Calorimetry, the science of measuring a quantity of heat (expressed in calories), as distinct from thermometry, the science of measuring the intensity of heat (expressed as temperature). A calorimeter is the instrument used to measure the amount of heat; one widely used type consists of an insulated container of water, a stirring device, and a thermometer. A heat source is placed in the calorimeter, the water is stirred until equilibrium is reached, and the rise of temperature is noted by reading the thermometer. Because the heat capacity of the calorimeter is known (or can be measured by using a standard heat source), the amount of heat liberated can be readily calculated. When the heat source is a hot object of known temperature, the specific and latent heat may be measured as the object cools. Latent heat, which is not associated with a change in temperature, is the heat evolved or absorbed by a substance as it changes from one state to another, as from liquid to solid or vice versa. When the heat source is a chemical reaction, such as the burning of a fuel, the reacting substances are placed in a heavy steel vessel called a bomb . The bomb is placed within the calorimeter, and the reaction is started by ignition with an electric spark.

Calorimetry.