Exothermisk

Exothermisk is a term used in chemistry to describe processes that release heat to their surroundings. The term corresponds to exothermic in English. During an exothermic reaction or transformation, energy is emitted as heat and the surrounding environment typically becomes warmer. In some cases the heat release is accompanied by light or sound. The opposite category is endothermisk, where the system absorbs heat from its surroundings.

Thermodynamically, exothermic processes have a negative enthalpy change (ΔH < 0) under constant pressure. The heat released equals the decrease in the system’s enthalpy. While the sign of ΔH is a thermodynamic property, the rate at which heat is released is governed by kinetics, which affects how fast the reaction proceeds but not whether it is exothermic. In an open system, the surroundings generally warm up as heat is transferred away from the reacting mixture.

Common examples include combustion of fuels, neutralization reactions between acids and bases, and oxidation reactions such as rusting. Exothermic changes also occur in physical processes like condensation of steam, freezing, and certain polymerizations. The extent of heat release depends on factors such as concentration, pressure, and temperature.

Practically, exothermicity is measured by calorimetry. Exothermic reactions are used in applications such as hand warmers and various industrial processes, but they require safety considerations to manage heat buildup. Understanding whether a process is exothermic helps in designing reactors, storage conditions, and thermal management strategies.