Hard water contains dissolved compounds such as calcium and magnesium salts.
The calcium and/or magnesium ions in hard water react with soap producing a precipitate called scum
One type of hard water can produce a solid scale when it is heated, reducing the efficiency of heating systems and kettles
Hard water is beter than soft water for developing and maintaining teeth and bones. It may also help to prevent heart disease
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Removing hardness
Soft water does not contain ions that produce scum or scale
Hard water can be softened by removing the ions that roduce scum and scale
Temporary hardness is removed from water by heating it. Permanent hardness is not changed by heating.
The hydrogencarbonate ions in temporary hard water dcompose on heating. The carbonate ions formed react with Ca2+ (aq) and Mg2+ (aq) ions, making precipitates
Either type of hard water can be softened by adding washing soda or by using an ion- exchange resin to remove calcium and magnesium ions
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Water treatment
Water for drinking should contain only low levels of dissolved substances and microbes
Water is made fit to drink by filtering it to remove solids and adding chlorine to reduce the number of microbes
We can make pure water by distillation but this requires large amounts of energy which makes it expensive
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Water issues
Chlorine is added to water to sterilise it by kiling microbes
Fluoride helps to improve dental health
Some argue against the fluoridation of public water supplies. For example, they think that people should have the right to choose if they want to take extra fluoride or not
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