CHEM162:LAB2IntermolecularForcesDemonstration

OVERVIEWThislabwillbeconductedonlineandisexpectedtotake3–4hourstocomplete.Studentswilllearnabouttheinformationtypicallykeptinageneralchemistrylaboratorynotebook.Severalformatsforlaboratorynotebookswillbesharedandstudentsareinvitedtochooseastyletheyprefer.Studentswillobservetheimpactofintermolecularforcesonphysicalpropertiesofsurfacetension,viscosity,solubility,andevaporativecooling.TECHNIQUESTOLEARN

• Howtowriteascientificobjective.• Howtosummarizeaprocedure.• Howtoanticipatethedatathatwillbecollectedandcreatedatatablesandgraphsbeforeperformingthelab.• Howtowriteahypothesisandanalyzedatatosupportorrefuteahypothesis.• Howtorecordobservationsanddatainalaboratorynotebook.

MATERIALS

• Notebook,scratchpaper,ortabletforwriting.• 2differentcoloredpens(blueandblack,orsimilar)• Noteaboutvideos:allvideoslinksforthislabwillbelistedinthisdocumentandtheywillbeembedded

inthecanvasassignmentpage.

CRITERIAFORSUCCESS

Studentsattempteachquestioningoodfaith.Shortanswerresponsesareformattedincompletesentences.

Allworkisshownforcalculationswhenrequested.Thesemaybeembeddedintheassignmentsubmittedorattachedseperatelyifnecessary.

Studentdemonstratesmasteryofthelab'slearningobjectives.Someerrorsmaybepresentintheassignment,about85%oftheanswersarecorrectwithnolargegapsinknowledgepresent.Theassignmentisformattedasalaboratorynotebook.Mistakesarelegibleandtheworkishandwritten.Scientificobjectiveiswrittenfromtheperspectiveofascientist(notstudent),anddescribesthegoalofthelabratherthenthetasksthatwillbecompleted.Studentsdemonstrateunderstandingofformatingalabnotebook,recordingobservations,andtheeffectofintermolecularforcesonphysicalproperties.Twocolorsofpenareused.Oneisusedtopreparethenotebookbeforewatchingthedemonstrationvideosandanothercolorisusedtorecordobservations.Theprocedureissummarizedbrieflyinthestudentsownwords.Observationsincludephysicalappearances,changes,andmeasurements.PartDtableisproperlyformattedandeasytoread,itincludesobservationsofintialtemperature,finaltemperature,andtime.CalculationsareshownforpartDConclusionparagraphaddressesintermolecularforcesforeachdemonstration.

Lab2:LabNotebooks&IMFDemo

General

Lab2

INTRODUCTIONThislabwillbeconductedonline.Tocompletethelabyouwill:

1) Readtheintroductionandwatchavideoabouthowtokeepalaboratorynotebook.2) ReadtheIMFDemoprocedureandusinganotebookorloosepaperpreparea“labnotebook”before

watchingtheDemovideos.3) Watchthedemovideosandrecordobservationnotesinthe“labnotebook”pages.4) Reflectonyourobservationsinaconclusionsparagraph.

LABORATORYNOTEBOOKSThescientistsgoalinkeepingalabnotebookistohavearecordofeverythingthathappenedinthelab.EVERYTHING.Thismeansthatmistakes,questions,observations,andmeasurementsareallrecorded.Havingasystematicwayofrecordinginformationmakesiteasierforascientisttofindinformation,analyzedata,andultimatelycommunicatetheirfindings.Inthisclassyouwillpracticelabnotebookskills.Thesearethesectionsyourlabnotebookmustincludeforthisclass.Boldedsectionswillbeincludedinalllabsregardlessofthelab’sprocedure.

