During combustion, the reaction is an oxidation–reduction (redox) reaction and, more specifically in school chemistry, it is usually classified as a combination (synthesis) reaction where a substance reacts rapidly with oxygen and releases heat and often light.

What actually happens in combustion?

  • A fuel (like methane, petrol, wood, or magnesium) reacts with an oxidising agent, most commonly oxygen from the air.
  • The fuel is oxidised (it loses electrons), and oxygen is reduced (it gains electrons), so the overall process is a redox reaction.
  • New substances are formed, typically oxides such as carbon dioxide and water for hydrocarbon fuels.
  • Energy is released as heat and sometimes light, which is why combustion is an exothermic process.

A classic example is the combustion of methane in air:
CH4+2O2→CO2+2H2O\text{CH}_4+2\text{O}_2\rightarrow \text{CO}_2+2\text{H}_2\text{O}CH4​+2O2​→CO2​+2H2​O

How you might phrase this in an exam

If your question is:

“During combustion what type of chemical reaction takes place?”

Any of the following would be scientifically correct, with the first being the most complete:

  • Combustion is an oxidation–reduction (redox) reaction in which a substance reacts rapidly with oxygen and releases heat.
  • Combustion is a redox reaction and also a combination reaction between a fuel and oxygen.
  • Combustion is an exothermic redox reaction involving a fuel and oxygen.

Mini story to remember it

Imagine a piece of wood as a “fuel hero” carrying extra electrons and oxygen as a “collector” waiting to grab them. When you light the match, the hero and the collector collide, electrons jump from the fuel to oxygen, and in that fast exchange you get new products (like carbon dioxide and water) plus a burst of heat and light. That fast electron hand‑off is exactly what makes combustion a redox reaction.

TL;DR: During combustion, a rapid, exothermic oxidation–reduction (redox) reaction occurs, typically also described as a combination reaction between a fuel and oxygen.

Information gathered from public forums or data available on the internet and portrayed here.