When you heat a substance and its temperature increases, the input of energy divided by the temperature increase is called the Heat Capacity. It could just as well be called the energy capacity since it has dimensions of energy per unit temperature change. The product of the molar mass (grams per mol) of a substance times its heat capacity is called Molar Heat Capacity. For certain applications it is useful to know the Gram Heat Capacity . (usually referred to as the Specific Heat) of a substance in units.