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Question
Compare evaporation, crystallization and distillation. In which situation, would you prefer each of these over the others?
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Answer
Evaporation throws the liquid away, crystallization purifies the solid, and distillation saves the liquid.
Explanation
| Method | What happens | When to choose it | Example |
|---|---|---|---|
| Evaporation | The solvent is heated away, or allowed to evaporate, and is not recovered | When only the dissolved solid is wanted, it is not damaged by heat, and the solvent has no value | Salt from sea water |
| Crystallization | A hot saturated solution is cooled slowly; pure crystals come out and impurities stay dissolved | When a very pure solid is needed, or the solid would break down on heating | Purifying copper sulfate |
| Distillation | The liquid is boiled and its vapour condensed back into liquid | When the liquid is also wanted, or two miscible liquids must be separated with a gap of more than 25 °C | Acetone and water |
One line — evaporation wastes the liquid, crystallization purifies the solid, distillation saves the liquid.
← Back to: 5.3 Methods of Separation of Homogeneous Mixtures
