exothermic
ek-soh-THUR-mik
/ˌɛksoʊˈθɜːrmɪk/
Accompanied by or requiring the release of heat energy into the surroundings.
Exothermic reactions release energy, usually in the form of heat or light, causing the temperature of the immediate surroundings to rise.
The story behind the word. Coined in 1877 by French chemist Marcellin Berthelot, 'exothermic' combines the Greek prefix 'exo-' (outside, external) with 'therme' (heat). It literally translates to 'heat going outward'.
Word relationships
- heat-releasing: Heat-releasing is a plain-English descriptive term, while exothermic is the formal scientific term used in chemistry and thermodynamics.
- endothermic: Endothermic describes a process that absorbs heat from its surroundings, which is the exact opposite of exothermic.
Commonly confused with
- exergonic: Exothermic specifically refers to the release of heat energy, while exergonic refers to the release of free energy (which can include work, not just heat).
Word family
- exothermically (adverb): In an exothermic manner.
- exotherm (noun): A chemical reaction that releases heat.
Collocations
- exothermic reaction
- exothermic process
- highly exothermic
- exothermic behavior
Example sentences
- "The dilution of concentrated sulfuric acid is highly exothermic and must be performed with extreme care." Chemistry lab safety instruction
- "Combustion is a classic example of an exothermic reaction where fuel reacts with oxygen to release heat." Scientific textbook description
Memory hook
Think of 'exit' and 'thermal'. Heat is 'exiting' the reaction and entering the surroundings. Heat exits the system.
When not to use
Do not use to describe processes that absorb heat from their surroundings, which are endothermic.
Fun facts
- Disposable hand warmers work using a simple exothermic reaction: when you open the package, iron powder inside reacts with oxygen in the air to rust rapidly, releasing cozy heat for hours.
Related words
Explore more words
incandescence, combustion, Adiabatic, caloric, absorb, ambient
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