How does distillation separate substances in a liquid mixture?

Distillation separates substances in a liquid mixture by exploiting differences in their boiling points. The process relies on the principle that the vapor above a liquid mixture has a different composition than the liquid itself, containing a higher proportion of the more volatile component—the substance with the lower boiling point.12

When a mixture is heated, the total vapor pressure increases until it equals the surrounding atmospheric pressure, causing the mixture to boil. As the liquid converts into vapor, the most volatile substance vaporizes first. This vapor is then collected and condensed back into a liquid, effectively separating it from the less volatile components that remain in the original mixture.12

For mixtures with closely related boiling points, fractional distillation is used. This method employs a column where rising vapors and descending liquid are brought into contact, allowing for repeated condensation and revaporization. This multistage process ensures that the most volatile component concentrates at the top of the column, enabling a sharper separation of the mixture's constituents.12