4.2 Fractional Distilliation
Crude oil is separated into fractions 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.
The vaporised oil rises up the column into various fractions. The further up the column the cooler it gets.
Low boiling point has a high volatility; low viscosity; highly flammability.
High boiling point has a low volatility; high viscosity; burns with a black smoke.