes, all involve

Compa

ny

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ny


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ny



Compa

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xplain them that neutralisation reactions involving acids and bases play a very important role in Compa

ny

xplain them that neutralisation reactions involving acids and bases play a very important role in

Limite

dgiven on page no. 2 to show the production of common salt (Sodium

Limite

dgiven on page no. 2 to show the production of common salt (Sodium

y run the video for the given topic using the R Code given at the end of the

Limite


SCIENCE 7 TEXT BOOK

51



Using resources



iscuss the exercises given at the end of the chapter.



TEXT BOOK ANSWERS


1. Turmeric Phenolphthalein

2. itmus

3. (a) Red (b) Magenta ( eep pink)

4. (a) Blue (b) Green (c) Pink (d) Red

5. (a) itmus (b) Turmeric paper

. (a) False (b) False (c) False (d) True (e) True

. Base

. Acidic

9. Basic

1 . itrogen dioxide and carbon dioxide

11. ydrochloric acid and nitric acid are strong acids. Tartaric acid and carbonic acid are some of the weak acids.

12. Sodium hydroxide and Potassium hydroxide are strong bases. Calcium hydroxide and Ammonium hydroxide are weak bases.

13. Formic acid

14. Baking soda solution

15. eutralisation reaction

1 . Phenolphthalein

1 . Sodium chloride

1 . a. Citric acid, actic acid b. sulphuric acid and nitric acid

1 . a. Acids have sour taste. b. Bases have bitter taste.

(C)

Ammonium hydroxide are weak bases.

(C)

Ammonium hydroxide are weak bases.

Formic acid

(C) Formic acid

14.(C) 14. Baking soda solution (C) Baking soda solution

15.(C)

15. eutralisation reaction (C)

eutralisation reaction

S Sodium hydroxide and Potassium hydroxide are strong bases. Calcium hydroxide and

S Sodium hydroxide and Potassium hydroxide are strong bases. Calcium hydroxide and

S Ammonium hydroxide are weak bases. S Ammonium hydroxide are weak bases.

Formic acid S Formic acid

Chand

itrogen dioxide and carbon dioxide

Chand

itrogen dioxide and carbon dioxide

ydrochloric acid and nitric acid are strong acids. Tartaric acid and carbonic acid are some

Chand

ydrochloric acid and nitric acid are strong acids. Tartaric acid and carbonic acid are some

of the weak acids. Chand

of the weak acids.

Sodium hydroxide and Potassium hydroxide are strong bases. Calcium hydroxide and Chand

Sodium hydroxide and Potassium hydroxide are strong bases. Calcium hydroxide and

And

(a) False (b) False (c) False (d) True (e) True

And

(a) False (b) False (c) False (d) True (e) True

Compa

ny Li

mited

Limite

d

Limite

dAssessment of understanding of the chapter could be done with the help of the given worksheet

Limite


SCIENCE 7 TEXT BOOK

52

2 . (a) acidic (b) neutralisation (c) salt water (d) Salt (e) Sodium chloride (f) indicator (g) indicators


21. Indicators are special type of chemicals which are used to test whether a given substance is an acid or base. itmus, China rose and Turmeric are naturally occurring indicators.

22. It is extracted from a type of plant called ‘lichen’. itmus is the most common indicator for testing acids and bases in the laboratory.

23. This is due to the fact that soap solution is basic in nature which changes the colour of turmeric in the curry stain to red.

24. Acidic vinegar, stomach juices, lemon juice Basic lime water, toothpaste, baking soda solution, milk of magnesia, ammonia solution

25. A salt is a substance formed by the reaction of an acid with a base. Sodium chloride and Sodium sulphate are two salts.

2 . Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two examples of neutral salts are sodium chloride and sodium sulphate. Those salts which form an acidic solution on dissolving in water are called acidic salts. The two examples of acidic salts are ammonium chloride and ammonium sulphate. Those salts which form basic solutions on dissolving in water are called basic salts. The two examples of basic salts are sodium carbonate and sodium hydrogen carbonate.

2 . Acid ic salts: ammonium chloride, ammonium sulphate Basic salts: sodium carbonate Neutral salts: sodium chloride, sodium sulphate

2 . Some heat is always evolved (or produced) in a neutralisation reaction. This heat raises the temperature of reaction mixture due to which the reaction mixture becomes hot.

2 . The reaction mixture will become hot. This is because a neutralisation reaction takes place

3 . Being basic in nature, antacids react with excess acid in the stomach and neutralise it. This gives relief to the person concerned.

31. This is because, being a base, baking soda solution (or calamine solution) neutralises the acidic liquid injected by the ant and cancels its effect.

32. When the soil is too acidic, it is treated with bases such as quicklime (calcium oxide) or slaked lime (calcium hydroxide). The bases such as quicklime (or slaked lime) neutralise the excess acid present in the soil and reduce its acidic nature.

33. If the soil is too basic, then decaying organic matter (called manure or compost) is added to it. The decaying organic matter releases acids which neutralise the excess bases present in the soil and reduce its basic nature.

34. Antacids are a group of mild bases which have no toxic effects on the body. Antacids are a group of mild bases which have no toxic effects on the body. Being basic in nature, antacids react with excess acid in the stomach and neutralise it. This gives relief to the person concerned. A common antacid used for curing indigestion due to acidity is milk of magnesia. Milk of magnesia contains a base called magnesium hydroxide.

(C) If the soil is too basic, then decaying organic matter (called manure or compost) is added

(C) If the soil is too basic, then decaying organic matter (called manure or compost) is added

to it.

(C) to it. The decaying organic matter releases acids which neutralise the

(C) The decaying organic matter releases acids which neutralise the

in the soil and reduce its basic nature. (C)

in the soil and reduce its basic nature.

34.(C)

34. Antacids are a group of mild bases which have no toxic effects on the body. Antacids (C)

Antacids are a group of mild bases which have no toxic effects on the body. Antacids

S slaked lime (calcium hydroxide). The bases such as quicklime (or slaked lime) neutralise

S slaked lime (calcium hydroxide). The bases such as quicklime (or slaked lime) neutralise the excess acid present in the soil and reduce its acidic nature. S the excess acid present in the soil and reduce its acidic nature.

If the soil is too basic, then decaying organic matter (called manure or compost) is added S If the soil is too basic, then decaying organic matter (called manure or compost) is added

Chand

The reaction mixture will become hot. This is because a neutralisation reaction takes place

Chand


Being basic in nature, antacids react with excess acid in the stomach and neutralise it. This

Chand

Being basic in nature, antacids react with excess acid in the stomach and neutralise it. This gives relief to the person concerned.

Chand

gives relief to the person concerned.

Chand

This is because, being a base, baking soda solution (or calamine solution) neutralises the

Chand

This is because, being a base, baking soda solution (or calamine solution) neutralises the acidic liquid injected by the ant and cancels its effect.

Chand

acidic liquid injected by the ant and cancels its effect.

When the soil is too acidic, it is treated with bases such as quicklime (calcium oxide) or Chand

When the soil is too acidic, it is treated with bases such as quicklime (calcium oxide) or slaked lime (calcium hydroxide). The bases such as quicklime (or slaked lime) neutralise Cha

nd

slaked lime (calcium hydroxide). The bases such as quicklime (or slaked lime) neutralise the excess acid present in the soil and reduce its acidic nature. Cha

nd

the excess acid present in the soil and reduce its acidic nature.

And sodium chloride, sodium sulphate

And sodium chloride, sodium sulphate

Some heat is always evolved (or produced) in a neutralisation reaction. This heat raises the

And Some heat is always evolved (or produced) in a neutralisation reaction. This heat raises the

temperature of reaction mixture due to which the reaction mixture becomes hot.

And

temperature of reaction mixture due to which the reaction mixture becomes hot.

The reaction mixture will become hot. This is because a neutralisation reaction takes place And


Being basic in nature, antacids react with excess acid in the stomach and neutralise it. This And

Being basic in nature, antacids react with excess acid in the stomach and neutralise it. This

Compa

ny

Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two

Compa

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Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two examples of neutral salts are sodium chloride and sodium sulphate. Those salts which

Compa

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examples of neutral salts are sodium chloride and sodium sulphate. Those salts which form an acidic solution on dissolving in water are called acidic salts. The two examples of

Compa

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form an acidic solution on dissolving in water are called acidic salts. The two examples of acidic salts are ammonium chloride and ammonium sulphate. Those salts which form basic

Compa

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acidic salts are ammonium chloride and ammonium sulphate. Those salts which form basic solutions on dissolving in water are called basic salts. The two examples of basic salts are

Compa

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solutions on dissolving in water are called basic salts. The two examples of basic salts are sodium carbonate and sodium hydrogen carbonate.

Compa

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sodium carbonate and sodium hydrogen carbonate.

ammonium chloride, ammonium sulphateCompa

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ammonium chloride, ammonium sulphate sodium chloride, sodium sulphate Com

pany

sodium chloride, sodium sulphate

Some heat is always evolved (or produced) in a neutralisation reaction. This heat raises the Com

pany

Some heat is always evolved (or produced) in a neutralisation reaction. This heat raises the

Limite

dThis is due to the fact that soap solution is basic in nature which changes the colour of

Limite

dThis is due to the fact that soap solution is basic in nature which changes the colour of

Acidic vinegar, stomach juices, lemon juice Basic lime water, toothpaste, baking soda

Limite

dAcidic vinegar, stomach juices, lemon juice Basic lime water, toothpaste, baking soda

A salt is a substance formed by the reaction of an acid with a base. Sodium chloride and Limite

dA salt is a substance formed by the reaction of an acid with a base. Sodium chloride and

SCIENCE 7 TEXT BOOK

53

35. ur stomach produces hydrochloric acid. This hydrochloric acid helps in digesting our food without harming the stomach. Sometimes, excess of hydrochloric acid is produced in the stomach due to various reasons (one being over-eating). The excess of acid in the stomach causes indigestion which produces pain and irritation (The person who has excess acid in the stomach is also said to suffer from acidity). In order to cure indigestion and get rid of pain, we can take bases called ‘antacids’.

3 . A common antacid used for curing indigestion due to acidity is milk of magnesia. Magnesium hydroxide neutralises the excess acid present in the stomach and cures indigestion.

3 . The sting of an ant contains an acid called formic acid. So, when an ant stings (or bites) a person, it injects an acidic liquid into the skin of the person which causes burning pain. If an ant stings a person, then rubbing a mild base like baking soda solution (or calamine solution) on the stung area of the skin gives relief.

3 . The drink with the sour taste is an acidic drink. The one with bitter taste is basic drink and the third one is neutral drink.

39. 1. Acids have sour taste. Bases have bitter taste. 2. Acids are not soapy to touch. Bases feel soapy to touch. 3. Acids turn blue litmus to red. Bases turn red litmus to blue.

4 . istilled water is neutral in nature. We can confirm the neutral nature of substances by performing the litmus test. For example, let us put one drop of distilled water on blue litmus paper and another drop of distilled water on red litmus paper. We will find that there is no change in the colour of blue litmus paper or red litmus paper. This shows that distilled water is neither acidic nor basic in nature. So, distilled water is neutral.


41. The rain which contains a higher level of acid than normal is called acid rain. Acid rain is caused by the acidic gases like sulphur dioxide, nitrogen dioxide and carbon dioxide which are released into the air as pollutants during the burning of various types of fuels. Sulphur dioxide gas dissolves in falling rain drops to form sulphuric acid nitrogen dioxide gas dissolves in rain drops to form nitric acid whereas carbon dioxide gas dissolves in rain drops to form carbonic acid. The presence of sulphuric acid, nitric acid and carbonic acid in rain water makes the rain water acidic. And when this acidic rain water falls on the earth, we call it acid rain. Acid rain causes damage to aquatic animals (like fish), trees, crop plants, metal structures and stone buildings and monuments.

42. Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two examples of neutral salts are sodium chloride and sodium sulphate. Those salts which form an acidic solution on dissolving in water are called acidic salts. The two examples of acidic salts are ammonium chloride and ammonium sulphate. Those salts which form basic solutions on dissolving in water are called basic salts. The two examples of basic salts are sodium carbonate and sodium hydrogen carbonate.

43. A substance which reacts with a base to form a salt (and water) is called an acid. Acids have sour taste. Acids turn blue litmus to red. Some of the examples of acids are Acetic acid, Citric acid.

(C) examples of neutral salts are sodium chloride and sodium sulphate. Those salts which

(C) examples of neutral salts are sodium chloride and sodium sulphate. Those salts which

form an acidic solution on dissolving in water are called acidic salts. The two examples of

(C) form an acidic solution on dissolving in water are called acidic salts. The two examples of

acidic salts are ammonium chloride and ammonium sulphate. Those salts which form basic

(C) acidic salts are ammonium chloride and ammonium sulphate. Those salts which form basic

solutions on dissolving in water are called basic salts. The two examples of basic salts are (C)

solutions on dissolving in water are called basic salts. The two examples of basic salts are sodium carbonate and sodium hydrogen carbonate. (C)

sodium carbonate and sodium hydrogen carbonate.

S Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two S Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two examples of neutral salts are sodium chloride and sodium sulphate. Those salts which S examples of neutral salts are sodium chloride and sodium sulphate. Those salts which form an acidic solution on dissolving in water are called acidic salts. The two examples of S form an acidic solution on dissolving in water are called acidic salts. The two examples of

Chand

which are released into the air as pollutants during the burning of various types of fuels.

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which are released into the air as pollutants during the burning of various types of fuels. Sulphur dioxide gas dissolves in falling rain drops to form sulphuric acid nitrogen dioxide

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Sulphur dioxide gas dissolves in falling rain drops to form sulphuric acid nitrogen dioxide

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gas dissolves in rain drops to form nitric acid whereas carbon dioxide gas dissolves in rain

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gas dissolves in rain drops to form nitric acid whereas carbon dioxide gas dissolves in rain drops to form carbonic acid. The presence of sulphuric acid, nitric acid and carbonic acid in

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drops to form carbonic acid. The presence of sulphuric acid, nitric acid and carbonic acid in rain water makes the rain water acidic. And when this acidic rain water falls on the earth,

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rain water makes the rain water acidic. And when this acidic rain water falls on the earth, we call it acid rain. Acid rain causes damage to aquatic animals (like fish), trees, crop plants,

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we call it acid rain. Acid rain causes damage to aquatic animals (like fish), trees, crop plants, metal structures and stone buildings and monuments. Cha

nd

metal structures and stone buildings and monuments.

Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two Chand

Salts can be of three types (i) eutral salts (ii) Acidic salts, and (iii) Basic salts. The two

And

The rain which contains a higher level of acid than normal is called acid rain. Acid rain

And

The rain which contains a higher level of acid than normal is called acid rain. Acid rain is caused by the acidic gases like sulphur dioxide, nitrogen dioxide and carbon dioxide And

is caused by the acidic gases like sulphur dioxide, nitrogen dioxide and carbon dioxide which are released into the air as pollutants during the burning of various types of fuels. And

which are released into the air as pollutants during the burning of various types of fuels. Sulphur dioxide gas dissolves in falling rain drops to form sulphuric acid nitrogen dioxide And

Sulphur dioxide gas dissolves in falling rain drops to form sulphuric acid nitrogen dioxide

Compa

ny 1. Acids have sour taste. Bases have bitter taste. 2. Acids are not soapy to touch. Bases feel

Compa

ny 1. Acids have sour taste. Bases have bitter taste. 2. Acids are not soapy to touch. Bases feel

soapy to touch. 3. Acids turn blue litmus to red. Bases turn red litmus to blue.

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ny

soapy to touch. 3. Acids turn blue litmus to red. Bases turn red litmus to blue.

istilled water is neutral in nature. We can confirm the neutral nature of substances by

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ny

istilled water is neutral in nature. We can confirm the neutral nature of substances by performing the litmus test. For example, let us put one drop of distilled water on blue litmus

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performing the litmus test. For example, let us put one drop of distilled water on blue litmus paper and another drop of distilled water on red litmus paper. We will find that there is

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paper and another drop of distilled water on red litmus paper. We will find that there is no change in the colour of blue litmus paper or red litmus paper. This shows that distilled

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no change in the colour of blue litmus paper or red litmus paper. This shows that distilled water is neither acidic nor basic in nature. So, distilled water is neutral.

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water is neither acidic nor basic in nature. So, distilled water is neutral.

Limite

dhydroxide neutralises the excess acid present in the stomach and cures indigestion.

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dhydroxide neutralises the excess acid present in the stomach and cures indigestion.

The sting of an ant contains an acid called formic acid. So, when an ant stings (or bites) a

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dThe sting of an ant contains an acid called formic acid. So, when an ant stings (or bites) a person, it injects an acidic liquid into the skin of the person which causes burning pain.

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dperson, it injects an acidic liquid into the skin of the person which causes burning pain. ant stings a person, then rubbing a mild base like baking soda solution (or calamine

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dant stings a person, then rubbing a mild base like baking soda solution (or calamine

The drink with the sour taste is an acidic drink. The one with bitter taste is basic drink and Limite

dThe drink with the sour taste is an acidic drink. The one with bitter taste is basic drink and

SCIENCE 7 TEXT BOOK

54

44. A substance which can neutralise an acid to form a salt (and water) is called a base. Bases turn red litmus to blue. Some of the examples of bases are Sodium hydroxide and Ammonium hydroxide.

45. The reaction in which an acid reacts with a base to form salt and water is called neutralisation. Some heat is always evolved (or produced) in a neutralisation reaction. This heat raises the temperature of reaction mixture due to which the reaction mixture becomes hot. In a neutralisation reaction, two new substances, salt and water, are formed. An example of neutralisation reaction is given. Sodium hydroxide is a base and hydrochloric acid is an acid. So, when sodium hydroxide is treated with hydrochloric acid, then a neutralisation reaction takes place to form sodium chloride (salt) and water. Sodium hydroxide ydrochloric acid → Sodium chloride Water


4 . (c) 4 . (d) 4 . (a) 4 . (d) 5 . (c)

51. (c) 52. (d) 53. (b) 54. (a) 55. (b)

5 . (b) 5 . (b) 5 . (c) 5 . (c) . (c)

1. (b) 2. (c) 3. (b) 4. (b) 5. (c)

. (a) . (c) . (b) . (c) . (b)


1. (a) Ammonium sulphate solution. Because it is acidic in nature (b) Sodium carbonate solution. Because it is basic in nature (c) Sodium carbonate solution. Because it is basic in nature (d) Sodium sulphate solution. Because it is neutral in nature.

2. The solution is either basic or neutral. This is because basic and neutral solutions do not change the colour of blue litmus paper ( nly acids turn blue litmus paper to red)

3. Baking soda solution Being basic, it neutralises excess acid in the stomach

4. (a) Turmeric (b) Basic (c) Phenolphthalein

5. Acidic solution will turn blue litmus red This red litmus will turn blue in basic solution istilled water will have no effect on any type of litmus paper.

(C) S

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nd Baking soda solution Being basic, it neutralises ex

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Baking soda solution Being basic, it neutralises ex

(a) Turmeric (b) Basic (c) Phenolphthalein

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(a) Turmeric (b) Basic (c) Phenolphthalein

Acidic solution will

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Acidic solution will turn blue litmus red This red litmus will turn blue in basic solution

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turn blue litmus red This red litmus will turn blue in basic solution

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istilled water will have no effect on any type of litmus paper.

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istilled water will have no effect on any type of litmus paper.

And solution. Because it is basic in nature (c) Sodium carbonate solution. Because it is basic in

And solution. Because it is basic in nature (c) Sodium carbonate solution. Because it is basic in

nature (d) Sodium sulphate solution. Because it is neutral in nature.

And nature (d) Sodium sulphate solution. Because it is neutral in nature.

either basic or neutral. This is because basic and neutral solutions do not

And

either basic or neutral. This is because basic and neutral solutions do not change the colour of blue litmus paper ( nly acids turn blue litmus paper to red) And

change the colour of blue litmus paper ( nly acids turn blue litmus paper to red) And

Baking soda solution Being basic, it neutralises exAnd

Baking soda solution Being basic, it neutralises ex

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5 .

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5 . (c)

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4.

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.

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. (c)

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(c)


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(a) Ammonium sulphate solution. Because it is acidic in nature (b) Sodium carbonate Compa

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(a) Ammonium sulphate solution. Because it is acidic in nature (b) Sodium carbonate solution. Because it is basic in nature (c) Sodium carbonate solution. Because it is basic in Com

pany

solution. Because it is basic in nature (c) Sodium carbonate solution. Because it is basic in nature (d) Sodium sulphate solution. Because it is neutral in nature. Com

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nature (d) Sodium sulphate solution. Because it is neutral in nature.

Limite

dneutralisation reaction is given. Sodium hydroxide is a base and hydrochloric acid is an acid.

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dneutralisation reaction is given. Sodium hydroxide is a base and hydrochloric acid is an acid. So, when sodium hydroxide is treated with hydrochloric acid, then a neutralisation reaction

Limite

dSo, when sodium hydroxide is treated with hydrochloric acid, then a neutralisation reaction takes place to form sodium chloride (salt) and water. Sodium hydroxide ydrochloric acid

Limite

dtakes place to form sodium chloride (salt) and water. Sodium hydroxide ydrochloric acid

SCIENCE 7 TEXT BOOK

55

WORKSHEET



(a) A natural indicator.

(b) A substance formed by the reaction of acid and base.

(c) The salt produced when hydrochloric acid reacts with sodium hydroxide.

(d) aturally occurring acids.


(a) Bases turn the yellow turmeric paper to . ......color.

(b) Phenolphthalein indicator is colorless in . ...... solution.

(c) . ...... acid is present in tamarind, unripe grapes and unripe mangoes.

(d) The rain which contains a higher level of acid than normal is called. ...... .


(a) Formic acid is a weak acid. (b) actic acid is present in sour milk.

(c) Acids turn red litmus to blue. (d) itric acid is a mineral acid.

4. entionthenameoftheacid asefoundinthefollowing:

(a) Spinach (b) emons (c) Washing soda (d) ime water



(a) Why do some fruits taste sour

(b) efine indicators. Give examples of natural and synthetic indicators.

(c) What is indigestion and how is it cured

(d) ow can too basic and too acidic soil be treated

(C) S

Cha

nd tors. Give examples of natural and synthetic indicators.

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tors. Give examples of natural and synthetic indicators.

tion and how is it cured

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oo basic and too acidic soil be treated

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oo basic and too acidic soil be treated

And questions

And questions in

And in short:

And short:

te sour

And

te sour

tors. Give examples of natural and synthetic indicators.And

tors. Give examples of natural and synthetic indicators.

tion and how is it curedAnd


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ny amarind, unripe grapes and unripe mangoes.

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ny amarind, unripe grapes and unripe mangoes.

tains a higher level of acid than normal is called. ...... .

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ny tains a higher level of acid than normal is called. ...... .

actic acid is present in sour milk.

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ny

actic acid is present in sour milk.

itric acid is a mineral acid.

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ny

itric acid is a mineral acid.

in

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ny

in the

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ny

the following:

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following:

(c) Washing soda

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(c) Washing soda

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dtor is colorless in . ...... solution.

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dtor is colorless in . ...... solution.

amarind, unripe grapes and unripe mangoes. Limite

damarind, unripe grapes and unripe mangoes.

tains a higher level of acid than normal is called. ...... . Limite

d

tains a higher level of acid than normal is called. ...... .

SCIENCE 7 TEXT BOOK

56

SAMPLE PAPER

M.M. 5

ame ............................................................... Class ......................... ate ...........................



(a) The base found in window cleaner.

(b) The acid secreted in our stomach.

(c) The organic acid found in oranges.

(d) The substances which are neither acidic nor basic in nature.

(e) A common antacid used to cure indigestion due to acidity.


(a) Calamine solution is applied on skin when bitten by an ant.

(b) There is no need to be careful while working with acids and bases in the laboratory.

(c) eat is produced during neutralisation reaction.

(d) Tap water is basic in nature.

(e) ime water is chemically magnesium hydroxide.

3. G ive one example of:

(a) A mineral acid (b) A synthetic indicator

(c) An organic acid (d) A weak base

(3) A natural indicator


(a) emons contain lactic acid.

(b) Sodium sulphate is a basic salt.

(c) The salts of hydrochloric acid are called carbonates.

(d) Acids feel soapy to touch.

(e) Acids turn china rose indicator to green color.



(a) What are salts ow are they formed

(b) ifferentiate between organic acids and mineral acids.

(c) ow is litmus obtained What is the use of this solution

(C) (e)

(C) (e)

(C) B. Subjective Type Questions(C) B. Subjective Type Questions(C)

5. Answer(C)

5. Answer

S The salts of hydr

S The salts of hydr

Acids feel soapy tS Acids feel soapy t

Acids turn china rose indicaS Acids turn china rose indica

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ator

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ator

wing statements:

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wing statements:

emons cont

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emons contain lactic acid.

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ain lactic acid.

Sodium sulphate is a basic salt.

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Sodium sulphate is a basic salt.

The salts of hydrChand

The salts of hydr

And er is chemically magnesium hydroxide.

And er is chemically magnesium hydroxide. Com

pany

ances which are neither acidic nor basic in nature.

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ny ances which are neither acidic nor basic in nature.

acid used to cure indigestion due to acidity.

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acid used to cure indigestion due to acidity.

Calamine solution is applied on skin when bitten b

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Calamine solution is applied on skin when bitten by an ant.

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y an ant.

areful while working with acids and bases in the laboratory.

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areful while working with acids and bases in the laboratory.

alisation reaction.

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alisation reaction.

er is chemically magnesium hydroxide. Compa

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er is chemically magnesium hydroxide.

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d

SCIENCE 7 TEXT BOOK

57

(d) After carrying out the neutralisation reaction, if we touch the test tube, it is hot. xplain.

(e) State whether distilled water is acidic, basic or neutral in nature. ow will you confirm it?


(a) What is meant by acid rain ow is it formed

(b) ifferentiate among acidic salts, basic salts and neutral salts with the help of examples.

(c) xplain neutralisation reaction with the help of an example.

(d) efine indicator. What are its types Give examples.

(e) Give three examples to show how neutralisation reactions play an important role in our life.


1. hereaction etweenanacidanda asetoformsaltandwateriscalled:

(a) Carbonation (b) ydrogenation (c) eutralization (d) Titration. 2. Whenanantstingsaperson itin ectsaliquidintothes inofthepersonwhichcontains:

(a) Acetic acid (b) Calcium hydroxide (c) Formic acid (d) Potassium hydroxide. . Acertainsolutiondoesnotchangethecolorofan indicator. hissolutionismostli el

to be:

(a) Vinegar solution (b) Baking soda solution

(c) Common salt solution (d) Washing soda solution

4. Which of the following d oes not cause acid rain?

(a) Sulphur dioxide (b) Carbon monoxide (c) Carbon dioxide (d) itrogen dioxide. 5. Whichofthefollowingcontainslacticacid?

(a) Ant’s sting (b) nripe mangoes (c) Sour milk (d) emons

(C) S

Cha

nd following

Chand

following contains

Chand

contains

(b) nripe mangoes

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(b) nripe mangoes

And (b) Baking soda solution

And (b) Baking soda solution

(d) Washing soda solution

And (d) Washing soda solution

Which of the following d oes not c

And

Which of the following d oes not cause acid rain?

And

ause acid rain?

(b) Carbon monoxide (c) Carbon dioxide And

(b) Carbon monoxide (c) Carbon dioxide containsAnd

contains

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(c) eutraliza

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(c) eutralization

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tion the

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the s in

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of the

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ydroxide.

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indicat

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dferentiate among acidic salts, basic salts and neutral salts with the help of examples.

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dferentiate among acidic salts, basic salts and neutral salts with the help of examples.

ee examples to show how neutralisation reactions play an important role in

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dee examples to show how neutralisation reactions play an important role in

called:Limite

d

called:

SCIENCE 7 TEXT BOOK

58

6

Lesson Plan



• The physical and chemical changes.

• The physical and chemical changes in our everyday life.

• About rusting and the methods to prevent it.

• About the process of crystallisation.



VOCABULARY

Physical change, chemical change, rusting, galvanisation, chrome-plating, crystallisation.


Physical changes (Page 79)

Learning Tools

Interactive warm up exercise: Discussing with the students the various examples of changes that we observe around us would be a good start for the topic. Ask students to list the properties in which they find the change occurring.

Chapter opening exercise: Students should be asked to list some of the common changes occurring in nature and to state its cause. Recapitulation of neutralisation reaction may be done and ask what changes were observed in that chemical reaction.


Discuss with them that the change in a substance is always brought about by a cause. There are

Physical and Chemical ChangesPhysical and Chemical Changes



(C) we observe around us would be a good start for the topic. Ask students to list the properties in

(C) we observe around us would be a good start for the topic. Ask students to list the properties in

which they find the change occurring.(C)

which they find the change occurring.


Chapter opening exercise: in nature and to state its cause. Recapitulation of neutralisation reaction may be done and ask what

(C)

in nature and to state its cause. Recapitulation of neutralisation reaction may be done and ask what

S Learning Tools S Learning Tools


Chand

Chand


Chand



Chand


Physical changes (Page 79) Chand

Physical changes (Page 79)

And

And

And

And

Physical change, chemical change, rusting, galvanisation, chrome-plating, crystallisation. And


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The physical and chemical changes in our everyday life.

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The physical and chemical changes in our everyday life.

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d

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d

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d

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d

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d


d


SCIENCE 7 TEXT BOOK

59

two types of changes- Physical changes and Chemical changes. Students should know that those changes in which no new substances are formed are called physical changes. It is a temporary change. Students should be able to cite examples of physical changes list the physical properties in which the change occurs.


What are physical changes? How is breaking of a glass tumbler an example of physical change?

ACTIVITIES FOR PERIODS 3 TO 5

Chemical changes (Page 82)


Discuss with them that those changes in which new substances are formed, are called chemical changes. They are permanent changes. Students should be able to cite examples of chemical changes and list their various characteristics. Explain the reaction between Baking soda and lime water to test the presence of Carbon dioxide gas. Students should realize the importance of chemical changes.

Using resources

• Conduct the activities given on page no. 4 to show the chemical changes associated with the burning of Magnesium ribbon and the subsequent dissolving of Magnesium oxide in water.

• Conduct the activity given on page no. to show the chemical change associated with the reaction of Copper sulphate solution and Iron.



How does the ozone layer act as a protective shield for us in the atmosphere?


Rusting of iron (Page 87)


Explain them that when an iron obj ect is left in damp air/ water for a considerable time, it gets covered with a red-brown flaky substance called rust. The process is called rusting of iron. Students should be able to express the process of rusting with the help of a word equation and show that that it is a chemical change. They should be able to list the conditions which are essential for the rusting of iron. They should realize that how rusting damages iron obj ects and should be familiarized with the ways to prevent rusting like galvanisation and chrome plating. Students should know that due to the presence of salts in sea water, the process of rusting is faster in ships. The topic can be



Explain them that when an iron obj ect is left in damp air/ water for a considerable time, it gets

(C) Explain them that when an iron obj ect is left in damp air/ water for a considerable time, it gets

covered with a red-brown flaky substance called rust. The process is called rusting of iron. Students (C)

covered with a red-brown flaky substance called rust. The process is called rusting of iron. Students (C)

should be able to express the process of rusting with the help of a word equation and show that (C)

should be able to express the process of rusting with the help of a word equation and show that

S Rusting of iron (Page 87)

S Rusting of iron (Page 87)


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Rusting of iron (Page 87) Chand

Rusting of iron (Page 87)

And page

And page no.

And no.

And solution

And solution

for

And

for the

And

the given

And

givenchapter on the Study Gear app. And


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ny Discuss with them that those changes in which new substances are formed, are called chemical

changes. They are permanent changes. Students should be able to cite examples of chemical changes

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ny changes. They are permanent changes. Students should be able to cite examples of chemical changes

and list their various characteristics. Explain the reaction between Baking soda and lime water to test

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ny

and list their various characteristics. Explain the reaction between Baking soda and lime water to test the presence of Carbon dioxide gas. Students should realize the importance of chemical changes.

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the presence of Carbon dioxide gas. Students should realize the importance of chemical changes.

to

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to show

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show the

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the chemical

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chemicalthe burning of Magnesium ribbon and the subsequent dissolving of Magnesium oxide in

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Discuss with them that those changes in which new substances are formed, are called chemical changes. They are permanent changes. Students should be able to cite examples of chemical changes Lim

ited

changes. They are permanent changes. Students should be able to cite examples of chemical changes

SCIENCE 7 TEXT BOOK

60

made interesting by taking students on an educational trip to utub Minar at elhi and showing them the iron pillar which was made 1 years ago and has still not rusted.

Using resources



List some ways to prevent the rusting of iron obj ects.


Crystallisation (Page 89)


Discuss that the process of cooling a hot, concentrated solution of a substance to obtain crystals is called crystallisation. It is an example of physical change.

Using resources

Conduct the activity given on page no. to obtain pure crystals of Copper sulphate from an impure sample.


How do the impurities from a solution get removed during crystallisation?



Using resources





Assessment of understanding of the chapter could be done with the help of the given worksheet for the chapter.(C

) (C

) Assessment of understanding of the chapter could be done with the help of the given worksheet (C) Assessment of understanding of the chapter could be done with the help of the given worksheet

for the chapter.(C)

for the chapter.

S S Discuss the exercises given at the end of the chapter.

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And

And How do the impurities from a solution get removed during crystallisation?

And How do the impurities from a solution get removed during crystallisation?

ACTIVITIES FOR PERIOD 8 And


Revise all the topics covered in the previous lessons.And


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Discuss that the process of cooling a hot, concentrated solution of a substance to obtain crystals

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Discuss that the process of cooling a hot, concentrated solution of a substance to obtain crystals

in

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in pure

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pure cry

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How do the impurities from a solution get removed during crystallisation? Com

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How do the impurities from a solution get removed during crystallisation?

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d

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d

SCIENCE 7 TEXT BOOK

61

TEXT BOOK ANSWERS


1. Z inc

2. When iron is mixed ( or alloyed) with carbon, chromium and nickel, then stainless steel is obtained.

3. Crystallisation

4. (a) vaporation (b) Crystallisation

5. Impure copper sulphate

. Carbon dioxide

7. ( a) False ( b) False ( c) True ( d) False ( e) True

. Physical changes: d, e, f

Chemical changes: a, b, c

. Physical changes: i, iii, v, vii, viii

Chemical changes: ii, iv, vi, ix, x

1 . ( a) chemical ( b) physical ; chemical ( c) chemical ( d) sodium hydrogen carbonate ( e) calcium carbonate (f) painting galvanisation (g) galvanisation (h) salt (i) crystallisation


11. They are painted regularly to protect them from rusting.

12. The iron pipes used in our homes to carry water are also galvanised/ coated with zinc to prevent rusting.

13. The tools and machine parts made of iron and steel are smeared with grease or oil to prevent their rusting.

14. When a coat of paint is applied to the surface of an iron obj ect, then air and moisture cannot come in contact with the iron object and hence no rusting takes place.

15. The rusting of iron is faster in coastal areas (sea-side areas) because the air at those places contains more water vapour ( or more moisture) .

1 . The process of depositing a thin layer (or coating) of zinc metal on iron objects is called galvanisation. Galvanisation is done by dipping an iron object in molten zinc metal. A thin layer of zinc metal formed on the surface of an iron object which protects it from rusting (because zinc metal remains unaffected by air and moisture).

17. Rusting of iron can be prevented by painting or applying grease or oil.

1 . When iron is mixed ( or alloyed) with carbon, chromium and nickel, then stainless steel is obtained. Stainless steel is an alloy of iron. Stainless steel does not rust at all.

1 . 1. No new substance is formed in a physical change. 1. New substance is formed in a chemical change. 2. A physical change is a temporary change. A chemical change is a permanent change. 3. A physical change is easily reversible. A chemical change is usually irreversible.

(C) (because

(C) (because

17.

(C) 17. Rusting

(C) Rusting

1 .(C)

1 . When iron is mixed ( or alloyed) with carbon, chromium and nickel, then stainless steel is (C)

When iron is mixed ( or alloyed) with carbon, chromium and nickel, then stainless steel is obtained. Stainless steel is an alloy of iron. Stainless steel does not rust at all. (C)

obtained. Stainless steel is an alloy of iron. Stainless steel does not rust at all.

S galvanisation.

S galvanisation.layer S layer ofS of zincS zinc(becauseS (because

Chand

When a coat of paint is applied to the surface of an iron obj ect, then air and moisture

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When a coat of paint is applied to the surface of an iron obj ect, then air and moisture contact

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contact with

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with

iron

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iron is

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is fast

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fast

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contains more water vapour ( or more moisture) .

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contains more water vapour ( or more moisture) .

processChand

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galvanisation.Chand

galvanisation. GalvanisationChand

Galvanisation

And The iron pipes used in our homes to carry water are also galvanised/ coated with zinc to

And The iron pipes used in our homes to carry water are also galvanised/ coated with zinc to

The tools and machine parts made of iron and steel are smeared with grease or oil to And

The tools and machine parts made of iron and steel are smeared with grease or oil to

When a coat of paint is applied to the surface of an iron obj ect, then air and moisture And

When a coat of paint is applied to the surface of an iron obj ect, then air and moisture

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SCIENCE 7 TEXT BOOK

62

2 . Iron + Oxygen + Water → Iron oxide

( Fe) ( O2) ( H2O) ( Fe2O3)

21. The explosion of a firework (like a cracker) is a chemical change because many new substances are formed in this process. The explosion of a firework also produces heat, light, sound and unpleasant gases.

22. o new substance is formed during the melting of ice, only a change of state (from solid to liquid) takes place during the melting of ice. So, the melting of ice (to form water) is a physical change.

23. The process of cooling a hot, concentrated solution of a substance to obtain crystals is called crystallisation. The process of crystallisation is used to obtain large crystals of a pure solid substance from the impure solid substance.

24. Take about 1 m of water in a beaker and add a few drops of dilute sulphuric acid to it. eat the water over a burner till it boils. Add copper sulphate powder slowly to the hot

water with constant stirring. Continue to add copper sulphate till no more copper sulphate can be dissolved. This will give us a saturated solution of copper sulphate. Filter the hot saturated solution of copper sulphate to remove insoluble impurities. Allow the hot and concentrated solution of copper sulphate to cool slowly. o not disturb the solution when it is cooling. After some time, we will see large copper sulphate crystals at the bottom of the beaker. Separate the copper sulphate crystals from solution by filtration and dry them. The soluble impurities present in copper sulphate do not crystallise and hence remain behind in the solution.

25. (a) Burning of magnesium ribbon in air to form magnesium oxide (b) Melting of ice to form water


2 . Those changes, in which no new substances are formed, are called physical changes. The changes in state, size, shape and colour of a substance are physical changes. Examples of physical changes are Melting of ice (to form water) Freezing of water (to form ice). Those changes, in which new substances are formed, are called chemical changes. A lot of energy ( in the form of heat, light, sound, etc.) is either absorbed or given out in chemical changes.

xamples of chemical changes are Souring of milk Formation of curd from milk.

27. When an iron object is left in damp air (or water) for a considerable time, it gets covered with a red brown flaky substance called rust. This is called rusting of iron. Two conditions are necessary for the rusting of iron to take place (i) presence of oxygen (of air), and (ii) presence of water or water vapour (called moisture). Rust is soft and porous, and it gradually falls off from the surface of a rusted iron object, and then the iron below starts rusting. Thus, rusting of iron is a continuous process which slowly eats up the iron objects and makes them useless.

2 . The reaction between copper sulphate (CuS 4) solution and iron (Fe) is a chemical change because it produces two new substances: iron sulphate ( FeSO4) solution and copper (Cu). Copper sulphate solution Iron → Iron sulphate solution Copper. It is a chemical change.

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SCIENCE 7 TEXT BOOK

63

2 . When baking soda and vinegar are mixed together, then bubbles of carbon dioxide gas are formed ( along with some other substances) . The reaction between baking soda and vinegar is a chemical change because it forms carbon dioxide as one of the new substances. Sodium hydrogen carbonate Acetic acid → Sodium acetate + Carbon dioxide + Water

3 . When carbon dioxide gas is passed through lime water, then calcium hydroxide combines with carbon dioxide to form a white solid substance ‘ calcium carbonate’ ( which makes lime water appear milky) . It is a chemical change.

Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water

31. It is a chemical change. Carbon dioxide gas is produced in the reaction which is a new substance formed.

32. The melting of wax is a physical change but the burning of wax is a chemical change. So, when a candle burns, then both physical and chemical changes take place. This is because when a candle burns, then some of the wax melts ( physical change) and some of the wax burns ( chemical change) .

33. Cu ng of wood is a physical change as no new product is formed. Burning of wood produces new products like carbon dioxide and thus, it is a chemical change.

34. When a magnesium ribbon is heated, it burns in air with a brilliant white light to form a powdery ash called magnesium oxide. This magnesium oxide is an entirely new substance. The burning of magnesium ribbon is a chemical change.

Magnesium + Oxygen → Magnesium oxide

35. When we dissolve magnesium oxide in water, then magnesium oxide combines with water to form a new substance called magnesium hydroxide. It is a chemical change.

Magnesium oxide + Water → Magnesium hydroxide


3 . (c) 3 . (c) 3 . (a) 3 . (a) 4 . (b)

41. (b) 42. (c) 43. (d) 44. (d) 45. (d)

4 . (c) 4 . (c) 4 . (b) 4 . (c) 5 . (d)


51. ( a) ( i) Magnesium oxide ( ii) Magnesium hydroxide ( b) Y turns red litmus paper blue ( c) Y is basic in nature ( d) Milk of magnesia

52. (a) Iron (b) Rusting (c) (i) xygen (of air) (ii) Water (or Water vapour) (d) inc

53. ( a) ( i) Hydrogen ( ii) Oxygen ( iii) Steam ( b) ( i) Chemical change ( ii) Physical change

54. (a) (i) Baking soda (ii) Vinegar (b) Acetic acid (c) Chemical change (d) Carbon dioxide

55. (a) Iron (b) Copper sulphate solution (c) Iron sulphate solution (d) Copper(C) 52. (a)

(C) 52. (a)

53.

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SCIENCE 7 TEXT BOOK

64

WORKSHEET

A. Objective Type Questions 1. Name the following:

( a) The metal used to galvanise iron so as to prevent its rusting.

( b) A salt purified by the process of crystallisation.

( c) A gas which turns lime water milky.

( d) A change in which no new substance is formed.


( a) Iron metal is extracted from its ore by .… … … ....… … ...... change.

( b) The .… … … ....… … ...... layer protects us from the harmful ultraviolet rays coming from the sun.

( c) Iron sulphate is .… … … ....… … ...... in color.

( d) Magnesium hydroxide is .… … … ....… … ...... in nature.


( a) The burning of Magnesium ribbon is a chemical change.

( b) A chemical change is a temporary change.

( c) Melting of ice is a physical change.

( d) Rust is a yellowish green substance.

4. entionwhichofthefollowingareph sicalorchemicalchanges:

( a) Burning of biogas ( b) Dissolving salt in water

( c) Condensation of steam ( d) Rusting of iron rod



( a) Differentiate between physical changes and chemical changes.

( b) List the conditions essential for rusting to take place.

( c) Write a word equation to describe the reaction between iron and copper sulphate solution.

( d) Define crystallisation. Give an example.

(C)

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SCIENCE 7 TEXT BOOK

65

SAMPLE PAPER

M.M. 5

Name: ............................................................... Class: ......................... Date: ...........................



( a) The changes in which new products are formed.

( b) The gas which protects us from the harmful ultraviolet radiations of the Sun.

( c) The reddish brown flaky substance which is formed when iron obj ects come in contact with damp air.

( d) The process of depositing a thin layer of zinc metal on iron obj ects.

( e) The process of cooling a hot concentrated solution of a substance to obtain its crystals.


( a) Rusting can be prevented by painting.

( b) Only oxygen is required for rusting of iron to take place.

( c) Copper sulphate solution is green in color.

( d) Lime water turns milky when it reacts with carbon dioxide gas.

( e) Baking soda is chemically sodium hydrogen carbonate.

