TOPIC 10

• what is potable water

  water that is Safe to drink
• whats the ideal quality of water

  suffiently low levels of dissolved salts and microbes
• why's potable water and pure water not the same

  in the chemical sense no because it contains dissolved substances
• steps for potable water: 1

  filtration

  pass the water through filter beds

  a wire mesh screens out large twigs and then gravel and sand bed filter out any other solid bits
• steps for potable water: 2

  sterilisation: the water is sterilised to kill any harmful bacteria or microbes

  this can be done by bubbling chlorine gas though it or by using ozone or uv light
• when do we use desalination

  if supplies of fresh water are limited

  in hot countries
• what is desalination


  can be done by distillation or by processs that use membranes such as reverse osmosis

  these processes require large amounts of energy to reduce the levels of dissolved minerals!!1
• why do we need waste water treatment

  urban lifestyles and industrial processes produce large amounts of waster water that require treatment before being released into the environment
• sewage treatment


  sewage is screened which is where we remove any large bits of material as well as grit
• what is sedimentation


  stands in a settlement tank and the heavier suspended solids sink to the bottom to produce sludge while the litter effluent floats on top
• what happens to the effluent in the settlement tank

  is moved and treated by biological aerobic digestion
• what is aerobic digestion

  where air is pumped through the water to encourage aerobic bacteria to break down any organic matter including other microbes in the water
• what happens to the sludge

  the sludge from the bottom of the settlement tank is also removed and transferred into large tanks here it gets broken down by aerobic digestion
• what happens during aerobic digestion to the sludge

  breaks down the organic matter in the sludge releasing methane gas
• what can be used as methane gas

  can be used as energy source and the remaining waste can be used as fertiliser
• what do we do to waster containing toxic substances

  treatment like adding chemicals or using membranes, uv radiation
• what is copper used for

  in electronic equipment such as phones
• what are happening to copper ores

  they are becoming scarce (running out)
• since copper ores are becoming scarce what do we have to do,

  extract copper from low grade ores
• what do low grade ores contain

  a small amount of copper
• what is phytomining


  uses plants to absorb metal compounds

  the plants are harvested and then burned to produce ash that contains metal compounds
• what is bleaching


  uses bacteria to produce leachate solution that contains metal compound
• what happens in bleaching

  bacteria are mixed with the low grade ore the bacteria then carry out chemical reactions and they produce a solution called a leachate
• what does a leachate contain

  the metal compounds we want
• what happens at the end of both bioleching and phyotmining

  the metal compound we want has been extracted from the low grade ore
• what do we do to extract the metal from the compound

  if copper compound:

  displace the copper using iron

  iron is more reactive then copper

  or using electrolysis
• what are rw materials often obtaiend by

  quarrying or mining
• whats wrong with this

  harmful to environment

  large amounts of dust and destroys habitats

  chemicals to environment
• why do we reuse our recycle

  will help save limited resources and energy also reduce the amounts of waste we produce
• what is corrosion


  the destruction of materials by chemical reactions

  with substances in the environment
• what is rusting


  example of corrosion

  both air and water are necessary to rust
• how can rusting be prevented

  paining/coating with plastic

  electroplating

  oiling/greasing
• whats electroplating


  uses electrolysis to reduce metal ions into an iron electrode

  it can be used to coat the iron with a layer of different metal that won't be corroded away
• whats oiling/greasing


  has to be used when moving parts are involved like on bike chain
• whats the sacrificial method

  placing a more reactive metal such as zinc or magnesium with iron

  water+oxygen react with the sacrificial metal instead of the iron
• whats an alloy


  contain a metal blended with other elements its a mixture
• bronze


  copper+tin

  bronze is harder then copper and is used to make medals, ornaments , statues
• brass


  copper+zinc

  malleable then bronze used in situations where lower friction is required in water fans
• gold is used as

  jewellery

  usually a alley with issued copper and zinc

  24 carats=pure gold

  18 carats=75%gold
• aluminium alloys


  low density

  pure is too soft