Filtration & Crystallisation

What are the 6 methods through which mixtures can be separated?

1. Filtration

2. Chromatography

3. Crystallisation

4. Evaporation

5. Simple Distillation

6. Fractional Distillation

What is filtration used for?

To separate insoluble solids from liquids

Describe the technique for filtration

1. Place a piece of filter paper in funnel and put the funnel over a beaker

2. Pour the mixture through the funnel

3. Any insoluble solids (residue) will be caught by the filter paper

4. Any liquid or dissolved substances (filtrate) will pass through

What is evaporation used for?

To separate a dissolved solid from a liquid

Describe the technique for evaporation

Heat solution until all solvent evaporates and only solid remains

Describe technique for crystallisation

1. Pour solution into evaporating dish

2. Heat using Bunsen Burner

3. Stop heating when crystals start to form, then let it cool

4. Either leave it to allow the remain water to evaporate or filter out crystals using filtration

What is the benefit of using crystallisation rather than evaporation as a separating technique?

The excess heat used in evaporation can sometimes cause the crystals to break down (thermal decomposition)

How could you isolate the sand and salt from a mixture of salt and sand?

1. Place mixture in water and stir, the salt will dissolve, not the sand

2. Pour mixture through filter paper and funnel, the sand will get stuck on filter paper

3. Evaporate water by heating, this will leave behind the salt

What is chromatography used for?

To separate the components of a mixture based on their solubility

What is a ‘pure’ substance?

A substance that only contains one type of element or compound

What is a solution?

A mixture that contains a solute (solid) dissolved in a solvent (liquid)

What do soluble and insoluble mean?

Soluble - substance that can dissolve in liquid

Insoluble - substance that can’t dissolve in liquid