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Compounds and mixtures

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Separating mixtures

The different substances in mixtures are usually easily separated from one another. The method you use depends upon the type of mixture you have.

Chromatography

This is good for separating dissolved substances that have different colours, such as inks and plant dyes. It works because some of the coloured substances dissolve in the liquid better than others, so they travel further up the paper.

Separating dissolved substances

A pencil line is drawn, and spots of ink or plant dye are placed on it. There is a basin containing solvent

Filtration

Filtration is good for separating an insoluble solid from a liquid. (An insoluble substance is one that does not dissolve).

Sand, for example, can be separated from a mixture of sand and water using filtration. That's because sand does not dissolve in water.

Separating insoluble solids

Shows a beaker with a mixture of solid and liquid in it. Another beaker has a funnel with some filter paper in.

Evaporation

This is good for separating a soluble solid from a liquid (a soluble substance does dissolve, to form a solution).

For example copper sulphate crystals can be separated from copper sulphate solution using evaporation. Remember that it is the water that evaporates away, not the solution.

Separating a soluble solid

A solution is placed in an evaporating basin and heated with a bunsen burner.

Simple distillation

This is good for separating a liquid from a solution. For example, water can be separated from salty water by simple distillation. This method works because the water evaporates from the solution, but is then cooled and condensed into a separate container. The salt does not evaporate and so it stays behind.

Separating a liquid from a solution

Salty water is heated

Fractional distillation

This is good for separating two or more liquids from each other. For example, ethanol (alcohol) can be separated from a mixture of ethanol and water by fractional distillation. This method works because the two liquids have different boiling points.

Separating two or more liquids

Water and ethanol solution are heated in a flask over a bunsen burner, pure vapour is produced in the air above the solution within the flask.

Water and ethanol solution is heated.

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Compounds and mixtures activity

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Elemental

Can you conquer the elements?

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