Methods of Separation & Purification
Chemistry: Cambridge International GCSE Supplement, topic 12.4.2
Methods of Separation and Purification
Separation and purification methods use solvents, filtration, crystallisation, and distillation for pure substances.
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Using a suitable solvent
- Chemistry uses solvents to dissolve specific substances.
- A suitable solvent dissolves the desired compound but not impurities.
- This method helps separate mixtures by selective dissolving.
- Chemists use this first step before other separation techniques.
Filtration
- Filtration separates solid particles from liquids or gases.
- Chemists pour mixtures through filter paper in a funnel.
- Solid particles remain on the paper; liquid passes through.
- This method works well to remove insoluble impurities.
Crystallisation
- Crystallisation separates dissolved solids from liquids.
- Chemists heat the solvent to evaporate it slowly.
- The dissolved solid forms pure crystals as the solvent evaporates.
- This method helps purify solids like salts.
Simple Distillation
- Simple distillation separates liquids with different boiling points.
- Chemists heat the mixture to evaporate the liquid with the lower boiling point first.
- Vapour cools in the condenser and collects as pure liquid.
- This method purifies solvents and separates substances like water from salt solution.
Fractional Distillation
- Fractional distillation separates mixtures of liquids with close boiling points.
- Chemists use a fractionating column.
- Vapours repeatedly condense and evaporate along the column.
- This method separates crude oil into fuels like petrol and diesel.
Test yourself on Methods of Separation & Purification
What is the primary purpose of using a suitable solvent in chemistry for separation?