Crude oil is a natural mixture of many different hydrocarbons. These hydrocarbons can be separated using a process known as fractional distillation.
The crude oil is heated in a fractioning column allowing the different hydrocarbons to evaporate. The column also has several different condensers at different heights which allow the hydrocarbons to be separated depending on their volatility (how easy it is for them to evaporate) and their density.
Hydrocarbons with the lowest density and smallest molecular size (e.g. propane) condense at the top of the column where it is the coolest. Conversely, the hydrocarbons with the highest density and largest molecular size (e.g. bitumen) condense at the bottom of the column where the temperature is the highest. Not all hydrocarbons will evaporate and condense it is common to have a collection of gases at the top of the column, liquids in the middle of the column and solids at the bottom of the column,
Once the hydrocarbons have been separated they can be used for different purposes. Below are common hydrocarbons that can be obtained through fractional distillation ordered from lowest density to the highest density:
Refinery gases (e.g. propane) – Used as bottled gases for portable stoves and barbeques
Petrol – Used as fuel in cars
Naphtha – Used in many chemical processes
Kerosene – Used as fuel in aircrafts
Diesel – Used as fuel in cars, lorries and busses
Oils – Used as fuel for ships and power stations
Bitumen – Used as a covering for roofs and pavements