Conceptual Help on Cv vs Cp

Yea Eun Lee 1H
Posts: 33
Joined: Fri Sep 29, 2017 7:06 am

Conceptual Help on Cv vs Cp

I understand mathetmatically how we find the equations for Cv and Cp, but I'm having a bit of trouble with this conceptually. How come Cv is change in internal energy/change in temperature? Why can't it be the change in enthalpy/change in temperature (and vice versa for Cp)?

Nicole Anisgard Parra 2H
Posts: 39
Joined: Sat Jul 22, 2017 3:01 am

Re: Conceptual Help on Cv vs Cp

Cv is change in internal energy/change in temperature because at constant volume, the gas can do no work as w=p*delta V. If w is zero, then delta U=q. We then can use the specific heat capacity relationship q=nCvdeltaT. For Cp, we can use change in enthalpy/change in temperature because the pressure is what is held constant. H= U +PV. The easiest way to understand them conceptually is through deriving their respective equations; there you can really see the relationships the two have with other variables.