1. The diagram shows the paper chromatograms of four substances, W, X, Y and Z.

Which two substances are pure?

2.Chromatography and fractional distillation can be used to separate compounds. In which type of separation is a thermometer needed for checking that complete separation has occurred?

3.Diagram 1 shows the paper chromatogram of substance X.

Diagram 2 shows the cooling curve for substance Y.

Which statement about X and Y is correct?

4. The diagram shows how to obtain pure water from seawater.Where do water molecules lose energy?

5 . A solid mixture contains an ionic salt, X, and a covalent organic compound, Y.Two students suggested methods of separating the mixture as shown.

Which methods of separation are likely to work?

6.Mixture 1 contains sand and water.

Mixture 2 contains salt and water.

Which method of separation could be used to obtain each of the required products from each mixture?

7.Some chemical compounds are purified by recrystallisation.What can be used to test the purity of the crystals?

8.Which change is condensation?

9.Some gas in a sealed plastic bag is cooled.How do the gas molecules behave when this happens?

10.A solid metal is heated until it turns to vapour.The graph shows the temperature of the metal during this process.Which part of the graph shows the melting of the metal?