Heat capacity is the quantity of heat energy required to raise the temperature of a substance by 1°C. It is a measure of how well a substance stores heat. Numerically it is represented by the mass of a substance multiplied by that substance's specific heat. Historically heat energy has been defined in units of calories. One calorie is the quantity of heat energy required to raise the temperature of 1g of water from 14.5 to 15.5°C. This means that the specific heat of water is 1.0 cal g-1 °C-1 .

According to the second law of thermodynamics, heat flows from a warm body, one with a higher relative temperature, to a cooler body, one with a lower temperature. Heat flows between the two bodies until they reach the same temperature. The quantity of heat energy required to change the temperature of a substance is...