Crude oil is separated into fractions by a technique called fractional distillation. This technique separates the hydrocarbons into fractions by heating the crude oil to about 400 degrees Celsius or 752 degrees Fahrenheit.
Crude oil is a raw material obtained from the Earth's crust. It is made from many different chemicals, most of which are hydrocarbons. These are chain molecules made exclusively from hydrogen and carbon and vary in length.
Crude oil becomes useful after it has been processed at an oil refinery. These refineries use the fractional distillation technique and what is called a fractioning tower. In this tower, the hottest molecules are found at the bottom, and the cooler molecules are found at the top. The smallest molecules move to the top due to their low boiling points while larger molecules with higher boiling points remain at the bottom. The fractions gathered are now useful mixtures, and most are used as energy sources. Smaller molecules can also be isolated by further refining.
The mixtures used as energy sources include fuel oil, heating oil, diesel, paraffin and petrol. In usage terms, these energy sources are oil for ships and power stations, central heating, buses, aircrafts and cars.