Endothermically

Endothermically is an adverb used to describe a process that absorbs energy, typically heat, from its surroundings. It characterizes endothermic processes, in which the system gains energy and the enthalpy change (ΔH) is positive. Because energy enters the system, the surroundings often experience cooling as heat is drawn away.

In scientific contexts, endothermicity is a property of chemical reactions, phase changes, or physical processes. Endothermic reactions require energy input from outside, rather than releasing energy to the surroundings. Common examples include the melting of ice, the photosynthetic reactions in plants that capture light energy, and the dissolution of certain salts such as ammonium nitrate in water. In each case, energy absorbed by the system can come from heat, light, or other sources.

Etymology and usage notes: endothermically derives from endothermic, with the adverbial suffix -ly. In thermodynamics and chemistry, it is used to specify the manner in which energy transfer occurs. The opposite term is exothermically, describing processes that release energy to the surroundings, typically with a negative enthalpy change (ΔH < 0). Endothermic descriptions are central to discussions of calorimetry, reaction energetics, and phase behavior, providing a concise way to indicate that heat absorption is involved in the process.