C10 - Using resources

• Using the earth's resources

  • Humans use the Earth’s resources 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.
• Sustainable development

  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.
• Potable water

  Water of appropriate quality is essential for life. For humans, drinking water should have sufficiently low levels of dissolved salts and microbes. Water that is safe to drink is called potable water. Potable water is not pure water in the chemical sense because it contains dissolved substances. The methods used to produce potable water depend on available supplies of water and local conditions.
• Production of potable water

  In the United Kingdom (UK), rain provides water with low levels of dissolved substances (fresh water) that collects in the ground and in lakes and rivers, and most potable water is produced by:

  • choosing an appropriate source of fresh water
  • passing the water through filter beds
  • sterilising.

  Sterilising agents used for potable water include chlorine, ozone or ultraviolet light.
• Desalination

  If supplies of fresh water are limited, desalination of salty water or sea water may be required. Desalination can be done by distillation or by processes that use membranes such as reverse osmosis. These processes require large amounts of energy.
• Waste water treatment - why do it?

  Urban lifestyles and industrial processes produce large amounts of waste water that require treatment before being released into the environment. Sewage and agricultural waste water require removal of organic matter and harmful microbes. Industrial waste water may require removal of organic matter and harmful chemicals.
• How to do waste water treatment

  Sewage treatment includes:

  • screening and grit removal
  • sedimentation to produce sewage sludge and effluent
  • anaerobic digestion of sewage sludge
  • aerobic biological treatment of effluent.
• Alternative methods of extracting metals - why?

  The 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.
• Alternative methods of extracting metals - how?

  • Phytomining uses plants to absorb metal compounds. The 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. For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis.
• What is a life cycle assesment?

  Life cycle assessments (LCAs) are carried out to assess the environmental impact of products in each of these stages:

  • 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.
• Types of life cycle assesments

  Use of water, resources, energy sources and production of some wastes can be fairly easily quantified. Allocating numerical values to pollutant effects is less straightforward and requires value judgements, so LCA is not a purely objective process.

  
  

  Selective or abbreviated LCAs can be devised to evaluate a product but these can be misused to reach pre-determined conclusions, eg in support of claims for advertising purposes.
• Why do we need to reduce use of resources?


  The 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.Metals, glass, building materials, clay ceramics and most plastics are produced from limited raw materials. Much of the energy for the processes comes from limited resources. Obtaining raw materials from the Earth by quarrying and mining causes environmental impacts.
• Reduce, reuse, recycle - glass


  Some products, such as glass bottles, can be reused. Glass bottles can be crushed and melted to make different glass products. Other products cannot be reused and so are recycled for a different use.
• Reduce, reuse, recycle - metal

  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. For example, 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.
• What is corrosion?

  Corrosion is the destruction of materials by chemical reactions with substances in the environment. Rusting is an example of corrosion. Both air and water are necessary for iron to rust.
• How to reduce corrosion?

  • Corrosion can be prevented by applying a coating that acts as a barrier, such as greasing, painting or electroplating. Aluminium has an oxide coating that protects the metal from further corrosion.
  • Some coatings are reactive and contain a more reactive metal to provide sacrificial protection, eg zinc is used to galvanise iron.
• Alloys as useful materials - copper alloys


  Bronze is an alloy of copper and tin. It is harder than copper and is used to make ornaments and medals.

  Brass is an alloy of copper and zinc. It is decorative and corrosion resistant, and is used for low friction ornamental purposes e.g. plumbing and carpentry.
• Alloys as useful materials - gold alloys


  Gold alloys are usually made with silver, copper, and zinc.

  • Used to make jewlerry
  • Carats represent the purity of gold jewlerry
  • Pure gold is 24 carat
• Alloys as useful materials - steel alloys


  • Steels are alloys of iron that contain specific amounts of carbon and other metals
  • High carbon steel is strong but brittle
  • Low carbon steel is softer and more easily shaped
  • Stainless steels (steel containing chromium and nickel) are hard and resistant to corrosion
• Alloys as useful materials - aluminium alloys

  • Aluminium is mixed with copper, manganese and silicon for aircraft body production as aluminium alloys tend to be stronger and lighter than pure aluminium
  • As well as being lighter and stronger, it is also more corrosion resistant than aluminium
• Glass types

  Most of the glass we use is soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone. Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures than soda-lime glass.
• Ceramics

  Clay ceramics, including pottery and bricks, are made by shaping wet clay and then heating in a furnace.
• Properties of polymers

  • The properties of polymers depend on what monomers they are made from and the conditions under which they are made. For example, low density (LD) and high density (HD) poly(ethene) are produced from ethene.
  • Thermosoftening polymers melt when they are heated. Thermosetting polymers do not melt when they are heated.
• Thermosoftening plastics

  Thermosoftening plastics melt when they are heated. Most plastics that we come across in everyday life are thermosoftening plastics. This means that they can be recycled, which involves melting them before making a new product.

  Thermosoftening plastics do not have covalent bonds between neighbouring polymer molecules, so the molecules can move over each other when heated and the plastic melts.

  
• Thermosetting plastics

  Thermosetting plastics do not melt when heated. They tend to char and burn when heated, but they are resistant to much higher temperatures than thermosoftening plastics. They are used to make electrical plugs, which must not melt, even if there is a malfunction and the wiring inside gets hot. The covalent bonds in this thermosetting plastic are strong and prevent the plastic melting when it is heated.

  
• Composites

  Most composites are made of two materials, a matrix or binder surrounding and binding together fibres or fragments of the other material, which is called the reinforcement.For example, wood or fibreglass
• What is The Haber Process?


  The Haber process is used to manufacture ammonia, which can be used to produce nitrogen-based fertilisers.The raw materials for the Haber process are nitrogen and hydrogen.
• What is the source for the nitrogen in the Haber Process?

  Air
• What is the source for hydrogen in the Haber Process?

  Natural gas
• What is the process of The Haber Process?

  • The purified gases are passed over a catalyst of iron at a high temperature (about 450°C) and a high pressure (about 200 atmospheres).
  • Some of the hydrogen and nitrogen reacts to form ammonia.
  • The reaction is reversible so some of the ammonia produced breaks down into nitrogen and hydrogen.
  • On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen are recycled.
• What are NPK fertilisers?

  • Compounds of nitrogen, phosphorus and potassium are used as fertilisers to improve agricultural productivity. NPK fertilisers contain compounds of all three elements.
  • Industrial production of NPK fertilisers can be achieved using a variety of raw materials in several integrated processes. NPK fertilisers are formulations of various salts containing appropriate percentages of the elements.
• What is ammonia used to manufacture?

  • Ammonium salts
  • Nitric acid
• How can you obtain potassium chloride, potassium sulphate, and phosphate rock?


  Mining
• Can phosphate rock be used directly as a fertiliser?

  No. It must be treated with nitric or sulfuric acid to produce soluble salts that can be used as fertilisers.