As the pressure increases, how does the boiling point change?
As external pressure increases, boiling point increases.
The boiling point of a liquid is defined as the temperature at which the vapour pressure of the liquid becomes equal to that of the ambient pressure, and bubbles of vapour form directly in the liquid. The normal boiling point is specified at atmospheric pressure, i.e. the vapour pressure of the liquid is
Under reduced pressure, therefore, many liquids can be purified by distillation in that their boilling points are substantially reduced.