. entionwhichofthefollowingareph sicalandchemicalchanges:

( a) Digestion of food ( b) Cutting pieces of wood

( c) Freezing of water ( d) Photosynthesis

( e) Formation of compost from dead and decaying leaves


( a) Burning of LPG is a physical change.

( b) Condensation of steam is a chemical change.

( c) Magnesium oxide is called limewater.

( d) Limewater turns milky due to the formation of calcium hydroxide.

( e) When iron is coated with a layer of zinc, the process is called chrome-plating.



( a) Write four physical properties of a substance in which changes occur.

( b) Why rusting of iron is faster in case of ships?

( c) When a candle burns, both physical and chemical changes are observed. Identify these changes.

(C) ( d)

(C) ( d)

( e)

(C) ( e) When iron is coa

(C) When iron is coa

(C)

B. Subjective Type Questions(C)


5. Answer(C

) 5. Answer

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ater

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ater

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wing statements:

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wing statements:

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Burning of LPG is a physic

Condensation of stChand

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Magnesium oxide is called lime

And er turns milky when it reacts with carbon dioxide gas.

And er turns milky when it reacts with carbon dioxide gas.

Baking soda is chemically sodium hy

And Baking soda is chemically sodium hydrogen carbonate.

And drogen carbonate.

following

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are ph sical

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ph sical

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en is required for rusting of iron to take place.

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en is required for rusting of iron to take place.

een in color. Compa

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een in color.

er turns milky when it reacts with carbon dioxide gas. Compa

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drogen carbonate. Com

pany

drogen carbonate.

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dects us from the harmful ultraviolet radiations of the Sun.

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dects us from the harmful ultraviolet radiations of the Sun.

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dddish brown flaky substance which is formed when iron obj ects come in contact

SCIENCE 7 TEXT BOOK

66

( d) Write the components of stainless steel.

( e) Why is curdling of milk considered a chemical change?


( a) List all the characteristics associated with chemical changes.

( b) What happens when baking soda is treated with vinegar? Give equations.

( c) Differentiate between physical and chemical changes.

( d) What happens when magnesium oxide is dissolved in water? Give equation.

( e) How are the pure crystals of copper sulphate prepared from its impure sample?


1. Burning of Magnesium ribbon is:

( a) Chemical change ( b) Physical change ( c) Periodic change ( d) None of the above 2. hecolorofcoppersulphatesolutionis:

( a) White ( b) Green ( c) Y ellow ( d) Blue . nadditiontonewproducts achemicalchangeisaccompanied :

( a) Heat ( b) Light ( c) Sound ( d) All of the above 4. hesaltwaterma estheprocessofrusting:

( a) Faster ( b) Slower ( c) Has no effect ( d) Depends on the presence of humidity 5. Somesu stancescan eo tainedinpurestatefromtheirsolutions theprocessof:

( a) Sedimentation ( b) Crystallisation ( c) Filtration ( d) Decantation

(C) S

Cha

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in

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( c) Y ellow accompanied

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rusting:

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ded in water? Give equation.

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ded in water? Give equation.

e crystals of copper sulphate prepared from its impure sample?

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de crystals of copper sulphate prepared from its impure sample?

SCIENCE 7 TEXT BOOK

67

7

Lesson Plan



• The difference between weather and climate.

• Factors which affect climate.

• Adaptations in animals living in different climates.

• About migration and its reasons.



VOCABULARY

Weather, climate, humidity, rain gauge, weather forecasting, meteorology, climate, adaptation, migration.


Weather (Page 94)

Learning Tools

Interactive warm up exercise: Discussing with the students the clothes that we wear when the weather is hot, cold, rainy and humid would be good start for the topic. Ask students what kind of fun activities they do in different weathers.

Chapter opening exercise: Students should be asked to collect weather forecasts of at least five days from the newspaper. Ask them to read it in the class.


Discuss with the students that the weather and climate are two different things. Humidity is the

Weather, Climate and Adaptations of Animals to Climate

Weather, Climate and Adaptations of Animals to Climate

(C) Learning Tools

(C) Learning Tools



(C)

weather is hot, cold, rainy and humid would be good start for the topic. Ask students what kind of (C)

weather is hot, cold, rainy and humid would be good start for the topic. Ask students what kind of fun activities they do in different weathers. (C

) fun activities they do in different weathers.

Chapter opening exercise: (C

) Chapter opening exercise:

S Weather (Page 94)

S Weather (Page 94)

Learning Tools S Learning Tools

Chand

Chand

Weather, climate, humidity, rain gauge, weather forecasting, meteorology, climate, adaptation,

Chand



Chand


Weather (Page 94) Chand

Weather (Page 94)

And

And

And

And

Weather, climate, humidity, rain gauge, weather forecasting, meteorology, climate, adaptation, And


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d

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d

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d


d


SCIENCE 7 TEXT BOOK

68

measure of water vapour in air. Students should know that it is expressed in percentage. They should also know that rain gauge is an instrument to measure the rainfall at a place in millimeters. Students should be able to define weather as the day to day condition of the atmosphere at a place and is produced by the heat of the sun and thus weather is never constant. Students should be able to define weather forecasting and meteorology. Students should know that the maximum temperature of the day is generally during the afternoon while the minimum temperature occurs during early morning.

Using resources



Collect the weather reports of your city for one week and paste it in copy.


Climate (Page 98)


Discuss with the students that the average weather pattern at a place taken over a long period of time is called climate of that place. Students should be able to know the four maj or types of climate and their description. Students should be aware that climate depends on our position on the earth and our distance from the sun. The tropical regions and the polar regions are the two regions on earth which have extreme climatic conditions, receiving maximum and minimum heat of the sun, respectively. Students should be able to list the factors which affect climate.

Using resources



Compare the climate of any two places of India.


Climate and adaptations (Page 100)


Explain them that the presence of specific body features which enable a plant or an animal to live in a particular habitat is called adaptation. Discuss the adaptations of some animals to two types of habitats- Polar regions and Tropical rainforests.

(C)

(C) Climate and adaptations (Page 100) (C) Climate and adaptations (Page 100)



S S Compare the climate of any two places of India.

S Compare the climate of any two places of India. Chand


Chand


Chand



Chand


Compare the climate of any two places of India. Chand

Compare the climate of any two places of India.

And and their description. Students should be aware that climate depends on our position on the earth

And and their description. Students should be aware that climate depends on our position on the earth

and our distance from the sun. The tropical regions and the polar regions are the two regions on

And and our distance from the sun. The tropical regions and the polar regions are the two regions on

earth which have extreme climatic conditions, receiving maximum and minimum heat of the sun,

And

earth which have extreme climatic conditions, receiving maximum and minimum heat of the sun, respectively. Students should be able to list the factors which affect climate. And

respectively. Students should be able to list the factors which affect climate.

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ny

Compa

ny

Discuss with the students that the average weather pattern at a place taken over a long period of

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Discuss with the students that the average weather pattern at a place taken over a long period of time is called climate of that place. Students should be able to know the four maj or types of climate Com

pany

time is called climate of that place. Students should be able to know the four maj or types of climate and their description. Students should be aware that climate depends on our position on the earth Com

pany

and their description. Students should be aware that climate depends on our position on the earth and our distance from the sun. The tropical regions and the polar regions are the two regions on Com

pany

and our distance from the sun. The tropical regions and the polar regions are the two regions on

Limite


Limite


Collect the weather reports of your city for one week and paste it in copy. Limite

dCollect the weather reports of your city for one week and paste it in copy.

SCIENCE 7 TEXT BOOK

69


Collect pictures of animals living in Polar regions and Tropical rainforests and paste it in your copy.


The Polar Regions (Page 101)


Discuss with the students that the polar regions of the earth have an extremely cold climate. Students should be familiarized with the two animals living in polar regions- polar bears and penguins. Students should be able to list the various adaptations in polar bears and penguins.


Write two adaptations in Polar bear and Penguins.


Migration (Page 102)


Explain them that the process in which a bird moves from one place to another in one season and returns again in a different season is called migration. Students should realize that migration is to escape the harsh and cold conditions of their normal habitat in winter so as to survive. Students should be able to name the most common migratory bird Siberian crane which comes to India every year. Students should be able to answer how migratory birds travel to the same place year after year.


What is migration? Collect picture of Siberian crane and paste it in your copy.


The Tropical Rainforests (Page 103)


Explain them that the area of earth near both sides of the equator is called tropical region. It has hot and humid climate. Students should know the places in India where tropical rainforests are found. Students should be able to name the maj or types of animals found here like- lion, tiger, elephants, red eyed frog, toucan, monkey and lion tailed macaque and list their adaptations.


List the adaptations in red eyed frog to survive in its habitat.



(C) Explain them that the area of earth near both sides of the equator is called tropical region. It has hot

(C) Explain them that the area of earth near both sides of the equator is called tropical region. It has hot

and humid climate. Students should know the places in India where tropical rainforests are found. (C)

and humid climate. Students should know the places in India where tropical rainforests are found. Students should be able to name the maj or types of animals found here like- lion, tiger, elephants, (C

) Students should be able to name the maj or types of animals found here like- lion, tiger, elephants, red eyed frog, toucan, monkey and lion tailed macaque and list their adaptations.

(C)

red eyed frog, toucan, monkey and lion tailed macaque and list their adaptations.

S The Tropical Rainforests (Page 103)

S The Tropical Rainforests (Page 103)


Chand

Chand


Chand



Chand



Chand


The Tropical Rainforests (Page 103) Chand

The Tropical Rainforests (Page 103)

And returns again in a different season is called migration. Students should realize that migration is to

And returns again in a different season is called migration. Students should realize that migration is to

escape the harsh and cold conditions of their normal habitat in winter so as to survive. Students

And escape the harsh and cold conditions of their normal habitat in winter so as to survive. Students

should be able to name the most common migratory bird Siberian crane which comes to India every

And

should be able to name the most common migratory bird Siberian crane which comes to India every year. Students should be able to answer how migratory birds travel to the same place year after year. And

year. Students should be able to answer how migratory birds travel to the same place year after year.

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Explain them that the process in which a bird moves from one place to another in one season and Compa

ny

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pany

escape the harsh and cold conditions of their normal habitat in winter so as to survive. Students

Limite

dDiscuss with the students that the polar regions of the earth have an extremely cold climate. Students

Limite

dDiscuss with the students that the polar regions of the earth have an extremely cold climate. Students should be familiarized with the two animals living in polar regions- polar bears and penguins.

Limite

dshould be familiarized with the two animals living in polar regions- polar bears and penguins. Students should be able to list the various adaptations in polar bears and penguins.

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dStudents should be able to list the various adaptations in polar bears and penguins.

SCIENCE 7 TEXT BOOK

70



Using resources






TEXT BOOK ANSWERS


1. Sun

2. During the summer days, we wear light coloured clothes because the weather is hot. In winter, we prefer to wear dark coloured clothes because the weather is cold.

3. Humidity

4. Rain gauge

5. ‘ millimetres’ ( mm)

6. Weather

7. (a) Kerela ( b) Raj asthan ( c) J ammu and Kashmir ( d) North-East India

8. Assam

9. Raj asthan

10. Polar bear; Penguin

11. Musk oxen and Reindeers

12. Penguin

13. Bharatpur in Raj asthan, Sultanpur in Haryana

14. The major types of animals living in the tropical rainforests are lions, tigers, leopards, elephants and monkeys.

15. ions and tigers

16. Toucan

17. The most outstanding feature of lion-tailed macaque is its silver-white ‘ mane’ which surrounds its head from the cheeks down to its chin.

18. ( a) False ( b) False

19. Hot and wet

(C) The major types of animals living in the tropical rainforests are lions, tigers, leopards,

(C) The major types of animals living in the tropical rainforests are lions, tigers, leopards,

elephants and monkeys.

(C) elephants and monkeys.

15.(C)

15. ions and tigers (C)

ions and tigers

16.(C)

16. Toucan (C)

Toucan

S Bharatpur in Raj asthan, Sultanpur in Haryana S Bharatpur in Raj asthan, Sultanpur in Haryana

The major types of animals living in the tropical rainforests are lions, tigers, leopards, S The major types of animals living in the tropical rainforests are lions, tigers, leopards,

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a) Kerela ( b) Raj asthan ( c) J ammu and Kashmir ( d) North-East India

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Polar bear; Penguin

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Polar bear; Penguin

Musk oxen and Reindeers

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Musk oxen and Reindeers

Penguin Chand

Penguin

Bharatpur in Raj asthan, Sultanpur in Haryana Chand

Bharatpur in Raj asthan, Sultanpur in Haryana

And

a) Kerela ( b) Raj asthan ( c) J ammu and Kashmir ( d) North-East India And


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During the summer days, we wear light coloured clothes because the weather is hot. In

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During the summer days, we wear light coloured clothes because the weather is hot. In winter, we prefer to wear dark coloured clothes because the weather is cold.

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winter, we prefer to wear dark coloured clothes because the weather is cold.

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d

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SCIENCE 7 TEXT BOOK

71

20. ( a) climate ( b) weather ( c) hot ; dry ( d) polar regions ; tropical regions ( e) shorter ( f) Western; Assam


21. (i) The maximum temperature of the day generally occurs in the afternoon, and (ii) The minimum temperature of the day generally occurs in the early morning.

22. uring summers, we feel miserable in the afternoon because the maximum temperature of the day is reached in the afternoon (making the surroundings very hot and unbearable).

n the other hand, we feel comparatively cool and comfortable in the early morning during summers because the minimum temperature of the day is reached in the early morning ( making the surroundings somewhat cooler) .

23. The daily weather report carries information about the temperatures, humidity and rainfall during the past 24 hours. It also gives the timings of sunrise, sunset, moonrise and moonset. The weather report also predicts the weather for the day.

24. Rainfall is measured by an instrument called ‘ rain gauge’. Rain gauge is basically a measuring cylinder with a funnel at the top to collect rainwater. Rain gauge measures the rainfall at a place in the unit of ‘ millimetres’ ( mm) .

25. The animals living in the polar regions have adapted to the extremely cold climate by having some special features such as white colour, thick layer of fur, thick skin, a layer of fat under the skin, strong sense of smell, and big feet (big paws) for walking on soft snow and swimming, etc.

26. Due to white colour, polar bear is not visible easily in the snowy white background and hence its prey is unable to see it. This adaptation (of white colour) helps the polar bear to catch its prey. The white colour of polar bear also protects it from its predators ( who kill and eat it) because it mixes well with the snowy white surroundings due to which the predators cannot see it easily.

27. Polar bear has two thick layers of fur on its body. It has a thick layer of fat under its skin.

28. Fur protects the polar bear from extreme cold by preventing the loss of heat from its body. Thus, the two thick layers of fur keep the polar bear warm in extremely cold climate ( by keeping its body heat in) . The polar bear also has fur on its feet and toes. This protects it from cold when it walks on snow and ice. The layer of fat insulates the body of polar bear against heat loss and keeps it warm in cold climate. Thus, the thick layer of fat also protects the polar bear from extreme cold.

29. The very strong sense of smell helps the polar bear in locating and catching its prey for food.

30. Polar bear has big feet ( or big paws) to spread the weight of its body on snow which prevent it from sinking into snow and make it walk on snow easily.

31. The big feet ( or big paws) help the polar bear to swim well. Being a fast swimmer helps the polar bear to catch its prey ( like seal) in water very easily. While swimming under water, polar bear can close its nostrils and remain under water for long durations.

(C) The very strong sense of smell helps the polar bear in locating and catching its prey for

(C) The very strong sense of smell helps the polar bear in locating and catching its prey for

food.

(C) food.

30.(C)

30. Polar bear has big feet ( or big paws) to spread the weight of its body on snow which prevent (C)

Polar bear has big feet ( or big paws) to spread the weight of its body on snow which prevent it from sinking into snow and make it walk on snow easily. (C)

it from sinking into snow and make it walk on snow easily.

S against heat loss and keeps it warm in cold climate. Thus, the thick layer of fat also protects

S against heat loss and keeps it warm in cold climate. Thus, the thick layer of fat also protects the polar bear from extreme cold. S the polar bear from extreme cold.

The very strong sense of smell helps the polar bear in locating and catching its prey for S The very strong sense of smell helps the polar bear in locating and catching its prey for

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see it easily.

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see it easily.

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Polar bear has two thick layers of fur on its body. It has a thick layer of fat under its skin.

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Fur protects the polar bear from extreme cold by preventing the loss of heat from its body.

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Fur protects the polar bear from extreme cold by preventing the loss of heat from its body. Thus, the two thick layers of fur keep the polar bear warm in extremely cold climate ( by

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Thus, the two thick layers of fur keep the polar bear warm in extremely cold climate ( by keeping its body heat in) . The polar bear also has fur on its feet and toes. This protects it

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keeping its body heat in) . The polar bear also has fur on its feet and toes. This protects it from cold when it walks on snow and ice. The layer of fat insulates the body of polar bear Cha

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from cold when it walks on snow and ice. The layer of fat insulates the body of polar bear against heat loss and keeps it warm in cold climate. Thus, the thick layer of fat also protects Cha

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against heat loss and keeps it warm in cold climate. Thus, the thick layer of fat also protects

And Due to white colour, polar bear is not visible

And Due to white colour, polar bear is not visible

unable to see it. This adaptation (of white colour) helps the polar bear

And unable to see it. This adaptation (of white colour) helps the polar bear

to catch its prey. The white colour of polar bear also protects it from its

And

to catch its prey. The white colour of polar bear also protects it from itskill and eat it) because it mixes well with theAnd

kill and eat it) because it mixes well with the

see it easily. And

see it easily.

Polar bear has two thick layers of fur on its body. It has a thick layer of fat under its skin. And


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ny Rainfall is measured by an instrument called ‘ rain gauge’. Rain gauge is basically a measuring

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ny Rainfall is measured by an instrument called ‘ rain gauge’. Rain gauge is basically a measuring

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cylinder with a funnel at the top to collect rainwater. Rain gauge measures the rainfall at

The animals living in the polar regions have adapted to the extremely cold climate by

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The animals living in the polar regions have adapted to the extremely cold climate by having some special features such as white colour, thick layer of fur, thick skin, a layer of

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having some special features such as white colour, thick layer of fur, thick skin, a layer of fat under the skin, strong sense of smell, and big feet (big paws) for walking on soft snow

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fat under the skin, strong sense of smell, and big feet (big paws) for walking on soft snow

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dof the day is reached in the afternoon (making the surroundings very hot and unbearable).

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dof the day is reached in the afternoon (making the surroundings very hot and unbearable). n the other hand, we feel comparatively cool and comfortable in the early morning during

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dn the other hand, we feel comparatively cool and comfortable in the early morning during summers because the minimum temperature of the day is reached in the early morning

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dsummers because the minimum temperature of the day is reached in the early morning

The daily weather report carries information about the temperatures, humidity and rainfall

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during the past 24 hours. It also gives the timings of sunrise, sunset, moonrise and moonset.

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32. The trunk helps the elephant in many ways. The elephant uses the trunk to smell. Because of the trunk, elephant has a strong sense of smell. It is also used for breathing. The elephant uses its long trunk to pick up food ( like grass and plants, etc.) and put into its mouth. Elephant uses the tusks to tear off the bark of trees which it eats as food. When the temperature rises, the elephants flap their large ears and use them as fans to cool themselves. So, the large ears also help the elephant to keep cool in the hot and humid climate of the tropical rainforest.

33. Tusks are the big and long pointed teeth which come out from the closed mouth of the elephant. Tusks are the modified teeth of elephant. Tusks are actually the incisor teeth of elephant. lephant uses the tusks to tear off the bark of trees which it eats as food.

34. The large ears of elephant help it to hear even very soft sounds. ue to large ears, an elephant can hear even the slightest sound made by its predator behind him that way it can sense the danger and run away to safety. When the temperature rises, the elephants flap their large ears and use them as fans to cool themselves. So, the large ears also help the elephant to keep cool in the hot and humid climate of the tropical rainforest.

35. Red-eyed frog has developed sticky pads on its feet which help it to climb easily on the trees on which it lives. The sticky pads on feet also allow the red-eyed frog to attach itself to the branches and leaves of the trees.

36. The long and large beak helps a toucan to reach the fruits attached to the ends of even thin branches of trees which are too weak to support its weight. Thus, long and large beak is an adaptation in toucan for ge ng the otherwise unreachable fruits at the ends of very thin branches of trees. The large beak also helps in the temporary storage of fruits being collected by toucan.

37. Monkeys are expert climbers, have very good eyesight, have long and strong gripping tails which they use for grasping branches of trees and eat fruits, seeds, leaves, roots and insects as food.

38. The lion-tailed macaque is also called ‘ beard ape’. The lion-tailed macaques live in the rainforests of Western Ghats in India.

39. The lion-tailed macaque is a good climber and spends most of its time high up in trees. The lion-tailed macaque has very good eyesight which helps it in leaping between the branches. The lion-tailed macaque feeds mainly on fruits on the trees.

40. 1. Penguin is black and white in colour but still it merges well with the white background of ice and snow. 2. Penguin has thick skin and a layer of fat below its skin which protect it from extreme cold. 3. Penguins live together in large numbers. Penguins huddle together to keep themselves warm. 4. Penguin has streamlined body, flipper-like wings and webbed feet which make it a good swimmer. Being a good swimmer helps penguin in catching fish as prey.

41. Penguin has thick skin and a layer of fat below its skin which protect it from extreme cold. Penguins live together in large numbers. They huddle together to keep themselves warm.

42. Penguins live together in large numbers. They huddle together to keep themselves warm.

(C) from extreme cold. 3. Penguins live together in large numbers. Penguins huddle together

(C) from extreme cold. 3. Penguins live together in large numbers. Penguins huddle together

to keep themselves warm. 4. Penguin has streamlined body, flipper-like wings and webbed

(C) to keep themselves warm. 4. Penguin has streamlined body, flipper-like wings and webbed

feet which make it a good swimmer. Being a good swimmer helps penguin in catching fish (C) feet which make it a good swimmer. Being a good swimmer helps penguin in catching fish

as prey. (C)

as prey.

S 1. Penguin is black and white in colour but still it merges well with the white background

S 1. Penguin is black and white in colour but still it merges well with the white background of ice and snow. 2. Penguin has thick skin and a layer of fat below its skin which protect it S of ice and snow. 2. Penguin has thick skin and a layer of fat below its skin which protect it from extreme cold. 3. Penguins live together in large numbers. Penguins huddle together S from extreme cold. 3. Penguins live together in large numbers. Penguins huddle together

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The lion-tailed macaque is also called ‘ beard ape’. The lion-tailed macaques live in the

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The lion-tailed macaque is also called ‘ beard ape’. The lion-tailed macaques live in the rainforests of Western Ghats in India.

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rainforests of Western Ghats in India.

The lion-tailed macaque is a good climber and spends most of its time high up in trees. The

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The lion-tailed macaque is a good climber and spends most of its time high up in trees. The lion-tailed macaque has very good eyesight which helps it in leaping between the branches.

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lion-tailed macaque has very good eyesight which helps it in leaping between the branches. The lion-tailed macaque feeds mainly on fruits on the trees.

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The lion-tailed macaque feeds mainly on fruits on the trees.

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And Monkeys are expert climbers, have very good eyesight, have long and strong gripping tails

And Monkeys are expert climbers, have very good eyesight, have long and strong gripping tails

which they use for grasping branches of trees and eat fruits, seeds, leaves, roots and insects

And

which they use for grasping branches of trees and eat fruits, seeds, leaves, roots and insects

The lion-tailed macaque is also called ‘ beard ape’. The lion-tailed macaques live in the And

The lion-tailed macaque is also called ‘ beard ape’. The lion-tailed macaques live in the

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ny flap their large ears and use them as fans to cool themselves. So, the large ears also help

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the elephant to keep cool in the hot and humid climate of the tropical rainforest.

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ny the elephant to keep cool in the hot and humid climate of the tropical rainforest.

Red-eyed frog has developed sticky pads on its feet which help it to climb easily on the

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Red-eyed frog has developed sticky pads on its feet which help it to climb easily on the trees on which it lives. The sticky pads on feet also allow the red-eyed frog to attach itself

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trees on which it lives. The sticky pads on feet also allow the red-eyed frog to attach itself

The long and large beak helps a toucan to reach the fruits attached to the ends of even

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thin branches of trees which are too weak to support its weight. Thus, long and large beak is an adaptation in toucan for ge ng the otherwise unreachable fruits at the ends of very

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dTusks are the big and long pointed teeth which come out from the closed mouth of the

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dTusks are the big and long pointed teeth which come out from the closed mouth of the elephant. Tusks are the modified teeth of elephant. Tusks are actually the incisor teeth of

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delephant. Tusks are the modified teeth of elephant. Tusks are actually the incisor teeth of elephant. lephant uses the tusks to tear off the bark of trees which it eats as food.

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delephant. lephant uses the tusks to tear off the bark of trees which it eats as food.

The large ears of elephant help it to hear even very soft sounds. ue to large ears, an

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the elephant to keep cool in the hot and humid climate of the tropical rainforest.

SCIENCE 7 TEXT BOOK

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43. Penguin has streamlined body, flipper-like wings and webbed feet which make it a good swimmer. Being a good swimmer helps penguin in catching fish as prey.

44. The process in which a bird ( or other animal) moves from one place to another in one season and returns again in a different season is called migration. Migration of birds (or other animals) is an adaptation to escape the harsh and cold conditions of their normal habitat in winter so as to survive.

45. The birds which migrate from very cold regions to warmer regions in winter and go back after the winter gets over are called migratory birds. ne of the most common migratory bird which comes to India every year for a few months is the Siberian crane.

46. The tropical regions have hot and humid climate. In tropical regions, days and nights are almost equal in length throughout the year. An important feature of the tropical regions of earth is the tropical rainforests.

47. In India, tropical rainforests are found in Western Ghats and Assam.

48. Because of highly favourable climatic conditions in tropical rainforests (such as continuous warmth and rain) , a large variety of plants and animals are found in tropical rainforests.

49. When winter sets in Siberia, and it gets extremely cold, the Siberian crane flies thousands of kilometres and comes to warmer places in India such as Bharatpur in Raj asthan, Sultanpur in Haryana, some wet lands of North– East, and some other parts of India. The Siberian cranes stay in the warmer places in India for a few months. The Siberian cranes fly back to Siberia when the winter ends there and climate becomes favourable. Thus, the adaptation of migration in Siberian crane is to escape the extremely cold winter conditions in Siberia and survive by moving to warmer regions.

50. The big cats (lion and tiger) have a highly developed sense of smell which helps them to locate their prey ( and kill for obtaining food) . The ‘ yellow-brown colour’ of lion and the ‘yellow-brown colour with black stripes’ of tiger helps them to hide in the forest (without being seen easily). This camouflage (or blending with the surroundings) helps the big cats in catching their prey.


51. The day-to-day condition of the atmosphere at a place and time with respect to the temperature, pressure, humidity, wind speed and wind direction, sunshine, clouds, rainfall (or snowfall), etc., is called weather at that place at that time. The major elements of weather at a place are temperature, pressure, humidity, wind speed and wind direction, sunshine, clouds, and rainfall ( or snowfall) .

52. Weather is produced by the heat of the sun and the effect it has on the atmosphere. This happens as follows: The sun is a huge sphere of hot gases at a very high temperature. Though the distance of the sun from the earth is very large, even then it is the source of all heat and light on the earth. The heat energy of the sun absorbed and reflected by the earth’s surface, oceans and atmosphere, plays an important role in determining the weather at any place. For example, the sun’s heat causes water from the oceans and land to evaporate. This water vapour rise high up in the atmosphere, get cooled, condense and form clouds in the atmosphere which produce rain leading to ‘ rainy’ weather. Similarly,

(C) sunshine, clouds, and rainfall ( or snowfall) .

(C) sunshine, clouds, and rainfall ( or snowfall) .

52.

(C) 52. Weather is produced by the heat of the sun and the effect it has on the atmosphere. This

(C) Weather is produced by the heat of the sun and the effect it has on the atmosphere. This

happens as follows: The sun is a huge sphere of hot gases at a very high temperature. (C)

happens as follows: The sun is a huge sphere of hot gases at a very high temperature. Though the distance of the sun from the earth is very large, even then it is the source (C)

Though the distance of the sun from the earth is very large, even then it is the source

S (or snowfall), etc., is called weather at that place at that time. The major elements of

S (or snowfall), etc., is called weather at that place at that time. The major elements of weather at a place are temperature, pressure, humidity, wind speed and wind direction, S weather at a place are temperature, pressure, humidity, wind speed and wind direction, sunshine, clouds, and rainfall ( or snowfall) . S sunshine, clouds, and rainfall ( or snowfall) .

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being seen easily). This camouflage (or blending with the surroundings) helps the big cats

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being seen easily). This camouflage (or blending with the surroundings) helps the big cats in catching their prey.

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in catching their prey.


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weather at a place are temperature, pressure, humidity, wind speed and wind direction,

And and survive by moving to warmer regions.

And and survive by moving to warmer regions.

The big cats (lion and tiger) have a highly developed sense of smell which helps them to

And The big cats (lion and tiger) have a highly developed sense of smell which helps them to

locate their prey ( and kill for obtaining food) . The ‘ yellow-brown colour’ of lion and the

And

locate their prey ( and kill for obtaining food) . The ‘ yellow-brown colour’ of lion and the ‘yellow-brown colour with black stripes’ of tiger helps them to hide in the forest (without And

‘yellow-brown colour with black stripes’ of tiger helps them to hide in the forest (without And

being seen easily). This camouflage (or blending with the surroundings) helps the big cats And

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ny Because of highly favourable climatic conditions in tropical rainforests (such as continuous

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ny warmth and rain) , a large variety of plants and animals are found in tropical rainforests.

When winter sets in Siberia, and it gets extremely cold, the Siberian crane flies

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dafter the winter gets over are called migratory birds. ne of the most common migratory

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dafter the winter gets over are called migratory birds. ne of the most common migratory

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d

Because of highly favourable climatic conditions in tropical rainforests (such as continuous

SCIENCE 7 TEXT BOOK

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heat from the sun heats the earth’s surface. The hot surface of earth heats the air near it. This hot air (being lighter) rises up creating an area of low pressure. Air from high pressure area moves towards the low pressure area. The air moving from high pressure area to low pressure area is called wind. So, it is the sun’s heat which causes wind to blow and gives us ‘windy’ weather. The weather changes so frequently because the condition of the earth’s atmosphere keeps changing frequently due to the various effects produced by the sun’s heat.

53. The average weather pattern at a place taken over a long period of time (say, 25 years) is called the climate of that place. For example, if the temperature at a place is high most of the time, then we say that the climate of that place is hot. And if there is also heavy rainfall on most of the days at that place, then we say that the climate of that place is hot and wet ( or hot and humid) . There are four maj or types of climates in the world: polar climate, temperate climate, tropical climate and desert climate.

54. ( i) Temperature and rainfall are the two most important factors which determine the climate at a place. (ii) Another factor which affects the climate of a place is its altitude whether it is located on high mountains or on plains (flat ground). A place at higher altitude will have a cooler climate than another place on plains (flat ground). This is why hill stations always have a cool climate. (iii) A yet another factor which affects the climate at a place is its location with respect to the sea whether it is located near the sea or far away from the sea. Sea-water heats up slowly and also cools down slowly. This has a moderating effect on the climate of coastal areas. The temperatures in coastal areas are neither very high nor very low. Srinagar is situated at high altitude on a mountain in the orthern part of India whereas Thiruvananthapuram is situated on plains (flat ground) at sea-level in the South-West part of India. Srinagar is located very far away from the sea whereas Thiruvananthapuram is located near the sea. Srinagar is located quite far away from the equator whereas Thiruvananthapuram is comparatively nearer to the equator. So, due to their totally different positions on earth, Srinagar and Thiruvananthapuram have entirely different climates. (i) In Srinagar, the temperatures round the year are neither very low nor very high. Also, the rainfall is neither very low nor very high. Thus, Srinagar has a moderately hot and wet climate. In general we can say that J ammu and Kashmir has a moderately hot and wet climate. It is like a temperate climate. ( ii) In Thiruvananthapuram, the temperatures round the year are quite high. Also, the rainfall is very high. Thus, Thiruvananthapuram has a very hot and wet climate. In general we can say that Kerala state has a very hot and wet climate. Actually, Kerala has a typical tropical climate.

55. The areas situated near the poles of the earth are called Polar Regions. Some of the well known countries that belong to the polar regions of the earth are Canada, Greenland ( Denmark) , Iceland, Norway, Sweden, Finland, Alaska in USA and Siberian region of Russia. The polar regions of the earth have an extremely cold climate. The Polar Regions are covered with ice and snow, and it is extremely cold for most part of the year. For six months, the sun does not set at the poles while for the next six months, the sun does not rise ( above the horizon) . During winter in Polar Regions, the temperature can be as low as, – 37° C ( minus 37° C) .

56. The presence of specific body features (or certain habits) which enable an animal or a plant to live in a particular habitat (or surroundings) is called adaptation. For example,

(C) The areas situated near the poles of the earth are called Polar Regions. Some of the well

(C) The areas situated near the poles of the earth are called Polar Regions. Some of the well

known countries that belong to the polar regions of the earth are Canada, Greenland

(C) known countries that belong to the polar regions of the earth are Canada, Greenland

( Denmark) , Iceland, Norway, Sweden, Finland, Alaska in USA and Siberian region of Russia.(C) ( Denmark) , Iceland, Norway, Sweden, Finland, Alaska in USA and Siberian region of Russia.

The polar regions of the earth have an extremely cold climate.(C)

The polar regions of the earth have an extremely cold climate.with ice and snow, and it is extremely cold for most part of the year. For six months, the sun (C)

with ice and snow, and it is extremely cold for most part of the year. For six months, the sun

S a very hot and wet climate. In general we can say that Kerala state has a very hot and wet

S a very hot and wet climate. In general we can say that Kerala state has a very hot and wet climate. Actually, Kerala has a typical tropical climate. S climate. Actually, Kerala has a typical tropical climate.

The areas situated near the poles of the earth are called Polar Regions. Some of the well S The areas situated near the poles of the earth are called Polar Regions. Some of the well known countries that belong to the polar regions of the earth are Canada, Greenland S known countries that belong to the polar regions of the earth are Canada, Greenland

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their totally different positions on earth, Srinagar and Thiruvananthapuram have entirely

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their totally different positions on earth, Srinagar and Thiruvananthapuram have entirely different climates. (i) In Srinagar, the temperatures round the year are neither very low nor

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different climates. (i) In Srinagar, the temperatures round the year are neither very low nor very high. Also, the rainfall is neither very low nor very high. Thus, Srinagar has a moderately

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very high. Also, the rainfall is neither very low nor very high. Thus, Srinagar has a moderately hot and wet climate. In general we can say that J ammu and Kashmir has a moderately hot

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hot and wet climate. In general we can say that J ammu and Kashmir has a moderately hot and wet climate. It is like a temperate climate. ( ii) In Thiruvananthapuram, the temperatures

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and wet climate. It is like a temperate climate. ( ii) In Thiruvananthapuram, the temperatures round the year are quite high. Also, the rainfall is very high. Thus, Thiruvananthapuram has

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round the year are quite high. Also, the rainfall is very high. Thus, Thiruvananthapuram has

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a very hot and wet climate. In general we can say that Kerala state has a very hot and wet Chand

a very hot and wet climate. In general we can say that Kerala state has a very hot and wet climate. Actually, Kerala has a typical tropical climate. Cha

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climate. Actually, Kerala has a typical tropical climate.

And part of India whereas Thiruvananthapuram is situated on plains (flat ground) at sea-level

And part of India whereas Thiruvananthapuram is situated on plains (flat ground) at sea-level

in the South-West part of India. Srinagar is located very far away from the sea whereas

And in the South-West part of India. Srinagar is located very far away from the sea whereas

And

Thiruvananthapuram is located near the sea. Srinagar is located quite far away from the

And

Thiruvananthapuram is located near the sea. Srinagar is located quite far away from the equator whereas Thiruvananthapuram is comparatively nearer to the equator. So, due to And

equator whereas Thiruvananthapuram is comparatively nearer to the equator. So, due to their totally different positions on earth, Srinagar and Thiruvananthapuram have entirely And

their totally different positions on earth, Srinagar and Thiruvananthapuram have entirely different climates. (i) In Srinagar, the temperatures round the year are neither very low nor And

different climates. (i) In Srinagar, the temperatures round the year are neither very low nor

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ny ( i) Temperature and rainfall are the two most important factors which determine the climate

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ny ( i) Temperature and rainfall are the two most important factors which determine the climate

at a place. (ii) Another factor which affects the climate of a place is its altitude whether

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ny at a place. (ii) Another factor which affects the climate of a place is its altitude whether

it is located on high mountains or on plains (flat ground). A place at higher altitude will

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it is located on high mountains or on plains (flat ground). A place at higher altitude will have a cooler climate than another place on plains (flat ground). This is why hill stations

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have a cooler climate than another place on plains (flat ground). This is why hill stations always have a cool climate. (iii) A yet another factor which affects the climate at a place

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always have a cool climate. (iii) A yet another factor which affects the climate at a place is its location with respect to the sea whether it is located near the sea or far away from

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is its location with respect to the sea whether it is located near the sea or far away from the sea. Sea-water heats up slowly and also cools down slowly. This has a moderating

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the sea. Sea-water heats up slowly and also cools down slowly. This has a moderating effect on the climate of coastal areas. The temperatures in coastal areas are neither very

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effect on the climate of coastal areas. The temperatures in coastal areas are neither very high nor very low. Srinagar is situated at high altitude on a mountain in the orthern Com

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high nor very low. Srinagar is situated at high altitude on a mountain in the orthern part of India whereas Thiruvananthapuram is situated on plains (flat ground) at sea-level Com

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part of India whereas Thiruvananthapuram is situated on plains (flat ground) at sea-level in the South-West part of India. Srinagar is located very far away from the sea whereas Com

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in the South-West part of India. Srinagar is located very far away from the sea whereas

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dThe average weather pattern at a place taken over a long period of time (say, 25 years) is

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dThe average weather pattern at a place taken over a long period of time (say, 25 years) is called the climate of that place. For example, if the temperature at a place is high most of

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dcalled the climate of that place. For example, if the temperature at a place is high most of the time, then we say that the climate of that place is hot. And if there is also heavy rainfall

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dthe time, then we say that the climate of that place is hot. And if there is also heavy rainfall on most of the days at that place, then we say that the climate of that place is hot and

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don most of the days at that place, then we say that the climate of that place is hot and

There are four maj or types of climates in the world: polar climate,

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dThere are four maj or types of climates in the world: polar climate,

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d( i) Temperature and rainfall are the two most important factors which determine the climate at a place. (ii) Another factor which affects the climate of a place is its altitude whether Lim

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at a place. (ii) Another factor which affects the climate of a place is its altitude whether

SCIENCE 7 TEXT BOOK

75

polar bears have two thick layers of fur and a thick layer of fat under their skin. Both these body features of polar bears are the adaptations to make them withstand the extremely cold climate of polar region so that they may survive in their habitat. The polar bear lives in extremely cold climate of polar regions due to the following adaptations 1. Polar bear has white colour which matches with its surroundings. Due to white colour, polar bear is not visible easily in the snowy white background and hence its prey is unable to see it. 2. Polar bear has two thick layers of fur on its body. This fur protects the polar bear from extreme cold by preventing the loss of heat from its body. 3. Polar bear has a thick layer of fat under its skin. This layer of fat insulates the body of polar bear against heat loss and keeps it warm in cold climate. 4. Polar bear has a rounded body and small ears to keep the body surface area to a minimum ( compared to the body weight) . This reduces the heat loss from the body of polar bear. 5. Polar bear has big feet ( or big paws) to spread the weight of its body on snow which prevent it from sinking into snow and make it walk on snow easily. 6. Polar bear is a good swimmer. The big feet ( or big paws) help the polar bear to swim well. 7. Polar bear has a very strong sense of smell. The very strong sense of smell helps the polar bear in locating and catching its prey for food.

57. a. An important feature of the tropical regions of earth is the tropical rainforests. Tropical rainforests are found in India, South-east Asia, Central America and Central Africa. b. Some of the adaptations in animals living in tropical rainforests are A skin colour which helps them to camouflage (mix up with the surroundings and hide) in order to catch prey or protect themselves from predators ; Running very fast ( to catch prey or escape from predators) ;

evelopment of trunk, tusks, and large ears and feet Sharp eyesight, Sensitive hearing and Thick skin ; Living on trees; Development of strong, gripping tails ; Long and large beaks ; Bright colours and Loud voice ; Living on diet of fruits, etc.

58. a. Climate has a great effect on all the living organisms (animals as well as plants). A living organism can survive in a particular habitat only if its body is suited (or adapted) to the climate of that habitat. For example, polar bears have two thick layers of fur and a thick layer of fat under their skin. Both these body features of polar bears are the adaptations to make them withstand the extremely cold climate of polar region so that they may survive in their habitat. Because of highly favourable climatic conditions in tropical rainforests (such as continuous warmth and rain), a large variety of plants and animals are found in tropical rainforests. The maj or types of animals living in the tropical rainforests are Lions, Tigers, Leopards, Elephants, Monkeys, Apes, Lion-tailed macaque, Gorillas, Birds, Snakes, Lizards, Frogs and Insects, etc.

b. Those which live in tropical regions: elephant, lion-tailed macaque, toucan, red-eyed frog.

Those which live in Polar Regions musk oxen, reindeer, penguin, seal, Siberian crane, arctic fox.

59. Weather is the day-to-day condition of the atmosphere at a place whereas climate is the average weather pattern at a place taken over a long period of time. a. Moderately hot and wet climate. b. V ery hot and humid climate c. Wet d. Hot and dry

60. a. Migration of birds (or other animals) is an adaptation to escape the harsh and cold conditions of their normal habitat in winter so as to survive. ne of the most common

(C) b. Those which live in tropical regions: elephant, lion-tailed macaque, toucan, red-eyed

(C) b. Those which live in tropical regions: elephant, lion-tailed macaque, toucan, red-eyed

frog.

(C) frog.

(C)

Those which (C)

Those which fox. (C)

fox.

S Leopards, Elephants, Monkeys, Apes, Lion-tailed macaque, Gorillas, Birds, Snakes, Lizards,

S Leopards, Elephants, Monkeys, Apes, Lion-tailed macaque, Gorillas, Birds, Snakes, Lizards, Frogs and Insects, etc. S Frogs and Insects, etc.

b. Those which live in tropical regions: elephant, lion-tailed macaque, toucan, red-eyed S b. Those which live in tropical regions: elephant, lion-tailed macaque, toucan, red-eyed

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climate of that habitat. For example, polar bears have two thick layers of fur and a thick

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climate of that habitat. For example, polar bears have two thick layers of fur and a thick layer of fat under their skin. Both these body features of polar bears are the adaptations to

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layer of fat under their skin. Both these body features of polar bears are the adaptations to make them withstand the extremely cold climate of polar region so that they may survive in

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make them withstand the extremely cold climate of polar region so that they may survive in their habitat. Because of highly favourable climatic conditions in tropical rainforests (such

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their habitat. Because of highly favourable climatic conditions in tropical rainforests (such as continuous warmth and rain), a large variety of plants and animals are found in tropical

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as continuous warmth and rain), a large variety of plants and animals are found in tropical rainforests. The maj or types of animals living in the tropical rainforests are Lions, Tigers, Cha

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rainforests. The maj or types of animals living in the tropical rainforests are Lions, Tigers, Leopards, Elephants, Monkeys, Apes, Lion-tailed macaque, Gorillas, Birds, Snakes, Lizards, Cha

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Leopards, Elephants, Monkeys, Apes, Lion-tailed macaque, Gorillas, Birds, Snakes, Lizards, Frogs and Insects, etc. Cha

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Frogs and Insects, etc.

And Thick skin ; Living on trees; Development of strong, gripping tails ; Long and large beaks ;

And Thick skin ; Living on trees; Development of strong, gripping tails ; Long and large beaks ;

Bright colours and Loud voice ; Living on diet of fruits, etc.

