using resources (c10)

• Renewable energy resources

  Sources of power that quickly replenish themselves and can be used again (only includes plants/wood if they continue to be re-planted)
• Finite resources

  Have a limited supply that will eventually run out
• Potable water

  Water that is safe to drink
• Potable water is not 'pure' because it contains dissolved substances, although to be safe it must have sufficiently low levels of dissolved salts and microbes
• Methods used to produce potable water

  1. Select an appropriate source of fresh water

  2. Pass the water through filter beds to remove different sized insoluble solids

  3. Sterilise the water to kill microbes (using ozone, UV light or chlorine)
• Desalination of salty/sea water

  1. Can be done by distillation

  2. Can be done using processes with membranes (e.g. reverse osmosis)
• Both distillation and reverse osmosis for desalination are very expensive
• Waste water treatment

  1. Pass water through a mesh screen to remove large bits

  2. Add chemicals to make solids and microbes stick together to form sediment and sink

  3. Anaerobic digestion of sewage sludge

  4. Sterilise the water with chlorine to kill any microbes left
• It is relatively cheaper and easier to obtain potable water from groundwater and wastewater than salt water, although seawater is a plentiful raw material, so is good for countries with little fresh water
• The Earth's resources of metal ores are limited
• Copper ores

  • Becoming scarce
  • New ways of extracting copper from low-grade ores include phytomining and bioleaching
• Phytomining

  1. Uses plants to absorb metal compounds

  2. Plants are harvested and then burned to produce ash that contains metal compounds
• Bioleaching

  Uses bacteria to produce leachate solutions that contain metal compounds
• The metal compounds can be processed to obtain the metal
• Obtaining copper

  • From solutions of copper compounds by displacement using scrap iron
  • By electrolysis
• Life cycle assessment

  Assessing the environmental impact of products in each stage: 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
• Use of water, resources, energy sources and production of some wastes can be fairly easily quantified in life cycle assessment
• Allocating numerical values to pollutant effects is less straightforward and requires value judgements, so life cycle assessment is not a purely objective process
• Selective or abbreviated life cycle assessments can be devised to evaluate a product but these can be misused e.g. in support of claims for advertising purposes
• Ways of reducing the use of resources

  • Reduction in use, reuse and recycling of materials by end users reduces the use of limited resources, use of energy sources, waste and environmental impacts
• Materials produced from limited raw materials

  • Metals
  • Glass
  • Building materials
  • Clay ceramics
  • Most plastics
• Much of the energy for the processes of producing materials from limited raw materials comes from limited resources
• Obtaining raw materials from the Earth by quarrying and mining causes environmental impacts
• Reuse

  Some products, such as glass bottles, can be reused by crushing and melting to make different glass products
• Recycling

  Other products cannot be reused and so are recycled for a different use
• Recycling metals

  1. Melting and recasting or reforming into different products

  2. Amount of separation required depends on the material and the properties required of the final product
• Some scrap steel can be added to iron from a blast furnace to reduce the amount of iron that needs to be extracted from iron ore
• Corrosion

  Destruction of materials by chemical reactions with substances in the environment
• Corrosion

  • Rusting
• Rusting

  • Both air and water are necessary for iron to rust
• Corrosion prevention

  Applying a coating that acts as a barrier, such as greasing, painting or electroplating
• Corrosion prevention

  • Aluminium has an oxide coating that protects the metal from further corrosion
  • Zinc is used to galvanise iron (sacrificial protection)
• Sacrificial protection

  The more reactive metal donates electrons to any ions of the other metal that may have formed so they don't corrode
• Alloys

  • Most metals in everyday uses are alloys
  • Pure metals are too soft for everyday uses and are mixed with small amounts of similar metals to make them harder
• The Haber process

  Used to manufacture ammonia, which is used to produce nitrogen-based fertilisers
• Alloys

  • Gold in jewellery is usually an alloy with silver, copper and zinc
  • Bronze is an alloy of copper and tin
  • Brass is an alloy of copper and zinc
  • Steels are alloys of carbon and iron
  • Aluminium alloys are low density and used for aircraft
• Soda-lime glass

  Made by heating a mixture of sand, sodium carbonate and limestone (most commonly used glass)
• Raw materials for the Haber process

  • Nitrogen obtained from the air
  • Hydrogen may be obtained from natural gas or other sources
• Borosilicate glass

  Made from sand and boron trioxide, melts at higher temperatures than soda-lime glass
• Clay ceramics

  Made by shaping wet clay and then heating in a furnace