chemistry - topic 10

• What is the primary source of fresh water in the UK?

  Rain
• What are the main steps in producing potable water from fresh water?

  • Choosing an appropriate source of fresh water
  • Passing the water through filter beds to remove solids
  • Sterilising to kill microbes
• Why is water quality essential for life?


  It ensures drinking water has low levels of dissolved salts and microbes
• What is the term for water that is safe to drink?

  Potable water
• How does potable water differ from pure water?

  Potable water contains dissolved solid substances, while pure water does not
• What are some sterilising agents used for potable water?

  Chlorine, ozone, and ultra-violet light
• What is a disadvantage of using chlorine as a sterilising agent?

  It is a toxic gas that must be carefully monitored
• What is the advantage of using ultraviolet light for sterilisation?


  It avoids adding chemicals to the water
• What is desalination?


  The process of turning salty water or sea water into drinking water
• What are two methods of desalination?

  Distillation and reverse osmosis
• Why does distillation have high energy costs?

  It requires heat to boil the water
• What are the main steps in waste water treatment?

  • Screening and grit removal
  • Sedimentation to produce sewage sludge and effluent
  • Anaerobic digestion of sewage sludge
  • Aerobic biological treatment of effluent
• What is reverse osmosis?

  A process where sea water is passed through a membrane that allows only water molecules to pass
• What is required to push water through the membrane in reverse osmosis?

  High pressure
• What is the role of chemistry in sustainable development?

  It helps improve agricultural and industrial processes to provide new products
• What are the advantages of phytomining and bioleaching for extracting copper?

  • Need less energy than traditional methods
  • Can extract from low-grade ores
  • Mining not required
  • Avoid disadvantages of traditional mining
• What is the equation for the displacement reaction using scrap iron to obtain copper?

  Fe + CuSO4 → Cu + FeSO4
• What are the stages of a Life Cycle Assessment (LCA)?

  • Extracting and processing raw materials
  • Manufacturing and packaging
  • Use and operation during its lifetime
  • Disposal at the end of its useful life
• Why is LCA not a purely objective process?

  Allocating numerical values to pollutant effects requires value judgements
• What are the advantages of recycling?

  • Less acid rain (pollution)
  • Metal ore reserves last longer
  • Energy for extraction saved
  • Less mining and quarrying
  • Less waste and landfill
  • Creates local employment
• What are the disadvantages of recycling?

  • Collection problems
  • Transport problems/cost of transport
  • Difficult to separate metals from appliances
• What is corrosion?

  The destruction of materials by chemical reactions with substances in the environment
• What is rusting?


  An example of corrosion that requires air and water
• What is the chemical equation for rusting?

  Iron + oxygen + water → hydrated iron oxide
• How can corrosion be prevented?

  • Applying a coating (greasing, painting, electroplating)
  • Using sacrificial protection (more reactive metals)
• What is sacrificial protection?


  A method where a more reactive metal corrodes instead of the less reactive one
• What is an alloy?


  A mixture of different metals
• What are some common alloys and their uses?

  • Bronze (copper and tin) for statues
  • Brass (copper and zinc) for taps
  • Stainless steel (iron, chromium, nickel) for cutlery
• What is the carat measurement in gold alloys?

  It measures the proportion of gold, with pure gold being 24 carat
• What are the properties of low carbon and high carbon steels?

  • Low carbon steel: softer, easily shaped
  • High carbon steel: strong but brittle
• What are thermosetting and thermosoftening polymers?

  • Thermosetting polymers: do not melt on heating, linked by strong cross-links
  • Thermosoftening polymers: soften on heating, can be remoulded
• How do the properties of polymers depend on their monomers?

  Different monomers and conditions lead to different properties
• What is soda-lime glass made from?

  • Sand
  • Sodium carbonate
  • Limestone
• What are composites and give examples?

  • Composites are made of a matrix and reinforcement
  • Examples: reinforced concrete (steel bar and concrete), carbon fibre composites
• What are the raw materials for the Haber process?

  Nitrogen and hydrogen
• What is the chemical equation for the formation of ammonia in the Haber process?

  N2 + 3 H2 ⇌ 2NH3
• What are the optimal conditions for the Haber process?

  • Temperature: 450°C (higher yield but slower rate at lower temperatures)
  • Pressure: 200 atm (higher yield but expensive at higher pressures)
  • Catalyst: Iron to speed up reaction
• What are the uses of NPK fertilisers?


  • Improve agricultural productivity
  • Contain compounds of nitrogen, phosphorus, and potassium
• What is the reaction for producing ammonium sulfate from ammonia and sulfuric acid?

  2NH3 + H2SO4 → (NH4)2SO4
• What is the reaction for producing ammonium nitrate from ammonia and nitric acid?

  NH3 + HNO3 → NH4NO3