Crude oil is separated into its different components (fractions) by a process known as fractional distillation. The mixture of hydrocarbons is heated as it enters the fractionating column. This is a large tower which is much hotter at its base (~ 370^oC) than at its top. The fractions which boil the most easily ( bpt < 40^oC ) remain gaseous and are tapped off from the top of the tower. Those fractions which have higher boiling points will condense and be tapped off at the higher temperatures lower down the column. Since each fraction has a different boiling point they will condense at different levels in the column and are therefore separated from each other.