And Bright colours and Loud voice ; Living on diet of fruits, etc.

a. Climate has a great effect on all the living organisms (animals as well as plants). A living

And

a. Climate has a great effect on all the living organisms (animals as well as plants). A living organism can survive in a particular habitat only if its body is suited (or adapted) to the And

organism can survive in a particular habitat only if its body is suited (or adapted) to the climate of that habitat. For example, polar bears have two thick layers of fur and a thick And

climate of that habitat. For example, polar bears have two thick layers of fur and a thick layer of fat under their skin. Both these body features of polar bears are the adaptations to And

layer of fat under their skin. Both these body features of polar bears are the adaptations to

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ny swim well. 7. Polar bear has a very strong sense of smell. The very strong sense of smell

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ny swim well. 7. Polar bear has a very strong sense of smell. The very strong sense of smell

helps the polar bear in locating and catching its prey for food.

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a. An important feature of the tropical regions of earth is the tropical rainforests. Tropical

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a. An important feature of the tropical regions of earth is the tropical rainforests. Tropical rainforests are found in India, South-east Asia, Central America and Central Africa. b. Some of

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rainforests are found in India, South-east Asia, Central America and Central Africa. b. Some of the adaptations in animals living in tropical rainforests are A skin colour which helps them

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the adaptations in animals living in tropical rainforests are A skin colour which helps them to camouflage (mix up with the surroundings and hide) in order to catch prey or protect

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to camouflage (mix up with the surroundings and hide) in order to catch prey or protect themselves from predators ; Running very fast ( to catch prey or escape from predators) ;

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themselves from predators ; Running very fast ( to catch prey or escape from predators) ; evelopment of trunk, tusks, and large ears and feet Sharp eyesight, Sensitive hearing and

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evelopment of trunk, tusks, and large ears and feet Sharp eyesight, Sensitive hearing and Thick skin ; Living on trees; Development of strong, gripping tails ; Long and large beaks ; Com

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Thick skin ; Living on trees; Development of strong, gripping tails ; Long and large beaks ; Bright colours and Loud voice ; Living on diet of fruits, etc. Com

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Bright colours and Loud voice ; Living on diet of fruits, etc.

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dextreme cold by preventing the loss of heat from its body. 3. Polar bear has a thick layer

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dextreme cold by preventing the loss of heat from its body. 3. Polar bear has a thick layer of fat under its skin. This layer of fat insulates the body of polar bear against heat loss and

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dof fat under its skin. This layer of fat insulates the body of polar bear against heat loss and keeps it warm in cold climate. 4. Polar bear has a rounded body and small ears to keep the

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dkeeps it warm in cold climate. 4. Polar bear has a rounded body and small ears to keep the body surface area to a minimum ( compared to the body weight) . This reduces the heat loss

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dbody surface area to a minimum ( compared to the body weight) . This reduces the heat loss from the body of polar bear. 5. Polar bear has big feet ( or big paws) to spread the weight

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dfrom the body of polar bear. 5. Polar bear has big feet ( or big paws) to spread the weight of its body on snow which prevent it from sinking into snow and make it walk on snow

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dof its body on snow which prevent it from sinking into snow and make it walk on snow easily. 6. Polar bear is a good swimmer. The big feet ( or big paws) help the polar bear to Lim

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easily. 6. Polar bear is a good swimmer. The big feet ( or big paws) help the polar bear to swim well. 7. Polar bear has a very strong sense of smell. The very strong sense of smell Lim

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swim well. 7. Polar bear has a very strong sense of smell. The very strong sense of smell

SCIENCE 7 TEXT BOOK

76

migratory bird which comes to India every year for a few months is the Siberian crane. b. The trunk of an elephant is basically an elongated nose ( which is also capable of grasping things) . The trunk helps the elephant in many ways. The elephant uses the trunk to smell. Because of the trunk, elephant has a strong sense of smell. It is also used for breathing. The elephant uses its long trunk to pick up food ( like grass and plants, etc.) and put into its mouth. The trunk of elephant can reach up to the branches of trees and help it eat tree leaves as food. The elephant uses trunk for drinking water (by sucking up water and pu ng it into the mouth) . The elephant also uses the trunk to bathe itself.


61. ( a) 62. ( d) 63. ( a) 64. ( b) 65. ( b)

66. ( b) 67. ( a) 68. ( c) 69. ( d) 70. ( b)

71. ( b) 72. ( d) 73. ( b) 74. ( b) 75. ( c)

76. ( d) 77. ( b) 78. ( d) 79. ( c) 80. ( b)


81. ( i) a, d, e, g, h, i ( ii) b, c, f, j ( iii) e, g, h

82. ( a) Siberian crane ( b) ( i) Bharatpur ( ii) Sultanpur ( c) Migratory birds ( d) Winter season

83. ( a) ( i) Polar bear ( ii) Penguin ( b) Surroundings covered with ice and snow ( c) The thick layer of fat insulates the body of these animals against heat loss and keeps them warm in extremely cold climate ( d) Animal Q ( It is a penguin)

84. ( a) ( i) Tiger ( ii) Lion ( b) Tropical rainforest ( c) These animals have eyes in front of their head. aving eyes in front of the head enables these animals to have a correct idea of the location

of their prey. This helps in catching the prey ( d) Carnivores

85. ( a) Toucan ( b) Long and large beak ( c) Red-eyed frog ( d) Big and bulging bright-red eyes ( which ‘ pop-up’ suddenly and frighten the predator)

(C) S

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( which ‘ pop-up’ suddenly and frighten the predator) And ( a) ( i) Tiger ( ii) Lion ( b) Tropical rainforest ( c) These animals have eyes in front of their head.

And ( a) ( i) Tiger ( ii) Lion ( b) Tropical rainforest ( c) These animals have eyes in front of their head.

aving eyes in front of the head enables these animals to have a correct idea of the location

And aving eyes in front of the head enables these animals to have a correct idea of the location


And


And

an ( b) Long and large beak ( c) Red-eyed frog ( d) Big and bulging bright-red eyes And

an ( b) Long and large beak ( c) Red-eyed frog ( d) Big and bulging bright-red eyes ( which ‘ pop-up’ suddenly and frighten the predator) And

( which ‘ pop-up’ suddenly and frighten the predator)

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tpur ( ii) Sultanpur ( c) Migratory birds ( d) Winter season

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tpur ( ii) Sultanpur ( c) Migratory birds ( d) Winter season

( a) ( i) Polar bear ( ii) Penguin ( b) Surroundings covered with ice and snow ( c) The thick

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( a) ( i) Polar bear ( ii) Penguin ( b) Surroundings covered with ice and snow ( c) The thick layer of fat insulates the body of these animals against heat loss and keeps them warm in

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layer of fat insulates the body of these animals against heat loss and keeps them warm in

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extremely cold climate ( d) Animal Q ( It is a penguin) Compa

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extremely cold climate ( d) Animal Q ( It is a penguin)

( a) ( i) Tiger ( ii) Lion ( b) Tropical rainforest ( c) These animals have eyes in front of their head. Compa

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d65.

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d65. ( b)

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d( b)

70.

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75.Limite

d75.

SCIENCE 7 TEXT BOOK

77

WORKSHEET

A. Objective Type Questions 1. Name the following:

( a) The measure of water vapour in air.

( b) A sea bird which cannot fly.

( c) The unit in which rainfall is measured.

( d) The instrument used to measure the rainfall at a place.


( a) Weather is produced by the heat of the .… … … … … .......... and the effect it has on the atmosphere.

( b) The maximum temperature of the day generally occurs in the .… … … … … .......... .

( c) Days are .… … … … … .......... in winter than in summer.

( d) A climate having very high temperature and high humidity is called .… … … … … .......... climate.


( a) The polar regions of earth receive the maximum amount of sun’s heat.

( b) Rainfall is high in the tropical rainforests.

( c) A thick layer of fat under the skin of polar bear protects it from extreme cold.

( d) Reindeer is a migratory animal.

4. entiontheha itatofthefollowing:

( a) Lion tailed macaque ( b) Polar bear ( c) Red eyed frog ( d) Penguins



( a) Differentiate between weather and climate.

( b) Mention the factors which affect climate.

( c) List the types of climate of the world.

( d) How is rainfall measured? Mention the unit used to express the rainfall at a place.

(C) S

How is rainS How is rainChand


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following

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following questions

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questions

entiate between weather and climate.

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entiate between weather and climate.

Mention the fact

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And following: Com

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ving very high temperature and high humidity is called .… … … … … ..........

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e the maximum amount of sun’s heat.

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e the maximum amount of sun’s heat.

opical rainforests.

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opical rainforests.

at under the skin of polar bear protects it from extreme cold.

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at under the skin of polar bear protects it from extreme cold.

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dproduced by the heat of the .… … … … … .......... and the effect it has on the

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dproduced by the heat of the .… … … … … .......... and the effect it has on the

ature of the day generally occurs in the .… … … … … .......... .

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dature of the day generally occurs in the .… … … … … .......... .

SCIENCE 7 TEXT BOOK

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SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) Term used for animals which sleep during the day and become active at night.

( b) Another name for lion tailed macaque.

( c) Instrument used to measure rainfall at a particular place.

( d) Measure of water vapour in air.

( e) The scientific study of weather.


( a) The prediction of weather in advance is called weather forecasting.

( b) Our climate is produced by the heat of the sun and the effect it has on the atmosphere.

( c) Humidity of air is expressed as a percentage.

( d) Temperate climate has the coldest climate.

( e) Tropical rainforests grow on both sides of the equator of earth.

. entionifthefollowingarepolarregionsorhavetropicalrainforests:

( a) Finland ( b) Kenya ( c) Alaska ( d) Greenland ( e) Indonesia


( a) A climate which is neither very hot in summer nor very cold in winter is called desert climate.

( b) The mammal which is known to migrate seasonally in search of favourable climatic conditions and food is African elephant.

( c) The climate of Raj asthan is very hot and wet.

( d) The minimum temperature of the day generally occurs in the night.

( e) Prediction of weather in advance is called meteorology.



( a) Differentiate between Temperate climate and Tropical climate.

( b) List the various factors which affect climate at a place.

( c) What is migration? Name a migratory bird.

( d) Why do penguins huddle together?

(C) ( e)

(C) ( e)

(C) B. Subjective Type Questions


5. Answer(C)

5. Answer

S The climate of Raj as

S The climate of Raj as

The minimum temperaS The minimum tempera

Prediction of weaS Prediction of wea

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wing statements:

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wing statements:

A climate which

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A climate which is neither very hot in summer nor very cold in winter is called desert

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is neither very hot in summer nor very cold in winter is called desert

The mammal which is known t

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The mammal which is known tconditions and food is African elephant.

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conditions and food is African elephant.

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The climate of Raj asChand

The climate of Raj as

The minimum temperaChand

The minimum tempera

And al rainforests grow on both sides of the equator of earth.

And al rainforests grow on both sides of the equator of earth.

polar

And

polar regions

And

regions

( b) Keny And

( b) Kenya And

a ( c) Alaska And

( c) Alaska

wing statements:And

wing statements:

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ther in advance is called weather forecasting.

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ther in advance is called weather forecasting.

mate is produced by the heat of the sun and the effect it has on the atmosphere.

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centage.

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te climate has the coldest climate. Compa

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dy and become active at night.

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dy and become active at night.

SCIENCE 7 TEXT BOOK

79

( e) An elephant has a long trunk. How does this adaptation help the elephant to live and survive in the tropical rainforest?


( a) Differentiate between weather and climate.

( b) What do you understand by adaptation? How is the toucan adapted to live in tropical rainforests?

( c) What are polar regions? State the adaptations in any one organism living in polar region.

( d) How does migration help in the survival of birds? How do they travel to the same place year after year?

( e) Name the four maj or types of climate and list the examples of areas having these climates.


1. Weather is the state of the atmosphere with respect to:

( a) Temperature ( b) Wind ( c) Humidity ( d) All of these 2. heamountofwatervapourpresentinairiscalled:

( a) Climate ( b) Humidity ( c) Weather ( d) Longitude . lacesin orth ndiawheremigrator irdsgoare:

( a) Bharatpur ( b) Bharatpur and Chandigarh ( c) Bharatpur and Sultanpur ( d) Sultanpur 4. Whichofthefollowingis nownastheshipofhedesert?

( a) Elephant ( b) Lion ( c) Tiger ( d) Camel 5. Whichoneoffollowing estdescri esatropicalrainforest?

( a) Hot and humid ( b) Moderate temperature, heavy rainfall ( c) Cold and humid ( d) Hot and dry

(C) S

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( b) ModeratCold and humid

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as

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( b) Lion

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Weather is the state of the atmosphere with respect to:

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Weather is the state of the atmosphere with respect to:

( c) Humidity

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( c) Humidity called:

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( c) Weather

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irds go

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dpolar regions? State the adaptations in any one organism living in polar

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dpolar regions? State the adaptations in any one organism living in polar

ation help in the survival of birds? How do they travel to the same place

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dation help in the survival of birds? How do they travel to the same place

maj or types of climate and list the examples of areas having these

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dmaj or types of climate and list the examples of areas having these

SCIENCE 7 TEXT BOOK

80

8Lesson Plan



• That air exerts pressure.

• That air expands on heating.

• How winds are produced.

• How thunderstorm and cyclone are formed.

• The precautions that may be taken during a thunderstorm, cyclone and tornado.



VOCABULARY

Atmosphere, pressure, atmospheric pressure, expansion, monsoon, anemometer, wind vane, storm, lightning, thunder, thunderstorm, cyclone, hurricane, typhoon, tornado.


Air exerts pressure (Page 112)

Learning Tools

Interactive warm up exercise: Discussing with the students the properties of air would be a good start for the topic. Students should be asked the definition of atmosphere and its importance may be discussed

Chapter opening exercise: Students should be asked to inflate a balloon. Ask them the property of air shown by the filling of air in the balloon.


Discuss that the continuous physical force exerted on an obj ect by something in contact with it, is

Winds, Storms and CyclonesWinds, Storms and Cyclones

(C) Learning Tools

(C) Learning Tools



start for the topic. Students should be asked the definition of atmosphere and its importance may (C)

start for the topic. Students should be asked the definition of atmosphere and its importance may be discussed (C

) be discussed



S Air exerts pressure (Page 112)

S Air exerts pressure (Page 112)


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SCIENCE 7 TEXT BOOK

81

called pressure. Students should be aware of the fact that air exerts pressure. Familiarize them with the term atmospheric pressure. Explain that wind also exerts a force or pressure on the obj ects on which it strikes. Students should know that the direction of the wind determines whether the movement of an obj ect will be easy or difficult. They should cite examples from daily life to show that moving air exerts pressure.

Using resources

• Conduct the activity given on Page no. 114 of the book to show that air around us exerts pressure.



When we are flying a kite, then the wind coming from our back side helps. Give reason.


Air expands on heating (Page 116)


Discuss that when air is heated, its volume increases and it occupies a bigger space and this is called expansion of air. Students should know that hot air is lighter than cold air and thus, it rises up.

Using resources

• Conduct the activity given on Page no. 11 of the book to show that air expands on heating.



How do hot air balloons rise up?


How wind is produced (Page 118)


Explain them that the wind is the movement of air which depends on the difference in air pressure in the two regions. Students should know that greater the difference in air pressure, the faster the air moves. Students should realize that the uneven heating on the earth in the different regions is the main cause of wind movements.


Which parts of the earth receive the minimum heat from the sun and the maximum heat from the sun and why?



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SCIENCE 7 TEXT BOOK

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Wind is produced due to uneven heating on the earth by the sun (Page 118)

Teacher to the students guided discussion

Discuss that the wind is produced due to the uneven heating on the earth by the sun. Explain them that unven heating of earth ( wich produces winds) can take place under two situations; uneven heating between the equator and poles of the earth. Uneven heating of land and water of the oceans. Students should know the reasons and cite examples.

Using resources



Why does the wind blow from the land towards the ocean during winter?


High speed winds are accompanied by reduced air pressure (Page 120)


Explain them that the high speed winds are accompanied by reduced air pressure. Students should be aware that the fast moving air blowing over an obj ect can also lift the obj ect up by producing a region of low pressure above it. They should be able to name the instrument with which the wind speed is measured and the instrument by which the direction of wind at a place is found. Students should be aware of the terms storms, lightning and thunder.


How are storm, lightning and thunder caused?


Thunderstorm (Page 122)


Explain that a storm with thunder and lightning is called thunderstorm. It is accompanied by heavy rains or hail. Students should know the details of its formation. They should be aware of the precautions to be taken during a thunderstorm.


List the precautions to be taken during a thunderstorm.

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SCIENCE 7 TEXT BOOK

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Cyclone (Page 124)


Explain them that a cyclone is a huge revolving storm caused by very high speed winds blowing around a central area, called the ‘ eye of the cyclone’, of very low pressure in the atmosphere. Students should realize that cyclones revolve due to the force exerted by the rotation of earth. They should know the details of how it is formed taken and should realize the destruction caused by it. They should be aware of the safety measures taken by the Government, action to be taken by the people before a cyclone hits the area and after it.


List the advanced technologies that have helped in protection from cyclones.


Tornado (Page 127)


Explain to the students that a tornado is a violent storm with a column of rapidly rotating winds, having the appearance of a dark, funnel shaped cloud that reaches from the sky to the ground. Students should know the details of its formation, destruction caused by it and the precautions to be taken for protection from tornado.


List the precautions to be taken for protection from a tornado.



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SCIENCE 7 TEXT BOOK

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TEXT BOOK ANSWERS


1. Air pressure ( or Atmospheric pressure)

2. Air around us exerts pressure

3. We find it very di cult to ride a bicycle against the direction of wind. This is because in this case the blowing wind exerts a force on us in the direction opposite to the motion of our bicycle. And since the wind opposes our motion, we have to pedal very hard to keep the bicycle moving against the wind.

4. Hot air is lighter than cold air.

5. a. The region around the equator of earth ( called equatorial region) gets the maximum heat from the sun. b. The poles of the earth ( orth Pole and South Pole) are at the maximum distance from the sun and hence get the minimum heat from the sun.

. a. Hurricane b. Typhoon

7. Reduced air pressure

8. a. Anemometer b. Wind vane

9. Monsoon winds

1 . The monsoon winds coming from the south-west direction in summer carry a lot of water vapour from the Indian Ocean and bring heavy rains.

11. ( a) False ( b) False ( c) True ( d) False ( e) True

12. Thunderstorms, cyclones, tornadoes

13. Thunderstorm

14. ( a) East coast ( b) West coast

15. Cyclone

1 . (a) Releases heat (b) Absorbs heat

1 . Cyclones

1 . Tornado

1 . Centre called ‘eye’ of cyclone

2 . ( a) wind ( b) pressure ( c) expands ; contracts ( d) lighter ( e) warm ; cold ( f) uneven ( g) high; low (h) faster (i) reduced (j) rotation (k) eye (l) cyclone (m) tornado (n) west east (o) hurricane ; typhoon


21. Holes are usually made in hanging banners and hoardings so that high speed wind may pass through them easily without damaging them or bringing them down with its huge force or pressure.

22. (i) When air is filled into a balloon with our mouth, the balloon gets inflated. This observation shows that air exerts pressure. (ii) When air is filled into a bicycle tube with a pump, the

(C) hurricane ; typhoon

(C) hurricane ; typhoon


(C) B. Short Answer Type Questions

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SCIENCE 7 TEXT BOOK

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bicycle tube gets inflated and makes the bicycle tyre feel hard. This observation also shows that air exerts pressure.

23. When air is filled into a bicycle tube with a pump, the bicycle tube gets inflated and makes the bicycle tyre feel hard. This observation also shows that air exerts pressure.

24. It is the pressure exerted by air filled in a bicycle tube which keeps the tube ‘tight’ and makes the bicycle tyre feel ‘ hard’.

25. If we go on filling more and more air into bicycle tube with a pump, then ultimately the air pressure in the bicycle tube will increase too much due to which the bicycle tube may even burst.

2 . A football also gets inflated when air is filled in it. The football gets inflated because the air filled in it exerts pressure.

27. When the air blows, then the leaves of trees, flags and banners start fluttering (moving with irregular motion). It is due to the pressure exerted by moving air (or wind).

28. While rowing a boat in the lake, we find it easier to row the boat forward if the wind is coming from behind us. This is because the blowing wind exerts pressure on the boat ( and on the persons si ng in it) in the direction of their motion and helps it move forward. It shows that moving air or wind exerts a force ( or pressure) on all the obj ects which come in its way.

29. When we are flying a kite, then the wind coming from our back side helps. This is because the wind coming from our back side, strikes the kite and exerts pressure on the kite to make it fly higher and higher. It shows that moving air or wind exerts a force (or pressure)on all the obj ects which come in its way.

3 . When air is heated, its volume increases and it occupies a bigger space. We say that air expands on heating.

31. When air gets heated at a place, it expands, becomes lighter and rises up in the sky. In other words, hot air ( or warm air) rises up.

32. Smoke is produced by the burning of a substance, therefore, smoke is always accompanied by hot air ( or warm air) . Since warm air is lighter ( than cold air) , therefore, smoke contained in warm air always rises up.

33. No. If we want to buy a house, then we should buy a house having windows as well as ventilators. The windows are for bringing in fresh air from outside into the house. The ventilators (located near the roof of house) take out the warm and stale air from inside the house. The presence of ventilators in the house increases our comfort.

34. neven heating on the earth in different regions is the main cause of wind movements.

35. The uneven heating on the earth (which produces winds) can take place under two situations (i) neven heating between the equator and poles of the earth, and (ii) neven heating of land and water of oceans.

3 . The regions close to the equator of earth get the maximum heat from the sun, so the air in equatorial regions gets heated and becomes warm. The warm air rises in the equatorial regions of earth creating an area of low air pressure. The cooler air from the regions of up to 3 degrees latitude belt on both the sides of the equator (being at higher pressure),

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SCIENCE 7 TEXT BOOK

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rushes towards the equator to take the place of warm, rising air. This makes the wind to blow from the north and south directions towards the equator. Again, the air at latitudes of about degrees on both sides of the equator is warmer than at the poles (which is very cold). So, the warmer air at about degrees latitudes rises up creating regions of low air pressure and cold air from the polar regions ( being at higher pressure) rushes in to take its place. This makes the winds blow from the poles of the earth towards the warmer regions up to about degrees latitudes. These winds also blow from the north and south directions towards the warmer latitude regions.

37. The winds produced by the uneven heating of the earth between the equator and the poles do not blow in the exact north-south direction because a change in the direction of winds is caused by the rotation of the earth on its axis.

38. In summer, land near the equator of earth heats up faster than the water in oceans, so most of the time, the temperature of land is higher than that of water in oceans. The air over the land gets heated and rises creating a low pressure area. The cooler air from over the oceans ( being at higher pressure) , rushes towards the land. This causes the wind to blow from the oceans towards the land.

39. When we blow air over the surface of paper strip, the fast moving air creates a region of low air pressure above the paper strip. The air pressure below the paper strip, being higher, pushes the paper strip upwards and lifts it up.

4 . This activity shows that fast moving air is accompanied by low air pressure (or reduced air pressure) .

41. When we blow air ( or wind) between the balloons, then the fast moving air ( or fast moving wind) creates a region of low air pressure in the space between the two balloons. The air pressure on the outside of the balloons being higher, pushes the two balloons towards each other and makes them come closer. So, this activity shows that the fast moving air ( or fast moving wind) creates a region of low air pressure ( or reduced air pressure) .

42. When we blow air into the mouth of the bottle, then the air in the neck of bottle has high speed. This fast moving air reduces the air pressure in the neck of the bottle. The air pressure inside the bottle being higher, constantly pushes the paper ball out and does not allow it to go inside the bottle. So, this activity shows that increased wind speed accompanied by a reduced air pressure make it di cult to force the paper ball into the bottle.

43. If the roofs of houses are weak, then higher air pressure from below will lift up the roofs which can then be blown away by the fast winds. Thus, weak roofs of houses (like the tin roofs or thatched roofs) can be lifted and blown away by high speed winds during a wind-storm.

44. ( a)

45. The winds blowing from the oceans towards the land in summer are called monsoon winds. The summer monsoon is very important to the farmers in our country because most of the annual rainfall occurs at this time and helps in growing crops. Many farmers in our country depend mainly on rains for the irrigation of their crops.

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SCIENCE 7 TEXT BOOK

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4 . A tornado is a violent storm with a column of rapidly rotating winds, having the appearance of a dark, funnel-shaped cloud that reaches from the sky to the ground. A tornado causes considerable damage as it passes over land. This happens as follows: ( i) Tornado uproots trees, electric poles and telephone poles disrupting power supply and telecommunications. (ii) Tornado lifts people and vehicles off the ground and hurls them hundreds of metres away. This causes death of many people and damage to vehicles. ( iii) Tornado can cause extensive damage to buildings. When a tornado passes over a building, it sucks up air from around the building. This makes the pressure on the outside of the building much lower than that on the inside, and the building can explode. The following precautions should be taken for protection during a tornado (i) Take shelter in a room situated deep inside the house having no windows or in a basement ( underground room) . This is the best tornado shelter. ( ii) If a room without windows or basement is not available, then shut all the doors and windows of the house and take shelter under a sturdy table ( where falling debris cannot reach) . Bend down on your knees and protect your head and neck using your arms. Stay indoors until it is safe to come out. (iii) If a person is in a vehicle when a tornado begins, he should get out of the vehicle, go to a ditch or low-lying area and lie flat in it. (iv) Stay away from fallen electric wires and stay out of damaged areas.

4 . A cyclone is a huge revolving storm caused by very high speed winds blowing around a central area of very low pressure in the atmosphere. A cyclone is formed over warm sea-water and it is about 1 to 15 kilometres high. A cyclone revolves due to the force exerted by the rotation of earth. Factors like temperature, humidity, wind speed, wind direction and rotation of earth, contribute to the development of a cyclone. The centre of cyclone is called the ‘ eye’ of the cyclone.

4 . The cyclones bring with them extremely high speed winds which cause a lot of destruction. The tremendous force of high speed winds accompanying a cyclone can topple trees, electric poles, telephone poles and vehicles; damage houses; and hurt people through air, etc., causing a great loss of life and property. The fast moving flood waters brought in by a cyclone, destroy roads and railway tracks, wash away vehicles, damage houses, drown people and animals, and damage crops causing a great loss of life and property. The floods caused by cyclone also reduce the fertility of soil in the cyclone hit areas. Cyclones bring with them torrential rains. The continuous heavy rains brought by cyclones may further worsen the flood situation in the area. This increases the problems of the cyclone affected people. The floods caused by cyclones pollute drinking water sources. rinking of polluted water spreads water-borne diseases ( like typhoid and dysentery) . These diseases kill more people in the cyclone affected areas. If a person lives in an area which has just been hit by a cyclone, the following precautions should be observed (i) o not drink water that could be contaminated by floods (to avoid water-borne diseases). rink only clean water which has been stored for emergencies. ( ii) Do not touch wet electric switches and fallen electric power lines. Do not use electrical appliances, if wet. ( iii) Do not enter damaged buildings or flood waters. Avoid driving on roads through standing water as floods may have damaged the roads. ( iv) Do not go out j ust for the sake of fun. Keep listening to local radio for advice. Go out only when it is safe to do so. ( v) Do not pressurise the rescue teams by making

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SCIENCE 7 TEXT BOOK

88

unnecessary demands. Co-operate with the rescue teams and help your neighbours and friends.

4 . A storm with thunder and lightning is called thunderstorm. The sun heats the surface of earth. The hot surface of earth warms the air in contact with it. The warm air ( being lighter) rises up creating a low pressure area. And cool air rushes in to take its place in the form of strong winds. As the warm air rises, it transfers heat to the upper levels of atmosphere and begins to cool. The water vapour present in the rising air cool and condense to form a cloud. The cloud grows upwards into areas where the temperature is close to the freezing point of water ( C). Some of the water vapour of cloud forms tiny water droplets and some of it turns into ice particles. The water droplets are carried upwards in the cloud (by convection currents) but the ice particles drift downwards. The friction between fast rising ‘water droplets’ in the cloud and falling ‘ice particles’ produces opposite electric charges on them (the water droplets ge ng positive electric charge and ice particles acquiring negative electric charge). ue to this, the top of cloud becomes positively charged and the bottom of cloud becomes negatively charged. When a large amount of opposite electric charges build up in the cloud, a tremendous amount of electric current passes through the air in the cloud which produces a big electric spark within the cloud. This electric spark is the lightning. The spark of lightning heats the nearby air too much. This extremely hot air expands explosively causing a loud sound called thunder. When electric charges from the bottom of the electrically charged cloud flow down through the air to the ground, then we see the flash of lightning coming towards the earth. The big water drops in the thundercloud fall to the earth as heavy rain ( or hail) . In this way, a thunderstorm brings strong winds, thunder, lightning and heavy rains ( or hail) . Lightning and thunder are the two characteristic features of a thunderstorm.

5 . Thunderstorms develop in hot and humid tropical areas ( like India) very frequently. This is because the heat of tropical area warms up the air and makes it rise up, whereas humidity provides the water vapour for the formation of clouds. We should take the following precautions during a thunderstorm to protect ourselves from lightning - (i) We should not sit near a window during lightning. Open garages, storage sheds and metal sheds are also not safe places to take shelter during lightning. ( ii) We should not take shelter under an umbrella with a metallic end during lightning. This is because metallic end of umbrella may act as a conductor for lightning and harm us. ( iii) We should not take shelter under an isolated and tall tree. This is because an isolated tall tree is more likely to be hit by lightning due to its nearness to the clouds. We should take shelter under a small tree. We should, however, not lie on the ground during lightning. ( iv) A car ( or a bus) is a safe place to take shelter during lightning ( because its metal body can conduct lightning to earth safely, without harming us) . ( v) If we are in water ( as in a swimming pool or on a beach) when the thunderstorm begins and lightning takes place, we should get out of water and go inside a building.


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SCIENCE 7 TEXT BOOK

89

1. (b) 2. (a) 3. (c) 4. (b) 5. (c)

. (a) . (d) . (c) . (c) . (c)


1. The empty boiling tube contains air. This air expands on heating and inflates the balloon

2. Amritsar is unlikely to be affected by a cyclone. This is because a cyclone develops over a sea and Amritsar is very far away from the sea

3. The tin can gets crushed n pouring cold water, the hot steam cools and gets condensed to form water due to which pressure inside the tin can is reduced too much. The large air pressure (or atmospheric pressure) acting on the tin can from outside crushes the tin can inwards

4. (a) latitude has the coldest air (because it is nearer to the orth pole of the earth than 3 latitude) (b) quator has the warmest air (because equator is at the minimum distance from the sun)

75. ( a) Winter season ( b) Summer season

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SCIENCE 7 TEXT BOOK

90

WORKSHEET



( a) The instrument used to measure wind speed.

( b) Term used for cyclone on American continent.

(c) Coast of India more vulnerable to cyclones.

( d) Another term for moving air.

2 Fill in the blanks:

( a) Air moves from a region of .… … … … … .......... pressure to a region of .… … … … … ..........pressure.

( b) The centre of the cyclone is called .… … … … … .......... .

( c) The storm associated with funnel shaped cloud that reaches from the sky to the ground is .… … … … … .......... .

( d) Warm air is .… … … … … .......... than cold air.


( a) It is lightning which causes thunder.

( b) The wind speed is measured by an instrument called odometer.

( c) Wind is produced due to the uneven heating on the earth by the sun.

( d) The winds blowing from the land towards the ocean in summer are called monsoon winds.



( a) Holes are made in banners and hoardings. Give reason.

( b) How are winds produced by the uneven heating of earth between the equator and the poles?

( c) What will happen if high speed winds blow over a house having a weak tin roof? Give reasons for your answer.

( d) What are monsoon winds and why are they important for our country?

(e) Mention one precaution to be taken during

(i) Thunderstorm (ii) Cyclone (iii) Tornado

(C) (e) Mention

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SCIENCE 7 TEXT BOOK

91

SAMPLE PAPER

M.M. 5

ame ............................................................... Class ......................... ate ...........................



(a) Term used for cyclone in apan and Philippines.

( b) Storm accompanied by lightning followed by a loud sound from the clouds.

( c) Term used to describe the centre of the cyclone.

( d) A natural flow of high voltage electricity within a cloud which appears as a bright flash of light in the sky.

( e) The instrument by which direction of the wind at a place is found.


( a) The pressure exerted by wind is due to the kinetic energy possessed by it.

( b) While rowing a boat in the lake, we find it easier to row the boat forward if the wind is coming from the front.

( c) Air expands on heating and contracts on cooling.

(d) Cold air is lighter than hot air.

( e) Wind may be produced by the uneven heating of land and water of oceans.

3. State which of the following places are likely to be hit by cyclones:

(a) Chennai (b) elhi (c) Puri (d) Srinagar (e) Amritsar


( a) A cyclone revolves due to the force exerted by the revolution of earth.

( b) Tornadoes are the greatest storms on earth.

( c) A period of violent weather with strong winds, and usually rain is called thunder.

( d) The pellets of frozen rain or ice falling in showers are called lightning.

( e) The less the difference in air pressure, the faster the air moves.



( a) How can high speed winds be destructive?

( b) How is wind produced?

( c) Why are holes made in hanging banners and hoardings?

( d) How will you show that air exerts pressure?

( e) Describe the nature of hot air.

(C) ( e)

(C) ( e)



(C)

5. Answer(C)

5. Answer

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SCIENCE 7 TEXT BOOK

92


( a) List the precautions to be taken during a thunderstorm.

( b) How is a cyclone formed?

( c) Mention how a tornado causes considerable damage.

( d) State the effective safety measures taken by the Government during a cyclone.

( e) How will you show that air expands on heating?


1. Whichofthefollowingisnotacharacteristicofathunderstorm?

( a) Spark of light in atmosphere ( b) Rapidly rotating winds

( c) Loud noise ( d) Heavy rains or hail.

2. Windisalwa sassociatedwith:

( a) Kinetic energy ( b) Chemical energy

( c) Potential energy ( d) Gravitational energy.

. hunderstorms developver frequentl inareashaving:

(a) Polar climate (b) Tropical climate

( c) Desert climate ( d) Temperate climate.

4. Whichofthefollowingcanmoveoverthelandwithoutcomingtoanendquic l ?

(a) Cyclone (b) urricane (c) Typhoon (d) Tornado

5 . Whichofthefollowingregionismorevulnera letoc clonicstorms?

( a) Northern hills of India ( b) Western deserts of India

( c) East coast of India ( d) West coast of India

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SCIENCE 7 TEXT BOOK

93

9Lesson Plan



• The soil profile.

• The composition of soil.

• The types of soil.

• How water is absorbed by soil.

• How soil is important for growing crops.

• About soil erosion.



VOCABULARY

Humus, weathering, soil profile, sandy soil, clayey soil, loamy soil, percolation, soil erosion, soil pollution.


Soil and its formation (Page 132)

Learning Tools

Interactive warm up exercise: Discussing the importance of soil for plants would be a good start for the topic. Discuss that soil provides water and essential nutrients to plants from which we also derive our food.

Chapter opening exercise: Students should be taken to the school garden. They must be shown the top soil which is darker than the layers below. Explain that this layer consists of organic matter called humus.

SoilSoil

(C)


(C)


Learning Tools

(C) Learning Tools


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(C)

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SCIENCE 7 TEXT BOOK

94


Discuss with the students that soil is a dark brown solid material which is a mixture of rock particles of various sizes and decayed plant and animal matter called humus. Students should realize the importance of soil as a natural resource. They should be aware of the term weathering and humus. They should know how soil is formed.


List the important uses of soil.


Soil profile (Page 133)


Discuss with them that a vertical section through the soil showing the different layers of soil is called soil profile. Students should be able to name and describe the characteristics of the three layers of soil in the soil profile. They should be able to draw the diagram showing the soil profile.

Using resources



Draw a neat and well-labeled diagram of the soil profile.


Composition of soil (Page 134)


Explain them that the soil mainly consists of different sized rock particles, minerals, humus, air, water and living organisms. Students should be aware of the terms clay, silt, sand and gravel.

Using resources

Conduct the activity given on Page no. 135 to show that soil consists of rock particles of different sizes and humus.


Name the smallest and the largest rock particles present in the soil. Which soil is said to have a good top soil?

(C)

Using resources

(C)

Using resources

Conduct the activity given on Page no. 135 to show that soil consists of rock particles of different

(C) Conduct the activity given on Page no. 135 to show that soil consists of rock particles of different

sizes and humus. (C) sizes and humus.

Suggested home assignment(C)


S water and living organisms. Students should be aware of the terms clay, silt, sand and gravel.

S water and living organisms. Students should be aware of the terms clay, silt, sand and gravel.

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SCIENCE 7 TEXT BOOK

95


Types of soil (Page 136)


Discuss that on the basis of differences in the composition of the soil, it can be classified into three basic types. Students should know that sandy soil mainly consists of sand and very little humus and thus it is less fertile. Clayey soil contains mainly clay and also contains very less humus but because it is rich in minerals, it is more fertile than sandy soil. Loamy soil is a mixture of sand, clay, silt and humus in the right proportions and thus, it is the most fertile soil and best for growing crops. Students should be able to differentiate between sandy soil and clayey soil.


Differentiate between sandy soil and clayey soil.


Soil and crops (Page 137)


Explain them that the different types of crops grow well in different types of soil. Students should be able to determine which type of soil is best for a particular crop like cereals, paddy, lentils ( pulses) and cotton.


Name the type of soil used to grow cotton and paddy.


Soil contains air and water (Page 137)


Discuss with the students some important properties of soil like soil contains air and water. Air is present in the spaces between soil particles. Students should know that sandy soil provides much more air to the plant roots than clayey soil. Explain that water is usually present as a thin film around the soil particles and even a dry looking soil has some moisture in it. Students should be able to calculate the percentage of water present in the soil.

Using resources

• Conduct the activity given on Page no. 13 of the book to show that soil contains air.

• Conduct the activity given on Page no. 13 of the book to show that air contains water.

(C) present in the spaces between soil particles. Students should know that sandy soil provides much

(C) present in the spaces between soil particles. Students should know that sandy soil provides much

more air to the plant roots than clayey soil. Explain that water is usually present as a thin film

(C) more air to the plant roots than clayey soil. Explain that water is usually present as a thin film

(C) around the soil particles and even a dry looking soil has some moisture in it. Students should be (C) around the soil particles and even a dry looking soil has some moisture in it. Students should be

able to calculate the percentage of water present in the soil. (C)

able to calculate the percentage of water present in the soil.

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SCIENCE 7 TEXT BOOK

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If we pass through a farmland during a hot summer day, we will see that the air above the soil is shimmering. Explain why?


Soil can absorb water (Page 139)


Explain that though soil usually contains some water, it can still absorb a lot of water. Students should be able to calculate the percentage of water absorbed by the soil.

Using resources

Conduct the activity given on Page no. 140 to find the percentage of water absorbed by a soil.


Numerical problem: 100 mL of water was taken in a measuring cylinder. This water was added drop wise to a 50 mL of dry soil kept on filter paper in a funnel. When the water j ust started dripping from the soil in the funnel, the amount of water left in the measuring cylinder was found to be 60 mL. Calculate the percentage of water absorbed by the soil.


Soil allows water to percolate (Page 141)


Explain that the percolation of water is a process in which water passes down slowly through the soil. Students should know that rate of percolation refers to how fast water passes down the soil. It is expressed in millimeters per minute. Students should know that percolation rate is highest in sandy soil and lowest in clayey soil. Soil with low percolation rate is the best for growing paddy. Students should be familiarized with the term vegetation.

Using resources

Conduct the activity given on Page no. 141 of the book to measure percolation rate of water in a soil.


Numerical problem: A student conducted an experiment to determine the percolation rate of water in a soil. e observed that it took 45 minutes for 1 m of water to percolate through the soil. Calculate the percolation rate of water in the soil.

(C) Suggested home assignment


Numerical problem: A student conducted an experiment to determine the percolation rate of water (C)

Numerical problem: A student conducted an experiment to determine the percolation rate of water soil.(C

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) Calculate the percolation rate of water in the soil.

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And Soil allows water to percolate (Page 141)

And Soil allows water to percolate (Page 141)

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SCIENCE 7 TEXT BOOK

97


Soil erosion (Page 142)


Explain that the removal of fertile top soil from land by wind or water is called soil erosion. It occurs easily in those areas of land which are not covered by vegetation. Students should know that that the roots of vegetation bind the particles of top soil firmly. Deforestation is one of the maj or causes of soil erosion. Students should be able to list the various effects of soil erosion and the ways to prevent soil erosion.

Using resources



List the preventive measures for soil erosion.


Soil pollution (Page 144)


Explain them that the contamination of soil with waste materials, pesticides, fertilizers, acid rain and industrial chemical wastes is called soil pollution. Students should be able to list the various effects and preventive measures of soil pollution.


List the effects of soil pollution.



Using resources






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S Revise all the topics covered in the previous lessons.

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SCIENCE 7 TEXT BOOK

98

TEXT BOOK ANSWERS


1. Air 2. Water

3. This air provides the oxygen required for respiration by the roots of plants and other organisms ( which live in soil) .

4. ( a) Clayey soil ( b) Sandy soil 5. Loamy soil

6. Loamy soil

7. Soil rich in clay and organic matter, and having very good capacity to retain water is ideal for growing paddy ( rice crop) .

. Loamy soil 9. Sandy-loam soil

10. Clay, silt, sand and gravel 11. Silt

12. Clay < Silt < Sand < Gravel 13. Humus

14. Weathering 15. Humus

16. Soil profile 1 . ( a) Clayey soil ( b) Sandy soil

1 . Loamy soil 19. Loamy soil

20. Soil profile

21. 1. A-horizon ( or Top-soil) 2. B-horizon ( or Sub-soil) 3. C-horizon ( or Sub-stratum)

22. A-horizon ( or Top-soil) 23. A-horizon ( or Top-soil)

24. Bed rock ( or Parent rock)

25. Bacteria, fungi, insects ( such as ants and beetles) , worms ( like earthworms) , rodents

26. ( a) Clayey soil ( b) Sandy soil

27. J ute/cloth bags

2 . ( a) Clayey soil, Sandy soil and Loamy soil ( b) Soil erosion

29. a. Soil erosion is caused mainly by the large scale cu ng down of forest trees and other plants (which is called deforestation). b. The roots of vegetation (trees and other plants) growing in the soil bind the particles of top-soil firmly.

30. (a) soil (b) horizon (c) top (d) B (e) profile (f) soil (g) loose (h) wind (i) erosion (j) polythene ( k) mL/min


31. a. We will find that the water poured on the cemented floor flows down, it is not absorbed by the cemented floor. b. If we pour water from the second test-tube on the soil kept in a flower pot, we will see that the soil absorbs the water quite rapidly.

32. Cemented floor does not absorb water because it is not porous. The soil absorbs water because it is porous (having tiny pores in it).

33. Sand particles are quite large. Sand particles cannot fit closely together, so there are large spaces between sand particles. The large spaces between sand particles are filled with air.



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SCIENCE 7 TEXT BOOK

99

Due to this, sandy soil provides much more air to the plant roots. On the other hand, clay particles (being much smaller) pack tightly together leaving little space for air. So, clayey soil provides much less air to the plant roots which grow in it.

34. Some of the important properties (or characteristics) of soil are as follows

1. Soil contains air.

2. Soil contains water ( or moisture) .

3. Soil can absorb water ( or soak up water) .

4. Soil allows water to percolate ( or pass down through it) .

35. Loamy soil has the right water-holding capacity for the growth of plants. The excess water can also drain out through it easily. Loamy soil has also adequate air spaces between its particles to hold su cient air needed by plant roots. oamy soil can also be ploughed easily. oamy soil contains su cient amount of humus. So, loamy soil has all the necessary nutrients for the growth of plants. oamy soil is the most fertile soil. It is the best soil for growing crops.

36. No. A disadvantage of sandy soil is that it cannot hold much water in it because the water gets drained out quickly through large spaces between its particles. So, sandy soil dries out quickly which is not good for plants.

