Hard water

Hard water

1. It's more difficult to form a lather with soap and water.

   • Hard water is more expensive because we need to use more soap.

2. Produces scum with water

3. To investigate the hardness of water samples, you can add 1cm3 of soap solution at a time. Put a stopper on each sample and shake the tube after each addition. Continue until a permanent lather is formed. The more soap needed, the harder the water.

4. Hard water contains dissolved calcium and magnesium ions. These dissolve when streams and rivers flow over rocks containing calcium/magnesium compounds.

5. Limestone, which contains mainly calcium carbonate, is another rock which causes hardness in water. As rain falls through the air, carbon dioxide dissolves in it. The carbon dioxide makes the rainwater slightly acidic. The water in streams and rivers becomes slightly acidic too.

6. Calcium carbonate reacts with the weakly acidic solution. Calcium hydrogencarbonate is formed which is soluble in water. Calcium ions Ca2+, get into the water, making it hard.

   • The carbonate in scale is calcium carbonate.

7. One type of hard water can produce a solid scale (limescale) when heated. It forms in washing machines, pipes, and other parts of hot water systems. This can reduce the efficiency of heating systems and kettles.

   • The scale forms in our kettles. This ‘furring up’ of the heating element makes them less efficient. The scale is a poor conductor of energy, so it takes longer to boil the water and uses more energy. This costs more money.

8. • Calcium ions in drinking water help in the development of strong bones and teeth

9. • There is evidence it helps to reduce heart disease.