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Compare evaporation, crystallization and distillation. In which situation, would you prefer each of these over the others?
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Evaporation removes the solvent to get a solid solute — preferred when the solute is stable on heating and you do not need the solvent back (e.g. getting salt from salt water).
Crystallization forms pure crystals by cooling a saturated solution — preferred when you need a pure solid and want to leave impurities behind (e.g. purifying copper sulfate).
Distillation boils and condenses — preferred when you want to recover the solvent, or separate two miscible liquids with different boiling points (e.g. acetone and water).
| Evaporation | Crystallization | Distillation | |
|---|---|---|---|
| What you recover | The dissolved solid only — the solvent is lost | A pure solid , as well-formed crystals | The liquid — solvent or the lower-boiling liquid |
| How it works | The solvent is allowed to vaporise away | A hot saturated solution is cooled slowly | The mixture is boiled, then the vapour is condensed |
| Prefer it when… | the solute is heat-stable and you do not need the solvent back (salt from seawater) | you need a pure solid and want the impurities left in solution (copper sulfate) | you want the solvent back, or you must split two miscible liquids (acetone and water) |