37. ( i) b ( ii) c ( iii) a ( iv) e ( v) d

3 . Humus

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40. If there is vegetation (trees and other plants) on land, then the roots of vegetation (trees and other plants) growing in the soil bind the particles of top-soil firmly. Due to the binding of soil particles by the roots of trees and plants, the blowing wind and flowing rainwater are not able to carry away top-soil and hence soil erosion does not occur. On the other hand, the soil not covered by vegetation (trees and other plants) is easily eroded because there are no roots of trees and plants in it which can bind the soil particles together and prevent them from being carried away by strong winds or flowing rainwater (Actually, in the absence of plant roots, the soil becomes loose) .

41. If there is vegetation (trees and other plants) on land, then much of the falling rain hits the trees and plants before it hits the soil. In this way, the cover of vegetation softens (or reduces) the effect of heavy rains on the soil. The soil does not become loose easily and the flowing rainwater is not able to carry away topsoil. ue to this, soil erosion does not occur. If, however, there is no vegetation (trees and other plants) on land to soften the effect of heavy rains, the bare soil becomes loose quickly by the force of falling rainwater and erodes easily. This is because, being loose, it is easily carried away by flowing rainwater or strong winds.

42. Soil erosion can be prevented in the following ways: 1. Soil erosion can be prevented by preventing large scale cu ng down of forest trees. The large scale cu ng down of forest trees is called deforestation. So, we can also say that soil erosion can be prevented by preventing deforestation. 2. Soil erosion can be prevented by afforestation (large scale growing of forest trees in place of cut down trees) . If the trees have to be cut down from

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SCIENCE 7 TEXT BOOK

100

the forests for various needs, then new trees should be planted in place of the cut down trees. In this way the forests will continue to have su cient number of trees all the time. And this tree cover will prevent soil erosion of the forest land. 3. Soil erosion can be prevented by increasing the green cover (vegetation) around us by planting more trees and plants ourselves.

43. The main differences between sandy soil and clayey soil are given as

( i) Sandy soil contains mainly big rock particles whereas clayey soil contains mainly fine rock particles.

( ii) Sandy soil cannot hold much water but clayey soil has very good water-holding capacity.

( iii) Sandy soil provides good aeration ( air) to plant roots but clayey soil is not able to trap enough air for the roots of plants.

( iv) Sandy soil is loose, light and non-sticky whereas clayey soil is compact, heavy and sticky.

( v) Sandy soil is less fertile whereas clayey soil is comparatively more fertile.

44. Some of the important uses of soil are given as:

1. Soil is used for growing food ( like grains, pulses, fruits and vegetables, etc.) .

2. Soil is used to grow trees for obtaining wood for building purposes ( timber) , for burning as fuel ( firewood) and for making paper.

3. Soil is used to grow cotton plants which give us cotton clothes. Soil is also used to grow mulberry trees for rearing silkworms which provide us silk for making silk clothes.

4. Soil is used to make bricks and mortar for building houses.

5. Soil is used to make earthenware or pottery ( such as matkas, surahis, etc.) , crockery ( cups and plates) , toys and statues, etc.

45. There is a demand to ban polythene bags and plastics because they cause soil pollution and may also kill the living organisms.


46. A vertical section (or cu ng) through the soil showing the different layers of soil is called ‘soil profile’. Refer to figure 1 for the diagram. We can see the soil profile at a place (showing the inner layers of soil) in the following situations

( i) Soil profile can be seen by looking at the sides of a recently dug trench ( or ditch) .

( ii) Soil profile can be seen while digging a well or foundation of a building.

47. Sandy soil contains mainly sand (having large particles with large spaces). Sandy soil contains very little humus. Sandy soil is less fertile. Clayey soil contains mainly clay (having very small particles with very small spaces). Clayey soil also contains very little humus. Clayey soil is more fertile than sandy soil. oamy soil is a mixture of sand, clay, silt and humus in the right proportions. oamy soil contains su cient amount of humus. oamy soil is the most fertile soil.

4 . Soil is a dark brown (or black) solid material which is a mixture of ‘rock particles of various sizes’ and decayed plant and animal matter called ‘humus’. Soil is formed from rocks by

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SCIENCE 7 TEXT BOOK

101

the process of weathering. In weathering, rocks are broken down very slowly by the action of sun’s heat, wind, rain, flowing river water, etc., to form tiny rock particles. These tiny rock particles then mix up with humus to form fertile soil. The nature of any soil depends on the rocks from which it has been formed and the type of vegetation that grows in it. We take some dry soil in a hard glass beaker and cover it with a lid ( such as a watch glass) .

eat the beaker by using a burner. We will see that tiny drops of water are formed on the inner side of the lid. This shows that even the soil which appears to be dry to us, contains some water.

49. The removal of fertile top-soil from land by wind or water is called soil erosion. Soil erosion is caused mainly by the large scale cu ng down of forest trees and other plants (which is called deforestation). The important effects of soil erosion are as follows 1. Soil erosion can turn lush green forests into deserts and spoil the environment. When the fertile top-soil in a forest gets removed by soil erosion, then the infertile sub-soil is left behind. o forest plants can grow in this remaining infertile soil due to which the once lush green forest can gradually turn into a desert. This spoils our environment. 2. Soil erosion can lead to famines (excessive scarcity of food). When the fertile top-soil is removed by soil erosion, then the food crops do not grow well in the remaining infertile soil. And due to bad crops, there is an excessive shortage of food-grains in that area. The people do not get su cient food to eat and this leads to starvation deaths. 3. Soil erosion can cause floods. The soil carried away from land by the flowing rainwater gradually deposits on river beds (decreasing their depth) . So, when it rains heavily, the river cannot take away all the rainwater quickly.

ue to this, river water overflows from its banks and causes severe floods by submerging surrounding areas. These floods cause damage to life and property.

50. The contamination of soil with waste materials (especially used polythene bags and plastics), pesticides, fertilisers, acid rain and industrial chemical wastes, etc., is called soil pollution.

umping of waste materials (such as polythene bags, plastics, glass and metal objects), use of pesticides in agriculture, excessive use of fertilisers in agriculture and dumping of industrial wastes can cause soil pollution. The soil pollution can be prevented in the following ways:

( i) The use of polythene bags should be avoided to prevent soil pollution. This can be done by using bags made of paper, cloth or j ute.

( ii) Wherever possible, used plastic obj ects should be sent to factories for recycling to prevent soil pollution. Discarded glass and metal obj ects can also be recycled.

( iii) The use of pesticides in agriculture should be minimised to reduce soil pollution.

( iv) The use of excessive chemical fertilisers should be avoided in agriculture to prevent soil pollution.

( v) Steps should be taken to reduce the emission of acidic gases like sulphur dioxide and nitrogen oxides from factories which cause acid rain.

( vi) The industrial chemical wastes should be treated properly to make them harmless before dumping into soil.

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SCIENCE 7 TEXT BOOK

102


51. ( c) 52. ( b) 53. ( c) 54. ( a) 55. ( b)

5 . (c) 5 . (b) 5 . (c) 5 . (b) . (d)

61. ( c) 62. ( c) 63. ( b) 64. ( b) 65. ( c)


. Sandy soil ighest percolation rate of water

67. Soil B; Paddy ( rice crop) needs a lot of standing water for its growth

. The soil in the farmland contains some water. n a hot summer day, this water of soil evaporates forming water vapour. The water vapour coming out of the soil reflects the sunlight irregularly due to which the air above the soil seems to be shimmering

69. 10 per cent

70. 50 per cent

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SCIENCE 7 TEXT BOOK

103

WORKSHEET



( a) The most important natural resource in which our food is grown.

( b) Large scale cutting of trees that causes soil erosion.

( c) The process in which water passes down slowly through the soil.

( d) Component of soil which makes the air above the soil in a farmland shimmer on a hot summer day.


( a) Soil erosion does not occur where the land is covered by .… … … … … ...... .

( b) The percolation rate of water in a soil is the volume of water in .… … … … … ...... which passes down the soil per minute.

( c) The soil absorbs water because it is .… … … … … ..... .

( d) Soil contains .… … … … … ...... in the spaces between its particles and .… … … … … ...... as moisture.


( a) Sandy soil contains high amount of humus.

( b) For growing lentils, clayey soil is the best.

( c) The layer of soil which is j ust below the top-soil is called B-horizon.

( d) Soil is used to make bricks and mortar or building houses.

4. Which crops are grown in the following types of soil?

( a) Clayey soil

( b) Loamy soil

( c) Sandy-loam soil



( a) Differentiate between sandy soil and clayey soil.

( b) Mention the essential uses of soil.

( c) How is soil formed?

( d) What is soil erosion?

(C) ( c)

(C) ( c)

( d)

(C) ( d) What is soil erosion?

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SCIENCE 7 TEXT BOOK

104

SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) The layer of soil which is j ust below the sub-soil.

( b) Decayed plant and animal matter present in the soil.

( c) The smallest rock particles present in the soil.

( d) The most fertile soil.

( e) The removal of fertile top soil from land by wind or water.


( a) Roots of the vegetation bind the particles of top soil firmly.

( b) The sandy soil has the lowest percolation rate.

( c) V egetation covers the soil like a green sheet spread on the surface of earth.

( d) Dumping of waste materials in the soil causes soil erosion.

( e) Soil erosion can cause floods.

. entionthet peofsoilwhichisappropriateforgrowing:

( a) Paddy ( b) Wheat ( c) Lentil ( d) Cotton ( e) Gram 4. Correct the following statements:

( a) Clayey soil is loose, light and non-sticky.

( b) Loamy soil cannot be ploughed easily.

( c) B-horizon contains the maximum amount of humus.

( d) The maj or components of soil are air and water.

( e) The rock particles in soil which are larger than silt particles form clay.



( a) Define weathering and humus.

( b) List the important characteristics of soil.

( c) Define the rate of percolation of water in a soil. Mention its unit.

( d) What is the cause of soil erosion?

( e) List the important uses of soil.

(C)


(C)


5. Answer

(C) 5. Answer

( a)(C)

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SCIENCE 7 TEXT BOOK

105


( a) Write the effects of soil pollution.

( b) How can soil pollution be prevented?

( c) Describe the three types of soil.

( d) What is soil profile? Describe it with the help of a diagram.

( e) State the composition of soil.


1. One of the following is not a type of soil. This one is:

( a) Loamy soil ( b) Silty soil ( c) Clayey soil ( d) Sandy soil. 2. hecomponentofsoilwhichma estheaira ovethesoilinafarmlandshimmerona

hotsummerda sis:

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( a) Clay ( b) Silt ( c) Humus ( d) Sand 4. The best soil for growing cereals is:

( a) Clayey soil ( b) Sandy soil ( c) Loamy soil ( d) Sandy-loam soil 5 . Loam is a mixture of:

( a) Sand and clay ( b) Sand and silt ( c) Clay and gravel ( d) Clay and silt

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SCIENCE 7 TEXT BOOK

106

10

Lesson Plan



• How the process of respiration is important for living organisms.

• Difference between breathing and cellular respiration.

• To distinguish between aerobic respiration and anaerobic respiration.

• About respiration in human beings and other organisms.

• The respiration in plants.



VOCABULARY

Respiration, aerobic respiration, anaerobic respiration, breathing, haemoglobin


Respiration (Page 149)

Learning Tools

Interactive warm up exercise: Discussing with the students the activities which require energy for performance would be a good topic to start the chapter. Ask students if only human beings require energy. Students should be asked why we feel hungry after swimming or doing any similar strenuous physical exercise.

Chapter opening exercise: Students should be asked the difference between breathing and respiration, which will help in the recapitulation of the topic covered in Class V I. Ask the students the names of the gases taken in and given out during the process of breathing.

Respiration in OrganismsRespiration in Organisms

(C) Learning Tools

(C) Learning Tools



for performance would be a good topic to start the chapter. Ask students if only human beings (C)

for performance would be a good topic to start the chapter. Ask students if only human beings (C)

require energy. Students should be asked why we feel hungry after swimming or doing any similar (C)

require energy. Students should be asked why we feel hungry after swimming or doing any similar strenuous physical exercise.

(C)

strenuous physical exercise.

S Respiration (Page 149)

S Respiration (Page 149)

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SCIENCE 7 TEXT BOOK

107


Discuss that the process of releasing energy from the food with the help of oxygen taken in to burn food in the cells of the body, and then eliminating the waste products ( carbon dioxide and water) is called respiration. Students should know that that all living organisms respire to obtain energy and for their survival. They should be able to express the process of respiration in the form of a word equation. Students should realize that respiration is the reverse process of photosynthesis that takes place in plants. Since the process of respiration takes place inside the cells of the body, it is called cellular respiration.


Define cellular respiration.


Aerobic respiration and anaerobic respiration (Page 150)


Discuss with them that when the breakdown of glucose ( food) occurs with the use of oxygen, it is called aerobic respiration. Students should be able to express it in the form of word equation and name the organisms which carry out aerobic respiration. Discuss that when the breakdown of glucose ( food) occurs without the use of oxygen, it is called anaerobic respiration. Students should be able to express it in the form of a word equation and name the organisms which carry out anaerobic respiration. Students should know that anaerobic respiration takes place in our muscle cells during any vigorous physical activity when oxygen gets used up faster in the muscle cells than can be supplied by blood. Students should know the reason for muscle cramps and the ways to treat them.


Differentiate between aerobic and anaerobic respiration.


Breathing (Page 153)


Explain them that breathing is a continuous process by which air rich in oxygen is taken inside the body of an organism and air rich in carbon dioxide is expelled from the body. Students should know that breathing consists of one inhalation and one exhalation. Students should be able to define breathing rate and tell the breathing rate of an adult human being. They should know that breathing takes place in our lungs and involves the movement of ribcage and diaphragm.

Using resources

• Conduct the activity given on Page no. 15 to understand the mechanism of breathing.



Explain them that breathing is a continuous process by which air rich in oxygen is taken inside the

(C) Explain them that breathing is a continuous process by which air rich in oxygen is taken inside the

(C)

body of an organism and air rich in carbon dioxide is expelled from the body. Students should know (C)

body of an organism and air rich in carbon dioxide is expelled from the body. Students should know that breathing consists of one inhalation and one exhalation. Students should be able to define (C

) that breathing consists of one inhalation and one exhalation. Students should be able to define

S Breathing (Page 153)

S Breathing (Page 153)


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And out anaerobic respiration. Students should know that anaerobic respiration takes place in our

And out anaerobic respiration. Students should know that anaerobic respiration takes place in our

muscle cells during any vigorous physical activity when oxygen gets used up faster in the muscle

And muscle cells during any vigorous physical activity when oxygen gets used up faster in the muscle

cells than can be supplied by blood. Students should know the reason for muscle cramps and the

And

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SCIENCE 7 TEXT BOOK

108

• Conduct the activity given on Page no. 15 to show that carbon dioxide is produced during respiration.

• Students may run the video for the given topic using the QR Code given at the end of the chapter on the Study Gear app.


Mention the Y oga exercises which help in smooth breathing process in our body.


Respiration in humans (Page 158)


Discuss that the main organs of human respiratory system are nose, nasal passages, trachea, bronchi, lungs and diaphragm. Students should be familiarized with the term alveoli which are thin pouch like air sacs where exchange of air and blood take place and haemoglobin which is a red colored pigment present in the blood and carries oxygen to all parts of the body. The topic can be made interesting by discussing the mechanism of sneezing and yawning. Students should be made aware of the ill effects of smoking.

Using resources



Paste picture of the lungs of a non-smoker person and the lungs of a person who smokes a lot.


Breathing and respiration in other organisms (Page 161)


Discuss with the students the mechanism of breathing in earthworm ( through skin) , frog ( through lungs and skin) , fish ( through gills) , dolphins and whales ( through blowholes) and insects ( through spiracles and trachea) .


How does the earthworm breathe?


Respiration in plants (Page 162)

(C)

lungs and skin) , fish ( through gills) , dolphins and whales ( through blowholes) and insects ( through

(C)

lungs and skin) , fish ( through gills) , dolphins and whales ( through blowholes) and insects ( through spiracles and trachea) .

(C) spiracles and trachea) .

(C)



How does the earthworm breathe? (C)

How does the earthworm breathe?

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like air sacs where exchange of air and blood take place and haemoglobin which is a red colored

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SCIENCE 7 TEXT BOOK

109


Explain them that the respiration in plants takes place through stomata present in the leaves and through the root hair in the roots.


Differentiate between photosynthesis and respiration.



Using resources






TEXT BOOK ANSWERS


1. Respiration 2. Oxygen and Carbon dioxide

3. ( a) True ( b) False ( c) True ( d) False ( e) True ( f) True ( g) False ( h) False ( i) True

4. arthworm 5. Frog

. Fish . Insects

8. Y east 9. Y east

1 . Anaerobic respiration 11. actic acid

12. east 13. a. Increases b. Slows down

14. (a) Rib cage (b) iaphragm 15. Exhaled air

1 . xhaled air 1 . Exhaled air

1 . (a) Inhaled air xygen 21 Carbon dioxide . 4

( b) Exhaled air xygen 1 .4 Carbon dioxide 4.4

1 . Lungs 2 . ( a) Oxygen ( b) Carbon dioxide

21. (a) xygen (b) Carbon dioxide 22. Lungs ( Alveoli)

23. aemoglobin 24. Nostrils

25. Smoking 2 . Insects

(C) (a)

(C) (a)

1 .

(C) 1 . xhaled

(C) xhaled

1 .(C)

1 . ((C)

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And TEXT BOOK ANSWERS

And TEXT BOOK ANSWERS


And


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SCIENCE 7 TEXT BOOK

110

2 . The average breathing rate in an adult human being at rest is 15 1 times per minute.

2 . Tracheae 2 . Spiracles

3 . Stomata 31. Stomata and roots

32. Plant parts

33. The roots of a plant take up air from the spaces between the soil particles.

34. It is used to make wine and beer by the process of anaerobic respiration.

35. (a) photosynthesis (b) oxygen (c) oxygen (d) alcohol (e) single (f) increases (g) diaphragm rib (h) deep (i) inhalation (j) exhalation (k) lungs (l) skin (m) gills (n) tracheae (o) blowholes (p) glucose energy


3 . The process of releasing energy from food is called respiration.

Glucose + Oxygen → Carbon dioxide + Water + Energy

Aerobic respiration takes place in the presence of oxygen. Anaerobic respiration takes place in the absence of oxygen.

3 . There are two main parts in the process of respiration (i) Breathing (taking in oxygen from air and releasing carbon dioxide) and ( ii) Using oxygen in the cells of the organism for releasing energy from food (like glucose). a. Anaerobic respiration b. Aerobic respiration

38. ( i) c ( ii) d ( iii) a ( iv) e ( v) b ( vi) f ( vii) g

39. Aerobic respiration produces much more energy because complete breakdown of glucose (food) occurs during aerobic respiration by the use of oxygen.

4 . 1. In aerobic respiration, energy is produced by the breakdown of food (like glucose). In anaerobic respiration also energy is produced by the breakdown of food (like glucose). 2. Aerobic respiration takes place in the cells of the organism. Anaerobic respiration also takes place in the cells of the organism.

41. 1. Aerobic respiration takes place in the presence of oxygen. Anaerobic respiration takes place in the absence of oxygen.

2. Complete breakdown of food occurs in aerobic respiration. Partial breakdown of food occurs in anaerobic respiration.

3. The end products in aerobic respiration are carbon dioxide and water. The end products in anaerobic respiration may be alcohol and carbon dioxide ( as in yeast) , or lactic acid ( as in muscles) .

4. Aerobic respiration produces a considerable amount of energy. Much less energy is produced in anaerobic respiration.

42. Running makes a person breathe faster because the faster breathing rate supplies more oxygen to the body cells for the speedy breakdown of food for releasing more energy required for running.

43. When the breathing rate increases, greater amount of air goes into the lungs. With more air going into the lungs, the blood can absorb oxygen at a faster rate. Thus, faster breathing

(C) 4.

(C) 4. Aerobic r

(C) Aerobic r

produced in anaerobic respiration. (C)

produced in anaerobic respiration.

42.(C)

42. Running makes a person breathe faster because the faster breathing rate supplies more (C)

Running makes a person breathe faster because the faster breathing rate supplies more

S The end products in aerobi

S The end products in aerobiin anaerobic respiration may be alcohol and carbon dioxide ( as in yeast) , or lactic acid S in anaerobic respiration may be alcohol and carbon dioxide ( as in yeast) , or lactic acid S ( as in muscles) . S ( as in muscles) .

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SCIENCE 7 TEXT BOOK

111

supplies more oxygen to the body cells for producing more energy ( by the rapid breakdown of food) needed for heavy physical exercise, etc.

44. This is because during the race, the leg muscles of athlete have produced extra energy by doing anaerobic respiration (without using oxygen). By breathing faster and deeper, the athlete is giving back oxygen to the muscles which it could not give earlier at the time of running (due to lack of oxygen at that time).

45. This is because to provide extra energy for doing heavy physical exercise, the food has broken down very rapidly ( by faster breathing) and made us feel hungry.

4 . If a potted plant is over-watered for a long time, then the plant may ultimately die. This is because too much water expels all the air from in-between the soil particles. ue to this, oxygen is not available to the roots for aerobic respiration. nder these conditions, the roots of plant respire anaerobically producing alcohol. This may kill the plant.

4 . Exhaled air. It contains higher percentage of carbon dioxide than inhaled air.

48. The air which we inhale contains a lower proportion of carbon dioxide. ow, during respiration when oxygen breaks down glucose food, then some carbon dioxide is produced. So, the exhaled air that comes out after the process of respiration contains a higher proportion of carbon dioxide. Thus, exhaled air contains more carbon dioxide than inhaled air.

49. The air which we inhale contains a higher proportion of oxygen. ow, some of the oxygen of inhaled air is used up in breaking down glucose food during respiration. So, the exhaled air which comes out after the process of respiration contains a lower proportion of oxygen. Thus, exhaled air contains less oxygen than inhaled air.

5 . The air which we inhale contains only a little of water vapour. When glucose (food) is broken down by oxygen during respiration, then water is also produced (along with carbon dioxide). So, the exhaled air contains a lot more water vapour than inhaled air.

51. This is because the exhaled air coming from our mouth contains a lot of water vapour. This water vapour condenses on the mirror surface to form tiny droplets of water (which appear as a patch of moisture) .

52. All the living organisms need to respire to get energy from food required for their survival.

53. east is a single-celled organism. It carries out anaerobic respiration.

54. The mountaineers carry oxygen cylinders with them for breathing because the amount of air available to a person for breathing at high altitude is much less than that available on the ground.

55. Sometimes, the particles of dust, smoke and pollens, etc., present in inhaled air get past the hair in the nasal passage and irritate the lining of nasal passage, as a result of which we sneeze. Sneezing expels all the unwanted particles from the inhaled air so that a dust free, clean air enters into our lungs.

5 . Some of the harmful effects of smoking are as follows (i) Smoking destroys the lung tissue gradually due to which breathing becomes very di cult. (ii) Smoking causes lung cancer. (iii) Smoking causes heart diseases. (iv) Smoking also damages the health of non-smokers who inhale the air containing tobacco smoke.

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SCIENCE 7 TEXT BOOK

112

5 . The number of times a person breathes in one minute is called breathing rate. Children breathe about 2 to 3 times per minute while the average breathing rate in an adult human being at rest is 15 1 times per minute.

5 . (a) Gills ( b) Skin ( c) Skin and lungs ( d) Trachea

5 . (a) The earthworm breathes through its skin. The skin of earthworm is quite thin and moist. Gases can easily pass through the skin of earthworm. The skin of earthworm has a good blood supply. So, the earthworm absorbs the oxygen ( of air) needed for respiration through its thin and moist skin. This oxygen is then transported to all the cells of the earthworm by its blood where it is used in respiration ( production of energy) . The carbon dioxide produced during respiration is carried back by the blood. This carbon dioxide is expelled from the body of the earthworm through its skin.

( b) Though frogs have lungs for breathing, they can also breathe through their moist skin. Thus, frog is an animal which can breathe through lungs as well as its moist skin.

(c) The fish has special organs of breathing called ‘gills’. The gills help the fish to use oxygen which is dissolved in water (in which it lives). The fish has gills on both the sides of its head. The gills are covered by gill covers so they are not visible from outside. For breathing, the fish uses the oxygen which is dissolved in water. The fish breathes by taking in water through its mouth and sending it over the gills. When water passes over the gills, the gills extract dissolved oxygen from this water. The extracted oxygen is absorbed by the blood and carried to all the parts of the fish for respiration (release of energy). The carbon dioxide produced during respiration is brought back by the blood into the gills for expelling into the surrounding water.

(d) The breathing in all the insects takes place through tiny holes (called spiracles) and thin air-tubes (called tracheae). Air (rich in oxygen) enters into the insect through spiracles by the up and down movements of its body. This air goes into the network of thin air-tubes called tracheae. From the tracheae, oxygen of air diffuses into the body tissues of insect and reaches each and every cell of its body where it is utilised in respiration (production of energy). Carbon dioxide produced during respiration in the cells diffuses into tracheae and carried to the spiracles where it is expelled in the process of breathing. Thus, in insects the exchange of gases occurs through tracheae.

. (a) The exchange of gases ( oxygen and carbon dioxide) in the leaves during respiration takes place through stomata. Oxygen from air enters into a leaf through stomata and reaches all the cells by the process of diffusion. This oxygen is used in respiration in the cells of the leaf.

The carbon dioxide produced during respiration diffuses out from the leaf into air through the same stomata.

( b) The roots of a plant take up air from the spaces between the soil particles. Actually, the roots of a plant have a very large number of tiny hair on them which are called ‘root hair’. The root hair are in contact with the air in the soil particles. xygen from air in soil particles diffuses into root hair and reaches all the cells of the root where it is utilised in respiration. Carbon dioxide produced in the cells of the root during respiration goes out through the same root hair by the process of diffusion.

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SCIENCE 7 TEXT BOOK

113


1. (a) When the breakdown of glucose food occurs with the use of oxygen, it is called aerobic respiration. Most of the living organisms carry out aerobic respiration ( by using oxygen of air) . For example, humans ( man) , dogs, etc.

Glucose → Carbon dioxide + Water + Energy

( b) Anaerobic respiration

2. (a) When the breakdown of glucose ( food) occurs without the use of oxygen, it is called anaerobic respiration. The microscopic organisms like yeast ( and certain bacteria) obtain energy by anaerobic respiration.

Glucose → Alcohol + Carbon dioxide + Energy

( b) Aerobic respiration

3. (a) The main organs of human respiratory system are ose, asal passages (Passages in the nose), Trachea, Bronchi, ungs and iaphragm. b. Refer to figure 13 for the diagram.

4. Breathing is the process by which air rich in oxygen is taken inside the body of an organism and air rich in carbon dioxide is expelled from the body ( with the help of breathing organs) . The process of breathing takes place in our lungs. Lungs are connected to our nostrils ( holes in the nose) through nasal passage ( or nasal cavity) and windpipe. When we inhale air, it enters our nostrils, passes through nasal passage and windpipe, and reaches our lungs.

ur two lungs hang in an airtight space in our body called ‘chest cavity’. Around the sides of the chest cavity is the rib cage with sheets of muscles between the ribs. The rib cage encloses the lungs in it. At the bottom of the chest cavity is a curved sheet of muscle called diaphragm. iaphragm forms the floor of chest cavity. Breathing involves the movements of the rib cage and the diaphragm.

( a) Breathing in: When we breathe in ( or inhale) , then two things happen at the same time : ( i) the muscles between the ribs contract causing the rib cage to move upward and outward, and ( ii) the diaphragm contracts and moves downward [ see Figure 8( a) ] . The upward and outward movement of rib cage, as well as the downward movement of diaphragm, both increase the space in the chest cavity and make it larger. As the chest cavity becomes larger, air is sucked in from outside into the lungs. The lungs get filled up with air and expand. ( b) Breathing out: When we breathe out ( or exhale) , even then two things happen at the same time: ( i) the muscles between the ribs relax causing the rib cage to move downward and inward, and ( ii) the diaphragm relaxes and moves upward. The downward and inward movement of rib cage, as well as the upward movement of diaphragm, both decrease the space in our chest cavity and make it smaller. As the chest cavity becomes smaller, air is pushed out from the lungs.

5. (a) Y awning is caused by insufficient oxygen in the bod y. A person yawns when he is tired, bored, stressed, over-worked, feeling sleepy or drowsy.

( b) When we are tired, bored, stressed, overworked, feel sleepy or drowsy, we do not breathe as deeply as we normally do and hence our breathing rate slows down. Due to slower breathing rate, less oxygen ( of air) goes into our body which is insufficient

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SCIENCE 7 TEXT BOOK

114

for respiration ( production of energy) . Y awning helps in bringing more oxygen into our blood because during yawning our mouth opens wide and we take a long and deep breath of air.


. (b) . (b) . (a) . (b) . (c)

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5. (c)


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SCIENCE 7 TEXT BOOK

115

WORKSHEET

A. Objective Type Questions 1. Name the following: ( a) Tiny holes in the body of the insects through which they breathe. ( b) Special breathing organs of the fish. ( c) Red colored pigment present in blood which carries blood to all parts of the body. ( d) Taking in air that is rich in oxygen during the process of breathing. 2. Fill in the blanks: ( a) The end products of aerobic respiration are .… … … … … ............ and .… … … … … ............ . ( b) The process of respiration is the opposite of .… … … … … ............ . ( c) The roots of a plant take up air through .… … … … … ............ . ( d) Earthworm breathes through its .… … … … … ............ . 3. Write true or false: ( a) We sneeze when we inhale clean air. (b) Smoking is injurious for our health. ( c) The exchange of gases between air and blood in the human respiratory system takes

place in the alveoli. ( d) Lime water test can show that oxygen gas is produced during respiration. 4. entiononefunctionofthefollowingduringrespirationinorganisms: (a) Gills (b) Blowholes (c) iaphragm (d) Ribs

B. Subjective Type Questions 5. Answerthefollowingquestionsinshort: ( a) List the similarities between aerobic respiration and anaerobic respiration. ( b) How will we get relief from muscle cramps caused by heavy exercise? ( c) Differentiate between breathing and respiration. ( d) Write an activity to show that carbon dioxide gas is produced during the process of

respiration.

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SCIENCE 7 TEXT BOOK

116

SAMPLE PAPER

M.M. 5

Name: ............................................................... Class: ......................... Date: ...........................



( a) Muscular floor of the chest cavity in human beings.

( b) Main breathing organs of the human body where exchange of gases take place.

( c) The single celled organism which is used to make wine and beer by the process of anaerobic respiration.

( d) The skeletal structure surrounding the chest cavity in man.

( e) The air tubes in insects.


( a) Dolphins and whales breathe through gills.

( b) Running makes a man breathe faster.

( c) Respiration is similar to photosynthesis.

( d) Frog can breathe through lungs as well as moist skin.

( e) Oesophagus is a part of human respiratory system.

. entionthenameoftheorganismwherethefollowingorgansarepresent:

( a) Trachea ( b) Rib cage ( c) Root hair ( d) Gills 4. Correct the following statements:

( a) Y awning is caused when we inhale air containing dust, smoke or pollen.

( b) The alveoli are surrounded by very thin blood vessels called trachea.

( c) The exchange of gases between the air and blood takes place in the nasal passage.

(d) The exhaled air that we breathe out during respiration consists of 1 .4 carbon dioxide gas.

( e) As the chest cavity becomes smaller, air is sucked from outside into our lungs.



( a) Differentiate between inhalation and exhalation.

( b) Describe the movements of rib cage and diaphragm when we breathe during respiration.

( c) Why do we get muscle cramps after heavy physical exercise?

( d) Define cellular respiration. What is its importance?

(C) ( e)

(C) ( e)



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5. Answer

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SCIENCE 7 TEXT BOOK

117

( e) How is yeast used to form wine, beer and bread?


( a) Why do we sneeze?

(b) ow is smoking injurious for our health

( c) Mention the organs of human respiratory system. Draw a labeled diagram to show the same.

( d) Distinguish between aerobic respiration and anaerobic respiration.

( e) What is breathing rate? Which factors are responsible for the increase and decrease of breathing rate?


1. Y east converts glucose into:

( a) Starch ( b) Alcohol ( c) Lactic acid ( d) Y oghurt 2. uringrespirationinhumans thee changeofgasesta esplacein:

( a) Bronchi ( b) Alveoli ( c) Bronchioles ( d) Trachea . Whenairis lownfrommouthintoatest tu econtaininglimewater thelimewater

turns milky d ue to the presence of:

( a) Oxygen ( b) Carbon dioxide ( c) Nitrogen ( d) Hydrogen 4. The animal which can breathe through the lungs as well as through skin is:

( a) Fish ( b) Dolphin ( c) Frog ( d) Crocodile 5. ncoc roaches airentersthe od through:

( a) Lungs ( b) Spiracles ( c) Gills ( d) Skin

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SCIENCE 7 TEXT BOOK

118

11

Lesson Plan



• The circulatory system in human beings.

• About the blood, blood vessels and capillaries.

• Working of the heart and circulatory system.

• About the heartbeats and pulse.

• About the excretory system in human beings.

• The transport system in plants and mechanism of transpiration.



VOCABULARY

Blood, plasma, red blood cells, white blood cells, platelets, atrium, ventricles, arteries, veins, capillaries, pulmonary artery, pulmonary vein, heartbeat, stethoscope, pulse, pulse rate, excretion, nephrons, dialysis, sweat, tissue, vascular tissue, xylem, phloem, transpiration, stomata, root hair.


Transport in humans: Circulatory system (Page 169)

Learning Tools

Interactive warm up exercise: Discussing with the students the meaning of transport and its importance in the body of living organisms would be a good topic to start the chapter.

Chapter opening exercise: Students should be asked why it is important that oxygen gets transported to all cells of the body and the waste materials should be removed from the body.

Transport in Animals and PlantsTransport in Animals and Plants

(C)

(C)

(C) Transport in humans: Circulatory system (Page 169)

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SCIENCE 7 TEXT BOOK

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Discuss with them that the blood circulatory system makes food, water and oxygen available to every part of the body, and helps in removing waste materials from the body.


What does the human circulatory system consist of?


Blood (Page 170)


Discuss with them that the blood is a red colored liquid which flows in the blood vessels in our body. Students should know the components of blood and their importance. Students should realize the importance of blood in our body. They should be able to differentiate between oxygenated blood and deoxygenated blood.


List the functions of blood in our body.


Heart (Page 171)


Explain them that the heart is an organ which pumps blood to all parts of the body through blood vessels. Students should be familiarized with the four chambers of the heart and they should be able to define atria and ventricles. Students should be able to explain why heart is called a double pump.

Using resources

• se a chart showing the inside structure of human heart to explain its parts and the circulation of blood in the heart.



Draw a neat and labeled diagram of the heart showing the movement of blood inside it with the help of arrows.

(C) chapter on the Study Gear app.

(C) chapter on the Study Gear app.



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SCIENCE 7 TEXT BOOK

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Blood vessels (Page 172)


Discuss with the students that the blood vessels are a kind of tubes which carry blood throughout our body. Students should know the name of the three types of blood capillaries and the functions carried out by them. They should know arteries have thick and elastic walls, veins have valves to prevent backflow of blood and capillaries carry out the exchange of substances between the blood and body cells take place through capillaries.

Using resources



List the three types of blood vessels. Write an important function of each.


Working of circulatory system (Page 173)


Explain the detailed working of the circulatory system and make the students aware that it was discovered by an English scientist William Harvey.


Draw the chart to show the circulatory system ( Fig. 5) .


Heartbeats and pulse (Page 175)


Explain them that one complete contraction and relaxation of the heart is called heartbeat. Students should know the average heartbeat of an adult person. They should know the function of stethoscope to listen to heartbeat. Discuss that the expansion of an artery each time the blood is forced into it, is called pulse. Students should know the pulse rate of an adult person.


What is the average heartbeat and the average pulse rate of an adult person at rest?

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SCIENCE 7 TEXT BOOK

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Excretion in animals (Page 177)


Explain to the students that the removal of waste materials produced in the cells of the living organisms is called excretion. Students should know the various waste materials produced in the cells of the body. Students should be able to describe the human excretory system and its organs. They should be aware of the treatment given to the person having kidney failure. Maj or excretory products of other organisms should also be known by students.


List the organs of excretory system of human beings. Mention the maj or excretory product in human beings, bird and fish.


Transport in plants (Page 179)


Explain to the students that the plants need a transport system to carry water and to carry food to all parts of the plant. Students should be able to give the functions of xylem and phloem which are vascular tissues present in the plant. They should know how water reaches from the soil to xylem vessels in roots. The role and importance of transpiration should also be discussed.

Using resources

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TEXT BOOK ANSWERS


1. Platelets help in the clo ng of blood in a cut or wound.

2. Plasma 3. White blood cells

4. (a) Red blood cells (b) aemoglobin 5. Haemoglobin

6. Red blood cells carry oxygen from the lungs to all the cells of the body.

7. Platelets help in the clo ng of blood in a cut or wound.

. Plasma carries water and dissolved substances such as digested food and waste products from one part to another part in the body.

9. Haemoglobin binds with oxygen and transports it to all the parts of the body and ultimately to all the cells.

1 . (a) xygen (b) Carbon dioxide 11. (a) Red Blood Cells (b) White Blood Cells

12. Heart

13. The greenish-blue lines which we see j ust below the skin on our hands and legs are the veins.

14. Arteries 15. Capillaries

1 . (a) Arteries (b) Veins 1 . (a) Right side (b) eft side

1 . (a) Right side (b) eft side 1 . Lungs

2 . 5 21. Artery

22. Sponges and ydra 23. Kidneys

24. (a) Carbon dioxide (b) rea 25. ( a) Lungs ( b) Kidneys

26. The function of kidneys is to filter the blood to remove urea.

27. rine is a yellowish liquid which consists of 2.5 urea, 2.5 other waste salts and 5 water.

2 . Dialysis 29. (a) ylem (b) Phloem

3 . ( a) red ( b) capillaries ( c) heart ( d) four ( e) William Harvey ( f) heartbeat ( g) urea ( h) ureters (i) urethra (j) nephrons (k) cells (l) root hair (m) xylem (n) xylem (o) phloem (p) transpiration


31. All the living organisms ( animals and plants) need a transport system to supply them with food, water and oxygen, and to carry away the harmful waste materials produced in their bodies.

32. Blood is a red coloured liquid which flows in blood vessels and circulates in our body.

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SCIENCE 7 TEXT BOOK

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Blood is red because it contains a red pigment called haemoglobin. Blood consists of four components: plasma, red blood cells, white blood cells and platelets.

33. Blood is needed by all the parts of our body because it performs the following important functions in our body

1. Blood carries digested food from the small intestine to all the parts of the body.

2. Blood carries water to all the parts of the body.

3. Blood carries oxygen from the lungs to different parts of the body.

4. Blood carries the waste product carbon dioxide from the body cells to the lungs for breathing out.

5. Blood carries a waste product called urea from the liver to the kidneys for excretion in urine.

6. Blood protects the body from diseases. This is because white blood cells kill the bacteria and other germs which cause diseases.

34. If there were no platelets in the blood, then bleeding caused by a cut from an inj ury would not stop. This may cause loss of too much blood from the body of a person leading to death.

35. Blood performs the following important functions in our body

1. Blood carries digested food from the small intestine to all the parts of the body.

2. Blood carries water to all the parts of the body.

3. Blood carries oxygen from the lungs to different parts of the body.

4. Blood carries the waste product, carbon dioxide from the body cells to the lungs for breathing out.

5. Blood carries a waste product called urea from the liver to the kidneys for excretion in urine.

6. Blood protects the body from diseases. This is because white blood cells kill the bacteria and other germs which cause diseases.

3 . The heart is an organ which pumps blood to all the parts of our body through a network of tubes called blood vessels. ur heart ‘beats’ continuously to circulate blood in the body.

3 . Four chambers ( a) Atria ( b) V entricles

3 . There are three types of blood vessels in the body: arteries, veins and capillaries.

3 . ( i) Arteries are the blood vessels which carry blood from the heart to all the parts of the body. ( ii) V eins are the blood vessels which carry blood from all the parts of the body back to the heart. (iii) Capillaries are the extremely thin blood vessels which connect arteries to veins

4 . Blood carries food and oxygen to all parts of the body.

41. ne complete contraction and relaxation of the heart is called a heartbeat. A doctor listens to our heartbeats with the help of an instrument called stethoscope.

42. The average heartbeat of an adult person while resting is 2 to per minute. The number of heartbeats increase too much during and after a physical exercise or when a person is excited. The faster beating of heart pumps blood more rapidly to the body organs which supplies more oxygen to the body cells for rapid respiration to produce more energy.

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SCIENCE 7 TEXT BOOK

124

43. A doctor listens to our heartbeats with the help of an instrument called stethoscope. A stethoscope consists of three parts (i) a chest piece (which carries a sensitive diaphragm at its bottom). The diaphragm amplifies the sounds of heartbeats. (ii) two ear pieces (which are made of two metal tubes) . These are put by the doctor into his ears. ( iii) a rubber tube which j oins the chest piece to the ear pieces. The rubber tube transmits the sound from the chest piece into the ear pieces.

44. The expansion of an artery each time the blood is forced into it is called pulse. The pulse is traditionally taken above the wrist. The pulse rate of an adult person while resting is 2 to per minute.

45. We can feel our own pulse and find the pulse rate as follows The pulse can be felt with fingers placed gently on arteries at the wrist. We place the first two fingers (index finger and middle finger) of our right hand on the inner side of our left wrist and press it gently. We will feel some waves touching our fingers. These waves are the pulse. A small baby has higher pulse rate.

46. ydra, fish, sponges, amoeba, paramecium

47. In sponges and Hydra, the water ( in which they live) brings food and oxygen as it enters their bodies. The water also carries away carbon dioxide and other waste materials as it moves out of their bodies.

4 . ( i) b ( ii) d ( iii) a ( iv) c

49. The procedure used for cleaning the blood of a person by separating the waste product urea from it is called dialysis. A person having kidney failure cannot survive unless his blood is filtered periodically through kidney machine to remove urea (by a procedure called dialysis).

5 . Sometimes a person’s kidneys may stop working due to infection or injury. When the kidneys do not work properly, they are not able to remove the waste product urea from the blood. Complete failure of kidneys leads to the accumulation of too much urea in the blood of a person. rea is a toxic substance (or poisonous substance), so the accumulation of too much urea in the blood of a person can ultimately kill the person.

51. A person having kidney failure can survive if his blood is filtered periodically through kidney machine to remove urea ( by a procedure called dialysis) .

52. Sweat contains water, some salts and a little of urea. Sweating performs two functions (i) Sweating helps to remove excess water, some salts and a little of urea as liquid waste from the body, and (ii) Sweating helps to keep our body cool during hot summer days.

53. Sometimes in summer days, we see that white patches are formed on our clothes especially in areas like underarms. These white patches are formed by the the salts left on the clothes when the water present in sweat evaporates.

54. (a) The fish excretes cell waste in gaseous form ( ammonia) which directly dissolves in water.

( b) The land animals such as birds, lizards, snakes and insects excrete a white coloured waste called uric acid in semi-solid form.

55. (a) A tissue is a group of similar cells which work together to perform a particular function.

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SCIENCE 7 TEXT BOOK

125

( b) Those tissues which transport water, minerals and food to different parts of a plant, are called vascular tissues. There are two types of vascular tissues in a plant: xylem and phloem.

56. There are two types of vascular tissues in a plant xylem and phloem.

( i) The tissue which carries water and minerals from the roots to the leaves of a plant is called xylem.

( ii) The tissue which carries food from the leaves to other parts of the plant is called phloem.

57. Transpiration Water moves from the roots only upwards but food moves from the leaves upwards as well as downwards.

5 . The process of transpiration (evaporation of water from leaves) serves a very useful function in the plants because it generates a ‘suction force’ in xylem which can pull water from the roots up to great height in the tall trees. Another function of transpiration is that it cools the plant in hot weather.

