Benzene is a colourless liquid with a sweet odour. Benzene evaporates quickly, dissolves poorly in water, and is quite flammable. Benzene is present in the environment: in water, air and the soil. The substance was discovered in the 19th century and is extracted from coal tar. It is currently made primarily from petroleum. It is one of the most commonly produced chemical substances and is used as a raw material for making other chemicals, such as ethylbenzene, from which styrene and eventually plastics are made. Benzene can also be formed by natural processes, such as in volcanoes and forest fires.