Hydrocarbons are a class of organic compounds consisting entirely of hydrogen and carbon. Hydrocarbons are generally colourless and hydrophobic with only weak odours. Hydrocarbons are the principal constituents of petroleum and natural gas. They are used as fuels and lubricants as well as raw materials for the production of plastics, fibres, rubbers, solvents, explosives and industrial chemicals. Methane, ethane, propane, butane, etc., are examples of some common hydrocarbons.

A fuel is a substance that burns rapidly in the presence of oxygen to give a large quantity of useful heat, along with water vapour and carbon dioxide. fuel + oxygen → water vapour + carbon dioxide + heat