59. Stomata are the tiny pores found on the surface of leaves of plants. The opening and closing of the stomata controls the passage of gases and water vapour into and out of the leaf. For example (i) Carbon dioxide gas ‘enters in’ and oxygen gas ‘goes out’ through stomata during photosynthesis. (ii) Water vapour ‘passes out’ through stomata during transpiration.

. ( a) The tissue which carries water and minerals from the roots to the leaves of a plant is called xylem.

( b) The tissue which carries food from the leaves to other parts of the plant is called phloem.


1. The blood circulatory system makes food, water and oxygen available to every part of the body, and helps in removing waste materials of the body like carbon dioxide, etc. The human circulatory system consists of the heart, blood vessels ( arteries, veins, capillaries) and blood. Refer to figure 5 for the diagram.

62. The removal of waste materials produced in the cells of the living organisms is called excretion. The various waste materials produced in the cells of the human body are Carbon dioxide, urea and sweat. When our body uses food, water and air, it produces some unwanted substances called waste materials ( or j ust ‘ wastes’) . These waste materials are toxic ( or poisonous) and hence they are harmful for our body. The waste materials must be removed from the body so that a person may stay healthy.

3. The excretory system of human beings consists of the following organs: two kidneys, two ureters, a bladder and a urethra. Refer to figure 11 for the diagram.

64. Plants need a transport system (i) to carry water (and dissolved minerals) absorbed by the roots up to the leaves, and ( ii) to carry the food made in the leaves to all the parts of the plant ( including roots) . In order to carry water and dissolved minerals, as well as prepared food, a plant has a transport system inside it. The transport system in plants consists of long tubes ( or vessels) called xylem and phloem.

(C)

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SCIENCE 7 TEXT BOOK

126

65. The xylem vessel of a root is in the centre of the root and it is surrounded by a large number of other cells of the root. This means that the xylem vessel of a root is not in direct contact with the water present in the soil particles. For very short distances, water can move from cell to cell. So, the water present in soil and absorbed by root hair first moves from cell to cell in the outer part of a root till it reaches the xylem vessel in the centre of the root. Water from the soil enters the root through root hair. The large number of fine root hair increase the surface area of the root in contact with the soil water due to which more water can be absorbed by the root at a rapid rate. Thus, we conclude that water ( containing dissolved minerals) from the soil enters a plant through its root hair. From root hair, water moves from cell to cell in the root till it reaches xylem vessel in the centre of the root. From the xylem vessel in root, water moves upward to the xylem vessels in stem, branches and leaves.


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SCIENCE 7 TEXT BOOK

127

WORKSHEET



( a) The part of root which increases its surface area in contact with the soil water due to which more water can be absorbed by the root at a rapid rate.

(b) Process which pulls up water absorbed by the roots from the soil through a suction force.

( c) Tiny pores found on the surface of leaves of plants through which exchange of gases take place.

( d) The procedure used for cleaning the blood of a person by separating the waste product urea from it.


( a) The urine collected in the bladder is passed out from the body through the .… … … … … .................. .

( b) .… … … … … .................. is removed from the body by sweat glands through the skin.

( c) .… … … … … .................. is a waste product formed in the cells during respiration.

( d) The pulse rate of an adult person at rest is .… … … … … .................. per minute.

( e) In the .… … … … … .................., deoxygenated blood absorbs fresh oxygen to become oxygenated again.


( a) A doctor listens to our heartbeats with the help of stethoscope.

( b) Arteries carry deoxygenated blood to all organs of the body.

(c) Pulmonary artery carries oxygenated blood from heart to the lungs.

( d) V eins have valves to prevent backflow of blood.


(a) ephrons (b) Alveoli (c) Pulmonary vein (d) White Blood Cells



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( b) What is the function of plasma of blood?

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SCIENCE 7 TEXT BOOK

128

SAMPLE PAPER

M.M. 5

ame ............................................................... Class ......................... ate ...........................



( a) An organ which pumps blood to all parts of the body.

(b) Red colored liquid which flows in the blood vessels and circulates in our body.

( c) Thousands of tiny filters present in the kidney.

(d) Component of blood that helps in the clotting of blood in a cut or wound.

( e) The blood vessel which carries oxygenated blood from lungs into the left atrium.


(a) Capillaries are extremely thin blood vessels which connect arteries to veins.

( b) When the right ventricle of the heart contracts, it pumps oxygenated blood into the lungs.

( c) One complete contraction and relaxation of the heart is called a heartbeat.

( d) The heart in human beings is a single pump.

(e) rea is removed from the blood by the kidneys.

. iveonefunctionof:

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(a) ric acid is the major waste product in human beings.

( b) X ylem carries food from the leaves to all other parts of the plant.

( c) Every person has one kidney.

(d) Pulse rate of an adult person while resting is 15-1 per minute.

(e) Presence of plasma makes the blood red in color.


5 . Answerthefollowingquestionsinshort:

( a) Differentiate between the functions of red blood cells and white blood cells.

( b) List the composition and functions of sweat.

( c) What do you understand by pulse? How is the pulse rate traditionally taken?

( d) Explain the circulatory system in sponges and Hydra.

( e) Distinguish between the cell and tissue.

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SCIENCE 7 TEXT BOOK

129

6 . Answerthefollowingquestionsindetail:

( a) Explain the role of vascular tissues in transport in plants.

( b) How is a patient of kidney failure treated?

( c) Write the composition of urine in human beings. What is the amount of urine passed by an adult human in a day?

( d) Explain the working of the human circulatory system.

(e) ame the major organs of human excretory system and draw a neat diagram to show the same.


1. Whatpreventsthe ac flowof loodinsidetheheartduringcontraction?

( a) Thick muscular walls of ventricles ( b) V alves

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SCIENCE 7 TEXT BOOK

130

12

Lesson Plan



• The different methods of reproduction in plants.

• About asexual reproduction in plants.

• The means of vegetative propagation in plants.

• About sexual reproduction in plants.

• The process of pollination and fertilization.

• Formation of fruits and dispersal of seeds.



VOCABULARY

Reproduction, asexual reproduction, sexual reproduction, gametes, vegetative propagation, node, axil, bud, budding


Methods of reproduction in plants (Page 186)

Learning Tools

Interactive warm up exercise: Discussing the characteristics of living organisms would be a good topic to start the chapter. One of most important characteristics of living organisms is that they can produce new offspring.

Chapter opening exercise: Students should be asked why gardeners use the stem cuttings of rose plant to create new plants of rose. Similarly, ask students why the farmers sow seeds to grow new plants.

Reproduction in PlantsReproduction in Plants

(C) Methods of reproduction in plants (Page 186)

(C) Methods of reproduction in plants (Page 186)

Learning Tools (C) Learning Tools (C)


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SCIENCE 7 TEXT BOOK

131


Discuss with the students that there are two types of reproduction occur in plants- asexual reproduction and sexual reproduction. Students should know that gametes are the special cells involved in sexual reproduction and not involved in asexual reproduction. Students should be able to differentiate between asexual reproduction and sexual reproduction in plants on the basis of the formation of seeds.


Define asexual reproduction and sexual reproduction in plants.


Asexual reproduction in plants (Page 187)


Discuss with the students the various methods by which asexual reproduction in plants can take place- V egetative propagation, budding, fragmentation and spore formation. Students should know the meaning of the plant parts- axil, node and bud.


Define the terms: node, axil and bud


Vegetative propagation (Page 188)


Explain them that the vegetative parts of the plant refer to the stem, roots and leaves. Students should be able to cite examples of plants which reproduce by this method and state their plant parts.


Give the name of the plant part through which vegetative propagation takes place in the given plants: Money plant, Bryophyllum and Dahlia.


Budding (Page 191)


Discuss that in budding, a small part of the body of the parent plant grows out as a bulb like proj ection called the bud, which then detaches and becomes a new plant. Students should be able to cite the example of yeast which reproduces by this method.

(C)

(C)

(C)

Budding (Page 191) (C)

Budding (Page 191)

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SCIENCE 7 TEXT BOOK

132

Using resources

• Conduct the activity given on Page no. 1 1 to study the process of asexual reproduction in yeast by budding.



Draw a neat diagram to show how yeast reproduces by the method of budding.


Fragmentation and spore formation (Page 192)


Explain them that the breaking up of the body of a plant into two or more pieces on maturing, each of which subsequently grows to form a new plant, is called fragmentation. Students should be able to explain this by citing the example of Spirogyra which is a filamentous alga plant. Discuss that spores are asexual reproductive bodies and those plants which reproduce by spore formation are Rhizopus fungus, ferns and mosses.


Show the method of fragmentation in Spirogyra and formation of spores in common bread mould with the help of a neat diagram.


Sexual reproduction in plants (Page 193)


Explain to the students that most of the flowering plants reproduce by sexual reproduction method involving the fusion of sex cells called gametes. Students should know that after the fusion of gametes, fertilization takes place for the production of seeds. Seeds grow into new plants.


Define gametes


Structure of flower (Page 194)


Explain them that the reproductive part of the plant is the flower. Students should know the male and female parts of the flower.

(C)

(C) Define gametes

(C) Define gametes

Structure of flower (Page 194) (C

) Structure of flower (Page 194)

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SCIENCE 7 TEXT BOOK

133

Using resources

Dissect a flower and show the male and female parts of the flower to the students.


Draw a neat and well labeled diagram of the structure of flower showing its male and female parts.


Pollination (Page 195)


Explain that the transfer of pollen grains from the anther of the stamen to the stigma of the pistil is called pollination. It is of two types Self pollination is pollination in the same flower and Cross pollination is pollination from one flower to another flower. Students should be aware of the pollinating agents: wind, water and insects. They should be able to cite examples of plants where these agents are used.


Name the agent of pollination in: J asmine, Maize and Hydrilla.


Fertilisation (Page 196)


Explain that the process in which the male gamete present in pollen grain fuses with female gamete present in ovule to form a new cell called zygote is called fertilisation. Students should be familiarized of the process in detail.

Using resources



How does fertilisation in a flower take place?


Formation of fruits and seeds (Page 197)


Explain that after fertilisation, the ovule present in the ovary grows to form a seed and the ovary becomes a fruit.

(C)


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(C) How does fertilisation in a flower take place? S on the Study Gear app.


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SCIENCE 7 TEXT BOOK

134

Using resources



Give the fate of the following parts of flower after fertilisation Petals, sepals, ovary, ovules.


Dispersal of fruits and seeds (Page 197)


Explain them that dispersal of seeds means to scatter seeds over a wide area. Students should be able to list its importance to the plants. They should know that various types of seeds and fruits can be dispersed by wind, water, animals and by explosive mechanism. Students should be able to cite examples of plants whose seeds and fruits are dispersed by these agents.


How are the seeds of the following plants dispersed: Drumstick plant, Water lily plant, X anthium and Castor.



Using resources






TEXT BOOK ANSWERS


1. Rose 2. Potato

3. Sweet potato and Dahlia 4. Bryophyllum

5. Ferns 6. Y east

7. Stem cu ng method . Budding

(C)

A. Very Short Answer Type Questions (C)


S Assessment of understanding of the chapter could be done with the help of the given worksheet

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SCIENCE 7 TEXT BOOK

135

. Fragmentation 1 . Spore formation

11. (a) Sexual reproduction (b) Asexual reproduction

12. (a) Sexual reproduction (b) Asexual reproduction

13. Wheat, gram 14. Rose, potato

15. (a) east (b) Bread mould 1 . Water lily

1 . anthium 1 . Flower

1 . a. Stamen b. Pistil 2 . rumstick, Maple

21. Madar, sunflower 22. Grasses, orchids

23. i. Anther (stamen) ii. vary (pistil) 24. Pollen grains

25. (a) Pollen grains contain the male gametes (or male sex cells) of the plant.

( b) Ovules contain the female gametes ( or female sex cells) of the plant.

26. (a) Pollination (b) Fertilisation

27. ygote 2 . Ovary

2 . ( a) False ( b) True

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31. (a) Pollination is done by insects, wind and water.

( b) The main agents for the dispersal of seeds and fruits are wind, water and animals.

32. The transfer of pollen grains from the anther of a stamen to the stigma of a pistil is called pollination. Pollination can occur in two ways self-pollination and cross-pollination.

33. ( i) c ( ii) e ( iii) b ( iv) a ( v) d

34. (a) The flowers which contain only one reproductive organ ( either male or female) are called unisexual flowers. The flowers which contain both the reproductive organs ( male as well as female) are called bisexual flowers.

( b) The plants such as papaya, watermelon, corn, and cucumber have unisexual flowers.

( c) The plants such as rose, mustard, Hibiscus and petunia have bisexual flowers.

35. The seed contains embryo ( baby plant) and food for developing new plant. The two plants whose seeds are dispersed by an explosive mechanism involving the sudden bursting of their ripe fruits are Castor and Balsam.

36. The stems, roots and leaves are called vegetative parts of a plant.

37. The breaking up of the body of a plant into two ( or more) pieces on maturing, each of which subsequently grows to form a new plant, is called fragmentation. Spirogyra reproduces by the asexual method of reproduction called fragmentation.

3 . The leaves of Bryophyllum plant develop some buds in its margins ( or edges) . When a mature leaf of the Bryophyllum plant falls on the ground, then each bud can grow into a new plant. Sometimes, even before a leaf drops off from a Bryophyllum plant, we can see

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SCIENCE 7 TEXT BOOK

136

new plantlets already growing on it.

3 . Each potato plant produces more than one tuber, and each tuber has more than one bud ( which produces more than one new plant) .

4 . The reproduction of plants by the methods of vegetative propagation has the following advantages :

( i) The new plants produced by vegetative propagation take much less time to grow and bear flowers and fruits as compared to the plants grown from seeds.

( ii) The new plants produced by vegetative propagation are exactly like the parent plant ( because they are produced from a single parent) . So, all the desirable features of the parent plant will be replicated in the new plants. On the other hand, the plants produced from seeds ( made by sexual reproduction) have features of both the parents ( male and female) .

41. They reproduce asexually with the formation of spores.

42. They are the male and female organs of reproduction respectively.

43. When the pollen grains from the anther of a flower are transferred to the stigma of the same flower (or another flower on the same plant), it is called self-pollination. When the pollen grains from the anther of a flower on one plant are transferred to the stigma of a flower on another similar plant, it is called cross-pollination.

44. Pollination is done by insects such as bees and butterflies. The insects carry pollen from flower to flower and help in pollination. This happens as follows Certain flowers have a nectary near their base which contains a sugary liquid called nectar. When an insect sits on the flower of a plant for sucking nectar, then the pollen grains from the anther of this flower stick to its body. And when this insect now sits on another flower to suck nectar, then the pollen grains sticking to its body are transferred to the stigma of this second flower. In this way, the insects transfer pollen grains from flower to flower and carry out pollination.

45. When a pollen grain falls on the stigma of the pistil, the pollen grain grows a pollen tube downwards through the style towards the female gamete in the ovary. A male gamete moves down the pollen tube. The pollen tube enters the ovule in the ovary.

46. The process in which the male gamete present in pollen grain fuses ( j oins) with the female gamete present in ovule to form a new cell called zygote is called fertilisation. When a pollen grain falls on the stigma of the pistil, the pollen grain grows a pollen tube downwards through the style towards the female gamete in the ovary. A male gamete moves down the pollen tube. The pollen tube enters the ovule in the ovary. The tip of pollen tube bursts open and male gamete comes out of pollen tube. In ovary, the male gamete of pollen combines ( or fuses) with the female gamete present in ovule to form a ‘fertilised egg cell’ called ‘zygote’ (Actually, the male gamete fuses with the nucleus of the ‘female gamete’ or ‘egg cell’ to form zygote) . Z ygote develops into an embryo. Embryo is that part of a seed which develops into a new plant. An embryo is a kind of baby plant in dormant state (inactive state).

47. The production of new plants from existing plants by the fusion of their gametes (or sex cells) is called sexual reproduction. It is called sexual reproduction because sex cells (called gametes) are involved in this method for producing new plants. In sexual reproduction in

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SCIENCE 7 TEXT BOOK

137

plants, the fusion of male and female gametes leads to the formation of seeds. The seeds can then germinate to form plants. So, in sexual reproduction, new plants are obtained from existing plants through seeds.

4 . The seeds and fruits dispersed by wind either have wing like structures or they have hair or they are very small and light, which helps them to be easily carried away by the blowing wind. Some of the plants whose seeds or fruits are dispersed by wind are rumstick, Maple, Madar (Aak), Sunflower, Cotton.

4 . (a) by wind ( b) by animals ( c) by explosive mechanism ( d) by wind

5 . If all the seeds produced by a plant which fall directly underneath the plant germinate and grow there, then a large number of new plants would grow up close together in a small area of soil. The large number of new plants growing close together will compete with one another for water and minerals ( from the soil) , and sunlight, leading to shortage of water, minerals and sunlight. ue to insu cient water, minerals and sunlight, the newly growing plants will not be healthy and many plants would die. This will harm the plants in the long run because their further spreading will be prevented.

51. The seeds and fruits of some of the plants are dispersed by water. The seeds and fruits which are dispersed by water develop ‘floating ability’ in the form of ‘spongy’ or ‘fibrous’ outer coats. The seeds of water lily plant and coconut plant are dispersed by water.

52. (a) Wings Maple (b) air Sunflower

(c) Fibrous coat Coconut (d) ooks rena

(e) Property of bursting Balsam

53. The coconut fruits have a fibrous outer coat which enables them to float in water and carried away by flowing water to far off places. Coconut fruits floating in sea-water are carried hundreds of kilometres away by the sea currents to other parts of land. It is due to the dispersal of coconut fruits by sea-water that coconut trees grow in all the coastal areas ( sea-shore areas) .

54. Some fruits develop hooks on their surface by which they get attached to the hairy bodies of the passing animals and carried away to distant places. These fruits may be carried several kilometres by the moving animals before they are rubbed off from their body and fall to the ground. When the fruits are dispersed by an animal, the seeds present in them are automatically dispersed. The fruits of anthium and rena plants are covered with numerous hooks due to which they are dispersed by animals.

55. (a) By wind ( b) By wind ( c) By animals ( d) By explosive mechanism


56. The function of a flower is to make male and female gametes, and to ensure that fertilisation will take place to make seeds for growing new plants. In other words, flowers perform the function of reproduction in plants by producing seeds of the plant. refer to figure 12 for the diagram. The insect pollinated flowers have large, bright coloured, and scented petals as well as nectar to attract insects for pollination. They have large pollen grains which can stick to the body of insects. The insect pollinated flowers have anthers and stigmas inside the flower so that the insect can brush against them when it is drinking nectar.

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(C) C. Long Answer Type Questions

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SCIENCE 7 TEXT BOOK

138

57. (a) The production of new organisms from the existing organisms of the same species is called reproduction. There are two types of methods of reproduction ( or modes of reproduction) in plants: ( i) Asexual reproduction, and ( ii) Sexual reproduction. b. In vegetative propagation, new plants are produced from the parts of old plants (like stems, roots or leaves) . Some of the plants which are usually reproduced by the method of vegetative propagation are rose, champa (Magnolia), potato.

5 . (a) The production of new plants from existing plants without the involvement of gametes (or sex cells) is called asexual reproduction. Some of the plants which can be produced by asexual reproduction methods (without seeds) are rose, potato, ginger. b. The production of new plants from existing plants by the fusion of their gametes (or sex cells) is called sexual reproduction. Some of the plants which are produced by sexual reproduction method (from seeds) are wheat, gram (chana), maize.

5 . (a) The basic difference between asexual reproduction and sexual reproduction in plants is that (i) In asexual reproduction, new plants are produced without seeds. (ii) In sexual reproduction, new plants are produced from seeds. The asexual reproduction in plants can take place by the following methods:

( i) V egetative propagation, ( ii) Budding,

( iii) Fragmentation, and ( iv) Spore formation.

( b) Rose plants are propagated ( or reproduced) by means of cuttings from stems ( or branches) as follows: A piece of branch with a node ( where a leaf is attached) is cut from an existing rose plant with the help of a knife. This piece of branch is the rose ‘cutting’. It has a bud in the axil (near the node). The lower part of the cutting is buried in moist soil. The upper part of cutting having the node ( or bud) is kept above the ground. Water the planted cutting everyday. After a few days, the end of cutting buried in the soil develops roots. The bud develops into a shoot ( branch with leaves) . In this way, the branch cutting of a rose plant grows to become a new rose plant.

. (a) ‘ ispersal of seeds’ means ‘to scatter seeds over a wide area’. Seed dispersal is beneficial to the plants because it provides the following advantages to the plants:

( i) Seed dispersal prevents the overcrowding of plants in an area.

( ii) Seed dispersal prevents the competition for water, minerals and sunlight among the same kind of plants.

( iii) Seed dispersal helps the plants to grow in new places ( or new habitats) for wider distribution.

(b) 1. ispersal of Seeds and Fruits by Wind The seeds and fruits dispersed by wind either have wing like structures or they have hair or they are very small and light, which helps them to be easily carried away by the blowing wind. 2. Dispersal of Seeds and Fruits by Water: The seeds and fruits of some of the plants are dispersed by water. 3. Dispersal of Seeds and Fruits by Animals: Some fruits develop hooks on their surface by which they get attached to the hairy bodies of the passing animals and carried away to distant places.

(C) (b) 1.

(C) (b) 1.

have wing like structures or they have hair or they are very small and light, which

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SCIENCE 7 TEXT BOOK

139


1. ( b) 62. ( b) 63. ( c) 64. ( d) 65. ( d)

. (d) . (a) . (c) . (c) . (d)

1. (a) 2. (c) 3. (c) 4. (b) 5. (c)

. (d) . (c) . (d) . (c) . (c)

D. Questions Based on Higher Thinking Skills

1. (a) Pistil (b) vary (c) Stamen (d) Pollen grains (e)

2. (a) yphae (b) Sporangium (c) Spores

3. (a) Rose (b) Bryophyllum (c) Sweet potato (d) Fern (e) east (f) Spirogyra

4. (a) Papaya, Corn, Cucumber (b) Mustard, Rose, Petunia

5. (a) rumstick, Maple, Grass, Madar (Aak), Sunflower (b) Coconut (c) anthium, rena (d) Castor, Balsam

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SCIENCE 7 TEXT BOOK

140

WORKSHEET

A. Objective Type Questions 1. amethemodeofreproductioninthefollowing:

(a) Potato

( b) Bryophyllum

( c) Sweet potato

( d) Y east


( a) The fusion of male and female gametes is called .… … … … … .................. .

(b) Production of new individuals from the vegetative parts of the parent plant is called .… … … … … .................. .

( c) Seed dispersal takes place by the means of .… … … … … .................., .… … … … … .................. and .… … … … … ...................

( d) .… … … … … .................. is the male reproductive part of the flower.


( a) In self pollination, only one parent is involved.

(b) Cross pollination takes place between flowers of different types.

( c) Ferns and mosses reproduce by producing seeds.

( d) Dispersal of seeds is necessary for the better survival of plants.

4. G ive two examples of:

( a) Winged seeds ( b) Hard fruits

(c) Plants which reproduce by spores (d) Plants which reproduce by cuttings



( a) Differentiate between self pollination and cross pollination.

( b) How do spores help the plant to survive unfavourable conditions?

( c) Give two advantages of vegetative propagation.

( d) Define pollination and fertilization.

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SCIENCE 7 TEXT BOOK

141

SAMPLE PAPER

M.M. 5

ame ............................................................... Class ......................... ate ...........................


1. amethemodeofreproductioninthefollowingplants:

( a) Algae ( b) Ferns ( c) Money plant ( d) Dahlia (e) Cactus 2. G ive one example of plant reprod ucing through:

( a) Seeds ( b) Stem cuttings ( c) Roots ( d) Leaves ( e) Fragmentation 3. Correct the following statements:

( a) Leaves are known to be the reproductive part of the plant.

( b) The anther contains ovules.

( c) In a flower, male gametes are produced by ovary.

( d) The method of budding occurs in ferns.

( e) Seeds of Drumstick plant get dispersed by water.



( a) Differentiate between unisexual flowers and bisexual flowers.

( b) Give the fate of the following parts of the flower after fertilisation: petals, sepals, ovary and ovules.

( c) Explain the process of fragmentation in Spirogyra.

( d) What is pollination and name its various agents.

( e) What is germination?


( a) What is meant by dispersal of seeds? How do plants benefit from seed dispersal?

( b) What is the function of the flower? Show the various parts of the flower with the help of a diagram.

( c) Name the various means of vegetative propagation. Give examples of plants reproducing by these means.

( d) Distinguish between asexual reproduction and sexual reproduction in plants.

( e) Explain how fertilisation takes place in flowers of the plants?

(C) ( a)

(C) ( a)

( b)

(C) ( b) What is the function

(C) What is the function

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of a diagram.

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SCIENCE 7 TEXT BOOK

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1. Whichofthefollowingplantsisnotproduced thecu ngmethod?

( a) Rose ( b) Sugarcane ( c) Money plant ( d) Maize 2. heseeds fruitsofwhichofthefollowingplantarenotdispersed wind?

( a) Drumstick ( b) Grass ( c) Coconut ( d) Cotton 3. Bryophyllum can reprod uce by:

( a) Stem ( b) Leaves ( c) Roots ( d) Flowers 4. hestructurewhichproducesmalegametesinafloweris:

( a) Stem ( b) Pollen grains ( c) Ovary ( d) Stigma 5 . A spore prod ucing plant is:

( a) Rose ( b) Bread mould ( c) Potato ( d) Ginger

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SCIENCE 7 TEXT BOOK

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13

Lesson Plan



• The different types of motion.

• The concept of speed and measurement of speed.

• To represent motion graphically.

• The concept of time.

• About simple pendulum.


Periods allocated: 14 Periods

VOCABULARY

Rectilinear motion, circular motion, rotational motion, periodic motion, speed, speedometer, odometer, uniform motion, non-uniform motion, bar graph, pie chart, sun dial, sand clock, water clock, simple pendulum, oscillation, time period, amplitude.


Types of motion (Page 204)

Learning Tools

Interactive warm up exercise: Discussing with the students the term rest and motion would be good start for the topic and recapitulation of the content studied in Class V I.

Chapter opening exercise: Students should be asked the different types of motion- Rectilinear motion, circular motion, rotational motion and periodic motion.

Motion and TimeMotion and Time

(C) Types of motion (Page 204)

(C) Types of motion (Page 204)

Learning Tools (C)

Learning Tools (C)

Interactive warm up exercise:(C)


S S Types of motion (Page 204) S Types of motion (Page 204)

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Rectilinear motion, circular motion, rotational motion, periodic motion, speed, speedometer,

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Rectilinear motion, circular motion, rotational motion, periodic motion, speed, speedometer, odometer, uniform motion, non-uniform motion, bar graph, pie chart, sun dial, sand clock, water

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odometer, uniform motion, non-uniform motion, bar graph, pie chart, sun dial, sand clock, water clock, simple pendulum, oscillation, time period, amplitude.

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clock, simple pendulum, oscillation, time period, amplitude.

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SCIENCE 7 TEXT BOOK

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Discuss with them that rectilinear motion is motion in a straight line, circular motion is movement of an obj ect along a circular path, rotational motion is the spinning of an obj ect about a fixed axis and periodic motion is the motion which repeats itself after regular intervals of time. Students should be able to cite examples of all these types of motion.


State the type of motion in case of: ball rolling on the ground, blades of the moving fan.


Slow and fast moving objects (Page 205)


Discuss that the distance moved by an obj ect in a unit time is called speed of the obj ect. Students should know that a slow moving obj ect is said to have low speed and a fast moving obj ect is said to have a high speed.


Why does it take more time to reach school if you go by a bicycle than by the school bus?


Speed (Page 205)


Explain them that speed of an obj ect is the distance travelled in a unit time. Students should know that to calculate the average speed of a moving obj ect, the distance travelled is divided by the time taken. Students should be familiarized with the units of speed- the standard unit is metres per second and the largest unit is kilometres per hour. Students should be aware of the instruments used to measure speed and distance- Speedometer on the vehicle’s dashboard indicates the speed of the running vehicle and Odometer is used to measure the distance travelled by a vehicle.


Numerical Problem: Naina takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.


Measuring speed (Page 210)


Students should be able to define uniform motion as the motion of an obj ect along a straight line

(C)

(C) Numerical Problem: Naina takes 15 minutes from her house to reach her school on a bicycle. If the

(C) Numerical Problem: Naina takes 15 minutes from her house to reach her school on a bicycle. If the

bicycle has a speed of 2 m/s, calculate the distance between her house and the school.

(C) bicycle has a speed of 2 m/s, calculate the distance between her house and the school. S Suggested home assignmentS Suggested home assignment

Numerical Problem: Naina takes 15 minutes from her house to reach her school on a bicycle. If the S Numerical Problem: Naina takes 15 minutes from her house to reach her school on a bicycle. If the

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Explain them that speed of an obj ect is the distance travelled in a unit time. Students should know

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of the running vehicle and Odometer is used to measure the distance travelled by a vehicle.



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SCIENCE 7 TEXT BOOK

145

path with constant speed and non-uniform motion as the motion of an obj ect along a straight line path with changing speed.

Using resources



Numerical Problem: A sprinter attains a maximum speed of 10 m/s. what will be his speed in km/hr?


Graphical representation of motion (Page 212)


Explain them that the motion of obj ects can be represented in diagram form by drawing their distance-time graphs. Students should be able to represent distance and time on graph and state their advantages. They should be aware of the bar graph and pie chart also.

Using resources

Show the students how to represent distance and time of an obj ect with uniform speed, non uniform speed and stationary obj ect on a graph.


The distance covered by a cyclist is given in the following table. Represent it in the form of a line graph and calculate his speed.

Distance ( m) 3 5 9 11 14

Time ( s) 10 15 20 25 30


Time (Page 217)


Explain that time is a moment or duration in which things occur. Make the topic interesting by discussing the important time measuring devices used in ancient times like Sundial, sand clock and water clock. Students should know that the standard unit of time is second. They should be aware that clocks and watches which are used to measure time in the modern times are based on the principle of periodic motion.

Using resources


(C) Explain that time is a moment or duration in which things occur. Make the topic interesting by

(C) Explain that time is a moment or duration in which things occur. Make the topic interesting by

discussing the important time measuring devices used in ancient times like Sundial, sand clock

(C) discussing the important time measuring devices used in ancient times like Sundial, sand clock

(C)

and water clock. Students should know that the standard unit of time is second. They should be (C)

and water clock. Students should know that the standard unit of time is second. They should be aware that clocks and watches which are used to measure time in the modern times are based on (C

) aware that clocks and watches which are used to measure time in the modern times are based on

S Teacher guided discussionS Teacher guided discussion

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Time (Page 217)

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The distance covered by a cyclist is given in the following table. Represent it in the form of a line

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Explain them that the motion of obj ects can be represented in diagram form by drawing their distance-time graphs. Students should be able to represent distance and time on graph and state

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distance-time graphs. Students should be able to represent distance and time on graph and state their advantages. They should be aware of the bar graph and pie chart also.

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their advantages. They should be aware of the bar graph and pie chart also.

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SCIENCE 7 TEXT BOOK

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Explain briefly how sand clock was used to measure time in ancient times?


Simple pendulum (Page 219)


Explain them that a simple pendulum consists of a small metal ball called bob suspended by a long thread from a rigid support, such that the bob is free to swing back and forth. Students should be able to define periodic motion, oscillation, time period and amplitude. Explain the use of pendulum for measuring time and the reason why pendulum clocks have been replaced by quartz clocks and watches.


Describe a pendulum clock.


The latest trend in measurement of time: Use of Quartz crystals (Page 222)


Explain them that these days, the regular oscillations of a tiny quartz crystal are used for measuring time very accurately.


What is the smallest time interval that can be measured with commonly available clocks and watches?



Using resources






(C)

(C)


(C)


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S Using resources

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Using resources

And Explain them that these days, the regular oscillations of a tiny quartz crystal are used for measuring

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TEXT BOOK ANSWERS


1. metres/second 2. kilometres per hour 3. Speed

4. kilometres per hour 5. ( a) Odometer ( b) Speedometer

6. ( a) False ( b) False ( c) True ( d) False ( e) True ( f) True ( g) False

7. Bar graphs and pie chart. 8. Time 9. Second

10. Hour, minutes, seconds 11. 60 12. Sundial, sand clock

13. Pendulum 14. full moon and sunrise 15. bob

16. oscillatory motion (periodic motion) 1 . Quartz crystal

18. Clocks and watches

19. The smallest time interval that can be measured with commonly available clocks and watches is 1 second. The clocks and watches used in sports meets can measure time intervals that are one-tenth of a second or one-hundredth of a second.

20. Microsecond 21. Quartz clock 22. Quartz clock

23. 0.25 m/s 24. 50 km/h

25. An instrument on a vehicle’s dashboard which indicates the speed of the vehicle when it is running is called speedometer.

26. Odometer is an instrument for measuring the distance travelled by a vehicle.

27. When the object is stationary (not moving)

28. The distance moved by an object in a unit time is called speed of the object.

29. ‘ Distance travelled’ divided by ‘ Time taken’

30. ( a) speed ( b) non-uniform ( c) uniform ( d) straight ( e) month ( f) day ( g) periodic ( h) simple pendulum (i) time-period


31. (a) periodic motion (b) rectilinear motion (c) periodic motion (d) periodic motion

(e) rectilinear motion

32. A bar graph is a diagram which shows information as bars (thin rectangles) of different heights. Bar graphs are frequently used in newspapers, magazines and TV to present various types of information in an interesting way. Refer to figure 1 for bar graph representation. A pie chart is a kind of graph or diagram which shows the percentage composition of ‘something’ in the form of slices of a circle (the whole circle representing 1 per cent). Refer to figure 11 for the pie chart representation.

33. (a) rectilinear motion (b) circular motion (c) periodic motion (d) rectilinear motion

(e) rotational motion

34. (a) Refer to figure 4 for the graph. (b) Refer figure for the graph

35. 450 km 36. 4.5 hours 37. 10 cm/s

38. 2 km 39. 15 km 40. 60 km/h

(C) types of information in an interesting way. Refer to figure 1 for bar graph representation.

(C) types of information in an interesting way. Refer to figure 1 for bar graph representation.

A pie chart is a kind of graph or diagram which shows the percentage composition of

(C) A pie chart is a kind of graph or diagram which shows the percentage composition of

‘something’ in the form of slices of a circle (the whole circle representing 1 per cent). (C) ‘something’ in the form of slices of a circle (the whole circle representing 1 per cent).

Refer to figure 11 for the pie chart representation. (C)

Refer to figure 11 for the pie chart representation.

((C)

(

S A bar graph is a diagram which shows information as bars (thin rectangles) of different

S A bar graph is a diagram which shows information as bars (thin rectangles) of different heights. Bar graphs are frequently used in newspapers, magazines and TV to present various S heights. Bar graphs are frequently used in newspapers, magazines and TV to present various types of information in an interesting way. Refer to figure 1 for bar graph representation. S types of information in an interesting way. Refer to figure 1 for bar graph representation. A pie chart is a kind of graph or diagram which shows the percentage composition of S A pie chart is a kind of graph or diagram which shows the percentage composition of

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SCIENCE 7 TEXT BOOK

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41. 1.3 m/s 42. 16.66 m/s 43. 216 km/h

44. (a) niform motion (Constant speed) (b) on-uniform motion (Changing speed)

45. (a) circular motion b. periodic motion c. periodic motion d. periodic motion


46. An object moving along a straight line path is said to have uniform motion if its speed remains constant. The motion of a car running at a constant speed is an example of uniform motion. An object moving along a straight line path is said to have non-uniform motion if its speed keeps changing (it does not remain constant). The motion of a train starting from a Railway Station is an example of non-uniform motion. This is because when a stationary train starts from a Railway Station, its speed goes on increasing and it covers more and more distance in each ‘1 second’ time interval. And when the train approaches next station, its speed goes on decreasing due to which it covers less and less distance in each ‘ 1 second’ time interval.

47. ( b) Constant speed 48. ( b) 25 km

49. (a) Refer to figure for the graph. b. Some of the advantages of distance-time graphs are

1. The variation of distance travelled by an obj ect with time can be seen more easily from a distance-time graph than from the distance and time values given in the table form.

2. The data given in table form may give information about the distance moved by the obj ect only at certain definite time intervals but from a distance-time graph we can find the distance moved by the obj ect at any point of time.

3. The speed of an obj ect can be obtained from its distance-time graph.

50. (a) A simple pendulum consists of a small metal ball ( called bob) suspended by a long thread from a rigid support, such that the bob is free to swing back and forth. The time taken by pendulum bob to make one complete oscillation is called time-period of the pendulum.

( b) 1.8 s


51. ( b) 52. ( d) 53. ( a) 54. ( c) 55. ( b)

56. ( b) 57. ( d) 58. ( c) 59. ( d) 60. ( b)

61. ( d) 62. ( b) 63. ( c) 64. ( d) 65. ( c)

66. ( c) 67. ( c) 68. ( c) 69. ( c) 70. ( c)


71. V ehicle A is moving faster

72. ( a) Bar graph ( b) Line graph ( c) Pie chart

73. ( a) See Figure 4 on page 212 ( b) See Figure 7 on page 213 ( c) See Figure 6 on page 213

74. ( c)

5. The object is stationary (not moving)

(C)

( d)

(C)

( d)

66.

(C) 66. ( c)

(C) ( c)

E. Questions Based on Higher Order Thinking Skills(C)


71.(C)

71. V ehicle A is moving faster (C)

V ehicle A is moving faster

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SCIENCE 7 TEXT BOOK

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WORKSHEET



( a) The standard unit of speed.

( b) The instrument used to record the distance covered by a vehicle.

( c) Standard unit of time.

( d) A device used for measuring time in ancient times.


( a) The time taken by the pendulum to complete one oscillation is called .… … … … … ............ .

( b) The to-and-fro motion of a simple pendulum is an example of .… … … … … ............ motion.

( c) The time from one full moon to the next was called .… … … … … ............ .

( d) The distance moved by an obj ect in a unit time is called .… … … … … ............ .

. Statethet peofmotione hi ited thefollowing:

( a) Motion of a child in a merry go round.

( b) Motion of earth around the sun.

( c) Motion of a swinging pendulum.

( d) Motion of a swing moving to and fro.


( a) The basic unit of time is second.

( b) Speedometer indicates the speed in km/s.

( c) The speed of an airplane is expressed in m/h.

( d) The time period of a pendulum is not constant.



( a) Define speed. What is the formula for calculating speed?

( b) The distance between two stations is 240 km. A train takes 4 hours to reach its destination. Calculate the speed of the train.

( c) Define the terms Length and Amplitude of pendulum.

( d) Differentiate between uniform motion and non-uniform motion.

(C) ( c)

(C) ( c)

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SCIENCE 7 TEXT BOOK

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SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) A small metal bob in the simple pendulum.

( b) The standard unit of measuring time.

( c) A time measuring device used in ancient times.

( d) A moment or duration in which things occur.

( e) A diagram which shows information as bars of different heights.


( a) The speed of an obj ect can be obtained from its distance-time graph.

( b) An obj ect moving along a straight line path is said to have uniform motion if its speed is changing.

( c) The standard unit of distance is metre.

( d) When an obj ects spins about a fixed axis, it is called circular motion.

( e) A slow moving obj ect is said to have slow speed.

. Whatt peofmotionisrepresented thefollowing:

( a) Bullock cart moving on a straight road.

( b) Spinning of earth on its axis.

( c) Soldiers in a march past.

( d) Motion of a child in a see-saw.

( e) Motion of a simple pendulum.


( a) In modern times, we use pendulum clocks.

( b) The time from one sunrise to the next sunrise was called a month in ancient times.

( c) If the distance-time graph of an obj ect is a horizontal line parallel to the time axis, then the speed of the obj ect is changing.

( d) The motion of a train starting from a railway station is an example of uniform motion.

( e) The large speed values are expressed in the units metres per minute.



( a) Differentiate between rotational motion and circular motion.

(C) ( c)

(C) ( c)

then the speed of the obj ect is changing.

(C) then the speed of the obj ect is changing.

( d)(C)

( d)

( e)(C)

( e)

S In modern times, we use pendulum clocks.

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SCIENCE 7 TEXT BOOK

151

( b) Define speed. What is speedometer?

( c) What is meant by ‘ uniform motion’ and ‘ non-uniform motion’? Give one example motion and one of non-uniform motion.

( d) A bus takes 2 hours to cover a distance of 80 km. Calculate its speed in km/h and m/s.

( e) What are the limitations of a sundial?


( a) The distance covered by a cyclist is given in the following table. Represent it in the form of a line graph and calculate his speed.

Distance ( m) 3 5 9 11 14

Time ( s) 10 15 20 25 30

( b) What is a simple pendulum? Define the time period of a simple pendulum.

( c) State the advantages of drawing distance-time graphs for moving obj ects.

( d) Explain the mechanism of working of a pendulum clock.

( e) Mention an activity to determine the time period of a simple pendulum.


1. Whichofthefollowingisthemostappropriatetodemonstratetherunsscoredinthevarious overs of a cricket match?

( a) Time graph ( b) Bar graph ( c) Pie chart ( d) Line graph 2. hecloc sandwatchesareusedformeasuringtimeare asedon:

( a) Rectilinear motion ( b) Circular motion ( c) Periodic motion ( d) Rotational motion. . hesundialisadeviceformeasuring:

( a) Speed ( b) Distance ( c) Time ( d) Height 4. hespeedofamovingo ectisdeterminedto e . 6m s. hisspeedisequalto:

( a) 2.16km/h ( b) 1.08km/h ( c) 0.216km/h ( d) 0.0216km/h 5. Whichamongthefollowingisthesmallestunitoftime?

( a) Second ( b) Millennium ( c) Nanosecond ( d) Microsecond.

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SCIENCE 7 TEXT BOOK

152

14

Lesson Plan



• The components of an electric circuit.

• The symbols used to represent components of electric circuit.

• The heating effect of electric current.

• The magnetic effect of electric current.

• Electromagnets and their uses.

• Construction and working of electric bell.


Periods allocated:12 periods

VOCABULARY

Electric current, circuit, battery, resistance, electric fuse, short circuit, overloading, Miniature Circuit Breaker, electromagnet.


Electric current (Page 227)

Learning Tools

Interactive warm up exercise: Discussing with the students the uses of electricity in our daily life would be a good start for the topic. Ask the students why electricity is considered as dangerous.

Chapter opening exercise: Students should be asked to make a simple electric circuit using a small bulb, switch, connecting wires and cell. Ask them to light the bulb.

Electric Current and its EffectsElectric Current and its Effects

(C) Electric current (Page 227)

(C) Electric current (Page 227)

Learning Tools (C)

Learning Tools



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SCIENCE 7 TEXT BOOK

153


Discuss that the flow of electricity through a conductor is called electric current. Students should know that it is produced at power stations for distribution in our homes. In laboratories, students can use an electric cell to perform experiments.


Mention the possible dangers of electricity.


Electric circuits (Page 228)


Discuss with them that a continuous conducting path between the two terminals of a cell or battery along which electric current flows, is called a circuit. Students should be familiarized with the symbols for electrical components. They should be able to draw the electric circuit diagram. Explain that a group of cells j oined in series is called a battery. Students should know that for making a battery, the positive terminal of one cell is kept in contact with the negative terminal of another cell. Uses of battery should be known by students.


Draw a neat diagram of an electric circuit showing its various components.


Heating effect of electric current (Page 232)


Explain them that when an electric current is passed through a high resistance wire, the resistance wire becomes hot and produces heat and this is called the heating effect of current. Students should be able to define the term resistance and they should be aware that greater the resistance of a wire, greater will be the heat produced in it by a given current. The applications of heating effect of current should be known to students. Familiarize them with the electrical appliances, electric bulb, electric fuse and MCB. Students should be sensitized about the fact that wastage of electricity needs to be reduced and for that CFLs should be used. The cause of short circuit and overloading should be explained to students. Explain them why are MCB used in place of fuse these days.

