1. Grind up the rock salt into smaller grains to increase surface area.

2. Add the rock salt to water and stir. The salt, being soluble, dissolves in the water, while the insoluble sand does not.

3. Pour the salt solution through a filter to remove large insoluble sand particles.

4. Gently heat the solution until all the water evaporates away, leaving behind pure salt crystals.

1. Ink spots are put on paper and the bottom of the paper is placed in a solvent.

2. The solvent moves up the chromatography paper.

3. Dyes that are more soluble in the solvent move further up the paper.

4. This results in visible separation of the dyes into bands at different distances up the paper.

1. The impure liquid mixture is heated in a flask until it boils.

2. The water vapour rises, enters the condenser and cools, condensing back into a liquid.

3. Pure water drips out of the condenser and can be collected in a separate container.

4. Impurities are left behind in the original flask as they require a higher temperature to boil.

1. The liquid mixture is heated in a flask.

2. As the temperature rises, the fraction with the lowest boiling point boils first.

3. When the gas reaches the condenser it is cooled and returns to a liquid.

4. The condensed liquid is collected in a separate container.

5. As the temperature rises further, the next fraction starts to boil and condense.

6. This process results in separation of the mixture into fractions based on boiling point.

Scientists can test the melting and boiling points of a separated substance. If a substance contains impurities, the melting and boiling points will be different from the pure substance.

Pure water melts at 0°C.

Pure water boils at 100°C.