 The left-hand side is the specific heat at constant volume formula_2 of the material.For the heat capacity at constant pressure, it is useful to define the specific enthalpy of the system as the sum formula_70.An infinitesimal change in the specific enthalpy will then be
therefore
If the pressure is kept constant, the second term on the left-hand side is zero, and
The left-hand side is the specific heat at constant pressure formula_1 of the material.