C12- earths resources

• How do humans use the earths resources

  • warmth
  • Shelter
  • Food
  • Transport
• what does finite mean

  Resources cannot be replaced as quickly as they are being used
• What are some finite resources

  • fossil fuels
  • Metals
• aim of water practical

  Produce potable water by distillation and test its purity
• purifying water practical

  • use a Bunsen burner to boil water in a conical flask with a bung and tube leading to a test tube in a beaker of ice
  • due to the colder temperature the evaporated water will condense back into liquid form, but leaving behind any impurities
  • desalination is the term given to any process that removes salt from water
• what is drinking water required to have

  • Sufficiently low levels of dissolved salts (sodium chloride)
  • cannot have high levels of microbes (bacteria)
• What is potable water

  Water that is safe to drink
• what is pure water

  • contains no dissolved substances
  • has a pH of 7
• how do we get potable water

  • rain water - low levels of dissolved substances
  • Rainwater collects in aquifers, lakes, rivers and reservoirs
• steps of getting potable water

  1. choose a good source of fresh water ( a river )
  2. pass the water through filter beds
  3. removes materials such as leaves and suspended particles
  4. water is sterilised to kill microbes
  5. uk uses chlorine to sterilise
  6. some parts of the world use ozone or uv light
• when is desalination uses

  • in some countries fresh water is scarce and the only available water to drink may be too salty ( sea water )
  • sea water has very high levels of dissolved minerals
• what is desalination

  reducing the levels of dissolved minerals down to an acceptable level for potable water
• ways of desalination

  • distillation
  • Reverse osmosis - pass through membranes
  • Both reduce levels of dissolved minerals
  • Both require high energy and are very expensive
• What do humans use water for

  • personal hygiene - baths and showers
  • Flushing toilets
  • Washing clothes
  • Agriculture
• what does waste water contain

  large amount of organic molecules and harmful microorganisms
• Why may waste water need to be treated

  • human waste contains harmful bacteria and high levels of nitrogen compounds
  • industrial waste may contain harmful chemicals
  • Agricultural waste may contain fertilisers or pesticides
• stages of waste water treatment

  1. screening - passed through mesh to remove solids
  2. sedimentation - sewage in settlement tanks producing a liquid effluent and sludge which sinks
  3. sludge is digested by anaerobic bacteria - brakes it down to biogas or fertilisers for agriculture
  4. effluent is treated aerobically to reduce volume of solid waste and harmful microorganisms
• What is copper used for

  Electronic equipment
• what is a metal ore

  contains enough metal to make it economical to extract the metal
• what are low grade ores

  only contain a small amount of copper
• how is metal extracted from low grade ores - phytomining

  • plants are grown on land containing the metal compound we want
  • these plant absorb the metal and concentrate it in tissue
  • the plants are harvested and burnt
  • at the end the ash contains a relatively high concentration of the metal compound
• how is metal extracted from low grade ores - bioleaching

  • uses bacteria
  • bacteria are mixed with low grade ores
  • bacteria carry out chemical reactions and produce a solution called leachate - contains compound we want
• How is the metal extracted From the compound

  • at the end of both the metal compound has been extracted from the low grade ores but we need to extract the metal from the compound
  • In the case of copper compounds we can displace copper using cheap scrap iron
  • Can also be extracted through electrolysis
• similarities of phytoming and bioleaching

  • both allow us to economically extract metals from low grade ores - resources limited
  • do not involve digging, transporting and disposing of large amounts of rock unlike traditional mining
• What is a life-cycle assessment

  attempts to put a number on the environmental impact of a product
• stages of lifecycle assessment

  • asses the environmental impact of extracting and processing the raw materials
  • Asses manufacturing of the product
  • Assets he environmental impact of a product during its lifetime
  • Asses disposal of product at end of useful life
• problems of life cycle assessment

  • we can measure the use of water, energy and the production of some waste products
  • we cannot always be certain of how damaging these are to the enviroment
  • some cases we have to make estimates or value judgements that are not always accurate