Coal

By far the most important property of coal is that it combusts. When the pure carbon and hydrocarbons found in coal burn completely only two products are formed, carbon dioxide and water. During this chemical reaction, a relatively large amount of energy is released. The release of heat when coal is burned explains the fact that the material has long been used by humans as a source of energy, for the heating of homes and other buildings, to run ships and trains, and in many industrial processes.