Organic compounds consisting solely of carbon and hydrogen are known as hydrocarbons. Hydrocarbons are found within a range of organic materials including: coal, petroleum, and natural gas. Carbon has the ability to form long chains with interconnecting C-C bonds. The members of each series of hydrocarbons have a progressively longer chain i.e. more carbon atoms continuing along the series. Alkanes and alkenes are two series of hydrocarbons where compounds are composed of hydrogen atoms bonded to a chain of carbon atoms. Where each of the atoms in a hydrocarbon compound is linked together exclusively by single bonds it is referred to as a saturated compound. The cycloalkanes are a series of saturated compounds. Crude oil is largely made up a mix of alkanes and cycloalkanes.

The carbon molecules of alkenes have at least one double bond, and as such are unsaturated compounds. The simplest alkenes, with only one double bond and no other functional groups have the general formula CnH2n. The simplest alkene is ethylene, which also has the IUPC denomination ethene(C2H4).