What separation technique uses differences in boiling point to purify liquids?

Distillation separates and purifies liquids by exploiting differences in their boiling points.

When a liquid mixture is heated, the component that is more volatile—usually the one with the lower boiling point—becomes more concentrated in the vapor. That vapor is then cooled in a condenser and collected as a liquid called the distillate. The process is physical separation, not a chemical reaction.

Simple distillation works best when boiling points differ substantially, or when a volatile liquid must be separated from a non-volatile substance. Fractional distillation uses a fractionating column and repeated vaporisation and condensation to separate liquids with closer boiling points. This method is central to petroleum refining and laboratory purification.

Distillation is not always able to produce completely pure substances. Mixtures called azeotropes can boil with a fixed composition, limiting ordinary separation. Vacuum distillation lowers pressure so substances boil at lower temperatures, helping prevent heat-sensitive compounds from decomposing.