Combustion is a rapid chemical reaction between substances, typically with oxygen, producing heat and light. The reaction rate is high due to the chemical reaction and the inability of generated energy to escape, raising the temperature of reactants and accelerating the reaction. A lighted match exemplifies combustion; friction heats the match head, chemicals react, and generate more heat than can escape, resulting in a flame. Combustion encompasses diverse phenomena applied across industries and is based on physics, chemistry, and mechanics.

What common materials can undergo combustion?

Combustion is a rapid chemical reaction that produces heat and light, typically involving oxygen . Materials that undergo combustion are called combustible or flammable . Common examples include hydrogen , wood , paper , methane , carbon monoxide , and hydrocarbons . Combustion needs an initial energy input to start, such as a burning match or spark .

What is needed for combustion to happen?

Combustion is a rapid chemical reaction that produces heat and light. For combustion to occur, three elements must be present: fuel, heat, and oxygen. The fuel provides the substance that will burn, while heat initiates and sustains the combustion process. Oxygen acts as an oxidizer, combining with the fuel to release energy. When these three elements are in the proper proportion, a self-sustaining reaction occurs, releasing heat and light until the fuel is exhausted or the reaction is inhibited.

What are the main products of combustion?

Combustion is a complex chemical process that occurs between substances, typically with oxygen, producing heat and light. The main products of combustion are water and carbon dioxide. However, other products can also form. For example, carbon monoxide is a toxic gas that results from the incomplete combustion of carbon-containing fuels. Also, nitrogen oxides form when combustion temperatures are high enough for nitrogen and oxygen to react.

How does combustion relate to energy release?

Combustion is a chemical reaction that involves the rapid combination between substances, usually with oxygen, to produce heat and light. This process is exothermic, meaning it releases energy in the form of heat and light. During combustion, energy is required to break the bonds in the reactant molecules, and energy is released when new bonds form in the product molecules. If the energy released is greater than the energy required, the reaction is exothermic, resulting in a net release of energy. The heat produced raises the temperature of the surrounding air, causing it to expand and do work, such as in an internal combustion engine. Some of the released energy also appears as light.

How can combustion lead to pollution or be made more environmentally friendly?

Combustion, a chemical reaction that produces heat and light, can lead to pollution through the emission of noxious gases. These gases, produced by burning substances, include hydrocarbons, carbon monoxide, and nitrogen oxides. Incomplete combustion of materials like coal yields carcinogenic compounds, sulfur and nitrogen oxides that cause acid rain, and particulate matter that pollutes the air. To make combustion more environmentally friendly, emission control systems can be employed. These include: * Exhaust gas recirculation, which lowers combustion temperature to reduce nitrogen oxides * Air-injection systems, which inject air into the exhaust manifold to burn uncombusted hydrocarbons and carbon monoxide * Catalytic converters, which use catalysts to convert hydrocarbons, carbon monoxide, and nitrogen oxides into less harmful substances * Using alternative fuels that are less damaging to the environment than traditional fuels * Employing computerized control to ensure efficient combustion and lower pollutant generation

combustion

Images & Videos

Engraving of Antoine Lavoisier in eighteenth-century attire observing a laboratory experiment with glassware and scientific equipment on a table.

Engraving of Sir Humphrey Davy, shown from the waist up wearing a double-breasted coat and cravat, based on a painting by Sir Thomas Lawrence.

A lit Bunsen burner with a visible flame stands on a black laboratory countertop, with lab equipment blurred in the background.

New York City skyline tinted orange from wildfire smoke.

Diagram of a burning candle showing labeled stages in the combustion process, including the solid wax, melted wax, burning wick, different flame regions, unburned and cooled carbon particles, and the hottest part of the flame.

combustion

chemical reaction

Written by

Victor Nikolaevich Kondratiev

Fact-checked by

Britannica Editors

Last updated

Oct. 24, 2026 •History

Top Questions

What is combustion?
Combustion is a rapid chemical reaction between substances, typically with oxygen, producing heat and light. The reaction rate is high due to the chemical reaction and the inability of generated energy to escape, raising the temperature of reactants and accelerating the reaction. A lighted match exemplifies combustion; friction heats the match head, chemicals react, and generate more heat than can escape, resulting in a flame. Combustion encompasses diverse phenomena applied across industries and is based on physics, chemistry, and mechanics.
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What common materials can undergo combustion?
Combustion is a rapid chemical reaction that produces heat and light, typically involving oxygen. Materials that undergo combustion are called combustible or flammable.