Using resources


(C) of current should be known to students. Familiarize them with the electrical appliances, electric

(C) of current should be known to students. Familiarize them with the electrical appliances, electric

(C) bulb, electric fuse and MCB. Students should be sensitized about the fact that wastage of electricity

(C) bulb, electric fuse and MCB. Students should be sensitized about the fact that wastage of electricity

needs to be reduced and for that CFLs should be used. The cause of short circuit and overloading (C) needs to be reduced and for that CFLs should be used. The cause of short circuit and overloading (C)

should be explained to students. Explain them why are MCB used in place of fuse these days. (C)

should be explained to students. Explain them why are MCB used in place of fuse these days.

S be able to define the term resistance and they should be aware that greater the resistance of a

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And Draw a neat diagram of an electric circuit showing its various components.

And Draw a neat diagram of an electric circuit showing its various components.

ACTIVITIES FOR PERIODS 4 TO 6 And


Heating effect of electric current (Page 232) And


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SCIENCE 7 TEXT BOOK

154


What is the full form of: CFL and MCB.


Magnetic effect of electric current (Page 239)


Discuss with them that when electric current passes through a wire, the current carrying wire behaves like a magnet and this is called the magnetic effect of current. Explain that electromagnets are made by using electric current and it consists of a coil of insulated wire wrapped around a piece of iron that is magnetised only when electric current is passed through the coil. Students should realize the advantages of electromagnets over permanent magnets. They should be aware of the uses of electromagnets. Explain the construction and working of an electric bell in detail to the students.

Using resources

• Conduct the activity given on page no. 23 of the book to show the magnetic effect of current.



Draw a neat diagram showing the electric bell. Explain its working.



Using resources






TEXT BOOK ANSWERS


1. Switch 2. Connecting wires

(C)

(C)

(C) Assessment of understanding of the chapter could be done with the help of the given worksheet

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SCIENCE 7 TEXT BOOK

155

3. (a) Battery of two cells (b) lectric bulb ( lectric lamp)

4. Electric cell

5. ( a) False ( b) False ( c) True ( d) False ( e) False ( f) False ( g) False ( h) False ( i) True ( j ) True

6. (i) eating effect (ii) Magnetic effect . (a) eating effect (b) eating effect

8. ichrome . Tungsten

10. The heating effect of electric current is utilised in a safety device called ‘electric fuse’.

11. Compact fluorescent lamps 12. ( a) Short-circuit ( b) Overloading

13. ( a) Miniature circuit breaker ( MCB) ( b) Electric fuse

14. MCB

15. The magnetic effect of current was discovered by a scientist named ans Christian ersted.

16. The magnetic effect of current was discovered by a scientist named ans Christian ersted.

1 . Electromagnet 18. The piece of iron

1 . Electric motors, electric fans

2 . The magnet made by using electric current is called an electromagnet.

21. Iron 22. Magnetic effect

23. lectric bell 24. Electromagnets

25. Magnetic effect 2 . Copper

2 . lectromagnet 2 . No

2 . Miniature Circuit Breaker

3 . (a) electric circuit (b) positive (c) negative (d) battery (e) red-hot (f) fuse (g) electromagnet (h) magnetic (i) electromagnet (j) magnet


31. A continuous conducting path (consisting of wires, bulb, switch, etc.) between the two terminals of a cell or battery along which an electric current flows, is called a circuit. Refer to figure 3 for the diagram.

32. lectric cell and electric switch. Refer to figure 3 for the diagram.

33. Refer to figure 3 for the diagram.



3 . Refer to figure 3 for the diagram.

3 . Refer to figure 3 for the diagram.

3 . lectric cells are used in torches, radios, TV remote controls, cassette players, electric clocks.

3 . Some of the important applications of the heating effect of current are given below (i) The heating effect of electric current is utilised in the working of electrical heating appliances such as electric room heater, electric iron, electric kettle, electric toaster, electric oven, water heater (geyser), immersion rod, and soldering iron, etc. (ii) The heating effect of

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SCIENCE 7 TEXT BOOK

156

electric current is utilised in electric bulbs (or electric lamps) for producing light.

40. If the plastic insulation of the live wire and neutral wire gets torn due to wear and tear, then the two naked wires touch each other. The touching of live wire and neutral wire directly is known as short circuit.

41. When a house or some other building is wired, the wiring is protected by fuses. When a short circuit or overloading occurs, the fuse wire blows out cu ng off the electricity supply. This prevents the electric fires.

42. When too many electrical appliances are connected to a single socket, they draw an extremely large current from the household circuit. This is known as overloading ( the circuit) .

43. The fuse wire is usually made from tin-plated copper wire having low melting point so that it may melt easily. A copper metal wire ( or any other metal wire or metal strip) should not be used as a fuse wire because it has a high melting point due to which it will not melt easily when a large current passes through it.

44. A fuse consists of a short length of a thin, tin-plated copper wire having low melting point. The thin fuse wire has a much greater resistance than the rest of the electric wiring in the house. So, when the current in a household circuit suddenly increases too much, then the thin fuse wire gets heated too much, melts and breaks the circuit ( due to which current stops flowing in the circuit). Refer to figure 2 for diagram.

45. o, I would not agree. The fuse wire is usually made from tin-plated copper wire having low melting point so that it may melt easily. A copper metal wire (or any other metal wire or metal strip) should not be used as a fuse wire because it has a high melting point due to which it will not melt easily when a large current passes through it.

46. If there were no fuse in the household wiring, then the large current flowing through the wiring could heat up the wires to very high temperatures and cause electric fires. The large current flowing through electrical appliances such as TV and refrigerator could also damage them.

4 . An electric bulb is basically used for producing light but it also gives out heat. In fact, a major part of the electricity consumed by the filament of an electric bulb is converted into heat ( due to which the bulb becomes hot) , only a small part of electricity is converted into light. The production of heat by an electric bulb is not desirable because it leads to the wastage of electricity. So, the filament-type electric bulbs are not power e cient (because they waste a lot of electricity as heat) . The wastage of electricity can be reduced by using fluorescent tube lights and compact fluorescent lamps (CF s) for producing light.

48. We cannot use an electromagnet for separating plastic bags from a garbage heap. This is because plastic bags do not stick to the electromagnet.

4 . Some of the important uses of electromagnets are:

1. Electromagnets are used in the construction of a large number of devices like electric bells, loudspeakers, electric motors, electric fans, toys and telephone instruments, etc.

2. lectromagnets are used to lift heavy loads like big machines, steel girders and scrap iron obj ects for loading and unloading purposes. The electromagnets which are used

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SCIENCE 7 TEXT BOOK

157

for loading and unloading heavy iron and steel obj ects are fitted on cranes.

50. Only iron is used for making electromagnets. This is because when current is switched off in the coil of an electromagnet made of iron piece, then the iron piece loses all its magnetism. Steel is not used for making electromagnets because when current is switched off from the coil of an electromagnet made of a steel piece, the steel piece does not lose all its magnetism. The steel piece retains the magnetism and becomes a permanent magnet.


51. The magnet made by using electric current is called an electromagnet. We can make an electromagnet ourselves as follows Take about 5 centimetre long insulated copper wire ( The insulated copper wire should be quite thin) . Also take a large iron nail about 10 centimetre long. Wind the insulated copper wire round and round closely on the iron nail so that it may form a coil. The coil can be held on to the iron nail by pu ng some cellotape over it. Connect the free ends of the coil of wire to the two terminals of an electric cell through a switch. Switch on the current in the coiled wire by closing the gap in the switch.

ow, place some steel pins near one of the ends of iron nail. We will find that the steel pins cling to the iron nail. The iron nail attracts the steel pins because the electric current flowing in copper wire coil ( wrapped around it) has turned the iron nail into an electromagnet. Refer to figure 23 for the diagram.

52. Some of the advantages of the electromagnets over the permanent magnets are as follows:

1. The magnetism of an electromagnet can be switched on or switched off as desired. This is not possible with a permanent magnet.

2. An electromagnet can be made very strong (i) by increasing the number of turns in the coil, and ( ii) by increasing the current passing through the coil. On the other hand, a permanent magnet cannot be made so strong.

The electric bell has a -shaped electromagnet. Refer to figure 25 for the diagram.

53. When an electric current is passed through a high resistance wire ( like nichrome wire) , the resistance wire becomes hot and produces heat. This is called the heating effect of current. Room heater and electric iron work on the heating effect of current. The ‘elements’ of electric heating appliances (such as electric room heater, electric iron, etc.) become very hot or red-hot on passing electric current because they have very high resistance ( due to which the heat produced in them is very large) .

54. A group of cells joined in series is called a battery. When the positive terminal of one cell is joined with the negative terminal of the other cell, then the cells are said to be joined in series. The cells are j oined in such a way that the brass cap of one cell touches the zinc bottom of the other cell. Refer to figure for the diagram.

55. (a) The heating effect of electric current is utilised in the working of electrical heating appliances such as electric room heater, electric iron, electric kettle, electric toaster, electric oven, water heater ( geyser) , immersion rod, and soldering iron, etc.

( b) The deflection of compass needle here shows that the current-carrying wire placed above it is behaving like a magnet and producing a magnetic field around it. It is the magnetism produced by current-carrying wire which is exerting a force on the compass

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in copper wire coil ( wrapped around it) has turned the iron nail into an electromagnet.

Some of the advantages of the electromagnets over the permanent magnets are as follows:

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Some of the advantages of the electromagnets over the permanent magnets are as follows:

omagnet can be switched on or switched off as desired.

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omagnet can be switched on or switched off as desired. This is not possible with a permanent magnet. Com

pany

This is not possible with a permanent magnet.

very Compa

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strongthe coil, and ( ii) by increasing the current passing through the coil. On the other hand,

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the coil, and ( ii) by increasing the current passing through the coil. On the other hand,

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dThe magnet made by using electric current is called an electromagnet. We can make

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dThe magnet made by using electric current is called an electromagnet. We can make insulated

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dinsulated copper

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dcopperwire ( The insulated copper wire should be quite thin) . Also take a large iron nail about 10

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dwire ( The insulated copper wire should be quite thin) . Also take a large iron nail about 10

closely

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dclosely on

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don the

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dthe

pu ng

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dpu ng some

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dsome

over it. Connect the free ends of the coil of wire to the two terminals of an electric cell Limite

dover it. Connect the free ends of the coil of wire to the two terminals of an electric cell through a switch. Switch on the current in the coiled wire by closing the gap in the switch. Lim

ited

through a switch. Switch on the current in the coiled wire by closing the gap in the switch.

SCIENCE 7 TEXT BOOK

158

needle and deflecting it from its usual north-south position.


56. (c) 5 . (d) 5 . (c) 5 . (c) . (d)

1. (a) 2. (d) 3. (c) 4. (d) 5. (c)

. (b) . (c) . (c) . (b) . (d)


1. Problem The positive terminal of one cell is in touch with the positive terminal of the other cell ecessary changes eep the positive terminal of one cell in touch with the negative terminal of the other cell.

2. 3.

4. (a) ichrome (b) Tungsten

5. (a) o (b) All the bulbs will glow together.

Set 1 Set 2

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dnegativ

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d

SCIENCE 7 TEXT BOOK

159

WORKSHEET



( a) The device in which electromagnet is used.

( b) Metal used to make the filament of the bulb.

( c) Magnet made by using current.

( d) Material used for making electromagnet.


( a) .… … … … … ............... effect of electric current is utilized in an electric bell.

( b) .… … … … … ............... is used to load heavy iron girders on to a ship.

( c) Coil of an electromagnet is usually made on .… … … … … ............... .

( d) Full form of CFL is .… … … … … ............... .


( a) A car battery is j ust one cell.

( b) A battery is made by connecting positive terminal of one cell with the negative terminal of another cell.

( c) The magnetism of an electromagnet remains as long as the current is flowing in the coil.

( d) We use a thin wire in a fuse.

4. D raw the electric symbol for the following:

( a) Switch ( b) Bulb ( c) Cell ( d) Battery with two cells



( a) In an electromagnet, which of the two really becomes a magnet: The piece of iron or the coil of wire?

( b) Which of the two is used to load heavy iron girders on to a ship-an electromagnet or a permanent magnet?

(C) S

Which of the two is used to load

S Which of the two is used to load a permanent magnet? S a permanent magnet? Cha

nd B. Subjective Type Questions

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following

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following questions

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questions

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In an electromagnet, the coil of wire?

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the coil of wire?

Which of the two is used to load Chand

Which of the two is used to load a permanent magnet? Cha

nd

a permanent magnet?

And We use a thin wire in a fuse.

And We use a thin wire in a fuse.

D raw the electric symbol for the following:

And

D raw the electric symbol for the following:

( b) BulbAnd

( b) Bulb

Compa

ny Coil of an electromagnet is usually made on .… … … … … ............... .

Compa

ny Coil of an electromagnet is usually made on .… … … … … ............... .

tery is made by connecting positive terminal of one cell with the negative terminal

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tery is made by connecting positive terminal of one cell with the negative terminal

The magnetism of an electromagne Compa

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The magnetism of an electromagnet remains as long as the current is flowing in the Compa

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t remains as long as the current is flowing in the

Limite

dent is utilized in an electric bell.

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dent is utilized in an electric bell.

y iron girders on to a ship. Limite

dy iron girders on to a ship.

Coil of an electromagnet is usually made on .… … … … … ............... . Limite

d

Coil of an electromagnet is usually made on .… … … … … ............... .

SCIENCE 7 TEXT BOOK

160

( c) Write the full form of MCB and CFL.

( d) What is an electric circuit? Explain with the help of a diagram.

SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) The device used to make or break a circuit.

( b) The alloy used to make the heating elements of the electrical heating appliances.

( c) The device which is being used increasingly in the place of fuse.

( d) Effect of electric current utilized in electric bell.

( e) The scientist who discovered the magnetic effect of current.


( a) An electromagnet is a temporary magnet.

( b) An electric bell has an electromagnet.

( c) CFL works on the heating effect of current.

( d) An electromagnet does not attract a piece of iron.

( e) MCB works on the heating effect of current.

3. G ive the electric symbols of:

( a) A cell ( b) A battery of two cells ( c) A closed switch ( d) Electric bulb ( e) An open switch 4. Correct the following statements:

( a) Copper is used for making electromagnet.

( b) An electromagnet is a permanent magnet.

( c) The touching of live wire and neutral wire directly is called overloading.

( d) We should always use a thick wire for a fuse wire.

( e) Greater the magnitude of current passed through a given wire, lesser will be the heat produced in it.



( a) Why do we use iron for making an electromagnet and not steel?

( b) Explain why, when the current is switched on through a wire, the needle of a compass

(C)

( c)

(C)

( c)

( d)

(C) ( d)

( e)(C) ( e) Great(C) Great

S An electromagnet is a permanen

S An electromagnet is a permanen

The touching of live wirS The touching of live wir

We should alwaS We should alwa

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G ive the electric symbols of:

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( b) A batt

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( b) A batt

Electric bulb

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Electric bulb


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nd

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And An electric bell has an electromagnet.

ting effect of current.

And ting effect of current.

An electromagnet does not a

And

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And

ttract a piece of iron.

MCB works on the hea And

MCB works on the heating effect of current. And


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ny e the heating elements of the electrical heating appliances.

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ny e the heating elements of the electrical heating appliances.

The device which is being used increasingly in the place of fuse.

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The device which is being used increasingly in the place of fuse.

ect of electric current utilized in electric bell.

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ect of electric current utilized in electric bell.

overed the magnetic effect of current.

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overed the magnetic effect of current.

emporary magnet.

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emporary magnet.

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An electric bell has an electromagnet.

ting effect of current. Compa

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dDate: ...........................

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dDate: ...........................

SCIENCE 7 TEXT BOOK

161

kept nearby gets deflected from its north-south position.

( c) What is electric resistance? How is it used in an electric bulb?

( d) What are the causes of fire in electric circuits?

( e) What might happen if a fuse is not inserted in the household electric wiring?


( a) Mention the applications of heating effect of current.

( b) State the advantages of using CFLs.

( c) Explain short circuit and overloading.

( d) Why is MCB used in place of fuse nowadays?

( e) Write an activity to show the magnetic effect of current.


1. na lament t pe ul alotofelectricenerg iswastedintheformof:

( a) Magnetism ( b) Sound ( c) Light ( d) Heat 2. hemagnetice ectofelectriccurrentwasdiscovered :

( a) Maxwell ( b) Darwin ( c) Oersted ( d) Newton . hecompactfluorescentelectriclamphas. ............. lament:

( a) Nichrome ( b) Chromium ( c) Tungsten ( d) No filament 4. Whichofthefollowingmaterialso ersminimumresistancetotheflowofelectriccurrent?

( a) Copper ( b) Tungsten ( c) Nichrome ( d) Silver 5. hesoundproducedinadoor ellisdueto:

( a) Chemical effect of current ( b) Magnetic effect of current ( c) Heating effect of current ( d) Sound effect of current

(C) S

Cha

nd And

ell

And ell is

And is due

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fect of current

And

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ed . .............

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minimum

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en ( c) Nichrome Compa

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to:Compa

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of:

SCIENCE 7 TEXT BOOK

162

15

Lesson Plan



• Rectilinear propagation of light.

• The concept of reflection of light.

• Concave mirrors and convex mirrors, the nature of images formed by them and their uses.

• Concave lens and convex lens, the nature of images formed by them and their uses.

• The concept of dispersion of light.



VOCABULARY

Reflection, incident ray, reflected ray, mirror, image, real image, virtual image, lateral inversion, concave mirror, convex mirror, convex lens, concave lens, focal length, dispersion, rainbow.


Light travels in straight lines (Page 248)

Learning Tools

Interactive warm up exercise: Discussing with the students the working of pinhole camera would be a good topic to start the topic and recapitulation of the content studied in Class V I. Ask students the principle on which the pinhole camera is based.

Chapter opening exercise: Students should be asked what would happen if light from torch is allowed to fall on a mirror.

LightLight

(C) Learning Tools

(C) Learning Tools



be a good topic to start the topic and recapitulation of the content studied in Class V I. Ask students (C)

be a good topic to start the topic and recapitulation of the content studied in Class V I. Ask students

S S Light travels in straight lines (Page 248) S Light travels in straight lines (Page 248) Cha

nd

Chand

Reflection, incident ray, reflected ray, mirror, image, real image, virtual image, lateral inversion,

Chand

Reflection, incident ray, reflected ray, mirror, image, real image, virtual image, lateral inversion, concave mirror, convex mirror, convex lens, concave lens, focal length, dispersion, rainbow.

Chand

concave mirror, convex mirror, convex lens, concave lens, focal length, dispersion, rainbow.

And

And

And



pany


Compa


Concave mirrors and convex mirrors, the nature of images formed by them and their uses.

Compa

ny

Concave mirrors and convex mirrors, the nature of images formed by them and their uses.

Concave lens and convex lens, the nature of images formed by them and their uses.

Compa

ny

Concave lens and convex lens, the nature of images formed by them and their uses.

Limite

d

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d

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d

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d

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d


d


SCIENCE 7 TEXT BOOK

163


Discuss that the light rays always travel in straight lines. But its path changes when it falls on a mirror. Mirror changes the direction of light and this is called reflection of light.


Show a neat diagram to show the bouncing of light rays by polished surface/ mirror.


Reflection of light (Page 249)


Discuss with the students that the process of sending back the rays of light which fall on the surface of an obj ect is called reflection of light. Students should know why we can see our face in the mirror. Explain them that images are of two types: Real images and virtual images. Students should be familiarized with the characteristics of images formed by a plane mirror. They should be aware of the term lateral inversion.

Using resources



Give an example to show that image formed in a plane mirror is laterally inverted.


Spherical mirrors (Page 254)


Explain them that a spherical mirror is that mirror whose reflecting surface is the part of a hollow sphere of glass. Students should know that spherical mirrors are of two types: concave mirror and convex mirror. They should be able to differentiate between the concave mirror and convex mirror and explain why concave mirror is called a converging mirror and convex mirror is called a diverging mirror.


Draw a neat ray diagrams to show that concave mirror is a converging mirror and convex mirror is a diverging mirror.

(C) mirror and explain why concave mirror is called a converging mirror and convex mirror is called a

(C) mirror and explain why concave mirror is called a converging mirror and convex mirror is called a

diverging mirror.

(C) diverging mirror.

(C)



Draw a neat ray diagrams to show that concave mirror is a converging mirror and convex mirror is (C)

Draw a neat ray diagrams to show that concave mirror is a converging mirror and convex mirror is

S sphere of glass. Students should know that spherical mirrors are of two types: concave mirror

S sphere of glass. Students should know that spherical mirrors are of two types: concave mirror and convex mirror. They should be able to differentiate between the concave mirror and convex S and convex mirror. They should be able to differentiate between the concave mirror and convex mirror and explain why concave mirror is called a converging mirror and convex mirror is called a S mirror and explain why concave mirror is called a converging mirror and convex mirror is called a diverging mirror. S diverging mirror.

Chand

Chand


Chand



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Explain them that a spherical mirror is that mirror whose reflecting surface is the part of a hollow Chand

Explain them that a spherical mirror is that mirror whose reflecting surface is the part of a hollow sphere of glass. Students should know that spherical mirrors are of two types: concave mirror Cha

nd

sphere of glass. Students should know that spherical mirrors are of two types: concave mirror and convex mirror. They should be able to differentiate between the concave mirror and convex Cha

nd

and convex mirror. They should be able to differentiate between the concave mirror and convex

And

And


And




Compa

ny of an obj ect is called reflection of light. Students should know why we can see our face in the mirror.

Compa

ny of an obj ect is called reflection of light. Students should know why we can see our face in the mirror.

Explain them that images are of two types: Real images and virtual images. Students should be

Compa

ny Explain them that images are of two types: Real images and virtual images. Students should be

familiarized with the characteristics of images formed by a plane mirror. They should be aware of

Compa

ny

familiarized with the characteristics of images formed by a plane mirror. They should be aware of


Compa

ny


Limite

d

Limite

dDiscuss with the students that the process of sending back the rays of light which fall on the surface Lim

ited

Discuss with the students that the process of sending back the rays of light which fall on the surface of an obj ect is called reflection of light. Students should know why we can see our face in the mirror. Lim

ited

of an obj ect is called reflection of light. Students should know why we can see our face in the mirror.

SCIENCE 7 TEXT BOOK

164


Images formed by concave mirror (Page 256)


Discuss with them that the nature and size of the image formed by a concave mirror depends on the distance of the obj ect from the concave mirror. Students should be able to list the characteristics of image formed by concave mirror when- obj ect is placed at a distance many times the focal length of concave mirror; when it is placed at a distance greater than twice the focal length; when it is placed at a distance between focal length and twice the focal length of concave mirror; when it is placed at a distance less than its focal length. Discuss the uses of concave mirror.

Using resources

• Conduct the activities given on Pages 25 -2 of the book.


List the uses of concave mirror.


Images formed by convex mirror (Page 261)


Explain them that whether an obj ect is placed at a larger distance or it is close to the convex mirror, it always forms an image which is virtual, erect and smaller than the obj ect. Uses of convex mirrors should be discussed.

Using resources

• Conduct the activity given on Page no. 2 2 of the book.


Mention the uses of convex mirror.


Spherical lenses (Page 263)


Explain them that a lens is a piece of transparent glass bound by two spherical surfaces. Students should be able to identify convex lens and concave lens. Explain why convex lens is a converging lens and concave lens is a diverging lens.

(C)

(C)

(C) Spherical lenses (Page 263)

(C) Spherical lenses (Page 263)

(C)



S S Mention the uses of convex mirror.

S Mention the uses of convex mirror. Chand

Conduct the activity given on Pag

Chand

Conduct the activity given on Pag


Chand


Chand

Mention the uses of convex mirror. Chand

Mention the uses of convex mirror.

And

Explain them that whether an obj ect is placed at a larger distance or it is close to the convex mirror,

And

Explain them that whether an obj ect is placed at a larger distance or it is close to the convex mirror, it always forms an image which is virtual, erect and smaller than the obj ect. Uses of convex mirrors

And

it always forms an image which is virtual, erect and smaller than the obj ect. Uses of convex mirrors

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ny

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ny



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dimage formed by concave mirror when- obj ect is placed at a distance many times the focal length

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dimage formed by concave mirror when- obj ect is placed at a distance many times the focal length of concave mirror; when it is placed at a distance greater than twice the focal length; when it is

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dof concave mirror; when it is placed at a distance greater than twice the focal length; when it is placed at a distance between focal length and twice the focal length of concave mirror; when it is

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dplaced at a distance between focal length and twice the focal length of concave mirror; when it is placed at a distance less than its focal length. Discuss the uses of concave mirror.

Limite

dplaced at a distance less than its focal length. Discuss the uses of concave mirror.

SCIENCE 7 TEXT BOOK

165


Draw ray diagrams to show why convex lens is a converging lens and concave lens is a diverging lens.


Images formed by convex lens (Page 265)


Explain them that the nature and size of the image formed by a convex lens depends on the distance of the obj ect from it. Students should be able to list the characteristics of image formed by convex lens when- obj ect is placed at a distance many times the focal length of convex lens; when it is placed at a distance greater than twice the focal length; when it is placed at a distance between focal length and twice the focal length of convex lens; when it is placed at a distance less than its focal length. Discuss the uses of convex lens.

Using resources

• Conduct the activities given on Pages 2 5-2 of the book



Explain the working of a magnifying glass.


Image formed by concave lens (Page 269)


Explain them that whether an obj ect is placed at a larger distance or close to the concave lens, it always forms a image which is virtual, erect and smaller than the obj ect. Discuss the uses of concave lens.


Mention the uses of concave lens.


Dispersion of light (Page 270)


Explain them that the splitting of white light into seven colors on passing through a transparent medium like a glass prism is called dispersion of light. Students should comprehend that white light

(C)

(C) Mention the uses of concave lens.

(C) Mention the uses of concave lens.

Dispersion of light (Page 270) (C)

Dispersion of light (Page 270)



Mention the uses of concave lens. S Mention the uses of concave lens.

Chand


Chand



Chand


Explain them that whether an obj ect is placed at a larger distance or close to the concave lens,

Chand

Explain them that whether an obj ect is placed at a larger distance or close to the concave lens, it always forms a image which is virtual, erect and smaller than the obj ect. Discuss the uses of

Chand

it always forms a image which is virtual, erect and smaller than the obj ect. Discuss the uses of



And

And


And


Image formed by concave lens (Page 269) And


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ny

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es 2 5-2 of the book

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es 2 5-2 of the book

Students may run the video for the given topic using the R Code given at the end of the chapter

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ny

Students may run the video for the given topic using the R Code given at the end of the chapter

Limite

dExplain them that the nature and size of the image formed by a convex lens depends on the distance

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dExplain them that the nature and size of the image formed by a convex lens depends on the distance of the obj ect from it. Students should be able to list the characteristics of image formed by convex

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dof the obj ect from it. Students should be able to list the characteristics of image formed by convex lens when- obj ect is placed at a distance many times the focal length of convex lens; when it is

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dlens when- obj ect is placed at a distance many times the focal length of convex lens; when it is placed at a distance greater than twice the focal length; when it is placed at a distance between

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dplaced at a distance greater than twice the focal length; when it is placed at a distance between focal length and twice the focal length of convex lens; when it is placed at a distance less than its Lim

ited

focal length and twice the focal length of convex lens; when it is placed at a distance less than its

SCIENCE 7 TEXT BOOK

166

is a mixture of seven colors. Discuss that the rainbow is produced by the dispersion of sunlight by tiny rain drops suspended in the atmosphere.

Using resources

• Conduct the activity given on Page no. 2 1 of the book to show that white light consists of seven colours.

• Conduct the activity given on Page no. 2 2 of the book to show that mixing of seven colours of the spectrum can give us white light.


Why does a compact disc ( CD) placed in the sun shines by producing many colors?



Using resources






TEXT BOOK ANSWERS


1. Virtual 2. 1 cm

3. (a) V irtual ( b) Real 4. LEFT will seem laterally inverted

5. Surface of water in the lake . Plane mirror

. Laterally inversion . Reflection of light

9. When an obj ect is placed in front of a plane mirror, then the right side of obj ect appears to become the left side of image and the left side of object appears to become the right side of image.

1 . ateral inversion 11. ( a) True ( b) False ( c) False ( d) True ( e) True

12. (a) Convex mirror (b) Concave mirror 13. (a) Concave mirror ( b) Convex mirror

14. Concave 15. Convex mirror

1 . Concave lens

1 . When an obj ect is placed close to a concave mirror

(C) When an obj ect is placed in front of a plane mirror, then the right side of obj ect appears

(C) When an obj ect is placed in front of a plane mirror, then the right side of obj ect appears

to become the left side of image and the left side of object appears to become the right

(C) to become the left side of image and the left side of object appears to become the right

side of image. (C)

side of image.

1 .(C)

1 . ateral inversion (C)

ateral inversion

S Surface of water in the lake

S Surface of water in the lake

aterally inversion S aterally inversion

When an obj ect is placed in front of a plane mirror, then the right side of obj ect appears S When an obj ect is placed in front of a plane mirror, then the right side of obj ect appears

Chand

TEXT BOOK ANSWERS

Chand

TEXT BOOK ANSWERS


Chand


a) V irtual ( b) Real Chand

a) V irtual ( b) Real

Surface of water in the lake Chand

Surface of water in the lake

And

And Assessment of understanding of the chapter could be done with the help of the given worksheet

And Assessment of understanding of the chapter could be done with the help of the given worksheet

TEXT BOOK ANSWERSAnd

TEXT BOOK ANSWERS

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d

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dWhy does a compact disc ( CD) placed in the sun shines by producing many colors?

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dWhy does a compact disc ( CD) placed in the sun shines by producing many colors?

SCIENCE 7 TEXT BOOK

167

1 . Concave mirror

1 . Concave lens is diverging lens. Convex Lens is a Converging Lens.

2 . Concave lens 21. Convex lens

22. Convex Lens

23. To use a convex lens as a magnifying glass, the obj ect to be viewed should be placed close to the convex lens so that a magnified and erect image of the small object can be seen on looking through the convex lens.

24. Concave lens 25. Convex lens

2 . Glass prism 2 . Tiny drops of water

2 . ispersion of light 2 . White light consists of seven colors.

3 . (a) straight (b) reflection (c) real (d) virtual (e) plane (f) convex (g) concave (h) thicker thinner ( i) diverges; converges ( j ) concave; convex ( k) lens ( l) smaller ( m) seven ( n) seven ( o) white ( p) white ( q) seven


31. A spherical mirror is that mirror whose reflecting surface is the part of a hollow sphere of glass. Concave mirror forms real image.

32. The image which can be obtained on a screen is called a real image. A real image can be formed on a screen because light rays actually pass through it. The image which cannot be obtained on a screen is called a virtual image. Our image in a plane mirror is an example of virtual image. So, virtual images are also called unreal images. In the still water of a lake, virtual image is formed.

33. A concave surface means ‘ bent-in’ surface. A concave mirror is that spherical mirror in which the reflection of light takes place at the concave surface (or bent-in surface). A convex surface means ‘ bulging-out’ surface. A convex mirror is that spherical mirror in which the reflection of light takes place at the convex surface (bulging out surface). Concave mirrors are used by dentists to see the large images of teeth of patients. Big convex mirrors are used as ‘ shop security mirrors’.

34. The lens which is thicker in the middle than at the edges is called a convex lens. The lens which is thinner in the middle than at the edges is called a concave lens. Convex Lens is a Converging Lens. Concave Lens is a Diverging Lens. Convex lens is used as a magnifying glass. Concave lenses are used in making spectacles.

35. ( i) e ( ii) b; f ( iii) a ( iv) c ( v) f

3 . The characteristics of the images formed by a plane mirror are as follows

( i) The image formed in a plane mirror is behind the mirror.

( ii) The image formed in a plane mirror is virtual ( or unreal) . It cannot be obtained on a screen.

( iii) The image in a plane mirror is of the same size as the obj ect. It is neither enlarged nor diminished.

( iv) The image in a plane mirror is erect. It is the same side up as the obj ect.

(C) ( i) e ( ii) b; f ( iii) a ( iv) c ( v) f

(C) ( i) e ( ii) b; f ( iii) a ( iv) c ( v) f

3 .

(C) 3 . The characteristics of the images formed by a plane mirror are as follows

(C) The characteristics of the images formed by a plane mirror are as follows

( i)(C)

( i) The image formed in a plane mirr(C)

The image formed in a plane mirr

( ii)(C)

( ii)

S a Converging Lens. Concave Lens is a Diverging Lens. Convex lens is used as a magnifying

S a Converging Lens. Concave Lens is a Diverging Lens. Convex lens is used as a magnifying glass. Concave lenses are used in making spectacles. S glass. Concave lenses are used in making spectacles.

( i) e ( ii) b; f ( iii) a ( iv) c ( v) f S ( i) e ( ii) b; f ( iii) a ( iv) c ( v) f

Chand

surface means ‘ bulging-out’ surface. A convex mirror is that spherical mirror in which the

Chand

surface means ‘ bulging-out’ surface. A convex mirror is that spherical mirror in which the reflection of light takes place at the convex surface (bulging out surface). Concave mirrors

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reflection of light takes place at the convex surface (bulging out surface). Concave mirrors are used by dentists to see the large images of teeth of patients. Big convex mirrors are

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are used by dentists to see the large images of teeth of patients. Big convex mirrors are used as ‘ shop security mirrors’.

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used as ‘ shop security mirrors’.

The lens which is thicker in the middle than at the edges is called a convex lens. The lens

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The lens which is thicker in the middle than at the edges is called a convex lens. The lens which is thinner in the middle than at the edges is called a concave lens. Convex Lens is

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which is thinner in the middle than at the edges is called a concave lens. Convex Lens is

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a Converging Lens. Concave Lens is a Diverging Lens. Convex lens is used as a magnifying Chand

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glass. Concave lenses are used in making spectacles.

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A concave surface means ‘ bent-in’ surface. A concave mirror is that spherical mirror in

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A concave surface means ‘ bent-in’ surface. A concave mirror is that spherical mirror in which the reflection of light takes place at the concave surface (or bent-in surface). A convex

And

which the reflection of light takes place at the concave surface (or bent-in surface). A convex surface means ‘ bulging-out’ surface. A convex mirror is that spherical mirror in which the And

surface means ‘ bulging-out’ surface. A convex mirror is that spherical mirror in which the reflection of light takes place at the convex surface (bulging out surface). Concave mirrors And

reflection of light takes place at the convex surface (bulging out surface). Concave mirrors

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A spherical mirror is that mirror whose reflecting surface is the part of a hollow sphere of

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The image which can be obtained on a screen is called a real image. A real image can be

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The image which can be obtained on a screen is called a real image. A real image can be formed on a screen because light rays actually pass through it. The image which cannot be

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formed on a screen because light rays actually pass through it. The image which cannot be obtained on a screen is called a virtual image. Our image in a plane mirror is an example of

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obtained on a screen is called a virtual image. Our image in a plane mirror is an example of virtual image. So, virtual images are also called unreal images. In the still water of a lake, Com

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virtual image. So, virtual images are also called unreal images. In the still water of a lake,

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dWhite light consists of seven colors.

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dWhite light consists of seven colors.

(a) straight (b) reflection (c) real (d) virtual (e) plane (f) convex (g) concave (h) thicker

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thinner ( i) diverges; converges ( j ) concave; convex ( k) lens ( l) smaller ( m) seven ( n) seven

SCIENCE 7 TEXT BOOK

168

( v) The image formed in a plane mirror is at the same distance behind the mirror as the obj ect is in front of it.

( vi) The image in a plane mirror is laterally inverted ( sideways reversed) with respect to the obj ect.

3 . When the face is held close to a concave mirror, then an enlarged image of the face is seen in the concave mirror ( This helps a man in making a smooth shave) .

3 . The image formed by concave mirror is real, inverted and much smaller than the obj ect.

39. The image is virtual, erect, and larger than the object (enlarged or magnified).

4 . When an obj ect is placed close to a convex lens ( at a distance less than its focal length) , the image formed by convex lens is: ( i) virtual, ( ii) erect, and ( iii) larger than the obj ect (enlarged or magnified).

41. When an obj ect is placed at a distance greater than twice the focal length of convex lens, the image formed by convex lens is : ( i) real, ( ii) inverted, and ( iii) smaller than the obj ect ( or diminished) .

42. When an obj ect is placed at a distance between focal length and twice the focal length of a convex lens, then the image formed by convex lens is : ( i) real, ( ii) inverted, and ( iii) larger than the object (enlarged or magnified).

43. (a) Magnified (b) Smaller

44. epending on the distance of object, convex lens forms mainly two different kinds of images: ( i) real and inverted, and ( ii) virtual and erect. Whether an obj ect is placed at a large distance or it is close to the concave lens, a concave lens always forms an image which is virtual, erect and smaller than the obj ect.

45. Take a glass prism. Allow a narrow beam of sunlight through a small hole in the window of a dark room to fall on one face of the glass prism. Let the light coming out of the other face of the prism fall on a white sheet of paper or on a white wall ( which will act as screen) . A patch of seven colours will be formed on the sheet of white paper ( or on white wall) . This shows that sunlight consists of seven colours. Newton discovered by his experiments with glass prisms that white light ( like sunlight) consists of a mixture of lights of seven colours.

4 . If we shine a torch on a dark night, we will see that the beam of light produced by torch travels straight into darkness. This observation shows that light travels in straight lines. Similarly, the beams of light from the headlights of cars, scooters, buses, trucks, aeroplanes and engines of trains also go straight in the darkness of night showing that light travels in a straight line path. Newton discovered by his experiments with glass prisms that white light ( like sunlight) consists of a mixture of lights of seven colours.

4 . (a) Pencil would look very small Virtual image (b) Close to the convex lens (at a distance less than the focal length of convex lens)

4 . If a beam of white light is passed through a glass prism, then the white light splits to form a band of seven colours on a white screen. The band of seven colours formed on a white screen, when a beam of white light is passed through a glass prism, is called spectrum of white light.

49. It has seven colors. They are: red, orange, yellow, green, blue, indigo and violet.

(C)

a straight line path. Newton discovered by his experiments with glass prisms that white

(C)

a straight line path. Newton discovered by his experiments with glass prisms that white light ( like sunlight) consists of a mixture of lights of seven colours.

(C) light ( like sunlight) consists of a mixture of lights of seven colours.

4 .(C) 4 . (a) Pencil would look very small Virtual image (b) Close to the convex lens (at a distance (C) (a) Pencil would look very small Virtual image (b) Close to the convex lens (at a distance

less than the focal length of convex lens) (C)

less than the focal length of convex lens)

S Similarly, the beams of light from the headlights of cars, scooters, buses, trucks, aeroplanes

S Similarly, the beams of light from the headlights of cars, scooters, buses, trucks, aeroplanes and engines of trains also go straight in the darkness of night showing that light travels in S and engines of trains also go straight in the darkness of night showing that light travels in a straight line path. Newton discovered by his experiments with glass prisms that white S a straight line path. Newton discovered by his experiments with glass prisms that white light ( like sunlight) consists of a mixture of lights of seven colours. S light ( like sunlight) consists of a mixture of lights of seven colours.

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of the prism fall on a white sheet of paper or on a white wall ( which will act as screen) . A

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of the prism fall on a white sheet of paper or on a white wall ( which will act as screen) . A patch of seven colours will be formed on the sheet of white paper ( or on white wall) . This

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patch of seven colours will be formed on the sheet of white paper ( or on white wall) . This shows that sunlight consists of seven colours. Newton discovered by his experiments with

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shows that sunlight consists of seven colours. Newton discovered by his experiments with glass prisms that white light ( like sunlight) consists of a mixture of lights of seven colours.

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glass prisms that white light ( like sunlight) consists of a mixture of lights of seven colours.

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If we shine a torch on a dark night, we will see that the beam of light produced by torch

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If we shine a torch on a dark night, we will see that the beam of light produced by torch travels straight into darkness. This observation shows that light travels in straight lines.

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and engines of trains also go straight in the darkness of night showing that light travels in

And is virtual, erect and smaller than the obj ect.

And is virtual, erect and smaller than the obj ect.

Take a glass prism. Allow a narrow beam of sunlight through a small hole in the window of

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Take a glass prism. Allow a narrow beam of sunlight through a small hole in the window of a dark room to fall on one face of the glass prism. Let the light coming out of the other face

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a dark room to fall on one face of the glass prism. Let the light coming out of the other face of the prism fall on a white sheet of paper or on a white wall ( which will act as screen) . A And

of the prism fall on a white sheet of paper or on a white wall ( which will act as screen) . A patch of seven colours will be formed on the sheet of white paper ( or on white wall) . This And

patch of seven colours will be formed on the sheet of white paper ( or on white wall) . This

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a convex lens, then the image formed by convex lens is : ( i) real, ( ii) inverted, and ( iii) larger

epending on the distance of object, convex lens forms mainly two different kinds of

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epending on the distance of object, convex lens forms mainly two different kinds of images: ( i) real and inverted, and ( ii) virtual and erect.

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images: ( i) real and inverted, and ( ii) virtual and erect.large distance or it is close to the concave lens, a concave lens always forms an image which Com

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large distance or it is close to the concave lens, a concave lens always forms an image which is virtual, erect and smaller than the obj ect. Com

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is virtual, erect and smaller than the obj ect.

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dWhen an obj ect is placed close to a convex lens ( at a distance less than its focal length) ,

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dWhen an obj ect is placed close to a convex lens ( at a distance less than its focal length) , the image formed by convex lens is: ( i) virtual, ( ii) erect, and ( iii) larger than the obj ect

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dthe image formed by convex lens is: ( i) virtual, ( ii) erect, and ( iii) larger than the obj ect

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the image formed by convex lens is : ( i) real, ( ii) inverted, and ( iii) smaller than the obj ect

SCIENCE 7 TEXT BOOK

169

5 . es. Take a circular cardboard disc of about 1 cm diameter. ivide this disc into seven equal segments. Paint the seven colours of white light (red, orange, yellow, green, blue, indigo and violet) on these segments. Instead of painting the segments, we can also paste seven coloured papers on these segments. This disc painted with the seven colours of spectrum is called Newton’s disc. Make a small hole at the centre of the disc. Fix the disc loosely on the tip of a refill of a ball pen. Make sure that the disc can rotate freely. ow, rotate the disc quickly in daylight. When the disc is rotated very fast, all the seven colours mix together due to which the disc appears to be white.


51. (a) A lens is a piece of transparent glass bound by two spherical surfaces. Lenses are of two types 1. Convex lens, and 2. Concave lens. enses are used in making spectacles, cameras, microscopes, telescopes, film proj ectors.

( b) Convex lens

( c) Concave mirror

52. (a) The splitting up of white light into seven colours on passing through a transparent medium like a glass prism is called dispersion of light. The rainbow is produced by the dispersion of sunlight by tiny rain-drops suspended in the atmosphere.

( b) Lateral inversion

53. (a) The rainbow is an arch of seven colours seen in the sky. The rainbow is produced by the dispersion of sunlight by tiny rain-drops suspended in the atmosphere. The formation of rainbow having seven colours shows that white sunlight consists of seven colours.

( b) The word AMBULANCE on the hospital vans is written in the form of its mirror image. This is because when we are driving in our car and see the hospital van coming from behind in our rear-view mirror, then we will get the laterally inverted image of and read it as AMBULANCE.

54. (a) The image which can be obtained on a screen is called a real image. A real image can be formed on a screen because light rays actually pass through it. Example: images formed on a cinema screen.

( b) The image which cannot be obtained on a screen is called a virtual image. Our image in a plane mirror is an example of virtual image.

( c) The characteristics of the images formed by a plane mirror as follows:

( i) The image formed in a plane mirror is behind the mirror.

( ii) The image formed in a plane mirror is virtual ( or unreal) . It cannot be obtained on a screen.

( d) Whether an obj ect is placed at a large distance or it is close to the concave lens, a concave lens always forms an image which is virtual, erect and smaller than the obj ect.

55. (a) The table reflects the light of the sunlight in the room.

( b) Whether an obj ect is placed at a large distance or it is close to convex mirror, a convex mirror always forms an image which is virtual, erect and smaller than the obj ect.

