Chemistry C3.2
- Created by: Will Pound
- Created on: 06-03-14 18:47
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- Chemistry C3.2
- Hard water
- Hard water contains dissolved compounds such as calcium and magnesium salts
- The calcium & magnesium ions in hard water react with soap producing a precipitate called scum
- Temporary hard water can produce a solid scale when it is heated, reducing the efficiency of heating systems & kettles
- Hard water is better than soft water for developing and maintaining teeth & bones. It may also prevent heart disease
- Removing hardness
- Soft water does not contain salts that produce scum or scale
- Hard water can be softened by removing the salts that produce 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 decompose on heating
- The carbonate ions formed react with Ca²+ and MG²+, making precipitates
- Both types of hard water can be softened by adding washing soda or by using an ion-exchange resin to remove calcium & magnesium ions
- Water treatment
- Water for drinking should contain only low levels of dissolved substances & microbes
- Water is made fit to drink by filtering it to remove solids and adding chlorine to kill microbes
- We can make pure water by distillation but this requires large amounts of energy which makes it expensive
- Water issues
- There are advantages & disadvantages to any type of water treatment
- Water can be treated to remove hardness, to remove harmful microbes and to improve dental health
- Hard water
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