• Name• Date• Labnumberandtitle• ScientificObjective• Pre-labnotes:Theseshouldbeincludedasnecessarybasedonthelabprocedure.

o Hazards&Safetyinformationo Wastedisposalinformationo Listofchemicals,amounts,physicalpropertieso Chemicalreactions

• Proceduresummary• Spaceforobservations• Spaceforcalculations(ifthelabrequirescalculations)• Datatablescreatedandreadyforinformationtoberecorded.(ifthelabrequiresrecording

measurementsinatable)• Spaceforgraphs,ifpossiblecreateaxisandtitlebeforestartinglab(ifthelabincludesgraphingdata).• Spaceforconclusions

ScientificObjectives.In1–2sentencesstatethepurposeofthelabfromtheperspectiveofascientistratherthanastudent.Oftenscientificobjectivesletthereaderknowwhatthefinalcalculationswilldeterminefromcollecteddataorwhatquestionisbeingansweredbytheexperiment.Thesemayincludethetechniquesthatareusedinthelabbutnoproceduraldetailshouldbementioned.PleaseseeAppendixAofthislabforexamplescientificobjectives.ProcedureSummary.Thepurposeofsummarizingtheprocedureistwo-fold:1)studentscommunicatetheyarepreparedtoconductthemselvessafelyinlabbydemonstratingtheyhavecarefullyreviewedtheprocedure.2)Asummarycancreateashortroadmapoftheexperimentthatcanbereferencedwhilerecordingobservations.Thiscanreducetheamountoftimeittakestowriteyourobservationsinyournotebook,allowingthestudenttorecordmoredetails.PleaseseeAppendixBformoreinformationaboutformattingalabnotebook.Observations.Allobservationsmustbemadeinpen.Ifamistakeismadeasinglelineshouldbedrawnthroughanobservationtoindicatetheinformationisincorrect.Thecorrectinformationcanthenbewritten.Thegoalistorecordmistakesaswellasyoursuccesses,somistakesmuststillbelegibletothereader.Observationsshouldnotethephysicalappearanceofasolution,changesthatareobserved,measurementsofphysicalproperties

thatareperformed,andpossibleproceduralmistakesthataremadealongthewaythatshouldbeconsideredwhenanalyzingdatalater.FormoreinformationaboutobservationspleaseseeAppendixB.Conclusions.Attheendofanexperimentstudentsshouldrecordtheirinitialimpressionsoftheirwork.Reviewingthelabquestionsthatfollowtheprocedureandmakingafewnotesafterbeingseepedintheworkofthelabforhourswillmakeiteasiertorecalldetailsofthelabdaysorweekslater.Thiscanreducetheamountoftimespentansweringthequestionsafterthedatahasbeenanalyzed.INTERMOLECULARFORCESThestructureofamoleculeinformshowitwillinteractwithothermolecules.Overallpolarity,thepresenceofH-F,H-N,orH-Obonds,thesize,theshape,andthechargealldictatetheintermolecularforcesthatwillexistbetweenmolecules.Themoreintermolecularforcesthatexist,thestrongertheinteractions.Thephaseofthesubstance(solid,liquid,andgas)affecthowclosethemoleculesaretooneanother.Thecloserthemoleculesthestrongertheinteractions.Intermolecularforcesarelistedbelowinorderofincreasingstrength.LondonDispersionForces(weakestIMF)

Theseexistbetweenallmolecules(withanelectroncloud).Thisinteractionarisesfromtemporaryandspontaneousdipolemomentsthatarecreatedwhenelectronsfromonemoleculecomeclosetoelectrons,andrepelthem,inanothermolecule.

Dipole-DipoleInteractions Theseexistonlybetweenmoleculesthathaveoveralldipolemoments.Thepartialpositiveendofamoleculewillalignwiththepartialnegativeendofanothermolecule.

HydrogenBonding TheseexistonlybetweenmoleculeswithH-F,H-N,andH-Obonds.TheHydrogenatomhasalargepartialpositivechargeandtheF,N,orOhasalargepartialnegativechargeandlonepairsthatarecapableofinteractingwiththelargepartialpositivechargeofaHydrogenonanothermolecule.

Ion-DipoleInteractions(strongestIMF)

Theseexistinmixtureswhenacationinteractswiththepartialnegativeendofapolarmoleculeorananioninteractswiththepartialpositiveendofapolarmolecule.

Thislabwillincludeacomparisonofthephysicalpropertiesofpuresubstances.Reviewthechemicalstructuresofthemoleculesthatwillbecomparedineachpartoftheexperiment.Whatintermolecularforcesexistwithinapuresampleofeachcompound?

