When two bodies at different temperatures are kept in contact, heat flows from the body at a higher temperature to the body at a lower temperature. The measurement of heat is called calorimetry.
The SI unit of heat is joule (J). The other most commonly used unit of heat is calorie (cal). The heat energy required to raise the temperature of 1 g of water through 1°C is known as calorie.
A calorimeter is a cylindrical vessel that is used to measure the amount of heat gained or lost by a body when it is mixed with another body.