Thermodynamics
Questions and Answers
Updated 2026
ZerothBLawBofBThermodynamicsB-
BAnswerBAnBisolatedBsystemBwillBevolveBtoBequilibrium.
1stBLawBofBThermodynamicsB-
BAnswerBConservationBofBenergy.BdUB=B0BforBisolatedBsystem.
InternalBenergyBofBaBsystemBincreasesBbyBheatBaddedBandBdecreasesBbyBworkBdoneB
byBtheBsystem.B
dUB=BδQ-δW
IsochoricBandBrelateBtoBfirstBlawB-BAnswerBConstantBVolumeBprocess
SinceBdWB=BpdV,BdWB=B0,BthereforeBdUB=BdQ
IsobaricBandBrelateBtoBfirstBlawB-BAnswerBConstantBPressureBprocess
dUB=BδQB-BδWBandBdQB=BdUB+BpdVB=Bd(U+pV)B=BdHB(enthalpy)
AdiabaticBandBrelateBtoBfirstBlawB-BAnswerBδQB=B0BsoBdUB=B-δW
EnthalpyB-BAnswerBisobaric:BdQB=BdUB+BpdVB=Bd(U+pV)B=BdH
HB=BUB+pV
SpecificBHeatB-
BAnswerBCBisBtheBratioBofBheatBaddBtoBaBsystemBandBtheBcorrispondingBchangeBinBt
emperature.BCB=BdQ/dT
C_vB=B(dQ/dT)_vB=B(dU/dT)_v
, C_pB=B(dQ/dT)_pB=B(dH/dT)_p
IsothermalB-BAnswerBTemperatureBisBconstant.BdUB=B0;BdQB=BdW
pB=BnRT/VB=Bconst/V
WB=B∫pdVB=B∫nRT/VBdVB=BnRT*ln(V2/V1)
SecondBLawBofBThermodynamicsB-
BAnswerBStatesBthatBtheBentropyBofBanBisolatedBsystemBneverBdecreases,BbecauseBis
olatedBsystemsBspontaneouslyBevolveBtowardsBthermodynamicBequilibriumB--
BtheBstateBofBmaximumBentropy.
TheBtotalBentropyBofBanyBsystemBwillBnotBdecreaseBotherBthanBbyBincreasingBtheBent
ropyBofBsomeBotherBsystem.
Thomson'sBpostulate,BClausius'sBpostulate
EntropyB-
BAnswerBTheBmeasureBofBaBsystem'sBthermalBenergyBperBunitBtemperatureBthatBisBu
navailableBforBdoingBusefulBwork.B
dSB≥BδQ/TB
=BforBreversible,B>BforBirreversible.B
ifBreversibleBandBadiabaticBdSB=B0,BsoBEntropyBstaysBconstantBduringBthisBprocess.
EntropyBandB1stBlawBandB2ndBlawB-BAnswerBTdSB≥BdUB+BdW
andBdWB≤B-dUB+BTdSB≤B-d(UB-BTS)
IdealBGas:Blaw,BinternalBenergyBequ,BCpBandBCrBrelation,BisothermalBWork,BisobaricB
Work,BadiabaticBWorkB-BAnswerBpVB=BnRT
(dU/dV)_tB=B0BsoBdUB=BdQB=Bn*C_v*dT
C_pB=BC_vB+BR
W_tB=BnRT*ln(V2/V1)
W_pB=Bp∆VB=BnR∆T
Questions and Answers
Updated 2026
ZerothBLawBofBThermodynamicsB-
BAnswerBAnBisolatedBsystemBwillBevolveBtoBequilibrium.
1stBLawBofBThermodynamicsB-
BAnswerBConservationBofBenergy.BdUB=B0BforBisolatedBsystem.
InternalBenergyBofBaBsystemBincreasesBbyBheatBaddedBandBdecreasesBbyBworkBdoneB
byBtheBsystem.B
dUB=BδQ-δW
IsochoricBandBrelateBtoBfirstBlawB-BAnswerBConstantBVolumeBprocess
SinceBdWB=BpdV,BdWB=B0,BthereforeBdUB=BdQ
IsobaricBandBrelateBtoBfirstBlawB-BAnswerBConstantBPressureBprocess
dUB=BδQB-BδWBandBdQB=BdUB+BpdVB=Bd(U+pV)B=BdHB(enthalpy)
AdiabaticBandBrelateBtoBfirstBlawB-BAnswerBδQB=B0BsoBdUB=B-δW
EnthalpyB-BAnswerBisobaric:BdQB=BdUB+BpdVB=Bd(U+pV)B=BdH
HB=BUB+pV
SpecificBHeatB-
BAnswerBCBisBtheBratioBofBheatBaddBtoBaBsystemBandBtheBcorrispondingBchangeBinBt
emperature.BCB=BdQ/dT
C_vB=B(dQ/dT)_vB=B(dU/dT)_v
, C_pB=B(dQ/dT)_pB=B(dH/dT)_p
IsothermalB-BAnswerBTemperatureBisBconstant.BdUB=B0;BdQB=BdW
pB=BnRT/VB=Bconst/V
WB=B∫pdVB=B∫nRT/VBdVB=BnRT*ln(V2/V1)
SecondBLawBofBThermodynamicsB-
BAnswerBStatesBthatBtheBentropyBofBanBisolatedBsystemBneverBdecreases,BbecauseBis
olatedBsystemsBspontaneouslyBevolveBtowardsBthermodynamicBequilibriumB--
BtheBstateBofBmaximumBentropy.
TheBtotalBentropyBofBanyBsystemBwillBnotBdecreaseBotherBthanBbyBincreasingBtheBent
ropyBofBsomeBotherBsystem.
Thomson'sBpostulate,BClausius'sBpostulate
EntropyB-
BAnswerBTheBmeasureBofBaBsystem'sBthermalBenergyBperBunitBtemperatureBthatBisBu
navailableBforBdoingBusefulBwork.B
dSB≥BδQ/TB
=BforBreversible,B>BforBirreversible.B
ifBreversibleBandBadiabaticBdSB=B0,BsoBEntropyBstaysBconstantBduringBthisBprocess.
EntropyBandB1stBlawBandB2ndBlawB-BAnswerBTdSB≥BdUB+BdW
andBdWB≤B-dUB+BTdSB≤B-d(UB-BTS)
IdealBGas:Blaw,BinternalBenergyBequ,BCpBandBCrBrelation,BisothermalBWork,BisobaricB
Work,BadiabaticBWorkB-BAnswerBpVB=BnRT
(dU/dV)_tB=B0BsoBdUB=BdQB=Bn*C_v*dT
C_pB=BC_vB+BR
W_tB=BnRT*ln(V2/V1)
W_pB=Bp∆VB=BnR∆T
