Particles and Mixtures - 1.7 Filtration and Crystallisation

What are 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?

Filtration is used to separate insoluble solids from liquids.

Describe the technique for filtration

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

2. Pour your mixture through the funnel

3. Any insoluble solids will be caught by the filter paper, we call this the residue

4. Any liquid or dissolved substances will pass straight through, we call this the filtrate

What is evaporation used for?

Evaporation is used to separate a dissolved solid from a liquid.

Describe the technique for evaporation?

Heat your solution until all of the solvent evaporates and only solids remain (this is normally done by placing the solution in an evaporating dish on a tripod, and heating it with a Bunsen burner)

Describe the technique for crystallisation

1 pour the solution into an evaporating dish 2. Heat it using a Bunsen burner. 3. Stop heating it when Crystal starts to form (point of crystallisation.) and allow it to cool down 4. Either leave it to allow the rest of the water to evaporate or filter out the crystals using filter paper using a funnel. 5. Dry the crystals in a warming oven or desiccator

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 by thermal decomposition

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

1. Place the mixture in water and stir. The salt will dissolve but the sand won't.

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

3. Evaporate the water by heating. This will leave behind the salt.

What is chromatography used for?

Chromatography separates the components of mixtures based on their solubility

What is a 'pure' substance?

A pure substance is one that only contains one type of element or compound

What is a solution?

A solution that contains a solute (the solid) dissolved in a solvent (the liquid).

What do 'soluble' and 'insoluble' mean?

A soluble substance is one that can dissolve in liquid. An insoluble substance is one that cannot dissolve in liquid.