C12 - The Earth's Resources

• Resources used by humans


  • Warmth
  • Shelter
  • Food
  • Transport
• Natural resources and agriculture provide


  • Food
  • Timber
  • Clothing
  • Fuels
• Finite resources processed to provide


  • Energy
  • Materials
• Chemistry's role


  • Improving agricultural and industrial processes to provide new products
  • Supporting sustainable development, which meets the needs of current generations without compromising the ability of future generations to meet their own needs
• Potable water


  Water that is safe to drink, containing sufficiently low levels of dissolved salts and microbes
• Potable water is not pure water in the chemical sense because it contains dissolved substances
• Methods to produce potable water


  1. Choosing an appropriate source of fresh water

  2. Passing the water through filter beds

  3. Sterilising
• Sterilising agents for potable water


  • Chlorine
  • Ozone
  • Ultraviolet light
• Desalination of salty water or sea water


  1. Distillation

  2. Processes using membranes such as reverse osmosis
• Desalination processes require large amounts of energy
• Difference between potable water and pure water


  Potable water contains dissolved impurities, while pure water only contains H2O
• Waste water treatment


  • Removal of organic matter and harmful microbes from sewage and agricultural waste water
  • Removal of organic matter and harmful chemicals from industrial waste water
• Sewage treatment


  1. Screening and grit removal

  2. Sedimentation to produce sewage sludge and effluent

  3. Anaerobic digestion of sewage sludge

  4. Aerobic biological treatment of effluent
• The Earth's resources of metal ores are limited
• New ways of extracting copper from low-grade ores


  • Phytomining, using plants to absorb metal compounds
  • Bioleaching, using bacteria to produce leachate solutions containing metal compounds
• Obtaining metal from metal compounds


  1. Displacement using scrap iron

  2. Electrolysis
• Stages in life cycle assessments (LCAs)

  • Extracting and processing raw materials
  • Manufacturing and packaging
  • Use and operation during its lifetime
  • Disposal at the end of its useful life, including transport and distribution at each stage
• LCA is not a purely objective process as allocating numerical values to pollutant effects requires value judgements
• Selective or abbreviated LCAs can be misused to reach pre-determined conclusions, e.g. in support of claims for advertising purposes
• Students should be able to carry out simple comparative LCAs for shopping bags made from plastic and paper
• Ways to reduce use of limited resources


  • Reduction in use
  • Reuse
  • Recycling
• Metals, glass, building materials, clay ceramics and most plastics are produced from limited raw materials, and obtaining these raw materials causes environmental impacts
• Much of the energy for the processes to produce these materials comes from limited resources
• Reuse and recycling of materials

  • Glass bottles can be crushed and melted to make different glass products
  • Metals can be recycled by melting and recasting or reforming into different products
• The amount of separation required for recycling depends on the material and the properties required of the final product