Using resources

• In the UK, potable water is produced by:

  Choosing an appropriate source of fresh water

  Passing the water through filter beds to remove solid particles

  Sterilising to kill microbes
• What are the sterilising agents for potable water?

  Chlorine, ozone or ultraviolet light
• How is desalination carried out?

  By distillation or by processes that use membranes such as reverse osmosis

  These processes require large amounts of energy
• What is reverse osmosis?

  sea water is passed through a membrane that only allows through the water molecules

  It needs high pressure to push te water through the membrane.

  The high pressure requires a lot of energy to produce
• What are the processes involved in sewage treatment?

  > screening and grit removal

  > sedimentation to produce sewage sludge and effluent

  > anaerobic digestion of sewage sludge

  > aerobic biological treatment of effluent
• What is phytomining?

  Uses plants to absorb metal compounds from the soil

  The plants are harvested then burned to produce ash that contains metal compounds
• What is bioleaching?

  Uses bacteria to produce leachate solution that contain metal compounds
• What are the main advantages and disadvantages of phytomining and bioleaching?

  Require less energy than traditional methods

  Can work on low concentration ores

  Are slow to carry out
• How can corrosion be prevented?

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

  These methods stop the air or water coming into contact with the metal
• Describe the sacrificial protection:

  If 2 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 production because zinc is more reactive than iron
• Alloys:


  Bronze: copper and tin

  Brass: copper and zinc

  Gold: solver, copper and zinc

  Steels: alloys of iron that contain specific amounts of carbon and other metals
• How are the properties of polymers determined?

  > What monomers the are made from

  > The conditions under which they are made from

  -> e.g LD and HD poly(ethene) are produced from ethene using different catalysts and reaction conditions
• Describe the structures of thermosoftening and thermosetting polymers

  > Thermosetting polymers: do not melt on heating, the polymer molecules are linked to eachother by strong cross links

  > Thermosoftening polymers: soften easily on melting and can then be remoulded. The polymer molecules are attracted to each other by weak intermolecular forces
• How is glass made?

  Most of the glass used 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
• How are composites formed?

  Fibres or fragments of one material are surrounded by s binder/matrix material that holds these fibres/fragments together

  ->e.g fibreglass, glass fibres bound together in a polymer
• Outline the key stages of the Haber process:


  > The purified H2 and N2 gases are passed over Fe catalyst at a high temp (450 degrees) and a high pressure (200 atm)

  > Fe speeds up rate of reaction so a lower temp can be used

  > Some of the hydrogen and nitrogen reacts to from ammonia

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

  > On cooling, the ammonia liquifies and is removed. The remaining H2 and N2 are recycled so almost no material is wasted

  > Ammonia is used for production of nitrogen-containing fertilisers
• Explain why the Haber process uses high temp and pressure conditions

  The conditions are a compromise between the rate and yield

  > The reaction is exothermic. An optimum temp of 450 is used. A lower temp 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
• How are compounds of nitrogen, phosphorus and potassium used?

  Used a fertilisers to improve agricultural productivity

  NPK fertilisers contain compounds of all 3 elements
• How is the phosphate rock utilised in the production of fertilisers?


  > Phosphate rock is reacted with nitric Acid to produce phosphoric acid and calcium nitrate

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

  > Phosphate rock can be reacted with phosphoric acid to produce calcium phosphate