Fractional distillation of crude oil
Fran Scott explains fractional distillation - the separation of crude oil into fractions
In fractional distillation a mixture of several substances, such as crude oil, is distilled and the evaporated components are collected as they condense at different temperatures. is used to separate crude oil into simpler, more useful fractions. A fraction of crude oil is a group of A compound that contains hydrogen and carbon only. molecules of similar size with similar The temperature at which a substance rapidly changes from a liquid to a gas.. Their similar boiling points mean that they can be separated by fractional distillation.
Fractional distillation
During the fractional distillation of crude oil:
- heated crude oil enters a tall Piece of apparatus in which mixtures separate during fractional distillation. or tower, which is hot at the bottom and gets cooler towards the top
- vapours from the oil rise through the column
- vapours A change of state in which gas becomes liquid by cooling. when they become cool enough
- liquids are led out of the column at different heights
Trends in physical and chemical properties
All hydrocarbon molecules have very strong chemical bonds between atoms. They also have a weaker force of attraction between molecules. This is called an Weak attractive forces between molecules. When a simple molecular substance melts or boils, it is the intermolecular forces that are broken (not the covalent bonds in each molecule).. Longer hydrocarbon molecules have a stronger intermolecular force. More energy is needed to move them apart so they have higher The temperature at which a substance rapidly changes from a liquid to a gas.. This makes them less Evaporates easily. and therefore less Able to ignite and burn..
The longest hydrocarbons have very high boiling points. They leave the column as a hot liquid called bitumen.
Shorter hydrocarbon molecules have weaker intermolecular forces and lower boiling points. They are highly volatile and therefore extremely flammable.
The shortest hydrocarbons have very low boiling points. They do not condense, but leave the column in the gas state.