LAB2ACTIVITYInthisactivityyouwilllearnfirstaboutlabnotebooksandprepareyourownforaseriesofintermolecularforces(IMF)demos.YouwillthenwatchtheIMFdemosandrecordyourobservationsinthenotebookpagesyouprepared.Finally,youwriteaconclusionsparagraphusingtheprovidedquestionstoguideyourdiscussion.First,watchthenotebookvideolinkedbelowabouthowtopreparealabnotebookbeforeconductinganexperiment.Thevideowillalsoincludeinformationabouthowtorecordobservations.Thevideowillshowanexampleofhowtosetuplabnotebookpages,thisexperimentisnotthesameasthosecompletedinthislab.Usethisinformationandtheinformationprovidedintheintroductiontocompletequestion1oftheactivity.ThedocumentsshowninthevideocanbedownloadedfromtheLab2canvasassignmentpage.

WatchtheNotebookVideohere:https://youtu.be/BvpvyqpAX-o(about30minutes)Q1.Createyourprelabnotebookpages.Useanotebook,piecesofscratchpaper,oratablettopreparealabnotebookpagesfortheexperimentsdescribedintheprocedurethatfollowsthisquestion.Thisshouldbedonebeforewatchingthedemonstrationvideos.Yourpagesshouldinclude:

• Includeyourname,date,andalabtitle.• Writeascientificobjectiveforthelab.(ReviewingQ4canhelpyouwriteyourobjective)• Reviewtheprocedurebelowfortheintermolecularforcedemonstrationsandsummarizeitasa

shortparagraphorbulletpointswithspaceforobservations.• Leavespaceforyourobservations.• Createatablefortheevaporativecoolingexperiment.Thetableshouldincludeinitial

temperature,finaltemperature,time,andcalculatedrate.• Leavespaceforevaporativecoolingratecalculations.• Leavespaceforconclusions.

PartA: Water CookingOil(unsaturatedtrigylceride)

PartC: Isopropanol PropyleneGlycol Glycerol

PartD: Water Isopropanol Acetone

Q2.Recordobservations.Foreachexperimentdescribedintheprocedurewatchashortvideolinkedbelow.Recordyourobservationsinyourlabnotebookpagespreparedinquestion1.Pleaseuseadifferentcoloredpensoitiscleartomehowyoupreparedyournotebookandhowyourecordedobservations.

A. Solubility:https://youtu.be/sWxLhkhbGhoB. SurfaceTension:https://youtu.be/Qvi6dm9QeEIC. Viscosity:https://youtu.be/977wNbFiYlc?t=226(thevideowillstartatminute3:46)D. EvaporativeCooling:https://youtu.be/xqardSvsPOU?t=109(thevideowillstartatminute1:49)

Thedataiscollectedatthefollowingtimesinthevideo:Water:minute2:30 IsopropylAlcohol:minute3:55 Acetone:minute5:05

PROCEDUREFORIMFDEMOS

A.Solubility1. Pour50mLofoil(nonpolarbuthighmolecularweightmolecules)intoa250mLerlenmeyerflask.2. Add150mLofwatertothesameerlenmeyerflask.3. Addafewdropsofgreenwatersolubledye.4. Dothewaterandoilappeartoformahomogenoussolutionwithoutagitatingthemixture?5. Addaalkaseltzertablettotheflask.Thecarbondioxidebubblesformedasthetabletdissolvesin

waterwillagitateandmixthesolution.6. Dowaterandoilappeartoformahomogenoussolutionwhenagitatingthemixture?

B.SurfaceTension

7. Fillabowlwithtapwater.8. Carefullyplaceaneedle(withahigherdensitythenthewater)onthesurfaceofthewater.9. Doestheneedlefloatorsink?

