Petroleum is the general term for solid, liquid or gaseous hydrocarbons. Hydrocarbons are a class of organic compounds consisting only of carbon and hydrogen and which are the basis of oil, natural gas and coal.

Crude oil is naturally occurring petroleum.

Technically, crude oil consists of pentanes (hydrocarbon chains consisting of five carbon atoms and 12 hydrogen atoms) and heavier hydrocarbons (hydrocarbon chains longer than five carbon atoms in the formula). It may also contain other materials such as water, natural gas, sulphur and other minerals.

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