topic 10 chem

• potable water

  Safe for humans to drink- not pure
• Desalination


  the removal of salt from seawater to make it usable for drinking and farming
• Desalination processes


  distillation and reverse osmosis
• reverse osmosis


  - requires expensive membranes

  -large volume of waste water so less efficient
• Distillation


  -requires a lot of energy to boil and condense

  - difficult to dispose of waste water without harming environment
• how to treat sewage


  screening - remove large particles

  sedimentation-tiny particles and water separate

  sludge (waste)

  effluent (water)
• How is sludge treated?

  anaerobic respiration
• How is effluent treated?

  aerobic respiration
• processes to extract metals

  mining

  phytomining

  bioleaching
• advantages of mining


  get large quantities

  well established methods
• disadvantages of mining


  lots of energy required

  ruin habitats

  very expensive

  pollution
• advantages of phytomining


  reduces need of mining

  lower grade ores get used

  less environmental damage
• disadvantages of phytomining


  Slow

  low grade ores

  time consuming

  small quantity
• advantage of bioleaching


  cost effective

  lower grade ores get used
• disadvantage of bioleaching


  small quantity

  toxic substance produced
• brass


  copper and zinc
• use of brass


  instruments
• bronze

  copper and tin
• use of bronze


  statues
• gold

  silver and copper and zinc
• use of gold


  jewellery
• steel


  carbon and other metals
• use of steel


  cutlery
• what is corrosion


  oxidation of metals
• rust


  oxidation of iron
• how to stop rust


  barrier (painting)

  sacrificial (more reactive )
• conditions for rust


  Oxygen & water
• soda-lime glass


  sand +sodium+ limestone carbonate is heated together
• boron silicate glass


  boron trioxide + sand is heated together
• ceramics


  heat clay in a furnace
• composites


  have different properties than what they are made from
• Harber Process Conditions


  450 degrees

  200 atm

  iron catalyst
• what conditions increase the yield of ammonia

  high pressure

  low temperature