Mayer's relation


derived a relation between specific heat at constant pressure and the specific heat at constant volume for an ideal gas. The relation is:
where 'CP,m' is the molar specific heat at constant pressure, 'CV,m' is the specific heat at constant volume and R is the Universal Gas Constant.
For more general homogeneous substances, not just ideal gases, the difference takes the form,
, where is the heat capacity of a body at constant pressure, is the heat capacity at constant volume, is the volume, is the temperature, is the thermal expansion coefficient and is the isothermal compressibility.
From this relation, several inferences can be made: