1 Thermodynamics INTRODUCTION
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Transcript of 1 Thermodynamics INTRODUCTION
10/23/2015
1
Termodinamika Klasik (macroscopic approach )
• Sifat zat dilihat dari sudut pandang makroskopik
• Tidak memerlukan pengetahuan tentang prilaku(behaviour) molekul penyusun zat tersebut secaraindividu.
Termodinamika Statistik (microscopic approach )–Sifat zat dilihat dari sudut pandang mikroskopik–Diperlukan pengetahuan tentang prilaku(behaviour) molekul zat tersebut secaraindividu untuk mempelajari sifat zat yang disusunnya
DIMENSI DAN SATUAN
Dimensi sekunder
1. Velocity ( L t‐1 )
2. Volume ( L3 )
3. Energi ( m L2 t‐2 )
DIMENSI : menyatakan setiap besaran fisis
Dimensi primer1.Massa (m)2.Panjang (L)3.Waktu (t )4.Temperatur (T)5.Arus listrik (I)6.Cahaya (i)
SATUAN ( UNIT )1. Sistem British2. Sistem International , SI( Le System International d’Unites )
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Satuan Notasi British SI
Panjang L ft, inch m, cm
Massa m lb ( pounds ) kg, ...
Waktu t second, minutesecond, minute, ...
Temperatur T Fahrenheit, Rankine celcius, kelvin
Arus listrik I Ampere ampere
Cahaya i Candela candela
SATUAN (UNIT)
Konversi temperatur
T(R) = T(0 F)+ 459,67 T(K) = T(0C) + 273, 15 T( R ) = 1,8 T ( K ) T( K ) = T ( 0C )T(0F ) = 1,8 T ( 0C ) + 32 T( R ) = T ( 0F )
SISTEM TERMODINAMIKA
system
Batas sistem(Boundary)
Lingkungan(Surroundings)
1. Sistem TERTUTUP (Closed System)2. Sistem TERBUKA (Open System)
A thermodynamic system is that part of universe which is under thermodynamic study
A quantity of matter or a region in space chosen for study
ENERGYHEAT (KALOR), Q
WORK (KERJA), W
W (+)
Q(-)
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1. Sistem TERTUTUP (Closed System)disebut Massa atur (Control mass)
Mempunyai massa yang sudah tertentu jumlahnya dan tidak ada massa yang dapat melintasi batas sistemnya (tidak ada massa yang dapat masuk atau keluar dari sistem tertutup)
SISTEM
fixed boundary
EnergyYES
MassNO
• Energi dalam bentuk kalor atau kerja dapat melintasi batas sistem tertutup.
• Jika tidak ada energi yang dapat melintasi batas sistem, maka disebut sistem terisolasi atau ”Isolated System ”
SISTEM TERTUTUP ( Cont…..)
MassNO
EnergyYES
movingboundary
gas
gas
MassNO
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2. Sistem TERBUKA (OPEN SYSTEM)disebut Volume Atur (Control Volume )
• Selain energi, massa juga dapat melewati batas sistemnya ( massa masuk atau keluar )
mass massControl volume
energy
ENERGI SISTEM
Energi termal, mekanis, kinetik, potensial, listrik, magnet, kimia, nuklir.......
Energi total sebuah sistem (mengabaikan pengaruh-pengaruh energi listrik, magnetik, kimia)
Ek = ½ mv2 energi kinetikEp = m g z energi potensialU = internal energy
E = Ek + Ep + U kJ
Energi total tiap satuan massa sistem : kj/kg.
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Internal energy, U
• the energy stored in the atoms and molecules of the substance/system
–Related to molecular structure and the degree of the molecular activity
• Rapidly moving molecules (atoms) have a high temperature
• Slowly moving molecules (atoms) have a low temperature
SIFAT SISTEM ( Property of System )
• Keadaan ( “State” ) sebuah sistem dapat ditentukan oleh sifatnya ( property ), seperti : tekanan, temperatur, volume, massa, dll.
