using earths resources + obtaining potable water

• finite resource

  a resource we use faster than is naturally formed
• renewable resource

  resources that will not run out because they can be replaced at the same rate they are used
• what is sustainable development

  development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
• 3 example of finite energy resources

  oil

  gas

  coal
• 3 examples of natural products and what can replace them

  cotton for clothing - polyester

  silk for clothing - nylon

  rubber for tyres - synthetic polymers
• what is potable water

  water that is safe to drink
• why is potable water not considered pure water

  it contains low levels of salt and microbes
• why is sea water dangerous to drink

  dangerous levels of salt
• what is fresh water

  water with low levels of dissolved substances
• main steps to producing potable water from fresh water

  • choosing appropriate source of fresh water
  • passing water through filter beds
  • sterilising
• name the three sterilising agents

  ozone

  uv light

  chlorine
• why do you need to pass water through filter beds

  remove solid particles
• why do you need to sterilise

  to kill the microbes
• how can you get potable water in places where fresh water supply is limited

  desalination of sea water or salty water
• two methods of desalination

  distillation

  reverse osmosis
• what happens in reverse osmosis

  pressure is applied to force water through the partially permeable membrane from a low water concentration to high water concentration
• what is the problem is reverse osmosis and distillation

  both require lots of energy :

  distillation - energy to heat

  reverse osmosis - energy to force the water
• 3 types of waste water

  industrial

  agricultural

  sewage
• what needs to be removed from industrial waste

  organic matter and harmful chemicals
• what needs to be removed from agricultural and sewage waste

  organic matter and harmful microbes
• list 4 steps of sewage treatment

  • screening and grit removal
  • sedimentation to produce sludge and effluent
  • anaerobic digestion of sludge
  • aerobic biological treatment of effluent
• what happens during screening

  metal grid removes large solid objects
• what happens during sedimentation

  sludge pushes to the middle and allowed to settle and effluent flows through
• what is the difference between sludge and effluent

  sludge = solid sediment

  effluent = watery liquid which is treated
• what can the break down of sludge be used as

  fertiliser
• describe the relative ease of obtaining water water from waste, ground, salt water

  fresh water= easiest = least energy required

  waste water= moderate - several steps needed

  salt water= hardest - lots of energy required
• how can you test if a substance is pure

  test its boiling point- a pure substance will boil at a specific temperature and an impure will boil over a temperature range
• describe phytomining

  • Grow plants on land containing copper ores.
  • The plants absorb copper ions through their roots.
  • The plants are then harvested and burned to produce ash.
  • The ash is dissolved in acid to produce a solution of a copper compound.
  • metal can be extracted by displacement or electrolysis

  ​​
• how can you get copper from solutions of copper compounds

  displacement with iron or electrolysis
• describe bioleaching

  • Bacteria are used to break down low-grade copper ores
  • this produces a solution containing copper ions known as leachate.
  • The copper is then extracted from the leachate by displacement with a more reactive metal or by electrolysis.
• what is a leachate?

  the liquid solution containing metal ions formed when a metal is extracted from an ore using bacteria
• advantages of phytomining

  • uses low grade ores
  • less air pollution
  • less waste
  • less energy use than smelting
• disadvantages of phytomining

  • slow process
  • toxic chemicals released
  • large amounts of electricity needed
  • land needed to plant
• advantages of bioleaching

  • uses low grade copper ores
  • less energy used than smelting
  • less air pollution
  • less waste
• disadvantages of bioleaching

  • can produce toxic chemicals
  • very slow process
  • large amounts of electricity
• how is copper extracted from high grade copper ores?

  reduced with carbon in a furnace (smelting) and then purified using electrolysis
• Why are these methods used instead of traditional mining?

  • They're useful for extracting metals from low grade ores which aren't profitable to mine using conventional methods.