1. Water Hardness Hard water Soft water Removal of Hardness from water
Ms. Dunne, Junior Science

2. Hard water is water that does not lather easily with soap
Soft water is water that lathers easily with soap

3. Hard water is water caused by calcium ions Ca 2+ dissolved in the water
The calcium ions join with the soap making an insoluble substance, scum.
Calcium ions + Soap Scum

4. Where do all the calcium ions (Ca 2+ ) come from?
Calcium carbonate + Rainwater Calcium ions in
solution
Limestone
The calcium ions in solution cause hardness in water.

5. Advantages of Hard Water
Provides calcium for bones and teeth
Tastes nice
Good to use in brewing and tanning (making leather) industry.

6. Disadvantages of Hard Water
Blocks pipes and leaves a limescale on kettles and boilers
Wastes soap
Makes a scum with soap
Wastes electricity.

7. Limescale on the inside of hot water cylinders

8. Calgon is supposed to prevent the build up of limescale deposits on the inside of washing machines.

9. Hardness can be removed from water by Ion Exchange.
This process removes calcium ions (Ca 2+ ) from hard water. The water is passed through a column of resin.
The positive ions of calcium in the water are swapped for positive hydrogen ions (H + ) in the resin
Negative ions in the water are swapped for OH – ions in the resin.
The H+ ions and the OH- ions join to form water
The water is now soft and is called deionised water.