Liquid hydrocarbons can be converted to a mixture of gaseous hydrocarbons by:
Oxidation
Cracking
Distillation under reduced pressure
Hydrolysis
The process of breaking higher hydrocarbons with high boiling points into a variety of lower hydrocarbons that are more volatile (low boiling), is called cracking (or pyrolysis). For example, a higher hydrocarbon C10H22 splits according to the reaction.
The process of cracking or pyrolysis increases the relative amounts of the lower hydrocarbons, which exists in a gaseous state, while higher hydrocarbons exist in the liquid or solid state.