(C)

( d)(C)

( d)

S The characteris

S The characteris

( i)S ( i) The image formed in a plane mirrS

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( ii)S ( ii)

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read it as AMBULANCE.

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an be obtained on a screen is called a real image. A real image can be formed on a screen because light rays actually pass through it. Example: images

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formed on a cinema screen.

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And of rainbow having seven colours shows that white sunlight consists of seven colours.

And of rainbow having seven colours shows that white sunlight consists of seven colours.

on the hospital vans is written in the form of its mirror image.

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This is because when we are driving in our car and see the hospital van coming from

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behind in our rear-view mirror, then we will get the laterally inverted image of and read it as AMBULANCE. And


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of white light into seven colours on passing through a transparent

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of white light into seven colours on passing through a transparent medium like a glass prism is called dispersion of light. The rainbow is produced by the

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medium like a glass prism is called dispersion of light. The rainbow is produced by the dispersion of sunlight by tiny rain-drops suspended in the atmosphere.

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dispersion of sunlight by tiny rain-drops suspended in the atmosphere.

The rainbow is an arch of seven colours seen in the sky. The rainbow is produced by the

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The rainbow is an arch of seven colours seen in the sky. The rainbow is produced by the dispersion of sunlight by tiny rain-drops suspended in the atmosphere. The formation

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dispersion of sunlight by tiny rain-drops suspended in the atmosphere. The formation of rainbow having seven colours shows that white sunlight consists of seven colours. Com

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of rainbow having seven colours shows that white sunlight consists of seven colours.

on the hospital vans is written in the form of its mirror image. Compa

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on the hospital vans is written in the form of its mirror image.

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dA lens is a piece of transparent glass bound by two spherical surfaces. Lenses are of

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dA lens is a piece of transparent glass bound by two spherical surfaces. Lenses are of two types 1. Convex lens, and 2. Concave lens. enses are used in making spectacles,

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dtwo types 1. Convex lens, and 2. Concave lens. enses are used in making spectacles,

SCIENCE 7 TEXT BOOK

170

( c) Concave mirror. When a tooth is close to a concave mirror, then an enlarged image of the tooth is seen in the concave mirror. Due to this, it becomes easier to locate the defect in the tooth.

( d) It has seven colors. They are: red, orange, yellow, green, blue, indigo and violet.


5 . (b) 5 . (d) 5 . (c) 5 . (b) . (a)

1. (b) 2. (c) 3. (a) 4. (c) 5. (d)

. (b) . (c) . (b) . (c) . (b)

1. (c) 2. (b) 3. (c) 4. (c) 5. (d)


. (a) ess then 1 cm from concave mirror (b) Virtual (c) arger than the object

. (i) 15 cm (ii) cm (iii) 25 cm

. (a) Convex lens (b) Convex lens (c) Convex lens (d) Concave lens

. (i) 25 cm (ii) 15 cm (iii) cm

. m

1. 1.5 m s

2. (a) F (b) ateral inversion

3. (a) Convex lens (b) Concave lens

4. Similarity Both convex mirror and plane mirror always form a vitual and erect image of an object ifference Convex mirror always forms an image which is smaller than the object but a plane mirror always forms an image which is of the same size as the obj ect

5. A

(C) S

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convex mirror and plane mirror always form a vitual and erect image of an

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object ifference Convex mirror always forms an image which is smaller than the object

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but a plane mirror always forms an image which is of the same size as the obj ect

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but a plane mirror always forms an image which is of the same size as the obj ect

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x lens (b) Convex lens (c) Convex lens (d) Concave lens

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x lens (b) Convex lens (c) Convex lens (d) Concave lens

al inversion

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al inversion

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convex mirror and plane mirror always form a vitual and erect image of an Compa

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convex mirror and plane mirror always form a vitual and erect image of an object ifference Convex mirror always forms an image which is smaller than the object

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object ifference Convex mirror always forms an image which is smaller than the object

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d(d)

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.

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5.

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ave mirror (b) Virtual (c) arger than the object Limite

dave mirror (b) Virtual (c) arger than the object

SCIENCE 7 TEXT BOOK

171

WORKSHEET



( a) The kind of mirror required for obtaining a virtual image of the same size as the obj ect.

( b) The mirror used as a shaving mirror.

( c) The mirror used by doctors for examining the eyes, ears, nose and throat.

( d) Type of lens that can form real and inverted images, as well as virtual and erect image of an obj ect.


( a) Image formed on a cinema screen is an example of .… … .......… … … ...... image.

( b) The image which cannot be obtained on a screen is called a .… … .......… … … ...... image.

( c) The lens which is thinner in the middle than at the edges is called .… … .......… … … ...... lens.

( d) Big .… … .......… … … ...... mirrors are used as shop security mirrors.


( a) White light consists of a mixture of lights of five colors.

( b) A concave lens always forms a virtual image.

( c) A magnifying glass is a convex lens.

( d) Convex mirror is known as converging mirror.

4. entionthemirror lenswhich ndsusein:

( a) Magnifying glasses

( b) Making microscopes

( c) Making peep holes in the doors.

( d) Rear view mirrors in vehicles.



( a) What reflects light when we see the images of trees and other obj ect in a lake?

( b) When we sit in front of a plane mirror and write with our right hand, it appears in the mirror that we are writing with the left hand. Name the phenomenon responsible for the following effect.

( c) Which of the two is a converging lens: convex or concave?

( d) Where should an obj ect be placed in order to use a convex lens as magnifying glass? (C

) ( b)

(C)

( b)mirror that we are writing with the left hand. Name the phenomenon responsible for

(C) mirror that we are writing with the left hand. Name the phenomenon responsible for

the following effect.

(C) the following effect.

( c)(C)

( c)

( d)(C

) ( d)

S What re

S What re

When we sit in S When we sit in mirror that we are writing with the left hand. Name the phenomenon responsible for S mirror that we are writing with the left hand. Name the phenomenon responsible for

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Making microscopes

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Making peep holes in the doors.

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onsists of a mixture of lights of five colors.

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onsists of a mixture of lights of five colors.

ve lens always forms a virtual image.

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ve lens always forms a virtual image.

vex lens. Compa

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vex lens.

x mirror is known as converging mirror. Compa

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in:Com

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dt can form real and inverted images, as well as virtual and erect image

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dt can form real and inverted images, as well as virtual and erect image

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SCIENCE 7 TEXT BOOK

172

SAMPLE PAPER

M.M. 5

Name: ............................................................... Class: ......................... Date: ...........................



( a) Mirror whose reflecting surface is the part of a hollow sphere of glass.

( b) The process of sending back the rays of light which fall on the surface of an obj ect.

( c) The image which can be obtained on a screen.

( d) Another name of convex mirror.

( e) Mirror used as shop security mirror.


( a) The distance from the focus up to the centre of concave lens is called focal length of concave lens.

( b) Convex lens is a diverging lens.

( c) A magnifying glass is a concave lens.

( d) A concave lens always forms an image which is virtual, erect and smaller than the obj ect.

( e) Convex lens and concave lens both can be used to make spectacles.

. entionthemirror lenswhich ndsuseas:

( a) Rear view mirror in cars ( b) Shaving mirror ( c) Magnifying glass

( d) Microscope lens ( e) Lens in camera


( a) The rainbow is produced because of the reflection of sunlight.

( b) Convex lens is a diverging lens.

( c) When an obj ect is placed at a distance greater than twice the focal length of a concave mirror, the image formed by concave mirror is virtual and larger than the obj ect.

( d) The image which can be obtained on a screen is called a virtual image.

( e) Image in a plane mirror is an example of real image.



( a) Differentiate between concave mirror and convex mirror.

( b) Why concave lens is termed a diverging lens?

( c) Mention the uses of convex mirrors.

(C) ( d)

(C) ( d)

( e)

(C) ( e) Image in a plane mirror is an e

(C) Image in a plane mirror is an e

(C)



5. Answer(C

) 5. Answer

S When an

S When anmirror, the image formed by concave mirror is virtual and larger than the obj ect. S mirror, the image formed by concave mirror is virtual and larger than the obj ect.

The image which can be obS The image which can be ob

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or in cars

Microscope lens

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mirror, the image formed by concave mirror is virtual and larger than the obj ect.

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And x lens and concave lens both can be used to make spectacles.

which

And

which nds

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or in cars And

or in cars ( b) Shaving mirror And

( b) Shaving mirror

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om the focus up to the centre of concave lens is called focal length of

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x lens and concave lens both can be used to make spectacles.

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dflecting surface is the part of a hollow sphere of glass.

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dflecting surface is the part of a hollow sphere of glass.

ys of light which fall on the surface of an obj ect.

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dys of light which fall on the surface of an obj ect.

SCIENCE 7 TEXT BOOK

173

( d) Define dispersion of light. Name the scientist who discovered the splitting of light through a glass prism.

( e) Give the characteristics of image formed when an obj ect is placed at a distance greater than twice the focal length of a concave mirror.


( a) Explain the formation of rainbow. Name the scientific principle it is based on.

( b) What type of images can a convex lens make?

( c) Write the characteristics of images formed by a plane mirror.

( d) Write three characteristics of the image formed by a concave mirror when the obj ect is close to it.

( e) Why are concave mirrors used as shaving mirrors?


1. Ano ectisplacedatdistanceof15cmfromaconve lensoffocallength1 cm. heimageo tainedonthescreenis:

( a) upright and magnified ( b) inverted and magnified ( c) inverted and diminished ( d) upright and diminished. 2. Whenao ectis eptatan distanceinfrontofaconcavelens theimageformedis

always:

( a) virtual, erect and magnified ( b) virtual, inverted and diminished ( c) virtual, erect and diminished ( d) virtual, erect and same size as obj ect. . hespli ngupofwhitelightintosevencoloursonpassingthroughaglassprismiscalled:

( a) refraction ( b) deflection ( c) dispersion ( d) scattering 4. heimageformed aplanemirroris:

( a) virtual, behind the mirror and enlarged.

( b) virtual, behind the mirror and of the same size as the obj ect.

( c) real, at the surface of the mirror and enlarged.

( d) real, behind the mirror and of the same size as the obj ect.

5. Aconcavemirrorhasafocallengthof1 cm.Atwhichofthefollowingdistanceshouldano ect eplacedsothatitma formvirtual erectandmagni edimage?

(a) 12 cm (a) 25cm (c) cm (d) 15cm

(C) S

o ect

S o ect

12 cm S 12 cm Cha

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SCIENCE 7 TEXT BOOK

174

16

Lesson Plan



• The different states of matter.

• The important sources of water.

• Importance of groundwater.

• The reasons for water scarcity and depletion of water table.

• The distribution of water.



Vocabulary

Freshwater, saline water, water cycle, groundwater, transpiration, evaporation, condensation, clouds, precipitation, infiltration, water table, rain, aquifer, rainwater harvesting, bawri, drip irrigation


States of matter (Page 278)

Learning Tools

Interactive warm up exercise: Discussing the uses of water and its importance for the survival of living organisms would be a good topic to start the chapter.

Chapter opening exercise: Students should be asked the various processes taking place in the water cycle.

Water: A Precious ResourceWater: A Precious Resource

(C) Learning Tools

(C) Learning Tools

(C) Interactive warm up exercise: (C) Interactive warm up exercise:

living organisms would be a good topic to start the chapter. (C)

living organisms would be a good topic to start the chapter.



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SCIENCE 7 TEXT BOOK

175


Discuss with the students the water cycle occurring in nature. Explain that there are three states of water- soild, liquid and gas. Sensitize the students regarding the scarcity of water and discuss its causes.

Using resources



How many buckets of water have been recommended by the UN per person per day?


Groundwater as an important source of water (Page 281)


Discuss with them that water present below the surface of earth is called groundwater and its main source is the rain. The upper level of water under the ground which occupies all the spaces in the soil and rocks is called water table. Students should also know that aquifer is the underground layer of soil and permeable rocks in which water collects under the ground.

Using resources



How is groundwater recharged?


Depletion of water table (Page 282)


Explain them that due to some factors like increase in population, industrial and agricultural activities, scanty rainfall, deforestation etc., there is depletion of water table. Discuss all these factors in detail.


How is increasing population responsible for depletion of water table?

(C)


(C)


Explain them that due to some factors like increase in population, industrial and agricultural activities,

(C) Explain them that due to some factors like increase in population, industrial and agricultural activities,

scanty rainfall, deforestation etc., there is depletion of water table. Discuss all these factors in detail. (C) scanty rainfall, deforestation etc., there is depletion of water table. Discuss all these factors in detail.



S Depletion of water table (Page 282)

S Depletion of water table (Page 282)


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SCIENCE 7 TEXT BOOK

176


Distribution of water (Page 283)


Discuss how the mismanagement of water is taking place in our country. Suggest ways for proper management of water. Students should be sensitized towards their role to minimize the wastage of water.


What will be the effect of water scarcity on plants?



Using resources






TEXT BOOK ANSWERS


1. Water exists in three forms: solid, liquid and gas.

2. ( a) Ice ( or Snow) ( b) Water vapour 3. rip irrigation

4. ( a) False ( b) False ( c) True ( d) True ( e) False 5. Rain

6. Bawris 7. Aquifer

8. Rain 9. Water cycle

10. 50 L 11. Water table will fall drastically

12. (a) solid liquid gas (b) 1 (c) infiltration (d) hand-pumps tube-wells (e) aquifer (f) groundwater (g) aquifer (h) water (i) mismanagement (j) recharge (k) rainwater harvesting ( l) taps

(C) Bawris

(C) Bawris

8.

(C) 8. Rain

(C) Rain

10.(C)

10. 50 L (C)

50 L

12.(C)

12. (a) solid liquid gas (b) 1 (c) infiltration (d) hand-pumps tube-wells (e) aquifer (f) (C)

(a) solid liquid gas (b) 1 (c) infiltration (d) hand-pumps tube-wells (e) aquifer (f)

S ( a) Ice ( or Snow) ( b) Water vapour

S ( a) Ice ( or Snow) ( b) Water vapour

( a) False ( b) False ( c) True ( d) True ( e) False S ( a) False ( b) False ( c) True ( d) True ( e) False

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TEXT BOOK ANSWERS

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SCIENCE 7 TEXT BOOK

177


13. The earth appears blue from space because a maj or part of the surface of earth is covered with water in seas and oceans. It is this water on the earth which makes it appear blue.

14. The upper level of water under the ground which occupies all the spaces in the soil and rocks, is called water table. If there is more rainfall and more rainwater seeps into ground, the water table rises.

15. Some of the factors which affect the water table (or deplete the water table) at a place and make it go down are (i) Increase in population (ii) Industrial and agricultural activities (iii) Scanty rainfall (iv) eforestation, and (v) ecrease in the effective area for seepage of rainwater.

16. The underground layer of soil and permeable rocks in which water collects under the ground is called an aquifer. The top of aquifer is referred to as water table.

17. The water found below the water table is called groundwater. The main source of groundwater is the rain.

18. rip irrigation is a technique of watering plants by making use of a system of narrow pipes or tubes with small holes, which deliver water directly at the base of the plants. rip irrigation gives water directly to the root zone of plants at a slow rate so that it can be absorbed by the soil without any runoff (or wastage).

19. If the potted plants are not watered even for a few days, the plants will ‘wilt’ (become limp) and ultimately ‘dry up’. And if potted plants are not given water for a considerable time, they will die.

20. The scarcity of water will affect the nutrient uptake by the plants and the process of food making ( photosynthesis) in plants. So, due to scarcity of water, the plants will not be able to make su cient food for themselves and for animals (including human beings). This will lead to severe shortage of food leading to famine.

21. ( i) Get the leaking taps repaired immediately. Leaking taps waste a lot of water. Turn off the tap immediately after use. Do not keep the tap running all the time while brushing the teeth.

( ii) Take bath by filling water in a bucket and not directly under the flowing tap. Wash the utensils by filling water in a basin and not under the running tap.

( iii) Use the water from washing rice, vegetables or fruits for watering the plants at home.

22. We can minimise the use of water for the irrigation of plants and trees in the garden by using the drip irrigation technique.

23. When it rains, the rainwater seeps into the ground and the groundwater is recharged.


25. In order to attract the attention of everybody towards the importance of conserving water, 22nd March is celeberated as World Water D ay every year.

(C) using the drip irrigation technique.

(C) using the drip irrigation technique.

23.

(C) 23. When it rains, the rainwater seeps into the ground and the groundwater is recharged.

(C) When it rains, the rainwater seeps into the ground and the groundwater is recharged.

24.(C)

24. Refer to figure 4 for the diagram. (C)

Refer to figure 4 for the diagram.

25.(C)

25. In order to attract the attention of everybody towards the importance of conserving water, (C)

In order to attract the attention of everybody towards the importance of conserving water,

S Use the wa

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And making ( photosynthesis) in plants. So, due to scarcity of water, the plants will not be able

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And

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SCIENCE 7 TEXT BOOK

178


26. ( a) Mismanagement of Water by Water Supply Department. At many places water is supplied through a well-planned network of big and small pipes. When water is supplied by the Water Supply Department through pipes, not all the water may reach the destination. Many times we have seen the big water supply pipes leaking and a lot of water gushing out of these pipes. The leaking pipes lead to the wastage of precious water. It is the responsibility of the Water Supply Department of the town or city to stop this mismanagement of water by fixing the leaking water pipes quickly. Sometimes the dirty sewer water also gets mixed with the drinking water supply. This is also a case of mismanagement of water on the part of Water Supply Department.

( b) Mismanagement of Water at the Individual Level. All of us, knowingly or unknowingly, waste a lot of water while brushing teeth, shaving, bathing, washing clothes, washing utensils, watering the plants and during many other activities. Leaking taps in our houses are another source of huge water wastage.

27. Some of the steps which can be taken for the proper management of water are given below:

( i) Rainwater Harvesting. One way of increasing the availability of water to overcome its shortage is rainwater harvesting. The most important technique of rainwater harvesting is to make rainwater seep into the ground more efficiently by constructing percolation pits and recharge wells so as to recharge groundwater. This water can be pumped out in the times of water shortage.

( ii) Revival of Bawris. Bawri is a step-well ( in which a person can go down by using steps to fetch water) . Bawris were the ancient water storage and water recharge systems. Bawris were mainly set up in cities and big towns for collecting water so as to provide a water supply to the people during drought periods.

28. The increasing population needs more and more water for its day to day activities. As the population is increasing, more houses, shops, o ces, schools, industries, roads and pavements, etc., need to be constructed. A huge amount of water is required for the construction work. sually, groundwater is used for construction work. This leads to the consumption of a lot of groundwater. ow, when more and more houses, shops, o ces, schools, industries, roads and pavements, etc., are constructed, then the open spaces like parks and playgrounds having unpaved ground for the seepage of rainwater into ground are reduced. This decreases the seepage of rainwater into the ground. So, due to increasing population, on one hand we are consuming more groundwater and on the other hand we are allowing less rainwater to seep into the ground. This leads to the depletion of water table.

29. Industries produce ( or make) a large number of various types of things which we use in our everyday life. Almost everything that is made in industries needs water at some stage during its production process. ue to this, water is used by all the industries. As the population is increasing, the demand for various industrial goods is increasing, and hence the number of industries is also increasing continuously. Water used by most of the industries is drawn (or pumped out) from the ground. As the number of industries is increasing, the water drawn from the ground for their use is also increasing. This results in the depletion of water table.

(C) are allowing less rainwater to seep into the ground. This leads to the depletion of water

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table.

(C) table.

29.(C)

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SCIENCE 7 TEXT BOOK

179

30. The growing of various crops in agriculture requires a lot of water for irrigation. In India, a majority of farmers depend on rains for irrigating their crops. Irrigation systems such as reservoirs, dams and canals exist in some places but these irrigation systems usually get their water supply from rains. So, in the times of erratic rainfall (irregular rainfall) or scanty rainfall (inadequate rainfall), the farmers have to use groundwater for the irrigation of their crops. As more and more food has to be grown for the increasing population, the use of groundwater for agriculture is increasing day by day. This leads to the depletion of water table.


31. ( c) 32. ( d) 33. ( c) 34. ( b) 35. ( c)

36. ( d) 37. ( b) 38. ( d) 39. ( c) 40. ( d)

41. (a) groundwater (b) evaporation (c) condensation (d) clouds (e) transpiration (f) infiltration (g) precipitation


42. ( a) Area B is Assam ( b) Area A is Raj asthan

43. ( a) As snow ( or ice) on snow-covered mountains, glaciers and polar ice caps ( b) As water in seas and oceans, rivers, lakes, ponds and groundwater ( c) As water vapour in the atmosphere

44. W: Water; X : Photosynthesis; Y : Food; Z : Oxygen

45. P: Aquifer; Q: Soil; R: Permeable rocks; S: Water table

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SCIENCE 7 TEXT BOOK

180

WORKSHEET



( a) Water which is fit for use by the human beings.

( b) The gaseous form of air.

( c) The water which falls from the clouds as rain or snow.

( d) One use of water.


( a) The three states of water are .… … .......… … … ......, .… … .......… … … ...... and .… … .......… … … ...... .

( b) A rock which allows water to pass through it is called .… … .......… … … ...... rock.

( c) The upper level of water under the ground which occupies all the spaces in the soil and rocks is called .… … .......… … … ...... .

( d) The process of seeping of water into the ground is called .… … .......… … … ...... .


( a) The water table varies from place to place.

( b) The main source of groundwater is rain.

( c) Increasing population has not affected on the scarcity of water.

( d) 16th March is celebrated as the World Water day.

4. e ne:

( a) Rainwater harvesting ( b) Aquifer ( c) Bawri ( d) Drip irrigation



( a) How is groundwater recharged?

( b) Why does the earth appear blue from space?

( c) What are the various factors which affect water table?

( d) How will you minimize the wastage of water at home?

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SCIENCE 7 TEXT BOOK

181

SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) The water bearing layer of the earth.

( b) One way to increase the availability of water to overcome its shortage.

( c) Ancient water recharge system.

( d) Technique of watering plants directly at the base of plant.

( e) A factor which has been responsible for the depletion of water table.


( a) The top of aquifer is referred to as water table.

( b) The amount of water recommended by the United Nations for use per person per day is 25 mL.

( c) The process of water going into the ground is called seepage.

( d) Condensation of water vapour forms clouds.

( e) The water which is fit for use by human beings is called freshwater.

. e nethefollowing:

( a) Water table ( b) Rainwater harvesting ( c) Aquifer ( d) Water conservation

( e) Evaporation


( a) Bawris are ancient water storage system and there has been no effort to revive them.

( b) Evaporation leads to the formation of clouds.

( c) The water which falls from the clouds as rain or snow is called rainfall.

( d) Lakes are the ultimate source of freshwater.

( e) Mismanagement of water is not considered as a factor for depletion of water table.



( a) Explain the effects of water scarcity on plants.

( b) What is freshwater? What pollutes freshwater?

( c) Explain any on cause of water scarcity.

(C) ( e)

(C) ( e)

(C)



5. Answer(C)

5. Answer

S The wat

S The wat

Lakes are the ultimaS Lakes are the ultima

Mismanagement of wS Mismanagement of w

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Rainwa

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wing statements:

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wing statements:

Bawris are ancien

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Bawris are ancient water storage system and there has been no effort to revive them.

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t water storage system and there has been no effort to revive them.

EvaporChand

Evaporation leads to the formation of clouds. Cha

nd

ation leads to the formation of clouds.

The watChand

The water which falls from the clouds as rain or snow is called rainfall. Chand

er which falls from the clouds as rain or snow is called rainfall.

And ter vapour forms clouds.

And ter vapour forms clouds.

er which is fit for use by human beings is called freshwater.

And

er which is fit for use by human beings is called freshwater.

RainwaAnd

Rainwater harvesting And

ter harvesting

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ny tering plants directly at the base of plant.

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esponsible for the depletion of water table.

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esponsible for the depletion of water table.

eferred to as water table.

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eferred to as water table.

ter recommended by the United Nations for use per person per day

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ter recommended by the United Nations for use per person per day

ter going into the ground is called seepage. Compa

ny

ter going into the ground is called seepage.

ter vapour forms clouds. Compa

ny

ter vapour forms clouds.

Limite

do increase the availability of water to overcome its shortage.

Limite

do increase the availability of water to overcome its shortage.

SCIENCE 7 TEXT BOOK

182

( d) What role can you play to minimise the wastage of water?

( e) What are the different forms of water which occur in nature?


( a) Describe any two steps which can be taken for the proper management of water.

( b) Describe how the increasing population is responsible for depletion of water table?

( c) Explain how the increasing industrial activities are causing the depletion of water table?

( d) How are the agricultural activities responsible for the depletion of water table?

( e) Comment about the water scarcity in Raj asthan.


1. Which of the following d oes not d eplete water the water table?

( a) increasing snowfall ( b) scanty rainfall ( c) increasing deforestation ( d) increasing number of tube wells

2. hec damswere uiltontheriver u mavatianditstri utariesin u aratmainl to:

( a) generate hydropower ( b) provide water to wild animals ( c) grow crops ( d) recharge ground water

. heminimumamountofwaterrecommended the nited ationsperpersonperda is:

( a) 25 L ( b) 50 L ( c) 75 L ( d) 40 L

4. The water bearing layer of the earth is:

( a) aquifer ( b) water table ( c) hydrosphere ( d) none of these

5 . Water which falls from the cloud s as rain or snow is called :

( a) condensation ( b) precipitation ( c) infiltration ( d) transpiration

(C) S

Cha

nd ( b) precipita

Chand

( b) precipitaAnd er bearing layer of the earth is:

And er bearing layer of the earth is:

And

( b) wat

And

( b) water table

And

er table

Water which falls from the cloud s as rain or snow is called : And

Water which falls from the cloud s as rain or snow is called :

( b) precipitaAnd

( b) precipita

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( d) increasing number of tube wells

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tri utaries

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tri utaries in

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( b) provide w

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( b) provide water to wild animals

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ater to wild animals ( d) recharg

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( d) recharge ground water

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e ground water

recommended

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recommended

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the

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the nited

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nited

( c) 75 L Compa

ny

( c) 75 L

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dal activities responsible for the depletion of water table?

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dal activities responsible for the depletion of water table?

SCIENCE 7 TEXT BOOK

183

17

Lesson Plan



• Forests and its components.

• Importance of forests.

• How plants and animals are interdependent on each other.

• Deforestation and its threat to forests.



VOCABULARY

Decomposers, humus, scavengers, ecosystem, crown, canopy, understorey, shrubs, herbs, trees.


Forests and its components (Page 289)

Learning Tools

Interactive warm up exercise: Discussing the various living organisms which are found in a forest would be a good topic to start the chapter. Ask the names of flora and fauna found in the forests.

Chapter opening exercise: Students should be asked what happens to the dead and decaying plants and animals in the forest.


Discuss with them that the living organisms in a forest are the plants, animals and decomposers. These decomposers include the bacteria and fungi which break down the dead parts of plants

Forests: Our LifelineForests: Our Lifeline



(C) would be a good topic to start the chapter. Ask the names of flora and fauna found in the forests.

(C) would be a good topic to start the chapter. Ask the names of flora and fauna found in the forests.



and animals in the forest. (C)

and animals in the forest.



Chand

Chand


Chand



Chand


Forests and its components (Page 289) Chand

Forests and its components (Page 289)

And

And

And

And C

ompa


Compa


How plants and animals are interdependent on each other.

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ny

How plants and animals are interdependent on each other.

Limite

d

Limite

d

Limite

d

Limite

d

Limite

d


d


SCIENCE 7 TEXT BOOK

184

and dead bodies of animals into simple substances, which can be re-used by the plants. Students should be able to list the importance of decomposers and scavengers in removing the waste from the forest. Explain how forests are an ecosystem. Students should be aware of the terms crown of trees, canopy and understorey. They should understand the structure of forest consisting of canopy, understorey, shrubs, herbs and forest floor.

Using resources



There is no waste in a forest. Explain.


Importance of forests (Page 294)


Discuss with them that forests provide us with a large number of products; they have a profound effect on the air quality, water supply, soil maintenance and climate. Discuss the importance of forests in detail. Reasons for destruction of forests and its effects should be discussed. Students should be sensitized to conserve forests and its ways should be suggested.


List some ways to conserve forests.



Using resources





Assessment of understanding of the chapter could be done with the help of the given worksheet for the chapter. (C

) (C

) (C

) Discuss the exercises given at the end of the chapter.

(C)


Assessment of understanding of the chapter could be done with the help of the given worksheet (C)

Assessment of understanding of the chapter could be done with the help of the given worksheet for the chapter. (C

) for the chapter.

S S S Discuss the exercises given at the end of the chapter. S Discuss the exercises given at the end of the chapter. Cha

nd

Chand

Chand

Chand


Chand



Chand



Chand


And

And



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Discuss with them that forests provide us with a large number of products; they have a profound

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Discuss with them that forests provide us with a large number of products; they have a profound effect on the air quality, water supply, soil maintenance and climate. Discuss the importance of

Compa

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effect on the air quality, water supply, soil maintenance and climate. Discuss the importance of forests in detail. Reasons for destruction of forests and its effects should be discussed. Students

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forests in detail. Reasons for destruction of forests and its effects should be discussed. Students

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should be sensitized to conserve forests and its ways should be suggested. Compa

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should be sensitized to conserve forests and its ways should be suggested.

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d

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SCIENCE 7 TEXT BOOK

185

TEXT BOOK ANSWERS


1. Decomposers

2. Crown

3. Sal, Teak; Monkeys, Boar

4. Canopy

5. The uppermost branches and leaves of tall trees which act like a roof over the forest ground is called canopy.

6. Understorey

7. The layer of vegetation in a forest which is just below the understorey, is called shrub layer.

8. Herb layer

9. The herb layer is the lowest layer of vegetation in the forest (having leafy plants).

10. True

11. Saprotrophs

12. Humus

13. Canopy

14. Fruits, Oils, Spices, Natural rubber, Cork

15. (a) lowest (b) soil (c) air water (d) pollination (e) decomposers


16. The branchy part of a tree above the stem is known as the crown of the tree. Refer to figure 5 for the diagram.

17. The five layers (or zones) of a forest vegetation starting from top and going down are Canopy, nderstorey, Shrub layer, erb layer and Forest floor.

18. When an animal dies in a forest, then the dead animal becomes food for vultures, crows, jackals, hyena, some insects and beetles, etc.

19. Nobody has planted any trees in the natural forests. The natural forests contain trees and plants which have grown on their own.

20. (i) estruction of forests will lead to a shortage of wood and other forest products.

(ii) estruction of forests will disturb the balance of carbon dioxide and oxygen in the atmosphere. Due to cutting down of forest trees, the amount of carbon dioxide in the atmosphere will increase leading to an increase in earth’s temperature.

(iii) estruction of forests will cause soil erosion making the soil infertile to support crops.

21. The conservation of forests is necessary (i) to maintain the supply of wood and other forest products (ii) to maintain a healthy balance between carbon dioxide and oxygen in the atmosphere (iii) to maintain the water cycle in nature and bring su cient rain (iv) to prevent soil erosion and floods (v) to protect wild animals and plants from extinction, and (vi) to protect climate.

(C) (ii)

(C) (ii)

atmosphere. Due to cutting down of forest trees, the amount of carbon dioxide in the

(C) atmosphere. Due to cutting down of forest trees, the amount of carbon dioxide in the

atmosphere will increase leading to an increase in earth’s temperature. (C)

atmosphere will increase leading to an increase in earth’s temperature.

(iii)(C)

(iii)

S plants which have grown on their own.

S plants which have grown on their own.

estruction of forests will lead to a shortage of wood and other forest products. S estruction of forests will lead to a shortage of wood and other forest products.

estruction of S estruction of

Chand

The five layers (or zones) of a forest vegetation starting from top and going down are

Chand

The five layers (or zones) of a forest vegetation starting from top and going down are Canopy, nderstorey, Shrub layer, erb layer and Forest floor.

Chand

Canopy, nderstorey, Shrub layer, erb layer and Forest floor.

When an animal dies in a forest, then the dead animal becomes food for vultures, crows,

Chand

When an animal dies in a forest, then the dead animal becomes food for vultures, crows, jackals, hyena, some insects and beetles, etc.

Chand

jackals, hyena, some insects and beetles, etc.

Nobody has planted any trees in the natural forests. The natural forests contain trees and

Chand

Nobody has planted any trees in the natural forests. The natural forests contain trees and plants which have grown on their own. Cha

nd

plants which have grown on their own.

estruction of forests will lead to a shortage of wood and other forest products. Chand

estruction of forests will lead to a shortage of wood and other forest products.

And

The branchy part of a tree above the stem is known as the crown of the tree. Refer to figure

And

The branchy part of a tree above the stem is known as the crown of the tree. Refer to figure

The five layers (or zones) of a forest vegetation starting from top and going down are And

The five layers (or zones) of a forest vegetation starting from top and going down are

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ny The herb layer is the lowest layer of vegetation in the forest (having leafy plants).

Compa

ny The herb layer is the lowest layer of vegetation in the forest (having leafy plants).

(a) lowest (b) soil (c) air water (d) pollination (e) decomposers Compa

ny

(a) lowest (b) soil (c) air water (d) pollination (e) decomposers

Limite

dThe uppermost branches and leaves of tall trees which act like a roof over the forest ground

Limite

dThe uppermost branches and leaves of tall trees which act like a roof over the forest ground

The layer of vegetation in a forest which is just below the understorey, is called shrub layer.

Limite

dThe layer of vegetation in a forest which is just below the understorey, is called shrub layer.

The herb layer is the lowest layer of vegetation in the forest (having leafy plants). Limite

d

The herb layer is the lowest layer of vegetation in the forest (having leafy plants).

SCIENCE 7 TEXT BOOK

186

22. Paper is made from wood pulp that is produced from the wood of forest trees. So, to make paper, many trees have to be cut down from the forests. If all of us keep on collecting old newspapers, magazines, books and notebooks, etc., and send them to paper mills for recycling through a junk dealer (kabadi wala), we will be able to save many forest trees from being cut down.

23. The animals help the forests to grow and regenerate in two ways (i) The dead animals and animal wastes decay (by the action of decomposers) and provide nutrients to the forest soil and make it fertile. (ii) The animals carry out pollination in flowers, and also disperse the seeds of plants and trees throughout the forest.

24. (i) Forests are cut down to obtain firewood (wood used as fuel).

(ii) Forests are cut down to obtain timber (wood for building houses and furniture).

(iii) Forests are cut down to obtain wood for making paper.

25. Those animals which eat the dead animals are called scavengers. Vultures, crows, jackals and hyena eat the dead animals, so vultures, crows, jackals and hyena are scavengers.

26. When the animals die in a forest, they are eaten up by some other animals called scavengers (such as vultures, crows, etc.). The decomposer organisms (bacteria and fungi) decompose the dead plant material, dead animals and animal wastes present in the forest into mineral salts (in the form of humus), water and carbon dioxide, which go into soil and air (and hence recycled for the growth of plants). Since dead animals are eaten up, and the materials present in dead plants, dead animals and animal wastes are recycled, therefore, there is no waste left in a forest.

27. Grass is a kind of plant. In a forest, grass (or plant) is eaten by insects (such as grasshopper), the insects are eaten by frogs, the frog is eaten up by snake, and finally, the snake may be eaten up by an eagle.

28. Humus mixes up with the soil in the forest and the nutrients present in it are used for the growth of plants.

29. As leaves, trees, other plants and animals die, they all fall on the forest floor. The animal wastes (animal dung or droppings) also fall on the forest floor and collect there. n the forest floor, there are a large number of decomposers such as bacteria and fungi. The decomposers break down dead leaves, branches and tree trunks; dead animals; and animal wastes to form humus which contains the nutrients (mineral salts). umus mixes up with the soil in the forest and the nutrients present in it are used for the growth of plants. In this way, decomposers help in maintaining the supply of nutrients to the trees and other plants in the forest.

30. Refer to figure for the diagram.


31. As leaves, trees, other plants and animals die, they all fall on the forest floor. The animal wastes (animal dung or droppings) also fall on the forest floor and collect there. n the forest floor, there are a large number of decomposers such as bacteria and fungi. The decomposers break down dead leaves, branches and tree trunks; dead animals; and animal wastes to form humus which contains the nutrients (mineral salts). umus mixes up with

(C) plants in the forest.

(C) plants in the forest.

30.

(C) 30. Refer to figure for the diagram.

(C) Refer to figure for the diagram.

C. Long Answer Type Questions (C)


S the soil in the forest and the nutrients present in it are used for the growth of plants. In

S the soil in the forest and the nutrients present in it are used for the growth of plants. In this way, decomposers help in maintaining the supply of nutrients to the trees and other S this way, decomposers help in maintaining the supply of nutrients to the trees and other plants in the forest. S plants in the forest.

Chand

As leaves, trees, other plants and animals die, they all fall on the forest floor. The animal

Chand

As leaves, trees, other plants and animals die, they all fall on the forest floor. The animal wastes (animal dung or droppings) also fall on the forest floor and collect there. n the

Chand

wastes (animal dung or droppings) also fall on the forest floor and collect there. n the forest floor, there are a large number of decomposers such as bacteria and fungi. The

Chand

forest floor, there are a large number of decomposers such as bacteria and fungi. The

Chand

decomposers break down dead leaves, branches and tree trunks; dead animals; and animal

Chand

decomposers break down dead leaves, branches and tree trunks; dead animals; and animal wastes to form humus which contains the nutrients (mineral salts). umus mixes up with Cha

nd

wastes to form humus which contains the nutrients (mineral salts). umus mixes up with the soil in the forest and the nutrients present in it are used for the growth of plants. In Cha

nd

the soil in the forest and the nutrients present in it are used for the growth of plants. In

And Grass is a kind of plant. In a forest, grass (or plant) is eaten by insects (such as grasshopper),

And Grass is a kind of plant. In a forest, grass (or plant) is eaten by insects (such as grasshopper),

the insects are eaten by frogs, the frog is eaten up by snake, and finally, the snake may be

And the insects are eaten by frogs, the frog is eaten up by snake, and finally, the snake may be

Humus mixes up with the soil in the forest and the nutrients present in it are used for the And

Humus mixes up with the soil in the forest and the nutrients present in it are used for the

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ny and hyena eat the dead animals, so vultures, crows, jackals and hyena are scavengers.

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ny and hyena eat the dead animals, so vultures, crows, jackals and hyena are scavengers.

When the animals die in a forest, they are eaten up by some other animals called scavengers

Compa

ny When the animals die in a forest, they are eaten up by some other animals called scavengers

(such as vultures, crows, etc.). The decomposer organisms (bacteria and fungi) decompose

Compa

ny

(such as vultures, crows, etc.). The decomposer organisms (bacteria and fungi) decompose the dead plant material, dead animals and animal wastes present in the forest into mineral

Compa

ny

the dead plant material, dead animals and animal wastes present in the forest into mineral salts (in the form of humus), water and carbon dioxide, which go into soil and air (and hence

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salts (in the form of humus), water and carbon dioxide, which go into soil and air (and hence recycled for the growth of plants). Since dead animals are eaten up, and the materials

Compa

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recycled for the growth of plants). Since dead animals are eaten up, and the materials present in dead plants, dead animals and animal wastes are recycled, therefore, there is

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present in dead plants, dead animals and animal wastes are recycled, therefore, there is

Grass is a kind of plant. In a forest, grass (or plant) is eaten by insects (such as grasshopper), Compa

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Limite

dsoil and make it fertile. (ii) The animals carry out pollination in flowers, and also disperse

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dsoil and make it fertile. (ii) The animals carry out pollination in flowers, and also disperse

ts are cut down to obtain timber (wood for building houses and furniture).

Limite

dts are cut down to obtain timber (wood for building houses and furniture).

Those animals which eat the dead animals are called scavengers. Vultures, crows, jackals Limite

dThose animals which eat the dead animals are called scavengers. Vultures, crows, jackals and hyena eat the dead animals, so vultures, crows, jackals and hyena are scavengers. Lim

ited

and hyena eat the dead animals, so vultures, crows, jackals and hyena are scavengers.

SCIENCE 7 TEXT BOOK

187

the soil in the forest and the nutrients present in it are used for the growth of plants. In this way, decomposers help in maintaining the supply of nutrients to the trees and other plants in the forest.

32. The roots of trees and plants growing in the forest bind the particles of top soil and hold the soil together firmly. ue to this binding of soil particles, the strong winds and flowing rainwater are not able to carry away the top soil and hence the soil erosion is prevented.

33. By holding back rainwater and then releasing it slowly into rivers, the forests prevent the occurrence of floods in the rivers.

34. The green plants and trees of the forest absorb carbon dioxide from the atmosphere for the process of food making (called photosynthesis). In this way, the plants reduce the amount of carbon dioxide in the atmosphere. We also know that the green plants and trees of the forest release oxygen during the process of food making (called photosynthesis). So, forests are the major suppliers of oxygen needed by humans and other animals for breathing and respiration. Since the green plants and trees of the forest supply oxygen for breathing and respiration, therefore, forests are known as green lungs. Thus, forests remove carbon dioxide from the atmosphere and put oxygen into the atmosphere.

35. 1. Forests provide us many useful products: the various things which are obtained from the forests are called forest products. Forests give us a large number of useful products. Some of the important products which we get from the forests are: wood, honey, gum, sealing wax (or lac), catechu (kattha), fruits, oils, spices, natural rubber, cork, dyes, medicinal plants and fodder for cattle. 2. Forests maintain the balance between carbon dioxide and oxygen in the atmosphere. 3. Forests help in maintaining water cycle in nature. 4. Forests keep the climate cool.


36. (c) 3 . (d) 3 . (b) 3 . (b) 4 . (b)

41. (d) 42. (c) 43. (a) 44. (b) 45. (d)

4 . (c) 4 . (c)


4 . (a) (i) Bacteria (ii) Fungi (b) ecmposers (c) (i) utrients (ii) Carbon dioxide (iii) Water (d) Plants

4 . (a) Crow, Vulture (b) Mushroom, Toadstool (c) Birds, Insects

(d) Grass → Deer → Tiger

5 . (a) Scavengers (b) Vulture (c) ecomposers (d) Fungi (like mushrooms)

(C) (d) Grass

(C) (d) Grass

5 .

(C) 5 . (a) Scav

(C) (a) Scav

S Plants

S Plants

(a) CrowS (a) Crow, Vulture (b) Mushroom, Toadstool (c) Birds, Insects S , Vulture (b) Mushroom, Toadstool (c) Birds, Insects (a) Crow, Vulture (b) Mushroom, Toadstool (c) Birds, Insects (a) CrowS (a) Crow, Vulture (b) Mushroom, Toadstool (c) Birds, Insects (a) Crow

(d) Grass S (d) Grass

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(c)

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4 .

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4 . (c)

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(c)


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(a) (i) Bacteria (ii) Fungi (b) ecmposers (c) (i) utrients (ii) Carbon dioxide (iii) Water (d) Chand

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And C

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ny respiration. Since the green plants and trees of the forest supply oxygen for breathing

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ny respiration. Since the green plants and trees of the forest supply oxygen for breathing

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ny and respiration, therefore, forests are known as green lungs. Thus, forests remove carbon

dioxide from the atmosphere and put oxygen into the atmosphere.

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dioxide from the atmosphere and put oxygen into the atmosphere.

