C3: W A T E R

C3: W A T E R

1. Hard water!

   • Contains dissolved compounds such as calcium and magnesium salts
     • Because of these dissolved compounds hard water uses more soap to wash effectively as the compounds react with soap to form scum (insoluble solid)
   • The calcium and/or 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 efficiency of heating systems.
   • Water that lathers easily with soap is said to be soft water
   • Hard water is better than soft water for developing and maintaining teeth and bones . It may also help to prevent heart disease

2. 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 harness is not change my heating
   • The hydrocarbonate are use is temporary hard water decompose on heating. The carbonate ions formed react with Ca2+ (aq) and Mg2+ (aq), making precipitates.
   • Both types of hard water can be softened by adding washing soda or by using ion-exchange resin to remove calcium and magnesium ions

3. 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 kill microbes
   • We can make pure water by distillation but this requires large amount of energy which makes it expensive

4. Water issues

   • There are advantages and disadvantage to any type of water treatment
     • Advantages to softening hard water: uses less soap, does not produce scum, reduces the effects on heating systems.
     • Disadvantages to softening hard water: reduces health benefits, costs money.
   • Water can be treated to remove hardness, to remove harmful microbes and to improve dental health.
     • Example 1: Chlorine is particularly effective including microbes in the water. However chlorine is poisonous and temperatures are the toxic compounds
     • Example 2: Flore compounds are added to toothpaste and to water to help prevent tooth decay. However some arguments suggest people should get to choose whether they take extra floride or not