eksoterme

Eksoterme refers to processes or reactions that release heat to their surroundings. In thermodynamics and chemistry, such processes are called exothermic. The term derives from the Greek exo- 'outside' and therme 'heat'. In an exothermic reaction the enthalpy change ΔH is negative, indicating that the system loses energy as heat to the environment. The amount of heat released per mole of substance is described by the standard enthalpy change of reaction (ΔH°), typically measured at 25°C and 1 bar with calorimetry.

Exothermic processes contrast with endothermic ones, where ΔH is positive and the system absorbs heat. The overall spontaneity of a reaction also depends on entropy and temperature, described by the Gibbs free energy ΔG = ΔH − TΔS.

Common examples include combustion (for example methane burning: CH4 + 2 O2 → CO2 + 2 H2O, ΔH° ≈ −890 kJ/mol), neutralization reactions, and many oxidation processes such as rusting. Living organisms release heat through respiration, an exothermic metabolic process.

Applications range from practical heat sources, such as hand warmers or cement curing, to energy storage and chemical synthesis. Exothermic reactions can present safety concerns, as rapid heat release may cause overheating or thermal runaway if heat is not removed efficiently. See also exothermic, endothermic, calorimetry, enthalpy.