Ordinary people need fuel to keep warm and to cook food. Electricity is generated from the energy released by other fuels.
Common chemical fuels, such as coal, petroleum, and natural gas, come beneath the earth's surface. They have been formed over millions of years form organic (plant and animals) remains. In atomic fuels, the nuclear energy, which is locked up in the atom is released by a controlled fission (atom splitting) process to provide power.
Chemical fuels may be solids, liquids, or gases. Coal and wood are the chief solid fuels. Coal is burned to supply hear in homes and power in factories. Burning coal in a factory makes gas and coke, as well as many other useful products.
Wood was once mans most important fuel. It has now been largely replaced by other fuels, but is still used for open fires in old-fashoined fire places. Charcoal is a useful, slow-burning fuel in some manufacturing processes.
Main liquid fuels include gasoline, kerosene and diesel oil. They are separated in refiners from the crude petroleum that comes out of the ground.
Gas fuels may be both natural and man-made. Natural gas piped from underground wells provides a large part of the power needed by the cities. Light gases can be extracted from natural gas, such as propane and butane, which are used in portable gas stoves.
Manufactured gases are mostly produced from coal or coke. Coal gas is driven off from coal when it is heated to produce coke. Water gas is made by passing steam through hot coke.
Special chemical fuels are made to power jet and rocket engines. Jet engine fuels include hydrogen and boron compounds. Rocket fuels include alcohol and kerosene. Because rockets fly outside the atmosphere, where there is no oxygen to keep a fire alight, rocket fuels are combined with liquid oxygen, oxygen-rich compounds such as nitric acid.
