Water and purification

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  • Water and purification
    • Natural waters contain dissolved salts
    • Tests for water:
      • Boils at 100c
      • Cobalt chloride:
        • Dip paper in water-    blue-->pink
      • Hydrated copper sulphate:
        • Blue copper sulphate turns white when water is removed
          • Reversible reaction- when water added turns back blue
    • Purification
      • Slow sand filters:
        • biofilm contains bacteria, fungi and protozoa
          • Good bacteria destroys and kills the bad
            • Dirt and bacteria get trapped in sand
      • Ion resins:
        • Water goes through filter cartridge- activated carbon, an ion exchange resin and silver
          • Ion exchange resin removes calcium, magnesium, lead, copper and aluminium ions
      • Distillation:
        • separates pure liquids from mixtures- liquids have different boiling points.
      • Desalination:
        • removing dissolved salts- fresh water from seawater
    • Fluoridation:
      • Fluorine is added to water to help reduce tooth decay
        • Against: unnecessary, tooth staining, unethical
    • Chlorine is added to sterilise- remove microbes


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