C.Viscosity

10. Obtainthree100mLgraduatedcylinders.Eachwillbefilledwith100.0mLofadifferentsolvent.11. Fillthefirstgraduatedcylinder(tothefurthestleftinthevideo)withisopropanol,C3H8O.12. Fillthesecondgraduatedcylinder(inthemiddle)withpropyleneglycol,C3H8O2.13. Fillthethirdgraduatedcylinder(furthesttotherightinthevideo)withglycerol,C3H8O3.14. Atthesamestartingtimedropthreeweightedballsintothegraduatedcylindersandobservethe

relativeratetheyfalltothebottom.15. Inwhichliquiddoestheballtravelthefastest?Andtheslowest?

D.EvaporativeCooling

16. Obtainthree100mLbeakers.Eachwillbefilledwith50.0mLofadifferentsolvent.17. Fillthefirstbeaker(leftinthevideo)withwater,H2O.Fillthesecondbeaker(middleinvideo)with

isopropanol,C3H8O.Andfillthethirdbeaker(rightinthevideo)withacetone,C3H6O.18. Useathermometerthatcanautomaticallyrecordtemperaturemeasurementstwiceinonesecond.

Dipthethermometerintothesolutionandremoveitsoitisexposedtotheair.19. Oncethethermometerhasbeenremovedfromthesolutionrecordthetemperatureevery0.5

secondsuntilthetemperaturenolongerdecreases.20. Foreachliquidrecordtheinitialtemperature,thelowesttemperature,andtheamountoftime

(seconds)thatpassestoreachthelowesttemperature.

Q3.CalculatetheevaporativecoolingrateforeachsolventinpartDofthedemonstrations.Showyourworkinyournotebookpagesbelowyourobservations.ThenrecordyourcalculatedratesinthetableconstructedtocollectmeasurementsinyourobservationsfordemonstrationD.

𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑣𝑒𝑐𝑜𝑜𝑙𝑖𝑛𝑔𝑟𝑎𝑡𝑒 = ∆01234

unitsshouldbe°C/sQ4.Writeaconclusionparagraphthatsharesyourinitialthoughtsabouteachexperiment(A-D)andtheroleintermolecularforcesplayintheobservedphysicalproperties.Thequestionsbelowcanhelpguideyourdiscussion.(pleaselimitresponsestoapageorlesswithinyournotebook)

a. Dowaterandoilmix?Howcanintermolecularforcesexplainyourobservationofsolubility?b. Iftheneedleisdenserthenwater,whydoesitfloatratherthansink?c. Dothedifferencesinviscosityobservedforisopropanol,propyleneglycol,andglycerolmatchyour

expectationsbasedonthestrengthoftheintermolecularforcesforeachmolecule?d. Explainthedifferencebetweenevaporativecoolingratesofwater,isopropanol,andacetonein

termsoftheintermolecularforcesorstructuralfeatures(likeweight)ofeachmolecule.Tosubmitthisassignmentpleasetakeapictureofyourlabnotebookpagesandconvertthemtoapdffile.ThepdffilecanthenbeuploadedontheLab2assignmentpage.Ifyouhaveanyquestionsabouthowtogenerateapdffileorhowtosubmitanassignmentincanvaspleaseemailyourinstructor.Someusefulstrategiesinclude:

• Downloadingapdfscannerappontoasmartphone.Irecommendcamscanner.Theseappswilltakeapictureofadocument,orofmultipledocuments,andconvertittoapdfthatcanbeemailedtoyourself.Camscannerhastheabilitytouploadtocanvasaswellifyouusethecanvasphoneapp.

• Takeapicturewithacameraorphonecamera.Thenyouhaveafewoptions:o Opentheimageinimageviewingsoftwareandexportasapdf,saveasapdf,orprintto

pdf.o EmbedtheimageinaprogramlikeMicrosoftwordandprinttopdf.

Lab2AppendixA:ScientificObjectives

ExamplesofScientificObjectives:1) ThescientificobjectiveforanexperimentstandardizingtheconcentrationofNaOHcouldbe:

BAD“ThescientificobjectiveofthisexperimentistotitrateNaOHsolutionwithastrongacid.”

GOOD“ThescientificobjectiveofthistitrationistodeterminetheconcentrationofanunknownNaOHsolutiontofoursignificantfigures.”(Whyisthisanswerbetter?Itidentifiesthequantitybeingdetermined(concentration),thesolutioninquestion,andthemethodused.)

