How does fractional distillation work?

Fractional distillation works by using the fact that molecules of different sizes have different boiling points. Generally, the smaller a molecule, the lower its boiling point. When heating up a mixture of molecules, the lowest boiling compound will boil off first. While the compound is boiling, the temperature of the mixture will not increase above the lowest boiling point substance in the mixture as all the energy being put into the system is used to break intermolecular bonds and produce a gas. Once all of a substance boils off, then the tempertature of the mixture will increase to the next lowest boiling point and the process repeats again.