exothermic reaction

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What are exothermic and endothermic reactions?

exothermic reaction

chemical reaction

Also known as: exoergic reaction

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June 26, 2026

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A chemical reaction is a process where reactants transform into different substances called products. This transformation involves breaking bonds in the reactants and forming new bonds in the products. Energy is absorbed to break bonds and released when new bonds form.1

An exothermic reaction is a type of chemical reaction where energy, often in the form of heat, is released. This occurs when the energy evolved from forming new bonds is greater than the energy required to break the original bonds. Many common reactions, such as the combustion of fuels like methane, are exothermic. The formation of water from hydrogen and oxygen is another example.23

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alkali metal
Reactions with nonmetals
The reactions are highly exothermic, producing up to 235 kcal/mole for lithium fluoride. The alkali metals react with nonmetals in Groups 15 and 16 (Va and VIa) of the periodic table. Sulfides can be formed by the direct reaction of the alkali metals with elemental sulfur, furnishing a variety…
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The reactions are highly exothermic, producing up to 235 kcal/mole for lithium fluoride. The alkali metals react with nonmetals in Groups 15 and 16 (Va and VIa) of the periodic table. Sulfides can be formed by the direct reaction of the alkali metals with elemental sulfur, furnishing a variety…
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chemical energy
…heat; such reactions are called exothermic. Reactions that require an input of heat to proceed may store some of that energy as chemical energy in newly formed bonds. The chemical energy in food is converted by the body into mechanical energy and heat. The chemical energy in coal is converted…
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…heat; such reactions are called exothermic. Reactions that require an input of heat to proceed may store some of that energy as chemical energy in newly formed bonds. The chemical energy in food is converted by the body into mechanical energy and heat. The chemical energy in coal is converted…
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chemical reaction
Energy considerations
…endothermic is exothermic; in an exothermic reaction, energy as heat is evolved. The more general terms exoergic (energy evolved) and endoergic (energy required) are used when forms of energy other than heat are involved.
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…endothermic is exothermic; in an exothermic reaction, energy as heat is evolved. The more general terms exoergic (energy evolved) and endoergic (energy required) are used when forms of energy other than heat are involved.
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cluster
Chemical properties
, it is exothermic) in sufficient quantity to transform the cluster from solid to liquid, a cluster may melt as it reacts.
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, it is exothermic) in sufficient quantity to transform the cluster from solid to liquid, a cluster may melt as it reacts.
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heat of reaction
…to be endothermic; if negative, exothermic.
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…to be endothermic; if negative, exothermic.
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metallurgy
Pyrometallurgy
…and reduction reactions are either exothermic (energy-releasing) or endothermic (energy-absorbing). One example of an exothermic reaction is the oxidation of iron sulfide (FeS) to form iron oxide (FeO) and sulfur dioxide (SO₂) gas:
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…and reduction reactions are either exothermic (energy-releasing) or endothermic (energy-absorbing). One example of an exothermic reaction is the oxidation of iron sulfide (FeS) to form iron oxide (FeO) and sulfur dioxide (SO₂) gas:
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chemistry of industrial polymers
Industrial polymerization methods
… reactions described above are usually exothermic—that is, they generate heat. Heat generation is seldom a problem in small-scale laboratory reactions, but on a large industrial scale it can be dangerous, since heat causes an increase in the reaction rate, and faster reactions in turn produce yet more heat. This phenomenon,…
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… reactions described above are usually exothermic—that is, they generate heat. Heat generation is seldom a problem in small-scale laboratory reactions, but on a large industrial scale it can be dangerous, since heat causes an increase in the reaction rate, and faster reactions in turn produce yet more heat. This phenomenon,…
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