## Cp or Cv in temperature change

Volume: $\Delta S = nR\ln \frac{V_{2}}{V_{1}}$
Temperature: $\Delta S = nC\ln \frac{T_{2}}{T_{1}}$

Abigail Urbina 1K
Posts: 102
Joined: Thu Jul 27, 2017 3:01 am

### Cp or Cv in temperature change

When there is a temperature change and we are being asked to solve for delta S, how do we know whether to use Cp or Cv?

Rachel Lu_dis1H
Posts: 66
Joined: Fri Sep 29, 2017 7:06 am
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### Re: Cp or Cv in temperature change

When there are two variables changing like Temperature and Pressure, you would hold the other constant when solving for Delta S when theres change in temp (using equation deltaS=nCpln(T2/T1)
If the two variables are Temperature and Volume you would use the equation deltaS=nCvln(T2/T1)

allyz1F
Posts: 58
Joined: Sat Jul 22, 2017 3:00 am

### Re: Cp or Cv in temperature change

An easier way to think of it might be that whatever condition is constant is the specific heat used, so if volume is the only variable of the three not changing, you would use Cv in the deltaS equation.

Pooja Nair 1C
Posts: 55
Joined: Thu Jul 13, 2017 3:00 am

### Re: Cp or Cv in temperature change

Based on what information is given, you can tell which variable is staying constant and then accordingly use either Cp or Cv