Cambridge O Level Chemistry · Syllabus 5070 · Experimental Techniques and Chemical Analysis
Simple Distillation
What is Simple Distillation?
A separation method in which a liquid is boiled, the vapour is passed through a condenser where it is cooled back to a liquid, and the condensed liquid is collected as the distillate. It separates a solvent from a dissolved solid, or a liquid from components that do not vaporise under the conditions used. The thermometer bulb is placed level with the side-arm so that it measures the temperature of the vapour leaving the flask, and the cooling water enters the condenser at the lower end and leaves at the upper end.
This definition is part of the Experimental Techniques and Chemical Analysis chapter in Cambridge O Level Chemistry.
Common mistakes with Simple Distillation
- 10. “Filter the sea water to get pure water.” Why it fails The salts are dissolved, so they pass through the filter paper with the water. Filtration removes insoluble solid only. Correct Simple distillation: the water vaporises, is condensed and collected as the distillate; the salts stay behind as the residue. Check Sea water is filtered and then distilled. Which step removed the salt? Only the second.
- 27. “Use a separating funnel to separate the mixture.” Why it fails A separating funnel is not one of the five methods named in statement 12.4.1, so it is not the expected answer — and it only works at all for liquids that do not mix. Correct Choose from a suitable solvent, filtration, crystallisation, simple distillation and fractional distillation, and justify the choice from the property data. Check Ethanol and water are miscible, so no layers form; fractional distillation is the method.
Questions students ask about Simple Distillation
How should you choose a separation technique on an unfamiliar substance?
Match the technique to the property difference the question gives you: use a suitable solvent or filtration when solubility differs, crystallisation to recover a dissolved solid, simple distillation to separate a solvent from a dissolved solid or non-volatile component, and fractional distillation when two or more miscible liquids have different boiling points. A full-credit answer names the method, states the property difference that makes it work, and says what is kept.