Common examples include hydrogen, wood, paper, methane, carbon monoxide, and hydrocarbons. Combustion needs an initial energy input to start, such as a burning match or spark.
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What is needed for combustion to happen?
Combustion is a rapid chemical reaction that produces heat and light. For combustion to occur, three elements must be present: fuel, heat, and oxygen. The fuel provides the substance that will burn, while heat initiates and sustains the combustion process. Oxygen acts as an oxidizer, combining with the fuel to release energy. When these three elements are in the proper proportion, a self-sustaining reaction occurs, releasing heat and light until the fuel is exhausted or the reaction is inhibited.
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What are the main products of combustion?
Combustion is a complex chemical process that occurs between substances, typically with oxygen, producing heat and light.

The main products of combustion are water and carbon dioxide. However, other products can also form. For example, carbon monoxide is a toxic gas that results from the incomplete combustion of carbon-containing fuels. Also, nitrogen oxides form when combustion temperatures are high enough for nitrogen and oxygen to react.
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How does combustion relate to energy release?
Combustion is a chemical reaction that involves the rapid combination between substances, usually with oxygen, to produce heat and light. This process is exothermic, meaning it releases energy in the form of heat and light.

During combustion, energy is required to break the bonds in the reactant molecules, and energy is released when new bonds form in the product molecules. If the energy released is greater than the energy required, the reaction is exothermic, resulting in a net release of energy. The heat produced raises the temperature of the surrounding air, causing it to expand and do work, such as in an internal combustion engine. Some of the released energy also appears as light.
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How can combustion lead to pollution or be made more environmentally friendly?
Combustion, a chemical reaction that produces heat and light, can lead to pollution through the emission of noxious gases. These gases, produced by burning substances, include hydrocarbons, carbon monoxide, and nitrogen oxides. Incomplete combustion of materials like coal yields carcinogenic compounds, sulfur and nitrogen oxides that cause acid rain, and particulate matter that pollutes the air.

To make combustion more environmentally friendly, emission control systems can be employed. These include:
* Exhaust gas recirculation, which lowers combustion temperature to reduce nitrogen oxides
* Air-injection systems, which inject air into the exhaust manifold to burn uncombusted hydrocarbons and carbon monoxide
* Catalytic converters, which use catalysts to convert hydrocarbons, carbon monoxide, and nitrogen oxides into less harmful substances
* Using alternative fuels that are less damaging to the environment than traditional fuels
* Employing computerized control to ensure efficient combustion and lower pollutant generation
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

combustion, a chemical reaction between substances, usually including oxygen and usually accompanied by the generation of heat and light in the form of flame. The rate or speed at which the reactants combine is high, in part because of the nature of the chemical reaction itself and in part because more energy is generated than can escape into the surrounding medium, with the result that the temperature of the reactants is raised to accelerate the reaction even more.

A familiar example of a combustion reaction is a lighted match. When a match is struck, friction heats the head to a temperature at which the chemicals react and generate more heat than can escape into the air, and they burn with a flame. If a wind blows away the heat or the chemicals are moist and friction does not raise the temperature sufficiently, the match goes out. Properly ignited, the heat from the flame raises the temperature of a nearby layer of the matchstick and of oxygen in the air adjacent to it, and the wood and oxygen react in a combustion reaction. When equilibrium between the total heat energies of the reactants and the total heat energies of the products (including the actual heat and light emitted) is reached, combustion stops. Flames have a definable composition and a complex structure; they are said to be multiform and are capable of existing at quite low temperatures, as well as at extremely high temperatures. The emission of light in the flame results from the presence of excited particles and, usually, of charged atoms and molecules and of electrons.

Combustion encompasses a great variety of phenomena with wide application in industry, the sciences, professions, and the home, and the application is based on knowledge of physics, chemistry, and mechanics; their interrelationship becomes particularly evident in treating flame propagation.

In general terms, combustion is one of the most important of chemical reactions and may be considered a culminating step in the oxidation of certain kinds of substances. Though oxidation was once considered to be simply the combination of oxygen with any compound or element, the meaning of the word has been expanded to include any reaction in which atoms lose electrons, thereby becoming oxidized. As has been pointed out, in any oxidation process the oxidizer takes electrons from the oxidizable substance, thereby itself becoming reduced (gaining electrons). Any substance at all can be an oxidizing agent. But these definitions, clear enough when applied to atomic structure to explain chemical reactions, are not as clearly applicable to combustion, which remains, generally speaking, a type of chemical reaction involving oxygen as the oxidizing agent but complicated by the fact that the process includes other kinds of reactions as well and by the fact that it proceeds at an unusually fast pace. Furthermore, most flames have a section in their structure in which, instead of oxidations, reduction reactions occur. Nevertheless, the main event in combustion is often the combining of combustible material with oxygen.

combustion

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