2) Thescientificobjectiveforanexperimentthatmeasuresthechangeinfreezingpointofasolutionwhen

lauricacidisdissolvedinbenzoicacid;thisinfoisusedinthepost-labtocheckthemolarmassoflauricacid:BAD“Thescientificobjectiveofthisexperimentistomeasurethefreezingpointoflauricacidandbenzoicacid.”

GOOD“Thescientificobjectiveofthisexperimentistodeterminethemolarmassoflauricacidusingitsfreezingpointdepressioninabenzoicacidsolution.”(Whyisthisanswerbetter?Itcorrectlyidentifiestheendresultofthelab(molarmassdetermination)ratherthanjusttheintermediatedatathatiscollected.)

3) Thescientificobjectiveforanexperimentthatmeasureshowethanol’svaporpressurechangeswith

temperature,andwhichresultsinquestionsabouttheenthalpyofvaporizationofethanol:BAD“Thescientificobjectiveofthisexperimentistovarythevaporpressureastemperaturechanges.”

GOOD“Thescientificobjectiveofthisexperimentistodeterminetheenthalpyofvaporizationofethanolbyvaryingitstemperatureandmeasuringvaporpressure.”(Whyisthisanswerbetter?Itcorrectlyidentifiesthephysicalquantitybeingdetermined,thechemicalitisdeterminedfor,andthemethodused.)

Lab2AppendixB:PreparingyourLaboratoryNotebooksTheGeneralStructureofYourLaboratoryNotebookBeforeyoucometolab,youmustprepareyournotebook.Thismaytakequitesometime.Inprinciple,aneducatedpersonwhoisfamiliarwithchemistryshouldbeabletoreproduceyourexperimentbasedsolelyonwhatyouwriteinyournotebook,bothbeforeandduringlab.Keepinmindthatyouarewritingforsomeoneelse.Useplain,straightforwardlanguageandincludeasmanydetailsaspossible.Agoodlaboratorynotebookshould:

• sayexactlywhatwasdone,whenitwasdone,andwhyitwasdone;• makeclearwhodidit;• enablesomeoneelsetodothesamethingatsomefuturedate.

InChemistry161,youweregivenpre-formatteddatatablesforeveryexperiment.InChemistry162,youwillrecordallofyourdatainablanknotebook.Thiswillrequiremorepreparationonyourpart.Suchnotebooksarethetruerecordofthesciencedone,eventhoughmostotherscientistswillencountertheworkinanotherform,suchasapublishedresearcharticle.Introduction.Theintroductiontoyourexperimentalreportshouldhavethefollowing:

• YourNameandyourlabpartner’sname• TitleoftheExperiment.Thisshouldalsoappearonanyaddedpiecesofpaper,graphs,whatever,thatare

tapedintothenotebook.• ScientificObjective.Whyareyoudoingthisexperiment?Whatdohopetofind/show?Thisisthesame

objectivethatisrequiredforthepre-lab.• TheDate.Inindustryorresearchthisisexceedinglyimportant,butitisgoodpracticeforundergraduates

also.Writethedateunambiguouslyandincludetheyear-forexample:2July2000.Pre-LabLectureNotes.Leaveyourselfsomeroomtorecordnotesduringthepre-lablectures.Procedure. Although the lab manual for this course includes detailed instructions for the experimentalprocedure,youneedtowriteabriefsummaryoftheprocedureinyournotebook.Thepurposeofthisistomakeyouthinkaboutalloftheexperimentalpartsbeforeyousetfootinthelab.Remember:knowledgeispower.Donotcopytheprocedureinthemanualverbatimintoyournotebook.Thereisnoneedtodothis,sinceyouwillbe allowed to bring your labmanual with you to lab.What you should focus on are themajor stepsof theexperiment, not the tiny details. Write your procedure as a numbered list, using simple, direct statements.Comment on any special features of the materials to be used, such as special handling or waste-disposalprocedures.ExperimentalObservations. Theobservationsyoumakeand thedata that you recordwill lead to theacceptance or rejection of your hypothesis, and will decide what future experiments may be done. Theobservationsanddataarethereforecentraltothewholeexercise.Observationsareyournotesaboutcolorchanges,gasesorprecipitatesformed,solidsdissolving,colorsofsolutions,solids,liquidsorgases,meltingorboiling,heatevolvedorabsorbed(exothermicorendothermicreaction),rateofreaction(slow,moderate,fast,explosive?),soundsorsmells.Youshouldalsorecordany

