Separating crude oil
During the fractional distillation of crude oil:
- heated crude oil enters near the bottom of a tall fractionating column, which is hot at the bottom and gets cooler towards the top
- vapours from the oil rise through the column
- vapours condense when the temperature of the column is cool enough
- liquids are led out of the column at different heights
Some hydrocarbons have low boiling points. They do not condense, but leave the column as gases. Some hydrocarbons have high boiling points. They leave the column as hot liquid bitumen.
Crude oil fractions
The different, useful mixtures separated from crude oil are called fractions. This is because they are only part of the original crude oil.
Fuels obtained from crude oil or natural gas are called fossil fuels. They include:
- petrol, kerosene and diesel oil from crude oil
- methane from natural gas
These fuels are non-renewable - they are being used up faster than they are being formed. This means that they will run out one day if we carry on using them.
One way to remember the names of the fractions is: Good Penguins Keep Diving For Bass.