crude oil distillation

Higher and foundation tiers

Fractional distillation of crude oil

Crude oil despite being one of the most valuable natural resources is a useless, smelly and thick black "liquid" when it comes out of the ground, the reason for this is that it is a mixture. Crude oil is a mixture of compounds called hydrocarbons. Hydrocarbons are compounds containing only the elements hydrogen and carbon. There are thousands of different hydrocarbons all mixed together in crude oil. Some of the hydrocarbon molecules are small, some are medium sized and some are large. At an oil refinery the mixture of hydrocarbons present in the crude oil is separated into different fractions of hydrocarbons which contain similar sized molecules; this is easily done since similar sized molecules have similar boiling points.

The image below shows what happens to the crude oil at an oil refinery and explains how it is separated into its various fractions.

Explanation of what happens to crude oil at an oil refinery, how it is separated out into useful fractions.  Fractional distillation of crude oil

At the oil refinery: Chemistry student working in the school science lab

Key Points

Practice questions

Check your understanding - Questions on Fractional distillation of oil.

Check your understanding - Quick Quiz on fractional distillation of oil.