Editing Exothermic process (section)

==Energy release==
Exothermic refers to a transformation in which a closed system releases energy (heat) to the surroundings, expressed by

:<math>Q > 0.</math>

When the transformation occurs at [[Isobaric process|constant pressure]] and without exchange of [[electrical energy]], heat {{mvar|Q}} is equal to the [[enthalpy]] change, i.e.

:<math>\Delta H < 0,</math><ref name="Oxtoby8th">Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).''Principles of Modern Chemistry'', Brooks Cole. p. 617.  {{ISBN|978-1305079113}}</ref>

while at [[constant volume]], according to the [[first law of thermodynamics]] it equals [[internal energy]] ({{mvar|U}}) change, i.e.

:<math>\Delta U = Q + 0 > 0.</math>

In an [[adiabatic]] system (i.e. a system that does not exchange heat with the surroundings), an otherwise exothermic process results in an increase in temperature of the system.<ref>{{cite book |last=Perrot |first=Pierre |title=A to Z of Thermodynamics |publisher=Oxford University Press |year=1998 |isbn=0-19-856552-6 |pages=6–7}}</ref>

In exothermic chemical reactions, the heat that is released by the reaction takes the form of electromagnetic energy or [[kinetic energy]] of molecules.<ref>{{Cite web |date=2013-10-02 |title=Potential Energy |url=https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Thermodynamics/Energies_and_Potentials/Potential_Energy |access-date=2024-06-26 |website=Chemistry LibreTexts |language=en}}</ref> The transition of [[electron]]s from one quantum [[energy level]] to another causes light to be released. This light is equivalent in energy to some of the stabilization energy of the energy for the chemical reaction, i.e. the [[bond energy]]. This light that is released can be absorbed by other molecules in [[Solution (chemistry)|solution]] to give rise to molecular translations and rotations, which gives rise to the classical understanding of heat. In an exothermic reaction, the [[activation energy]] (energy needed to start the reaction) is less than the energy that is subsequently released, so there is a net release of energy.<ref>{{Cite book |title=Heinemann Chemistry |publisher=[[Pearson Education|Pearson]] |isbn=9780655700098 |edition=6 |volume=2 |pages=64–65 |language=en |chapter=Chapter 2 - Carbon-based fuels}}</ref>