Paper 2

• Sustainable development

  Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs
• Producing potable (safe to drink) water in the UK

  1. Choosing an appropriate source of fresh water

  2. Passing the water through filter beds to remove any solids

  3. Sterilising to kill microbes
• Sterilising agents for potable water

  Chlorine, ozone or ultraviolet light
• Chlorine

  • Toxic gas so the amount added to water has to be carefully monitored
• Ultraviolet light

  • Kills microbes without adding chemicals to the water but is more expensive
• Desalination

  1. Can be done by distillation or by processes that use membranes such as reverse osmosis

  2. These processes require large amounts of energy
• Reverse osmosis

  • Sea water is passed through a membrane that only allows through the water molecules
  • It needs high pressure to push the water through the membrane
  • The high pressure requires a lot of energy to produce
• 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
• 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
• New methods of mining avoid the disadvantages of traditional mining methods of digging, moving and disposing of large amounts of rock
• Phytomining

  • Uses plants to absorb metal compounds from the soil
  • The plants are harvested and then burned to produce ash that contains the metal compounds
• Bioleaching

  Uses bacteria to produce leachate solutions that contain metal compounds
• Phytomining and bioleaching

  • Need less energy than traditional methods, and can work on low concentration ores but are slow to carry out
• Life Cycle Assessments (LCAs)

  1. Extracting and processing raw materials

  2. Manufacturing and packaging

  3. Use and operation during its lifetime

  4. Disposal at the end of its useful life, including transport and distribution at each stage
• The reduction in use, reuse and recycling of materials by end users reduces the use of limited resources, energy consumption, waste and environmental impacts
• Advantages of recycling

  • Less acid rain (pollution)
  • Metal ore reserves last longer / conserved
  • Energy for extraction saved
  • Less mining / quarrying
  • Less waste
  • Less landfill
  • Creates local employment
• Disadvantages of recycling

  • Collection problems
  • Transport problems/ cost of transport
  • Difficult to separate metal from appliances/sort
• Corrosion

  The destruction of materials by chemical reactions with substances in the environment, e.g. rusting
• Preventing corrosion

  1. Applying a coating that acts as a barrier, such as greasing, painting or electroplating

  2. These methods stop the air or water coming into contact with the metal
• Sacrificial protection

  • Some coatings are reactive and may contain corrosion inhibitors or a more reactive metal
  • If two metals are in contact the more reactive metal will corrode instead of the less reactive one, e.g. zinc is used to galvanise iron and when scratched, provides sacrificial protection because zinc is more reactive than iron
• Alloys

  • Bronze - an alloy of copper and tin, used for making statues and decorative objects
  • Brass - an alloy of copper and zinc used for producing water taps and door fittings
  • Gold used as jewellery is usually an alloy with silver, copper and zinc (The proportion of gold in the alloy is measured in carats, with pure gold being 24 carat, e.g. 18 carat gold is 75% gold)
  • Aluminium-magnesium alloys are low density and used in aerospace manufacturing
  • Steels - 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. Steels containing chromium and nickel (stainless steels) are hard and resistant to corrosion
• Properties of polymers

  Depend on what monomers they are made from and the conditions under which they are made
• Thermosetting polymers

  • Do not melt on heating
  • The polymer molecules are linked to each other by strong cross-links
• Thermosoftening polymers

  • Soften easily on heating and can then be remoulded, keeping the new shape on cooling
  • The polymer molecules are attracted to each other by weak intermolecular forces
• Making glass

  1. Most of the glass we use is soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone

  2. Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures than soda-lime glass
• Making clay ceramics

  Shaped by shaping wet clay and then heating in a furnace
• Composites

  Fibres or fragments of one material (reinforcement) are surrounded by a binder/matrix material that holds these fibres/fragments together
• Haber process

  1. The purified H2 and N2 gases are passed over Fe catalyst at a high temperature (about 450 °C) and a high pressure (about 200 atm)

  2. Fe speeds up the rate of reaction, so that a lower temperature could be used in the process

  3. Some of the hydrogen and nitrogen reacts to form ammonia. N2 + 3 H2 ⇌ 2 NH3

  4. The reaction is reversible so ammonia breaks down again
• How composites are formed

  Fibres or fragments of one material (reinforcement) are surrounded by a binder/matrix material that holds these fibres/fragments together
• Key stages of Haber process

  1. The purified H2 and N2 gases are passed over Fe catalyst at a high temperature (about 450 °C) and a high pressure (about 200 atm)

  2. Fe speeds up the rate of reaction, so that a lower temperature could be used in the process

  3. Some of the hydrogen and nitrogen reacts to form ammonia. N2 + 3 H2 ⇌ 2 NH3

  4. The reaction is reversible so ammonia breaks down again into nitrogen and hydrogen

  5. On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen are recycled. This means almost no material is wasted

  6. Ammonia is used for production of nitrogen-containing fertilisers
• Compromise in Haber process conditions

  • The reaction is exothermic. An optimum temperature of 450 °C is used. Using a lower temperature would give a higher yield, but the rate of NH3 production would be too slow
  • A pressure of 200 atm is used. Using a higher pressure would give a higher yield, but would be too expensive, because of the cost of energy to produce the high pressure
• Use of compounds of nitrogen, phosphorus and potassium

  They are used as fertilisers to improve agricultural productivity. NPK fertilisers contain compounds of all three elements
• Industrial production of NPK fertilisers

  1. Ammonia can be used to manufacture ammonium salts. The ammonium sulfate, phosphate, and nitrate can be produced by reaction of ammonia with the requisite acid

  2. Phosphate rock is reacted with nitric acid to produce phosphoric acid and calcium nitrate

  3. Phosphate rock can be reacted with sulfuric acid to produce a mixture of calcium phosphate and calcium sulfate

  4. Phosphate rock can be reacted with phosphoric acid to produce calcium phosphate
• Proportions of gases in the modern atmosphere
• Formation of Earth's early atmosphere

  1. The Earth was hot when it was formed

  2. There was significant volcanic activity

  3. Gases have been released from these volcanoes

  4. These gases included CO2, N2, CH4, NH3, H2O
• Increase in oxygen in the atmosphere

  Algae and plants produced the atmospheric O2 by photosynthesis, which can be represented by the equation: 6 CO2+ 6 H2O → C6H12O6+ 6 O2. As the amount of gradually O2 increased, there were more plants that produced more oxygen
• Decrease in carbon dioxide in the atmosphere

  1. Some CO2 was dissolved in the oceans, where it reacted with metal ions to form insoluble carbonates, such as CaCO3, or was taken in by animals to become a part of skeleton. When animal dies, this becomes a sedimentary rock

  2. Some CO2 was used in photosynthesis to make oxygen
• Greenhouse effect

  Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life. They allow short wavelength radiation from the sun to pass through the atmosphere to the Earth's surface, but absorb the outgoing long wavelength radiation from the Earth causing an increase in temperature