Concept, reaction, stages, types and examples

We explain what combustion is, how it occurs and what are the stages of the reaction.Additions, classification and examples.

Combustion is a chemical reaction that releases light and heat energy.

What is combustion?

Combustion is a type of exothermic chemical reaction .It can involve matter in a gaseous state or in a heterogeneous state (liquid-gas or solid-gas). It generates light and heat and is produced more or less quickly.

Traditionally, combustion is understood as a process of rapid oxidation of certain combustible elements, that is, mainly constituted by hydrogen, carbon and sometimes Sulfur.In addition, necessarily takes place in the presence of oxygen .

Actually, combustions are forms of redox reaction (reduction-oxidation) that can occur both in a controlled manner, as in internal combustion engines, or uncontrolled, as in explosions. They involve the exchange of electrons between atoms of matter during the reaction, so they generate thermal and light energy.

They also result in other gaseous and solid substances, such as carbon dioxide (CO2) and water vapor, or solid residues of the fuel (the substance consumed in the reaction) and the oxidizer (the substance that promotes the reaction), always according to its chemical nature.

Thus, although in the traditional image of combustion there is always fire involved, it may not be generated, since it is only a plasma form (ionized gas) as a result of the release of heat from the chemical reaction.

See also: Enthalpy

How does combustion occur?

Combustion always results in CO2, water vapor, energy and other compound.

Combustions are a type of redox reaction , that is, reduction-oxidation.This means that in them one material oxidizes (loses electrons), while the other one reduces (gains electrons).

In the case of combustion, the oxidizing agent (oxygen) obtains electrons from the reducing agent (fuel) , or what is the same, between the oxidizer and the fuel.This usually occurs according to the following formula:

Compound + O2=Other compound + CO2 + H2O + Energy

Compounds may vary, depending on their nature, as well as energy levels may vary.But carbon dioxide and water vapor are constant in all types of combustion.

Types of combustion

There are three types of combustion, which are the following:

• Complete or perfect Combustion .Those reactions in which the combustible material is completely oxidized (consumed), and other oxygenated compounds are subproduced, such as carbon dioxide, sulfur dioxide or water vapor.


• Stoichiometric Combustion or neutral .This is called the ideal complete combustion, which uses just the right amounts of oxygen for its reaction and that usually occurs only in the controlled environment of a laboratory.


• Incomplete Combustion .Those in which compounds appear to oxidize (also called unburned) of combustion gases, such as carbon monoxide (CO), hydrogen, carbon particles, etc.

Combustion reaction

The combustion processes actually comprise a set of rapid and simultaneous chemical reactions, which may well be considered as one, which goes through the following phases or stages:

• Pre-reaction or first stage .The hydrocarbons present in the combustible material decompose and begin their reaction with the oxygen in the air, thus forming radicals, which are molecularly unstable compounds.initiates a chain reaction of appearance and disappearance of chemical compounds, tending to always create more than it destroys.


• Oxidation or second stage .At this stage most of the heat energy of the reaction is generated, as oxygen reacts with the radicals of the previous stage, thus giving a process of violent displacement of electrons.A large number of radicals leads to a massive and violent reaction, known as an explosion.


• End of the reaction or third stage .Occurs when the oxidation of the radicals is completed and the molecules of the released gases are formed.The combustible material will be completely depleted.

Examples of combustion

Within the engines there is combustion that releases energy for movement.

Some simple examples of combustion in everyday life are:

• The lighting of a match/match .It is the most emblematic case of combustion.When the phosphorus head (phosphorus and sulfur cover) is scratched against a rough surface, it heats up by friction and triggers a rapid combustion, which in turn produces a brief flame.


• The ignition of a gas stove .Domestic kitchens work by combustion of a hydrocarbon gas, usually a mixture of propane (C3H8) and butane (C4H10), which the device extracts from a pipe or from a container.Put in contact with the air, and provided an initial load of heat energy (such as the pilot's flame, or that of a phosphorus), the gas begins its reaction; but to keep the flame going, fuel must be supplied continuously.


• Strong bases and organic matter .Most strong bases (hydroxides) such as caustic soda, caustic potash and other extreme pH substances, generate violent oxidation reactions upon entering contact with organic matter.This means that we can burn by contact and even start fires with them, since these types of reactions are usually very exothermic.


• Internal combustion engines .Presents in cars, boats and other vehicles that operate with fossil fuel such as diesel, gasoline or kerosene, these devices are an example of controlled combustion.fuel hydrocarbons and small explosions are generated that, within the piston system, are transformed into motion, also byproducing polluting gases, which are released into the atmosphere.

Continue with: Endothermic reactions