What is Crude Oil?
Crude oil is a mixture of compounds called hydrocarbons. Many useful materials can be produced from crude oil. It can be separated into different fractions using fractional distillation, and some of these can be used as fuels.
How are they made?
Crude oil forms naturally over millions of years from the remains of living things. Most of the compounds in crude oil are hydrocarbons. These are compounds that contain hydrogen and carbon atoms only, joined together by chemical bonds called covalent bonds. There are different types of hydrocarbon, but most of the ones in crude oil are alkanes.
Examples of Crude Oils:
Methane - CH4 Ethane - C2H6
Propane - C3H8 Butane - C4H10
The diagram below summarises the main fractions from crude oil and their uses, and the trends in properties. Note that the gases leave at the top of the column, the liquids condense in the middle and the solids stay at the bottom.