Heat Capacities Constant Pressure vs. Volume

[Katie_Ho_1M]

Why are the heat capacities under constant pressure and constant volumes different? And will be need to be able to calculate them on a quiz using, for example Cp=5/2 R for monatomic ideal gasses at constant pressure?

[Andreea Voro 3A]

They're different because pressure and volume can affect the kinetic motion of molecules differently, (higher pressure means molecules can't move as fast so typically needs more heat to get the molecules moving so the heat capacity is higher). It might be on the quiz so I would study it to be sure.

[Lauren_Johnston_3F]

They are different because the molecules have different degrees of freedom, which means they have different types of motions in the system. It may be used on the quiz, but you probably won't have to calculate it itself.