1. Chapter 3: Separation Techniques
You will learn about:
Pure substances
Methods of purification:
- Chromatography
- Filtration
- Crystallization
- Distillation

2. How do we know which are the real products?

3. Melting and boiling points
Testing for Purity
Pure Substances
Mixtures
Composition
A single substance not mixed with anything else
Contains two or more substances
Melting and boiling points
Fixed points
Over a range of temperature
Chromatography
Produces a single spot on the chromatography paper.
Contain two or more spots.

4. A technique using a solvent to separate a mixture into its components.
(i) Chromatography
A technique using a solvent to separate a mixture into its components.
E.g separate dyes in ink, detect traces of banned food substances, identify poisons or drugs. 1

5. Procedure: Food colouring is applied to chromatography paper.
The paper is dipped into a solvent (e.g water, alcohol)
The solvent travels up the paper, dissolving and carrying the dye along with it.
Coloured spots are seen in different positions on the paper at the end of results.

7. Who wrote the ransom note?

10. Culprit

11. Ben Johnson stripped from his Olympic gold in 1988.

12. ii) Filtration: separating a solid from liquid

13. A mixture is poured into the filter funnel lined with filter paper.
Liquid particles are small enough to go through the pores of the filter paper but the solid particles are too large to go through.
Collect the filtrate that passes through the filter paper in a conical flask. The solid that remains in the filter paper is called residue.

14. iii) Evaporation to Dryness & Crystallisation

15. Procedure:
1. Pour some distilled water into the mixture to dissolve the soluble substance. 2. Filter the mixture. 3. Wash the residue with a little distilled water to remove all the salt solution from it. The residue is sand.
4. Evaporate the filtrate to dryness. Salt is recovered.

16. iv) Distillation: separating a liquid from a solution

17. Procedure: Solution is heated in a flask until the solution boils.
Pure liquid turns into a vapour and leaves the flask
Vapour is then cooled by a condenser, which changes it back into a liquid
Liquid is called the distillate and is collected in a conical flask.

18. How does simple distillation work?
2. In the condenser, water vapour condenses.
3. Pure water is collected as distillate.
1. In the distillation flask, water boils and enters the condenser.

19. SAFETY MEASUREMENTS: Thermometer
This ensures that the thermometer measures the boiling point of the substance that is being distilled.
Boiling Chips
To ensure smooth boiling.

20. If the distillate is volatile, the receiver can be put in a large container filled with ice.
This helps to keep the temperature of the distillate low so that it remains in the liquid state.

21. Eg. Finding out the dyes present in sweets

22. Paper chromatography a method of separating & identifying mixtures.
a suitable solvent is used.

25. Purity of Substances
pure substances have fixed melting and boiling points
melting points and boiling points are changed by the presence of impurities