problemsyouencounteredwithequipmentorchemicalsandhowyouaddressedthem.Ifyoudeviatedfromthelaboratorydirections,besuretorecordwhatyoudidinmoredetail.Acorrectlywrittenobservationincludesenoughinformationtoputtheobservationincontext.Itidentifiesthechemicalsreacting,theequipment,thechangeobserved,andthetime-frameinwhichitoccurred.Forexample:“StepIIparta.When6Mnitricacidwasaddedtothecalorimeter,thesolutionimmediatelybecamewarmtothetouch.”Eveninexperimentsthataremostlyquantitativeinnature,therearealwaysqualitativeobservationsthatshouldbemade,suchasdescriptionsofthesubstancesusedorchangestoprocedure.SometipsforrecordingObservationsandData:

• DOrecordobservationsanddatahonestly.Ifyoumessedup,youmustrightdownyourmess-upsothatyoucantroubleshootbaddatalater.

• DOrecordobservationsanddataasyougoalong,inthenotebook,inink,immediately.• DONOT trustyourmemory,notevenforaminute. It isveryeasyto forgetwhatyouhave justdone.

Further,youdonotwantyourmindoccupiedwithtrivialthingsandsmalldetails.Youneedtokeeptheoverallexperimentalplaninmind.

• DONOTuseoddscrapsofpapertorecordobservationsanddata.• DOrecordobservationsanddataascompletelyasispossible.Don'tworrytoomuchaboutinterpreting

thedataasyougoalong,anddon'tworryifsomeoftheobservationsappearbanal.• DO use good penmanship. Take care with numbers…DONOT over-write an incorrect value with the

correctone.Simplycrossouterroneousmaterialwithasinglelineandre-writethecorrectdatanexttoit.

• DONOTusewhite-out.• DO leavewhite space in your notebook for comments, notes, corrections, and redrawn tables. Your

notebookhasmorepaperthanyouwilluse.HandPlots.Aspartofyourfinalizedlabreport,youwillinmanycasespreparecomputer-generatedplotsofyourexperimentaldata.However,itisalwaysagoodideatoplotdatabyhandinyournotebookbeforeyouleavethelab.Lookingatyourdatagraphicallycanrevealerroneousvaluesthatyouwon’tnecessarilynoticesimplybylookingatadatatable.Thisgivesyouthechancetomeasurethatvalueagain,ifnecessary.But,justbecausethesearehandplotsisnoreasontoskimponproperformatting.Therefore,allhandplotsarerequiredtohave:

• Apropertitle,includingthetrialnumberifapplicable.• Appropriatelyscaledaxesthatallowthedatato“beitself.”• Properlylabeledaxes,includingunitsinparentheses.

DataTables.Youshouldknowwhatdatayouwillbecollectingbeforeyoucometo lab,andthereforeyoushouldknowwhatyourdatatablewilllooklikebeforeyoucometolab.Yourtablesmustbewritteninverticalcolumns,witheachcolumnheadedwith thequantityand theappropriateunits.Therows inyour tablesmayrepresenttrials,time-steps,volumeadded(asinatitration),etc.Theappropriaterowdesignationwilldependonthe particular experiment, but generally speaking, all the numbers in a given row should be related in somefashion.Insomecasesyoumayalsowanttoincludecolumnsfortheresultsofcalculationsusingtherawdata.

SampleDataTable

0.050 M NaOH time (min) [CV+] (M) 1/[CV+] (M) ln[CV+] (M)

0.00 1.50E-05

2.00 1.36E-05

4.00 1.24E-05

6.00 1.13E-05

8.00 1.02E-05

10.00 9.31E-06

12.00 8.47E-06

14.00 7.70E-06

16.00 7.00E-06