What is the difference between Cp and Cv?

Cp (specific heat at constant pressure) and Cv (specific heat at constant volume) represent the heat required to raise the temperature of a unit mass by one degree under respective conditions. Cp is always greater than Cv because at constant pressure, additional energy is needed for expansion work. For ideal gases, Cp - Cv = R (gas constant), and the ratio γ = Cp/Cv is important in analyzing isentropic processes.