1. Forests provide us many useful products: the various things which are obtained from the

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1. Forests provide us many useful products: the various things which are obtained from the forests are called forest products. Forests give us a large number of useful products. Some

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of the important products which we get from the forests are: wood, honey, gum, sealing wax (or lac), catechu (kattha), fruits, oils, spices, natural rubber, cork, dyes, medicinal plants

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wax (or lac), catechu (kattha), fruits, oils, spices, natural rubber, cork, dyes, medicinal plants and fodder for cattle. 2. Forests maintain the balance between carbon dioxide and oxygen

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and fodder for cattle. 2. Forests maintain the balance between carbon dioxide and oxygen in the atmosphere. 3. Forests help in maintaining water cycle in nature. 4. Forests keep the Com

pany

in the atmosphere. 3. Forests help in maintaining water cycle in nature. 4. Forests keep the

Limite

dThe green plants and trees of the forest absorb carbon dioxide from the atmosphere for the

Limite

dThe green plants and trees of the forest absorb carbon dioxide from the atmosphere for the process of food making (called photosynthesis). In this way, the plants reduce the amount

Limite

dprocess of food making (called photosynthesis). In this way, the plants reduce the amount of carbon dioxide in the atmosphere. We also know that the green plants and trees of the

Limite

dof carbon dioxide in the atmosphere. We also know that the green plants and trees of the forest release oxygen during the process of food making (called photosynthesis). So, forests

Limite

dforest release oxygen during the process of food making (called photosynthesis). So, forests are the major suppliers of oxygen needed by humans and other animals for breathing and Lim

ited

are the major suppliers of oxygen needed by humans and other animals for breathing and respiration. Since the green plants and trees of the forest supply oxygen for breathing Lim

ited

respiration. Since the green plants and trees of the forest supply oxygen for breathing

SCIENCE 7 TEXT BOOK

188

WORKSHEET



(a) A large area of land covered mainly with trees and other plants.

(b) Micro-organisms present in the forest floor.

(c) Animals which eat the dead animals.

(d) A self-sufficient unit of living things and non-living environment needing only the Sun’s energy for its functioning.


(a) ecomposers like . ....... ...... and . ....... ...... play an important role in sustaining the forests.

(b) xamples of scavengers are . ....... ...... and . ....... ...... .

(c) The branchy part of the tree above the stem is called . ....... ...... .

(d) nderstorey is above the . ....... ...... layer.

(e) . ....... ...... is the highest layer of vegetation in a forest.

(f) The third step in a food chain is always a . ....... ...... .

(g) . ....... ...... help in maintaining the supply of nutrients to the trees and other plants in the forest.

(h) . ....... ...... layer is the lowest layer of vegetation in the forest.

4. Match the following:

(a) Grass (i) Herbivore

(b) Grasshopper (ii) Producer

(c) Frog (iii) Large carnivore

(d) Snake (iv) Carnivore



(a) ist some products obtained from forests which are useful to us.

(b) What is humus

(c) What role do the decomposers play in the recycling of nutrients

(d) Why is there no waste in a forest (C) (b)

(C) (b)

(c)

(C) (c) What role do the dec

(C) What role do the dec

(d)(C)

(d) Why is there no w(C)

Why is there no w

S ist some products ob

S ist some products ob

What is humus S What is humus

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(iii)

Chand

(iii)

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Chand


theChand

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nd

following

ist some products obChand

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And . ....... ...... layer is the lo

And . ....... ...... layer is the lowest layer of vegetation in the forest.

And west layer of vegetation in the forest.

(i)

And

(i) Herbivore

And

Herbivore

(ii)And

(ii) ProducerAnd

Producer

(iii)And

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ny vengers are . ....... ...... and . ....... ...... .

ee above the stem is called . ....... ...... .

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orey is above the . ....... ...... layer.

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orey is above the . ....... ...... layer.

er of vegetation in a forest.

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er of vegetation in a forest.

ep in a food chain is always a . ....... ...... .

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ep in a food chain is always a . ....... ...... .

maintaining the supply of nutrients to the trees and other

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maintaining the supply of nutrients to the trees and other

west layer of vegetation in the forest. Compa

ny

west layer of vegetation in the forest.

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dficient unit of living things and non-living environment needing only the Sun’s

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dficient unit of living things and non-living environment needing only the Sun’s

like . ....... ...... and . ....... ...... play an important role in

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dlike . ....... ...... and . ....... ...... play an important role in

vengers are . ....... ...... and . ....... ...... . Limite

d

vengers are . ....... ...... and . ....... ...... .

SCIENCE 7 TEXT BOOK

189

SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



(a) The large scale cutting down of forest trees.

(b) Green lungs of the nature.

(c) The layer of vegetation in a forest which is just below the canopy.

(d) The uppermost branches and leaves of tall trees which act like a roof over the forest ground.

(e) A self sufficient unit of living things and non-living environment needing only the input of sunlight energy for its functioning.


(a) Saprotrophs play an important role in sustaining the environment.

(b) Green plants are called producers.

(c) Scavengers perform the function of decomposers.

(d) There is no waste in a forest.

(e) The branchy part of a tree above the stem is called canopy.

3. Match the following:

(a) Eagle (i) Producer

(b) Snake (ii) Herbivore

(c) Frog (iii) Carnivore

(d) Grasshopper (iv) Large carnivore

(e) Grass (v) Top carnivore


(a) xamples of decomposers are the scavengers like maggots, crows, jackals, etc.

(b) Bacteria and fungi are the scavengers and help in the cleansing of forests.

(c) Scientists usually divide a forest into seven layers of vegetation based on the living environment.

(d) Canopy consists of smaller trees and tree saplings.

(e) erb layer is the highest layer of vegetation in a forest.

(C) (a)

(C) (a)

(b)

(C) (b) Bacteria and fungi are the sc

(C) Bacteria and fungi are the sc

(c)(C)

(c)

S Correct the folloS Correct the follo

xamples of decomposerS xamples of decomposer

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(i)

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(i)

(ii)

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(ii)

Grasshopper

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Grasshopper

Grass Chand

Grass


Correct the follo

And engers perform the function of decomposers.

And engers perform the function of decomposers.

te in a forest.

And te in a forest.

ee above the stem is called canopy.

And

ee above the stem is called canopy.

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ny branches and leaves of tall trees which act like a roof over the forest

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lf sufficient unit of living things and non-living environment needing only the input

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lf sufficient unit of living things and non-living environment needing only the input

y an important role in sustaining the environment.

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y an important role in sustaining the environment.

engers perform the function of decomposers. Compa

ny

engers perform the function of decomposers.

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degetation in a forest which is just below the canopy. Lim

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egetation in a forest which is just below the canopy.

branches and leaves of tall trees which act like a roof over the forest Limite

d

branches and leaves of tall trees which act like a roof over the forest

SCIENCE 7 TEXT BOOK

190



(a) What happens if an animal dies in a forest

(b) Why is it necessary to conserve forests State any two ways to conserve forests.

(c) There is no waste in a forest. Give reasons.

(d) What is the importance of humus in a forest

(e) raw a flow chart to show how forests help in maintaining the balance of carbon dioxide and oxygen in the atmosphere (details not to be mentioned).


(a) Give the reasons for the large scale cutting down of forest trees.

(b) ow can forests grow and regenerate on their own

(c) Forests provide food and shelter to forest dwelling people. Give reasons.

(d) ow do forests prevent soil erosion

(e) ame the products obtained from the forests.


1. Whichofthefollowingdonothelpthefloweringplantsofaforestinpollination?

(a) Honeybees (b) Butterflies (c) Deers (d) Kingfishers 2. Whichofthefollowingwillhelpintheconservationofforest?

(a) Recycling of jute bags (b) Recycling of cotton bags (c) Rcycling of paper bags (d) Recycling of plastic bags. 3. Which of the following help in maintaining the supply of nutrients to the growing plants

andtreesinaforest?

(a) Saprotrophs (b) Autotrophs (c) Carnivores (d) Heterotrophs 4. Whichofthefollowingisnotaforestproduct?

(a) Gum (b) Plywood (c) Sealing wax (d) Kerosene 5. Seedlingsinaforestgerminateandgetnutritionfrom:

(a) Decaying animal dung (b) Microorganisms (c) Mushrooms (d) None of these

(C) S

M

S M Chand

(b)

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(b)

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following

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following is

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is not

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not

(b)

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(b)

a

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a forest

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forest germinate

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germinate

ecaying animal dung

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ecaying animal dung

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ushrooms Chand

ushrooms

And

Which of the following help in main

And

Which of the following help in maintaining the supply of nutrients to the growing plants

And

taining the supply of nutrients to the growing plants

(b) And

(b) AAnd

Autotrophs And

utotrophs

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ny ts provide food and shelter to forest dwelling people. Give reasons.

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ny ts provide food and shelter to forest dwelling people. Give reasons.

flowering

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flowering plants

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plants of

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of

(c)

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(c) D

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Deers

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eers conservationCom

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conservation

(b) Compa

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(b)

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da flow chart to show how forests help in maintaining the balance of carbon

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da flow chart to show how forests help in maintaining the balance of carbon dioxide and oxygen in the atmosphere (details not to be mentioned).

Limite

ddioxide and oxygen in the atmosphere (details not to be mentioned).

ts provide food and shelter to forest dwelling people. Give reasons. Limite

dts provide food and shelter to forest dwelling people. Give reasons.

SCIENCE 7 TEXT BOOK

191

18

Lesson Plan



• What is sewage.

• How sewage is harmful to the people and the environment.

• Treatment of wastewater in waste water treatment plant.

• Alternative arrangements for sewage disposal.

• How sanitation can be maintained at public places.



Vocabulary

Wastewater, sewage, sewer, sewerage, sewage treatment, screening, sludge, sanitation, disease, septic tanks, composting pits, chemical toilets, vermi-processing toilet.


Sewage (Page 302)

Learning Tools

Interactive warm up exercise: Discussing the necessity to have clean water for our day to day activities would be a good topic to start the chapter.

Chapter opening exercise: Students should be asked why it is necessary to re-use waste water after cleaning it. Discuss the topic of water scarcity and the reasons for the same.


Discuss with them that the used water is called wastewater. Students should know that wastewater may contain human excreta. Students should be familiarized with the terms sewage, sewer and sewerage. Discuss the composition of sewage in detail.

Wastewater StoryWastewater Story



activities would be a good topic to start the chapter.

(C) activities would be a good topic to start the chapter.


Chapter opening exercise: cleaning it. Discuss the topic of water scarcity and the reasons for the same. (C

) cleaning it. Discuss the topic of water scarcity and the reasons for the same.



Chand

Chand

Wastewater, sewage, sewer, sewerage, sewage treatment, screening, sludge, sanitation, disease,

Chand

Wastewater, sewage, sewer, sewerage, sewage treatment, screening, sludge, sanitation, disease, septic tanks, composting pits, chemical toilets, vermi-processing toilet.

Chand

septic tanks, composting pits, chemical toilets, vermi-processing toilet.

Sewage (Page 302) Chand

Sewage (Page 302)

And

And

And

And

Wastewater, sewage, sewer, sewerage, sewage treatment, screening, sludge, sanitation, disease, And

Wastewater, sewage, sewer, sewerage, sewage treatment, screening, sludge, sanitation, disease,

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How sewage is harmful to the people and the environment.

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ny

How sewage is harmful to the people and the environment.

Treatment of wastewater in waste water treatment plant.

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ny

Treatment of wastewater in waste water treatment plant.

How sanitation can be maintained at public places.

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ny

How sanitation can be maintained at public places.

Limite

d

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d

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d

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d

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ited


SCIENCE 7 TEXT BOOK

192


Write the composition of sewage.


Sewage is harmful to people and environment (Page 303)


Sensitize students that it is essential to treat sewage in a treatment plant because if it is discarded into rivers, it will contaminate water leading to death of aquatic organisms.


What will happen if drinking water is contaminated with sewage?


Waste water treatment plant (Page 304)


Explain them that a place where wastewater from houses and other buildings is brought for processing is called waste-water treatment plant. The various processes of treatment of wastewater should be discussed in detail.

Using resources



Make a flowchart to explain the various processes taking place in WWTP.


Sanitation and disease (Page 307)


Discuss with the students that poor sanitation and contaminated drinking water is the cause of large number of diseases. Students should be able to name the water borne diseases.


Write names of two water borne diseases.



Discuss with the students that poor sanitation and contaminated drinking water is the cause of (C)

Discuss with the students that poor sanitation and contaminated drinking water is the cause of large number of diseases. Students should be able to name the water borne diseases. (C

) large number of diseases. Students should be able to name the water borne diseases.

S Sanitation and disease (Page 307) S Sanitation and disease (Page 307)


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Sanitation and disease (Page 307) Chand

Sanitation and disease (Page 307)

And

Students may run the video for the given topic using the QR Code given at the end of the chapter And


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Explain them that a place where wastewater from houses and other buildings is brought for

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Explain them that a place where wastewater from houses and other buildings is brought for processing is called waste-water treatment plant. The various processes of treatment of wastewater

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processing is called waste-water treatment plant. The various processes of treatment of wastewater

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d

Limite

dSensitize students that it is essential to treat sewage in a treatment plant because if it is discarded

Limite

dSensitize students that it is essential to treat sewage in a treatment plant because if it is discarded

SCIENCE 7 TEXT BOOK

193


Alternative arrangements for sewage disposal (Page 307)


Explain them that in order to improve sanitation, low cost, onsite sewage disposal systems are being encouraged. Septic tanks, composting pits, chemical toilets, vermi-processing toilet and toilets in aeroplanes should be well explained to students.

Using resources



How is waste disposed off in the aeroplanes?


Sanitation at public places (Page 309)


Motivate students to become active citizens and maintain sanitation at public places by observing some simple practices like not throwing garbage in open, not spitting and not urinating on roadsides.


How can you maintain sanitation at public places?



Using resources






(C)

(C)

(C)

(C) Discuss the exercises given at the end of the chapter.

(C) Discuss the exercises given at the end of the chapter.

Assessment of understanding of the chapter could be done with the help of the given worksheet (C

) Assessment of understanding of the chapter could be done with the help of the given worksheet

S S Discuss the exercises given at the end of the chapter. S Discuss the exercises given at the end of the chapter.

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Chand

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Refer to the corresponding chapter in the CD given in the book. Chand


And some simple practices like not throwing garbage in open, not spitting and not urinating on roadsides.

And some simple practices like not throwing garbage in open, not spitting and not urinating on roadsides.

And

And

How can you maintain sanitation at public places?And

How can you maintain sanitation at public places?



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Motivate students to become active citizens and maintain sanitation at public places by observing some simple practices like not throwing garbage in open, not spitting and not urinating on roadsides. Com

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some simple practices like not throwing garbage in open, not spitting and not urinating on roadsides.

Limite


Limite


SCIENCE 7 TEXT BOOK

194

TEXT BOOK ANSWERS


1. Human faeces, Animal waste 2. Nitrates, Phosphates

3. Nitrogen and Phosphorus 4. Bacteria

5. Cholera and typhoid 6. Protozoa ( Dysentery)

7. Waste Water Treatment Plant 8. Chlorine and Ozone

9. Sludge 10. Biogas and Manure

11. Poor sanitation and contaminated drinking water is the cause of a large number of diseases in our country.

12. Cholera, Typhoid, Polio, Meningitis 13. True

14. (i) Septic tanks (ii) Composting pits 15. Septic tank toilets

16. Chemical toilets 17. Composting toilets

18. V acuum toilets

19. ( a) Anaerobic bacteria ( b) Aerobic bacteria

20. ( a) sewage ( b) pollutants ( c) sludge ( d) solid food remains ; sanitary towels ( e) health ( f) soil ; water ( g) earthworms ( h) chemical ( i) diseases


21. An underground pipe which carries away dirty drainage water and waste matter (such as from toilets) is called a sewer. Sewerage is an underground network of interconnected pipes ( called sewers) that transports or carries the sewage from the place where it is produced ( homes and other buildings) , to the sewage treatment plant ( or wastewater treatment plant) where it is processed.

22. The bar screen removes the large rubbish objects like rags, sticks, cans, plastic bags ( polythene bags) , napkins, sanitary towels, etc., from the wastewater ( because they cannot pass through the holes of bar screen.

23. The solid part of sewage is called sludge. The sludge is taken out from the bottom of first sedimentation tank and put into a large, closed tank called digester tank. In the digester tank, many types of anaerobic bacteria decompose the organic matter present in sludge to produce biogas ( also called sewage gas) . ( The anaerobic bacteria do not need oxygen of air to carry out the process of decomposition. That is why the digester tank is a closed tank) . The biogas produced here can be used as a fuel directly or it can be used to generate electricity. The digested sludge left after the removal of biogas is taken out, dried and used as a manure (or fertiliser).

24. The wastewater treatment ( or sewage treatment) gives us two useful products : ( i) biogas, and ( ii) sludge. The biogas is used as a fuel whereas sludge ( or rather ‘ digested sludge’) is used as manure (or fertiliser). The use of dried sludge as a manure returns the nutrients to the soil.

(C)

of air to carry out the process of decomposition. That is why the digester tank is a closed

(C)

of air to carry out the process of decomposition. That is why the digester tank is a closed tank) . The biogas produced here can be used as a fuel directly or it can be used to generate

(C) tank) . The biogas produced here can be used as a fuel directly or it can be used to generate

electricity. The digested sludge left after the removal of biogas is taken out, dried and used

(C) electricity. The digested sludge left after the removal of biogas is taken out, dried and used

as a manure (or fertiliser). (C)

as a manure (or fertiliser).

24.(C)

24. The wastewater treatment ( or sewage treatment) gives us two useful products : ( i) biogas, (C)

The wastewater treatment ( or sewage treatment) gives us two useful products : ( i) biogas,

S tank, many types of anaerobic bacteria decompose the organic matter present in sludge

S tank, many types of anaerobic bacteria decompose the organic matter present in sludge to produce biogas ( also called sewage gas) . ( The anaerobic bacteria do not need oxygen S to produce biogas ( also called sewage gas) . ( The anaerobic bacteria do not need oxygen S of air to carry out the process of decomposition. That is why the digester tank is a closed S of air to carry out the process of decomposition. That is why the digester tank is a closed tank) . The biogas produced here can be used as a fuel directly or it can be used to generate S tank) . The biogas produced here can be used as a fuel directly or it can be used to generate

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The bar screen removes the large rubbish objects like rags, sticks, cans, plastic bags

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The bar screen removes the large rubbish objects like rags, sticks, cans, plastic bags ( polythene bags) , napkins, sanitary towels, etc., from the wastewater ( because they cannot

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( polythene bags) , napkins, sanitary towels, etc., from the wastewater ( because they cannot pass through the holes of bar screen.

Chand

pass through the holes of bar screen.

The solid part of sewage is called sludge. The sludge is taken out from the bottom of first

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The solid part of sewage is called sludge. The sludge is taken out from the bottom of first sedimentation tank and put into a large, closed tank called digester tank. In the digester

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sedimentation tank and put into a large, closed tank called digester tank. In the digester tank, many types of anaerobic bacteria decompose the organic matter present in sludge Cha

nd

tank, many types of anaerobic bacteria decompose the organic matter present in sludge to produce biogas ( also called sewage gas) . ( The anaerobic bacteria do not need oxygen Cha

nd

to produce biogas ( also called sewage gas) . ( The anaerobic bacteria do not need oxygen

And from toilets) is called a sewer. Sewerage is an underground network of interconnected pipes

And from toilets) is called a sewer. Sewerage is an underground network of interconnected pipes

( called sewers) that transports or carries the sewage from the place where it is produced

And ( called sewers) that transports or carries the sewage from the place where it is produced

( homes and other buildings) , to the sewage treatment plant ( or wastewater treatment

And

( homes and other buildings) , to the sewage treatment plant ( or wastewater treatment plant) where it is processed. And

plant) where it is processed.

The bar screen removes the large rubbish objects like rags, sticks, cans, plastic bags And

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( a) sewage ( b) pollutants ( c) sludge ( d) solid food remains ; sanitary towels ( e) health ( f)

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( a) sewage ( b) pollutants ( c) sludge ( d) solid food remains ; sanitary towels ( e) health ( f) soil ; water ( g) earthworms ( h) chemical ( i) diseases

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soil ; water ( g) earthworms ( h) chemical ( i) diseases

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( called sewers) that transports or carries the sewage from the place where it is produced

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dPoor sanitation and contaminated drinking water is the cause of a large number of diseases

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dPoor sanitation and contaminated drinking water is the cause of a large number of diseases

SCIENCE 7 TEXT BOOK

195

25. Compressed air is bubbled through the watery waste in the aeration tank to provide oxygen to activate aerobic bacteria and make them grow rapidly in this water. The large number of aerobic bacteria produced in this way digest ( or consume) any human waste, food waste, soaps and other unwanted and harmful matter still remaining in the wastewater, leaving behind fairly pure water. In this way, aerobic bacteria clean the clarified watery waste and make it almost harmless.

26. The wastes such as solid food remains, used tea leaves, sanitary towels, polythene bags, used cotton, hair, and soft toys, etc., should not be thrown down the drain. This is because if these wastes are thrown in ‘ piped drains’ carrying wastewater, they block the drains ( or choke the drains), and do not allow the free flow of wastewater through them. By blocking the drains, these wastes also do not allow free flow of oxygen (of air) to the useful microbes in the drain which help to decompose the wastes. This hampers the natural process of purification of wastewater.

27. This is because cooking oils and fats can harden and block the drainage pipes. On the other hand, in an open drain, the fats clog (or block) the soil pores reducing its effectiveness in filtering water.

28. In the vermi-processing toilet, the human excreta is treated by earthworms in a pit. The earthworms gradually eat up all the organic matter present in human excreta, decompose it and pass out from their body in the form of worm castings (also called vermi-cakes). The vermi-cakes are a kind of high quality manure which can be added to soil for growing plants. The vermi-processing toilet is a low water-use toilet for the safe processing of human waste.

29. If all the wastes produced at public places are not disposed of regularly and properly, even epidemics could break out (An infectious disease that spreads quickly through a large part of the population, is called an epidemic).

30. We can become an active citizen and approach the Municipality (or Gram panchayat) and insist that the open dirty water drains in our area be covered at the earliest. The covering of open drains will make the environment healthy which will be free from disease-causing organisms.


31. The wastewater and faeces ( human excreta) from homes and other buildings which is carried away in sewers, is called sewage. Sewage includes household wastewater from kitchen sink, washing machine, washbasin, bathroom shower, bath tub and faeces ( human excreta) from the toilet. An underground pipe which carries away dirty drainage water and waste matter (such as from toilets) is called a sewer.

32. (a) The sewage ( or wastewater) released by houses and other buildings contains a large number of harmful substances and disease-causing micro-organisms. If this untreated sewage is discharged into rivers, lakes or ground, it will contaminate our freshwater sources ( like rivers, lakes and groundwater) . Drinking of water contaminated with sewage will spread diseases in people which can even lead to deaths. The discharge of untreated sewage into rivers ( and sea) can also kill fish and other aquatic animals. Since it is very harmful, untreated sewage should not be allowed to run into rivers, lakes, sea or underground.

(C) excreta) from the toilet. An underground pipe which carries away dirty drainage water and

(C) excreta) from the toilet. An underground pipe which carries away dirty drainage water and

waste matter (such as from toilets) is called a sewer.

(C) waste matter (such as from toilets) is called a sewer.

32.(C) 32. ((C) (a)(C) a) The sewage ( or wastewater) released by houses and other buildings contains a large (C) The sewage ( or wastewater) released by houses and other buildings contains a large

S carried away in sewers, is called sewage. Sewage includes household wastewater from

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insist that the open dirty water drains in our area be covered at the earliest. The covering

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insist that the open dirty water drains in our area be covered at the earliest. The covering of open drains will make the environment healthy which will be free from disease-causing

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of open drains will make the environment healthy which will be free from disease-causing


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nd

kitchen sink, washing machine,

And epidemics could break out (An infectious disease that spreads quickly through a large part

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We can become an active citizen and approach the Municipality (or Gram panchayat) and And

We can become an active citizen and approach the Municipality (or Gram panchayat) and And

insist that the open dirty water drains in our area be covered at the earliest. The covering And

insist that the open dirty water drains in our area be covered at the earliest. The covering of open drains will make the environment healthy which will be free from disease-causing And

of open drains will make the environment healthy which will be free from disease-causing

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ny This is because cooking oils and fats can harden and block the drainage pipes. On the other

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ny This is because cooking oils and fats can harden and block the drainage pipes. On the other

hand, in an open drain, the fats clog (or block) the soil pores reducing its effectiveness in

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ny hand, in an open drain, the fats clog (or block) the soil pores reducing its effectiveness in

In the vermi-processing toilet, the human excreta is treated by earthworms in a pit. The

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earthworms gradually eat up all the organic matter present in human excreta, decompose it and pass out from their body in the form of worm castings (also called vermi-cakes). The

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it and pass out from their body in the form of worm castings (also called vermi-cakes). The vermi-cakes are a kind of high quality manure which can be added to soil for growing plants.

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The vermi-processing toilet is a low water-use toilet for the safe processing of human waste.

If all the wastes produced at public places are not disposed of regularly and properly, even Compa

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dused cotton, hair, and soft toys, etc., should not be thrown down the drain. This is because

Limite

dused cotton, hair, and soft toys, etc., should not be thrown down the drain. This is because if these wastes are thrown in ‘ piped drains’ carrying wastewater, they block the drains ( or

Limite

dif these wastes are thrown in ‘ piped drains’ carrying wastewater, they block the drains ( or choke the drains), and do not allow the free flow of wastewater through them. By blocking

Limite

dchoke the drains), and do not allow the free flow of wastewater through them. By blocking the drains, these wastes also do not allow free flow of oxygen (of air) to the useful microbes

Limite

dthe drains, these wastes also do not allow free flow of oxygen (of air) to the useful microbes in the drain which help to decompose the wastes. This hampers the natural process of

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din the drain which help to decompose the wastes. This hampers the natural process of

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dThis is because cooking oils and fats can harden and block the drainage pipes. On the other hand, in an open drain, the fats clog (or block) the soil pores reducing its effectiveness in Lim

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hand, in an open drain, the fats clog (or block) the soil pores reducing its effectiveness in

SCIENCE 7 TEXT BOOK

196

( b) Sewage water should be treated suitably ( or processed) before releasing it back to the environment. The processing of sewage to remove pollutants and make it harmless so that it may be disposed of safely in the rivers, etc., is called sewage treatment ( or wastewater treatment) . The main purpose of sewage treatment is to reduce the pollutants ( or harmful substances) present in it to such a low level that it may not remain a health hazard for any one.


( i) Screening. The wastewater ( or sewage) entering the sewage treatment plant is first passed through bar screens ( This process is called screening) . The bar screen removes the large rubbish obj ects like rags, sticks, cans, plastic bags ( polythene bags) , napkins, sanitary towels, etc., from the wastewater ( because they cannot pass through the holes of bar screen) .

( ii) G rit and Sand Removal. The wastewater ( or sewage) passing through the bar screen is made to flow slowly through a tank called ‘ grit and sand removal tank’. As wastewater flows slowly, the grit and sand present in it settle down at the bottom of the tank.

( iii) First Sed imentation Tank. The wastewater ( or sewage) is then passed into a sedimentation tank and allowed to stand there for a while. Most of the solid organic matter ( faeces, etc.) settles down on the sloping bottom of the sedimentation tank in the form of sludge. Thus, the solid part of sewage is called sludge. In this way, the first sedimentation tank separates the solid organic sludge from the rest of wastewater.

( a) The sludge is taken out from the bottom of first sedimentation tank and put into a large, closed tank called digester tank. In the digester tank, many types of anaerobic bacteria decompose the organic matter present in sludge to produce biogas ( also called sewage gas) . Thus,

The wastewater treatment ( or sewage treatment) gives us two useful products : ( i) biogas, and ( ii) sludge.

( b) The wastewater left in the first sedimentation tank still has some organic waste in the form of tiny suspended particles ( which do not settle at the bottom of the tank) , as well as soluble organic matter. There may also be some oil and grease floating on the surface of wastewater in the sedimentation tank. These floating materials are removed by a skimmer. Thus, mainly watery waste is left in the first sedimentation tank. It is also called clarified water.

( iv) Aeration Tank. The mainly watery waste ( or clarified water) from the first sedimentation tank is passed into aeration tank ( The tank in which air is put into water is called aeration tank) . The watery waste already contains aerobic bacteria in it. Compressed air is bubbled through the watery waste in the aeration tank to provide oxygen to activate aerobic bacteria and make them grow rapidly in this water.

The large number of aerobic bacteria produced in this way digest ( or consume) any human waste, food waste, soaps and other unwanted and harmful matter still remaining in the wastewater, leaving behind fairly pure water. In this way, aerobic bacteria clean the clarified watery waste and make it almost harmless.

(C) aeration tank) . The watery waste already contains aerobic bacteria in it. Compressed

(C) aeration tank) . The watery waste already contains aerobic bacteria in it. Compressed

air is bubbled through the watery waste in the aeration tank to provide oxygen to (C) air is bubbled through the watery waste in the aeration tank to provide oxygen to

S Aeration Tank.S Aeration Tank.tank is passed into aeration tank ( The tank in which air is put into water is called S tank is passed into aeration tank ( The tank in which air is put into water is called

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( i) biogas, and ( ii) sludge.

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ewater left in the first sedimentation tank still has some organic waste

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ewater left in the first sedimentation tank still has some organic waste in the form of tiny suspended particles ( which do not settle at the bottom of the

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in the form of tiny suspended particles ( which do not settle at the bottom of the tank) , as well as soluble organic matter. There may also be some oil and grease

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tank) , as well as soluble organic matter. There may also be some oil and grease floating on the surface of wastewater in the sedimentation tank. These floating

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floating on the surface of wastewater in the sedimentation tank. These floating materials are removed by a skimmer. Thus, mainly watery waste is left in the first

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materials are removed by a skimmer. Thus, mainly watery waste is left in the first sedimentation tank. It is also called clarified water. Cha

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sedimentation tank. It is also called clarified water.

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Aeration Tank.

And anaerobic bacteria decompose the organic matter present in sludge to produce

And anaerobic bacteria decompose the organic matter present in sludge to produce

biogas ( also called sewage gas) . Thus,

And biogas ( also called sewage gas) . Thus,

And

ewater treatment ( or sewage treatment) gives us two useful products :

And

ewater treatment ( or sewage treatment) gives us two useful products : ( i) biogas, and ( ii) sludge. And


ewater left in the first sedimentation tank still has some organic waste And

ewater left in the first sedimentation tank still has some organic waste

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ny made to flow slowly through a tank called ‘ grit and sand removal tank’. As wastewater

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ny made to flow slowly through a tank called ‘ grit and sand removal tank’. As wastewater

flows slowly, the grit and sand present in it settle down at the bottom of the tank.

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ny flows slowly, the grit and sand present in it settle down at the bottom of the tank.

The wastewater ( or sewage) is then passed into a

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The wastewater ( or sewage) is then passed into a sedimentation tank and allowed to stand there for a while. Most of the solid organic

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sedimentation tank and allowed to stand there for a while. Most of the solid organic matter ( faeces, etc.) settles down on the sloping bottom of the sedimentation tank in

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matter ( faeces, etc.) settles down on the sloping bottom of the sedimentation tank in the form of sludge. Thus, the solid part of sewage is called sludge. In this way, the first

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the form of sludge. Thus, the solid part of sewage is called sludge. In this way, the first sedimentation tank separates the solid organic sludge from the rest of wastewater.

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sedimentation tank separates the solid organic sludge from the rest of wastewater.

e is taken out from the bottom of first sedimentation tank and put

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e is taken out from the bottom of first sedimentation tank and put into a large, closed tank called digester tank. In the digester tank, many types of Com

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into a large, closed tank called digester tank. In the digester tank, many types of anaerobic bacteria decompose the organic matter present in sludge to produce Com

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anaerobic bacteria decompose the organic matter present in sludge to produce biogas ( also called sewage gas) . Thus,

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biogas ( also called sewage gas) . Thus,

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d The wastewater ( or sewage) entering the sewage treatment plant is first

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d The wastewater ( or sewage) entering the sewage treatment plant is first passed through bar screens ( This process is called screening) . The bar screen removes

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dpassed through bar screens ( This process is called screening) . The bar screen removes the large rubbish obj ects like rags, sticks, cans, plastic bags ( polythene bags) , napkins,

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dthe large rubbish obj ects like rags, sticks, cans, plastic bags ( polythene bags) , napkins, sanitary towels, etc., from the wastewater ( because they cannot pass through the

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dsanitary towels, etc., from the wastewater ( because they cannot pass through the

The wastewater ( or sewage) passing through the bar screen is Limite

d The wastewater ( or sewage) passing through the bar screen is

made to flow slowly through a tank called ‘ grit and sand removal tank’. As wastewater Limite

dmade to flow slowly through a tank called ‘ grit and sand removal tank’. As wastewater flows slowly, the grit and sand present in it settle down at the bottom of the tank. Lim

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flows slowly, the grit and sand present in it settle down at the bottom of the tank.

SCIENCE 7 TEXT BOOK

197

( v) Second Sed imentation Tank. From the aeration tank, the treated watery waste goes into the second sedimentation tank and allowed to stand there. In this tank, the micro-organisms ( aerobic bacteria, etc.) used in the aeration tank settle down at the bottom of the tank forming a fine sludge called ‘activated sludge’. It is called activated sludge because active micro-organisms ( or living micro-organisms) such as aerobic bacteria, and oxygen are present in it.

Sometimes it may be necessary to disinfect the treated water with chemicals like chlorine or ozone before releasing it into the distribution system. The biogas is used as a fuel.

34. Sanitation means to create hygienic environment (or clean environment) around us which is essential for preventing diseases and keeping good health. Poor sanitation and contaminated drinking water is the cause of a large number of diseases in our country. In order to prevent water-borne diseases, people should not defecate in the open spaces ( or near the water bodies) . People should realise their responsibility in maintaining the ‘ water sources’ in a healthy state by preventing their pollution (or contamination).

35. A septic tank usually consists of a big, covered, underground tank made of concrete having an inlet pipe at one end and an outlet pipe at the other end. The toilet seat is connected to the inlet pipe of the septic tank. The human excreta from the toilet seat enters into the septic tank through the inlet pipe. The solid part of excreta keeps on collecting at the bottom of the septic tank in the form of a sludge whereas watery waste remains above it. Septic tanks (or septic tank toilets) are suitable for those places where there is no sewerage system. Refer to figure 4 for the diagram.


36. ( b) 37. ( c) 38. ( a) 39. ( c) 40. ( b)

41. ( a) 42. ( d) 43. ( c)


44. (a) Bar screen, Grit and sand removal tank, First sedimentation tank, Aeration tank, Second sedimentation tank (b) First sedimentation tank

45. (a) Vermi-processing toilets (b) Vacuum toilets (c) Chemical toilets (d) Composting toilets (e) Septic tank toilets.

(C) S

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(a) Bar screen, Grit and sand removal tank, First sedimentation tank, Aeration tank, Second

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(a) Bar screen, Grit and sand removal tank, First sedimentation tank, Aeration tank, Second sedimentation tank (b) First sedimentation tank

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sedimentation tank (b) First sedimentation tank

(a) Vermi-processing toilets (b) Vacuum toilets (c) Chemical toilets (d) Composting toilets

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(a) Vermi-processing toilets (b) Vacuum toilets (c) Chemical toilets (d) Composting toilets

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(e) Septic tank toilets.

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(e) Septic tank toilets.

And 38.

And 38. ( a)

And ( a)

43.

And

43.

And

E. Questions Based on Higher Order Thinking SkillsAnd


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ny A septic tank usually consists of a big, covered, underground tank made of concrete having

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ny A septic tank usually consists of a big, covered, underground tank made of concrete having

an inlet pipe at one end and an outlet pipe at the other end. The toilet seat is connected

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an inlet pipe at one end and an outlet pipe at the other end. The toilet seat is connected to the inlet pipe of the septic tank. The human excreta from the toilet seat enters into

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to the inlet pipe of the septic tank. The human excreta from the toilet seat enters into the septic tank through the inlet pipe. The solid part of excreta keeps on collecting at the

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the septic tank through the inlet pipe. The solid part of excreta keeps on collecting at the bottom of the septic tank in the form of a sludge whereas watery waste remains above it.

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bottom of the septic tank in the form of a sludge whereas watery waste remains above it. Septic tanks (or septic tank toilets) are suitable for those places where there is no sewerage

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Septic tanks (or septic tank toilets) are suitable for those places where there is no sewerage

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dThe biogas is used as a fuel.

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dThe biogas is used as a fuel.

Sanitation means to create hygienic environment (or clean environment) around us which is

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dSanitation means to create hygienic environment (or clean environment) around us which is essential for preventing diseases and keeping good health. Poor sanitation and contaminated

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dessential for preventing diseases and keeping good health. Poor sanitation and contaminated drinking water is the cause of a large number of diseases in our country. In order to prevent

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ddrinking water is the cause of a large number of diseases in our country. In order to prevent water-borne diseases, people should not defecate in the open spaces ( or near the water

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dwater-borne diseases, people should not defecate in the open spaces ( or near the water bodies) . People should realise their responsibility in maintaining the ‘ water sources’ in a

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A septic tank usually consists of a big, covered, underground tank made of concrete having Limite

d

A septic tank usually consists of a big, covered, underground tank made of concrete having

SCIENCE 7 TEXT BOOK

198

WORKSHEET



( a) The used water discarded from our homes and other buildings.

( b) The liquid waste which is carried away in sewers.

( c) An underground pipe which carries away dirty drainage water and waste matter.

( d) Process taking place in waste water treatment plant in which large pieces of rubbish from wastewater are removed.


( a) Poor .… … … … … ...... and contaminated drinking water is the cause of large number of diseases.

( b) The human waste can also be used for making .… … … … … ...... which can be used as a fuel.

( c) All the portable toilets are .… … … … … ...... toilets.

( d) .… … … … … ...... are suitable for those places where there is no sewerage system.


( a) The aeroplanes have special type of toilets called vacuum toilets.

( b) Open dirty water drains are breeding places for flies, mosquitoes and other disease causing organisms.

(c) In vermi-processing toilet, the human excreta is treated with chemicals in a pit.

( d) Chemicals like paints and solvents should be thrown down the drains.

4. Match the onsite sewage d isposal system with its place:

( a) V acuum toilet ( i) Places with no sewerage system

( b) Septic tanks ( ii) In Aeroplanes

( c) Composting pit ( iii) At construction sites

( d) Chemical toilets ( iv) Where water supply is limited



( a) Name two chemicals used to disinfect water.

( b) Name any four water-borne diseases which are caused by drinking contaminated water.

( c) Name any two low-cost, onsite sewage disposal systems for human waste.

( d) At a sewage treatment plants, what type of bacteria work in the digester tank and in the aeration tank.

(C) ( a)

(C) ( a)

( b)(C) ( b) Name an(C) Name an

S B. Subjective Type Questions

S B. Subjective Type Questions

5. AnswerS 5. Answer theS the

Name two chemicals used tS Name two chemicals used t

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Septic tanks

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Septic tanks

Composting pit

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Composting pit

Chemical toilets

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Chemical toilets

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And oilet, the human excreta is treated with chemicals in a pit.

And oilet, the human excreta is treated with chemicals in a pit.

ts and solvents should be thrown down the drains.

And

ts and solvents should be thrown down the drains.

Match the onsite sewage d isposal system with its place: And

Match the onsite sewage d isposal system with its place:

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ny aste can also be used for making .… … … … … ...... which can be used as a

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ny aste can also be used for making .… … … … … ...... which can be used as a

or those places where there is no sewerage system.

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or those places where there is no sewerage system.

e special type of toilets called vacuum toilets.

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e special type of toilets called vacuum toilets.

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er drains are breeding places for flies, mosquitoes and other disease

oilet, the human excreta is treated with chemicals in a pit. Compa

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oilet, the human excreta is treated with chemicals in a pit.

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darries away dirty drainage water and waste matter.

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darries away dirty drainage water and waste matter.

waste water treatment plant in which large pieces of rubbish

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dwaste water treatment plant in which large pieces of rubbish

and contaminated drinking water is the cause of large number of

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dand contaminated drinking water is the cause of large number of

aste can also be used for making .… … … … … ...... which can be used as a Limite

d

aste can also be used for making .… … … … … ...... which can be used as a

SCIENCE 7 TEXT BOOK

199

SAMPLE PAPER

M.M. 50

Name: ............................................................... Class: ......................... Date: ...........................



( a) Water borne disease.

( b) Type of bacteria which decomposes sludge.

( c) Chemical which should not be thrown down the drain.

( d) Tank used in WWTP in which grit and sand is removed.

( e) Kitchen waste which blocks the drainage pipe.


( a) Herbicides are organic impurities present in sewage.

( b) Manholes are provided at the j unction of two or more sewers.

( c) Poor sanitation leads to the spread of diseases.

( d) All the portable toilets are chemical toilets.

( e) Cotton and hair should be thrown down the drain as sewage.


( a) V ermi- processing toilets use .… … .......… … … ...... to treat human waste.

( b) Untreated human excreta is a .… … .......… … … ...... hazard.

( c) Dried sludge is used .… … .......… … … ...... .

( d) Untreated human excreta may cause .… … .......… … … ...... pollution and .… … .......… … … ......pollution.


( a) Mango trees are planted all along the sewage ponds because they absorb all the surplus wastewater from the sewage ponds rapidly.

( b) Copper sulphate is used to disinfect water.

( c) Sewage treatment gives only sludge as a useful product.

( d) Sewer is an underground network of interconnected pipes that transport and carry wastewater.

( e) Nitrogen and phosphorus are the organic impurities present in the sewage.



( a) What is sludge? Explain how it is treated.

(C) ( b)

(C) ( b)

( c)

(C) ( c) Sewag

(C) Sewag

( d)(C)

( d) Sewer (C)

Sewer

S surplus wastewater from the sewage ponds rapidly.

S surplus wastewater from the sewage ponds rapidly.

Copper sulphate is used tS Copper sulphate is used t

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ted human excreta is a .… … .......… … … ...... hazard.

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Dried sludge is used .… … .......… … … ...... .

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reated human excreta may cause .… … .......… … … ...... pollution and .… … .......… … … ......

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reated human excreta may cause .… … .......… … … ...... pollution and .… … .......… … … ......

pollution.

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pollution.

Correct the follo

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wing statements:

Mango trees arChand

Mango trees arsurplus wastewater from the sewage ponds rapidly. Cha

nd

surplus wastewater from the sewage ponds rapidly.

And own down the drain as sewage.

And own down the drain as sewage.

oilets use .… … .......… … … ...... to treat human waste.

And

oilets use .… … .......… … … ...... to treat human waste.

ted human excreta is a .… … .......… … … ...... hazard. And


Dried sludge is used .… … .......… … … ...... . And


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anic impurities present in sewage.

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anic impurities present in sewage.

vided at the j unction of two or more sewers.

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vided at the j unction of two or more sewers.

tion leads to the spread of diseases.

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tion leads to the spread of diseases.

ts are chemical toilets. Compa

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ts are chemical toilets.

own down the drain as sewage. Compa

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own down the drain as sewage.

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d

SCIENCE 7 TEXT BOOK

200

( b) Why should oils and fats not be released in the drain?

( c) What is a vermi-processing toilet?

( d) What is a septic tank?

( e) Give any 2 harmful effects of untreated or inadequately treated wastes.


( a) Explain the steps taking place in a waste water treatment plant with the help of a flowchart.

( b) Mention the composition of sewage.

( c) How can we maintain sanitation at public places?

( d) Mention some good housekeeping practices to minimise undesirable wastes going from our house into the sewers.

( e) Explain the sewerage system of a place.


1. Water from which slud ge has been removed :

( a) filtered water ( b) clarified water ( c) purified water ( d) clear water 2. ercentageofwaterinactivatedsludgeis:

( a) 75% ( b) 97% ( c) 99% ( d) 32% 3. Which of these statements about oz one is correct?

( a) it is essential for breathing ( b) it is used to disinfect water ( c) both ( a) and ( b) ( d) none of these 4. Bar screens in a treatment plant help to remove:

( a) sand, grit and pebbles ( b) rags, sticks and cans ( c) oil and grease ( d) all of these 5 . Which of the following is not a water borne d isease?

( a) typhoid ( b) cholera ( c) influenza ( d) hepatitis

(C) S

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nd

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Which of the following is not a w

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( b) cholera

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( b) cholera

And tment plant help to remove:

And tment plant help to remove:

Which of the following is not a wAnd


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( c) purified wat

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( c) purified water

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er

( c) 99%

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( c) 99% tements about oz one is correct?

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tements about oz one is correct?

( b) it is used to disinfCompa

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( b) it is used to disinf

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dood housekeeping practices to minimise undesirable wastes going

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dood housekeeping practices to minimise undesirable wastes going

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