Exothermica

Exothermica is a term used to describe processes that release heat energy to the surrounding environment. In chemistry and thermodynamics, an exothermic process is characterized by a decrease in the enthalpy of the system (ΔH < 0) at constant pressure, meaning energy is emitted as heat, light, or both. The term is often contrasted with endothermic processes, where heat is absorbed (ΔH > 0).

During an exothermic reaction, the total energy of the products is lower than that of the reactants, with the excess energy appearing as heat in the surroundings. The rate at which heat is released depends on reaction kinetics as well as thermodynamic feasibility; a process can be exothermic yet slow or have a low reaction rate.

Common examples include combustion of hydrocarbons (such as burning methane), acid–base neutralization, oxidation of metals, and cellular respiration in biological organisms. Exothermic phenomena also occur in phase changes, such as the condensation of water vapor releasing latent heat, freezing, and certain mineralization reactions.

Applications of exothermic processes span industrial and practical uses, including hand warmers, self-heating products, welding, and various energy-generation or material-processing operations. Safety considerations are important, as rapid heat release can lead to thermal runaway, ignition of flammable materials, or unintended damage if not properly managed.

Note: Exothermica describes enthalpy changes (ΔH < 0), while exergonic refers to changes in Gibbs free energy (ΔG < 0). A reaction can be exothermic yet non-spontaneous (ΔG > 0) under certain conditions, and conversely, a reaction can be endothermic yet spontaneous if ΔG < 0.