1. Intensive property :These variables or properties DO NOT depend on the amount of material (e.g. density, pressure, and temperature).
mVPT
½ m ½ m½ V ½ V
P PT T
Dibagi dua
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SIFAT SISTEM (cont….)
2. Extensive property :These variables or properties depend on the amount of
material present (e.g. mass, volume, total energy).
Keadaan ( ”State” ) sistem :ditentukan oleh watak ( property ) sistem.
Sistem sederhana ( simple system ) :pengaruh-pengaruh yang disebabkan oleh medan gaya-gaya luar ( external forces ) diabaikan.Keadaan (state) sistem sederhana ditentukan oleh 2 sifat intensive (p-T,p-v,T-v), v=1/
1. Temperature = “degree of hotness”
• Rapidly moving molecules (atoms) have a high temperature
• Slowly moving molecules (atoms) have a low temperature
High T Low T
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2. Pressure ‐ force per unit area
Impact
F
A
Weight
Satuan tekanan : N.m-2 ; lb.in-2 (psi) ; lb.ft-2 (psf) 1 N.m-2 = Pa (pascal)1 atm = 101325 Pa = 1,01325 bar
P vac
uum
Pab
s=
Pat
m+
Pga
ge
Pga
ge
Pat
m
Tekanan atmosfir
Tekanan nol absolute (vacuum)
P abs
Pat
m
Pabs=0
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3. Density ‐mass per unit volume
High densityLow density
KESETIMBANGAN ( Equilibrium )
• Kesetimbangan termal :• jika temperatur disetiap titik pada sistem sama semua.• Tidak ada gradient temperatur, sehingga tidak ada aliran
kalor dalam sistem.
• Kesetimbangan mekanik :• jika tekanan pada setiap bagian sistem sama semua.• ΣF = 0
• Kesetimbangan kimia :• komposisi kimia tidak berubah.• Tidak terjadi reaksi kimia dalam sistem.
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PROSES
Perubahan sistem dari satu kondisi setimbang ke kondisi setimbang yang lain.
Proses quasi static atau quasi equilibirium :Suatu proses yang berlangsung sangat lambat sehingga keadaan sistem setiap saat sangat dekat dengan kesetimbangannya.
GAS GAS
Non Quasi-static process Quasi-static process
LINTASAN PROSES ( PATH )
Suatu deretan keadaan ( state ) yang dilewati suatu sistem selama proses berlangsung.
SiklusProses mengalami satu siklus bila keadaan akhir dari proses tersebut kembali ke keadaan awal ( titik akhir berimpit dengan titik awal )
Lintasan proses
Tek
anan
, P
Volume , V
1 awal
2 akhir
Tek
anan
, P
Volume, V
2 akhir
1 awal
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Proses khusus
Isoprocesses
• apply 1st law of thermodynamics to closed system of an ideal gas(pv=RT)
• isoprocess is one in which one of the thermodynamic (state) variables are kept constant
• use pV diagram to visualise process
pvn = c
1. Isobaric Process
• process in which pressure is kept constant (p=c)
•Constant Pressure
•Work = Force x distance
•Force = Pressure x Area
•Work = Pressure x Area x Distance
W = P V
•Work is equal to the area under the PV diagram
W = PV
Q = mcp T
U =Q - WV
P
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2. Isochoric Process
• process in which volume is kept constant V=c
3. Isothermal Process• process in which temperature is held constant (T=c)
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4. Adiabatic Process
• process in which no heat transfer takes place (Q=0)
PHASE CHANGES
Heat must be added or removed to change a substance from one phase to another.
Energy is absorbed when change of phase in this direction
SOLIDGAZ
LIQUID
Energy is released when change of phase in this direction
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Phase changes occur at a constant temperature (at the melting point or the boiling point).
The quantity of heat required for a phase change is called the latent heat, which is different for each substance.
PHASE CHANGES
– Evaporation from liquid to gas phase.– Condensation from gas to liquid phase.– Freezing from liquid to solid phase.– Melting from solid to liquid phase.– Sublimation from solid to gas phase.– Ionization from gas to plasma phase.
SOLID LIQUID GAS PLASMA
Adding or removing energy from matter may cause it to change from one phase to another: