exothermically

Exothermically is an adverb describing a process, reaction, or change that releases heat to its surroundings. It is the adverbial form of exothermic and is commonly used in chemistry, physics, and materials science to indicate the manner of energy transfer during a process.

In thermodynamics, exothermic processes have a negative enthalpy change (ΔH < 0) at constant pressure, meaning heat flows from the system to the surroundings. The released heat can raise the temperature of the surroundings or be harnessed as useful energy. The rate at which heat is released depends on the reaction kinetics and may require containment to manage temperature rise.

Common exothermic examples include combustion of fuels, oxidation reactions, and many neutralization reactions between acids and bases. Certain phase changes, such as freezing or condensation, also proceed exothermically, releasing latent heat. Some materials or reactions generate heat when dissolving or polymerizing, and metabolic processes in living organisms release heat exothermically as part of energy production.

The term is often used to compare processes with endothermic ones, where heat is absorbed (ΔH > 0). Etymology: from exo- meaning outside and therm meaning heat, with the adverbial suffix -ically.