crude oil distillation

Higher and foundation tier

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. It 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 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 the oil refinery and explain how it is separated into its various fractions.

fractional distillation of crude oil

At the oil refinery:

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Practice questions

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