1. The problem statement, all variables and given/known data For a material given by U=C1PV2 and PV2=C2T Find the entropy 2. Relevant equations dS/dU = 1/T; dU/dV = -P I don't know if I require anything else 3. The attempt at a solution So from 2 equations I got U = C1 C2T But dU/dT is not equal to S. Which equation do I use to get the entropy? I was thinking of using F = U-TS. Which will give F = C1PV2 - TS And then doing dF/dT but then I didn't use the 2nd condition at all. What am I missing?