Editing Exothermic process (section)

==Two types of chemical reactions==
Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows:

=== Exothermic===
An exothermic reaction occurs when heat is released to the surroundings. According to the [[International Union of Pure and Applied Chemistry|IUPAC]], an exothermic reaction is "a reaction for which the overall standard [[enthalpy]] change Δ''H''⚬ is negative".<ref>{{Cite web |last= |first= |title=IUPAC - exothermic reaction (E02269) |url=https://goldbook.iupac.org/terms/view/E02269 |access-date=2024-06-26 |website=goldbook.iupac.org |publisher=The International Union of Pure and Applied Chemistry (IUPAC) |doi=10.1351/goldbook.e02269}}</ref> Some examples of exothermic process are fuel [[combustion]], [[condensation]] and [[nuclear fission]],<ref>{{Cite web |last=Bashyal |first=Jyoti |date=2023-02-20 |title=Exothermic reactions with Important Examples |url=https://scienceinfo.com/exothermic-reactions-with-important-examples/ |access-date=2024-06-26 |website=scienceinfo.com |language=en-US}}</ref> which is used in [[nuclear power plant]]s to release large amounts of energy.<ref>{{Cite web |title=Nuclear power plants - U.S. Energy Information Administration (EIA) |url=https://www.eia.gov/energyexplained/nuclear/nuclear-power-plants.php |access-date=2024-06-26 |website=www.eia.gov}}</ref>

===Endothermic===
In an [[Endothermic process|endothermic reaction]] or system, energy is taken from the surroundings in the course of the reaction, usually driven by a favorable [[entropy]] increase in the system.<ref>{{Cite book |last=Oxtoby |first=David W. |title=Principles of modern chemistry |last2=Gillis |first2=H. P. |last3=Butler |first3=Laurie J. |date=2016 |publisher=Cengage Learning |isbn=978-1-305-07911-3 |edition=8 |location=Andover |pages=617}}</ref> An example of an endothermic reaction is a first aid cold pack, in which the reaction of two chemicals, or dissolving of one in another, requires calories from the surroundings, and the reaction cools the pouch and surroundings by absorbing heat from them.<ref>{{Cite web |date=2020-06-01 |title=The Cold Pack: A Chilly Example of an Endothermic Reaction - Let's Talk Science |url=https://letstalkscience.ca/educational-resources/stem-in-context/cold-pack-a-chilly-example-endothermic-reaction |access-date=2024-06-26 |website=letstalkscience.ca |language=en}}</ref>

[[Photosynthesis]], the process that allows plants to convert carbon dioxide and water to sugar and oxygen, is an endothermic process: plants absorb [[radiant energy]] from the sun and use it in an endothermic, otherwise non-spontaneous process. The chemical energy stored can be freed by the inverse (spontaneous) process: combustion of sugar, which gives carbon dioxide, water and heat (radiant energy).<ref>{{Cite web |title=Photosynthesis - What happens during photosynthesis? - OCR 21st Century - GCSE Combined Science Revision - OCR 21st Century |url=https://www.bbc.co.uk/bitesize/guides/z9pjrwx/revision/1 |access-date=2024-06-26 |website=BBC Bitesize |language=en-GB}}</ref>