Why is the Cp value of any gas always greater than the Cv value?

Question

i dont want the mathematical proof from the formula....i want the physical intertpretation????

Answer 1

On these equations D is for Delta :

Dh = De +pDV (definition of enthalpy)
pDV = R DT (equation of state)
Dh = Cp DT (definition of enthalpy)
With first law of thermodinamics :
De = Dq +Dw = Dq ) Cv DT

So Cp DT = Cv DT + RDT

So Cp = Cv +R so Cp always greater than Cv

:

Answer 2

It can be shown that if heat is transferred to or from a gas at constant volume then the quantity of heat transferred is equivalent to the change in internal energy of the gas.(Joule's Law)
If heat is transferred to a gas at constant pressure while the gas expands, the heat transferred is equivalent to the increase in internal energy of the gas PLUS the work done by the gas in expanding.

Answer 3

Yay Fred. I should have paid more attention in Thermo class.

Answer 4

b'coz "P" comes before "V".