Hard water contains dissolved compounds in which calcium or magnesium ions are present.

Drinking hard water therefore has some health advantages. Discuss what these might be.

Hard water has some disadvantages when used in the following ways:

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When we use hard water for washing, a reaction takes place between soap and the calcium or magnesium ions dissolved in the water. This gives an insoluble solid called ‘scum’. Watch the animation below again.

What does ‘scum’ look like? How might it make washing yourself or your clothes more difficult?

Heating or boiling temporary hard water may bring insoluble compounds out of solution.

This kettle has been used many times for boiling hard water.

How does this explain the appearance of the heating element (normally grey and metallic) inside the kettle? Why has the efficiency of the heating element in this kettle been reduced?

The white solid or ‘fur’ that covers the heating element is called ‘limescale’.

Why might limescale be a problem in pipes carrying very hot water?