It is a heavy dark liquid, consisting of many different hydrocarbon compounds. Crude oil is extracted from the ground and fractionated into its components by volatility in an oil refinery. Some of the main products distilled from crude oil are:
Scientists believe that fossil fuels are the remains of huge amounts of plant material that was laid down millions of years ago, and altered in form under high temperatures and pressures. Others theorize that it is synthesized naturally by underground processes, slowly rising towards the surface for our use.