Combustion is the process of the burning of a fuel in the presence of oxygen. Combustion reactions are exothermic and produce heat and sometimes light energy. 

Common examples of  combustion are

  • the burning of coal in a power station
  • the burning of petrol in an automobile engine
  • the flame from Bunsen burner
  • cellular respiration or the 'burning' of glucose by cells in the body


The combustion of fossil fuels.

The combustion of fossil fuels uses oxygen gas and produces carbon dioxide gas and water.

The general word equation for the combustion of fuels is


Fossil fuel + oxygen gas → carbon dioxide gas + water



Complete and incomplete combustion

The Bunsen burner is commonly found in school science labs.

The burner was originally invented by Robert Bunsen.

That is why Bunsen is always spelt with a capitol letter.

Both types of combustion reactions occur in a Bunsen burner as shown in the following table.



Combustion reactions in a Bunsen Burner

Bunsen burner Complete combustion Incomplete combustion
Color of flame Blue Yellow
Air hole Open Closed
Noise Noisy Quiet
Name of flame Heating flame Safety flame


As oxygen gas is reduced by closing the air hole of a Bunsen burner the products change from carbon dioxide to carbon monoxide and carbon or soot.


Combustion equations

Complete combustion:  CH4(g) + 2 O2(g) →  CO2(g) + 2 H2O(l)

Incomplete combustion: CH4(g) + 1.5 O2(g) → CO(g) + 2 H2O(l)

Incomplete combustion: CH4(g) + 1 O2(g) → C(s) + 2 H2O(l)

Complete combustions needs the most oxygen. Insufficient oxygen produces incomplete combustion.



1. Complete the following. The word _____________________ means 'burning'.

2. What is the flame color of a Bunsen burner with the air hole open?

3. What is the color of the safety flame of a Bunsen burner?

4. What are three products of incomplete combustion?

5. What gas is used during the combustion of fossil fuels?

6. What gas is produced during the complete combustion of fossil fuels?

7. Does a closed air hole produce a noisy or quiet flame?

8. A yellow flame is produced from glowing carbon or soot particles. What type of combustion is this?

9. A blue flame is produced by what type of combustion?

10. What product is always produced from the combustion of fossil fuels?




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