Combustion or
burning is a high-temperature
exothermic redox chemical reaction between a
fuel and an
oxidant, usually atmospheric
oxygen, that produces oxidized, often gaseous products, in a mixture termed as
smoke. Combustion in a
fire produces a
flame, and the
heat produced can make combustion self-sustaining. Combustion is often a complicated sequence of
elementary radical reactions. Solid fuels, such as wood, first undergo
endothermic pyrolysis to produce gaseous fuels whose combustion then supplies the heat required to produce more of them. Combustion is often hot enough that
light in the form of either
glowing or a
flame is produced. A simple example can be seen in the combustion of
hydrogen and
oxygen into
water vapor, a reaction commonly used to fuel
rocket engines. This reaction releases 242 kJ/mol of heat and reduces the
enthalpy accordingly (at constant temperature and pressure):
- 2(g) + (g) → 2(g)
