Unit 10 · Materials Used in Daily LifeHardness of Water
Words of This Topic
- Hardness: the property of water, caused by dissolved calcium and magnesium salts, that stops soap from lathering.
- Soft water: water in which no soluble salts of calcium and magnesium are dissolved.
- Hard water: water in which soluble salts of calcium and magnesium are dissolved.
- Temporary hardness: hardness caused by bicarbonate salts, which goes away on boiling.
- Permanent hardness: hardness caused by sulphate and chloride salts, which does not go away on boiling.
- Soluble: able to dissolve in water.
- Insoluble: not able to dissolve in water.
- Calcium hydroxide, known as lime water: the substance used in the Clark method.
- Clark method: removing temporary hardness by using lime water.
- Washing soda: the substance used to remove permanent hardness.
- Zeolite: a substance used to soften water, whose sodium is displaced by calcium and magnesium ions.
- Permutit method: removing permanent hardness by using zeolite.