Pupils should:

(a) describe in outline the treatment of the public water supply, using filter beds and chlorination.

(b) be able to draw and interpret solubility curves using given data on change of solubility with temperature.

(c) know the causes of hardness in water and distinguish between a hard and a soft water by their action with soap.

(d) plan and carry out experiments to measure the type (temporary or permanent) and amount of hardness using soap solution.

(e) know how the methods of boiling, adding sodium carbonate and ion exchange work to soften water and discuss their advantages and disadvantages.

(f) evaluate the advantages and disadvantages of soft and hard water.