Crude oil has different sizes, weights and boiling temps, so fractional distillation separates the various types, collects them separately and allows them to pass on for storage.
Different substances vaporize at different temperatures. A fractional distillation takes crude oil through a series of temperature steps and extracts off the vapor at different temps. The vapor is cooled and purified chemicals condense out of the vapor. The process breaks the mixture (crude oil) into its purified component chemicals.
