Final answer:
The separation of liquid compounds by distillation depends on the differences in their boiling points, with the more volatile component being collected first through the process of vaporization and condensation.
Step-by-step explanation:
The separation of two or more liquid compounds by distillation depends on the differences in boiling points of the components in the mixture. The process involves heating the mixture until the more volatile component vaporizes. This component, with the lower boiling point, then condenses into a liquid in a condenser and is collected separately.
In the case of a solution with a dissolved solid, such as salt water, distillation allows the pure water to be collected by leaving the salt behind. Situations such as the refining of crude oil make use of fractional distillation, where a more complex apparatus is used to separate multiple liquids with different boiling points.