Fuels from crude oil
crude oil contains many different compounds that boiln at different temperatures. these burn under different conditions and so crude oil needs to be seperated to make useful fuels
we can seperate a mixture of liquids by distillation. simple distillation of crude oil can produce liquids that boil within different temperature ranges. these liquids are called fractions
most of the compounds in crude oil are hydrocarbons. this means that their molecules contain only hydrogen and carbon. many of there hydrocarbons are alkanes. alkanes contain as many hydrogen atoms as possible in each molecule and so we call them saturated hydrocarbons
we can represent molecules in different ways. a molecular formula shows the number of each type of atom in each molecule, eg C2H6 represents a molecule of ethane. we can represent molecules by a displayed formula that shows how the atoms are bonded together
crude oil is seperated into fractions at refineries using fractional distillation. this can be done because the boiling point of a hydrocarbon depends on the size of its molecule. the larger the molecule, the higher the boiling point of the hydrocarbon
the crude oil ia vaporised and fed into a fractionating column. this is tall tower that is hot at the bottom and gets cooler going up the column
inside the column there are many trays with holes to allow gases through.