Fractional distillation and crude oil.
The oil that we pump from the ground is a thick liquid, almost like molasses, as pictured on the right. It is known as crude oil and is formed from plant and animal matter that decayed millions of years ago and was buried deep under ground. Crude oil is a mixture of solid, liquid and gaseous hydrocarbons. These different compounds must be separated and processed. The gas is removed at the oil well. This is to avoid pressure build up in the delivery pipeline.
picture from www.nasaexplores.com
picture from sciencemuseum.org.uk/.

Separation of the different compounds that form crude oil is done by a process called fractional distillation. This process is performed in a fractionating tower. These tall structures are prominent features in all oil refineries.
During fractional distillation the many compounds of crude oil are separated according to their boiling temperature.
Continue with fractional distillation