Hard Water We use water every day to wash our clothes. In some areas, it is difficult for water to lather with soap or detergents. This type of water is called hard water.
Hard water contains a high concentration of calcium (Ca2+) and magnesium (Mg2+) ions. These ions enter the water as it flows over certain types of rock.
Key = Soft water
= Moderately hard water = Hard water
Sligo Belfast
Longford Galway Dublin Kildare Limerick Kilkenny
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Killarney Fig. 22.6.1
Types of water in Ireland
Instead of forming a lather with soap, hard water produces a dirty scum that settles on the surface of the water.
Adding soap to water and monitoring the lather (or scum) that is formed is a simple test for the degree of hardness in water samples.
1 Compare the above map to a geological map of Ireland. Which rock type do you think causes the hardness in Irish water?
The presence of calcium hydrogencarbonate and magnesium hydrogencarbonate in water is responsible for temporary hardness. Temporary hardness may be removed by heating the water, as shown by the limescale that builds up on the elements of kettles and washing machines.
2 Research the difference between temporary hardness and permanent hardness in water. Write a short report and present it to your classmates.
