Purifying and Testing Water

Purifying and Testing Water

1. water

   • lakes
   • rivers
   • reservoirs
   • aquifiers
     • wells
     • bore holes
   • uses
     • drinking
     • washing
     • household jobs
     • industry
       • cooling
       • solvent
       • raw material
   • some parts of Britain: demand higher than supply

2. water treatment

   • to purify it
     • safe to drink
   • untreated contains
     • microbes
     • pollutants
     • insoluble particles
     • dissolved salts and minerals
   • process
     • 1) sedimentation
       • insoluble particles sink
     • 2)filtration
       • remove very fine particles
     • 3) chlorination
       • kill microorganisms

3. water purification

   • tap water contains soluble materials
     • not removed in water treatment
   • distilled
     • lots of energy
       • expensive
     • huge amounts of energy would be needed to distil sea water
       • costly
       • expensive equipment
       • menas making drinking water from sea water is prohibited

4. pollution in water

   • nitrates
     • fertiliser
   • lead compunds
   • pesticides
     • spraying crops
   • difficult to remove

5. dissolved ions

   • dissolved ions of some salts: easy to identify
     • precipitation reactons
       • insoluble solid from mixing 2 solutions
   • barium chloride
     • detect sulfates
       • form barium sulfate
         • white precipitate
   • silver nitrate
     • detect halide ions
       • chlorides
         • white pecipitate
       • bromides
         • cream precipitate
       • iodides
         • pale yellow precipitate