3. Separation Techniques
1. Filtration
2. Evaporation and Crystallisation
Steps :
3. Simple Distillation
Things to note :
4. Fractional distillation
5. Paper Chromatography
6. Sublimation
7. Separating funnel
- Separates a mixture of insoluble solid & a liquid.
- Recovers the insoluble solid as the residue and the liquid as filtrate.
- e.g. mixture of calcium carbonate and water.
- Calcium carbonate is obtained as residue (insoluble solid) and water is obtained as the filtrate (liquid).
2. Evaporation and Crystallisation
- To recover solute from solution
- Evaporation: For solutes which do not decompose upon heating e.g. sodium chloride
- Crystallisation: For solutes which decompose upon heating e.g. nitrates, sulfates & hydrated crystals
Steps :
- Heat solution until it is saturated.
- Allow the saturated solution to cool to form crystals.
- Filter, wash and dry the crystals.
- Saturated solution is a solution which contains the maximum amount of solute in a given volume of solvent at a given temperature.
- The higher the temperature, the more solute can be dissolved.
3. Simple Distillation
- To recover solvent from a solution as distillate.
- e.g. pure water (distillate) is obtained from seawater.
Things to note :
- The bulb of the thermometer must be at same level as distilling arm to measure temperature of pure vapour.
- Boiling stones are added to ensure smooth boiling.
- Water enters from bottom of condenser and water exits from top of condenser.
4. Fractional distillation
- Separates mixtures of miscible liquids with different boiling points.
- First fraction is the one with the lowest boiling point.
- Separates components in liquid air & crude oil/petroleum
5. Paper Chromatography
- Principle: Different components in the mixture have different solubilities in the same solvent. The more soluble component, the further it travels up the chromatogram.
- Pure substance produces one spot only.
- Locating agent is used to make colourless components visible.
6. Sublimation
- A process whereby a substance changes from the solid sate to the gaseous state without melting.
- Recovers iodine & ammonium chloride.
7. Separating funnel
- Separates immiscible liquids e.g. oil and water