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A calorimeter is a device used to measure thermal quantity, such as specific heat capacity or latent heat capacity. The name comes from the old unit of heat, the calorie. A simple calorimeter may just consist of a thermometer attached to an insulated container. To find the enthalpy change per mole of a substance X in a reaction between two liquids X and Y, they are added to the calorimeter and the initial and final (after the reaction has finished) temperatures are noted. Multiplying the temperature change by the mass and specific heat capacities of the liquids gives a value for the energy given off during the reaction (assuming the reaction was exothermic.) Dividing the energy change by how many moles of X were present gives its enthalpy change of reaction.

There are many forms of calorimeters

See also: Calorimetry