Crude oil, also called petroleum, is a complex mixture of carbon and hydrogen (hydrocarbons), which exist as a liquid in the earth's crust. Crude oil has many compositions, some is black, thick and tar like, while other crude oils are lighter in color and thinner.
Distillation process of crude oil is the process of separating the many compounds present in crude petroleum. Distillation process of crude oil is called fractional distillation where the crude oil is heated; the various of the compounds boil at different temperatures and change to gases; and are later recondensed back into liquids.