10. Using resources

• potable water in not pure water as it contains dissolved salts and other impurities
• pure - only contains a single type of material that has not been contaminated by another substance
• To sterilise potable water, chlorine, ozone or ultraviolet is used
• Distillation involves heating sea water until it reaches boiling point. once it is boiling it will begin to evaporate. The steam rises and condenses to leave behind the salt
• Reverse osmosis involves forcing water through a membrane at a high pressure
• Water treatment

  1. Screening - this is where branches, twigs and grit is removed
  2. The water undergoes sedimentation - heavier solids sink and lighter effluent floats on the surface above the solids
  3. The effluent is then transferred to another tank were aerobic digestion takes place.
  4. The solids undergo anaerobic respiration where its broken down to produces fertiliser and methane gas which can be used for an energy resource
• Advantages of recycling

  • fewer finite resources need to be removed from the ground
  • Crude oil doesn't need to be extracted, so recycling avoids high energy cost and consumption
  • The amount of greenhouse gases will decrease
• Disadvantages of recycling

  • Transporting involves staff, fuel and vehicles
  • Some materials are difficult to sort
• LCA

  Stage 1 - raw material

  Stage 2 - manufacture

  Stage 3 - use

  Stage 4 - disposal
• Alloys

  Bronze - copper and tin - coins

  Brass - copper and zinc - instruments

  Gold - silver, zinc and copper - jewellery
• Steel is an alloy made up of iron mixed with certain amounts or carbon
• High-carbon steel is strong and brittle and used in the construction industry
• Low- carbon steel is softer and used for making car body panels
• Glass is made by melting a mixture of sand, limestone and sodium carbonate

  Soda lime glass is used for windows and bottles

  Borosilicate glass has a higher melting point