1. Chemistry C3 Part Two Revision PowerPoint - Big ideas Hard water

2. Causes of hard water Hard water is caused by calcium and magnesium ions dissolving when acidic rainwater flows through rocks. Temporary hard water is caused by calcium hydrogencarbonate, can be removed by boiling the water. Permanent hardness caused by calcium sulphate isn’t removed by boiling.

3. Softening and desalinating Washing soda and ion-exchange resins can soften hard water. Seawater can be desalinated by distillation which needs a lot of energy

4. Tap water treatment Water is filtered to remove solids and sterilised with chlorine to kill microbes. Dissolved substances are removed by specialised filters or by ion exchange.