A student separates a mixture of liquids using simple distillation. Describe how simple distillation works and explain why it is able to separate the liquids.

WJEC GCSE Chemistry (Wales) — 1.2 Atomic structure and the periodic table · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A student has a solution of salt dissolved in water. She wants to collect a sample of pure water from the solution using simple distillation.

Model answer (4 marks)

1. The solution is heated until the solvent reaches its boiling point.
2. The solvent (water) evaporates, forming vapour.
3. The vapour rises into a condenser where it is cooled and condenses back into liquid.
4. The condensed liquid is collected as pure water.

The separation occurs because the solvent has a much lower boiling point than the solute; only the solvent evaporates and is recovered, leaving the solute behind.

Examiner tips

  • Use the exact sequence of heating, evaporation, condensation and collection. Mention the lower boiling point of the solvent. Show the vapour‑to‑liquid conversion clearly.

Common mistakes

  • Confusing the solvent with the solute. Failing to state that the solvent has a lower boiling point. Omitting the cooling/condensation step.

Mark scheme (4 marks)

  1. The solution is heated
  2. The solvent (water) evaporates / turns to vapour / gas
  3. The vapour is cooled and condensed to collect the liquid
  4. It works because the solvent has a much lower boiling point than the solute, so only the solvent evaporates

Key terms in this question

simple distillation

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