using resources

• Using the Earth's resources and sustainable development


  • We use them to provide warmth, shelter, food and transport
  • Natural resources, supplemented by agriculture, provide food, timber, clothing and fuels
  • Finite resources from the Earth, oceans and atmosphere are processed to provide energy and materials
  • Chemistry plays an important role in improving agricultural and industrial processes to provide new products and in sustainable development, which is development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
• 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 in the UK

  1. An appropriate source of fresh water is selected (rain provides water with low levels of dissolved substances and this collects in the ground/rivers/lakes)

  2. The water is passed through filter beds to remove different sized insoluble solids

  3. The water is then sterilised, to kill microbes (sterilising agents include: 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)

  3. Both are very expensive
• Waste water treatment


  1. Water is passed through a mesh screen to remove large bits e.g twigs or grit

  2. Chemicals are added to make solids and microbes stick together to form sediment and sink

  3. There is then anaerobic digestion of sewage sludge

  4. The water is then sterilised 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
• Alternative methods of extracting metals

  • Earth's resources of metal ores are limited
  • Copper ores are becoming scarce and new ways of extracting copper from low-grade ores include phytomining, and bioleaching
  • These methods avoid traditional mining methods of digging, moving and disposing of large amounts of rock
• Phytomining


  1. Uses plants to absorb metal compounds

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


  1. Uses bacteria to produce leachate solutions that contain metal compounds

  2. The metal compounds can be processed to obtain the metal
• For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron or 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
• Conditions for iron to rust

  • Both air and water are necessary
• 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
  • 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
• 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
• Steels


  • Low-carbon steels are easily shaped, used for sheeting
  • High carbon steels are hard, used for cutting tools
  • Stainless steels (containing chromium and nickel) are resistant to corrosion, used for cutlery
• Aluminium alloys


  • Low density, used for aircraft
• Soda-lime glass


  Made by heating a mixture of sand, sodium carbonate and limestone (most commonly used glass)
• 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
• Polymers


  Properties depend on what monomers they are made from and the conditions under which they are made
• Low density polyethene


  • Weaker forces of attraction as the chains are further apart, meaning it has a low melting point and is soft