In chemistry, an endothermic reaction is one that requires heat to break the bonds of the reactants. In other words, the chemical reaction absorbs heat, causing its surroundings to get colder. Expressed in a chemical equation:

Reactants + Energy → Products

When using the calorimeter, the change in heat of the calorimeter is equal to the opposite of the change in heat of the system. This means that when the solution in which the reaction is taking place loses heat, the reaction is endothermic.

An endothermic reaction is the opposite of an exothermic reaction.

See also: homeothermic, homoiothermic, exothermic, thermodynamics, chemical thermodynamics.