Petroleum (oil;
crude oil):
A naturally
occurring complex mixture consisting mainly of hydrocarbons.
Formed by decomposition of prehistoric plant material under
pressure and temperature. Used mainly as a fossil fuel and as
feedstock for the chemical industry.
Petroleum is a complex mixture of
many thousands of substances. It is usually black or dark brown,
thin like water
to viscous like tar, and tends to have an unpleasant odor.
Purification and chemical modification in a refinery produces
a wide range of products such as gasoline,
solvents,
and other chemicals.
