Using resources

• Ceramics


  Hard, brittle, heat and corrosion resistant

  Nonmetallic materials e.g glass or clay

  clay: e.g china, brick or porcelain - shaped wet clay then heated in high temp to harden = high compressive strength

  glass: e.g soda lime glass - mixture of sand, sodium carbonate and limestone molten then cooled quickly

  borosilicate glass - heated boron trioxide = much higher melting point

  glass is transparent strong + good insulator
• Composites


  A Material that consists of two or more materials w different properties to make a more desirable material

  made by:

  -reinforcement = often long solid fibres or fragments

  -the matrix = binds the reinforcements together
• Polymers


  Large molecules of high relative molecular mass made by linking together large numbers of monomers

  Properties depend on the monomers used and conditions of chemical reaction

  generally they are flexible, easily shaped and good electrical and heat Insulators
• High vs low density polymers


  Poly(ethene) is one of the most common polymers

  low-density = LDPE and high-density = HDPE

  LDPE: condition - high pressure, moderate temp + catalyst

  properties - more flexible but weaker

  uses - carrier bags

  HDPE: conditions - low temp and pressure + catalyst

  properties - rigid but stronger

  uses - drainpipes
• Thermosoftening polymers 


  Polymers made from lots of polymer chains held be weak intermolecular forces so earlier break when heated causing it to melt then it can be moulded and harden
• thermosetting polymers


  Polymers made from polymer chains held by strong covalent bonds so requires lots of energy to break so doesn’t soften if heated they are hard strong and rigid
• Metals and alloys 


  Metals: malleable, ductile, good conductors of heat + electricity and high melting + boiling points

  alloys: are metals with other materials mixed in so are stronger, less malleable and useful for thing under high stress e.g buildings
• Corrosion 


  process by which metals are slowly broken down by reacting with substances in their environment
• Rusting


  Iron reacts w oxygen and water to form hydrated iron oxide (rust) redox reaction

  conditions : both oxygen and water need to be present
• Preventing rust


  Barrier method: prevent oxygen and water touching the iron e.g painting it , oil or grease it, electroplating (use electrolysis to coat it in another metal)

  sacrificial methods: add more reactive metal to the iron so the oxygen reacts with the other metal instead
• Galvanising 


  Coats iron object in layer of zinc which forms a barrier and even if a scratch appears the zinc will react with any oxygen so acts a a sacrificial method
• Sustainable development


  An approach to human and economic development that meets the need of current generations without damaging the further generations resources and lives
• how to develop sustainably

  Use renewable resources e.g wood not plastic

  recycle (I’d damaged) or reuse (for same or different purpose) = less waste
• Life cycle assessment


  4 stages:

  extracting and processing raw materials

  manufacturing and packaging products

  Using the product

  Disposing of the product
• Stage 1


  Often directly damage environment for mines and deforestation

  indirectly damage as lots of energy is required and pollutants released
• Stage 2


  Energy used and pollutants can damage environment

  as well as waste products discarded instead they should be used for making something else
• Stage 3 


  need to look at how much damage it does in its life time as well as how long it’s used for
• Stage 4 


  Landfills use us space for nature and can cause pollutants and chemicals that seep into ecosystems

  burning releases pollutants into atmosphere

  also consider energy needed to transport waste
• Plastic vs paper bags 


  Material: crude oil vs wood

  manufacturing: fractional distilation and polymerisation vs timber pulled (lots of waste + energy)

  using product: reusable vs single use

  Disposing: not biodegradable vs biodegradable
• Limitations of LCA


  almost impossible to quantify all stages

  Even with all data it’s difficult to assess harm of each step

  can easily be manipulated to support a company and is hard to notice
• Potable water


  Water that is safe to drink but it’s not pure as if often contains other substances
• Criteria of potable water

  -levels of dissolved substances needs to be fairly low

  -needs a pH of 6.5 to 8.5

  -no microorganisms in it
• Where is potable water from?

  Fresh water e.g rain to surface water (lakes rivers + reservoirs) or ground water (under ground like aquifers )
• Fresh water treatment 


  Take fresh water and filter with wire mesh = filters large things

  then filter through sand + gravel = filters small things

  Finally sterilise to kill harmfull microorganisms by:

  -expose to ultra violet light

  -expose to ozone

  -bubble chlorine gas through it
• Desalination


  Extracts potable water from sea water
• distillation 


  Desalinates water

  like simple distillation but with large bodies of water

  very expensive
• Reverse osmosis


  Water passes through a membrane only allowing water through not other molecules

  very expensive
• waste water (domestic)


  Household waste like from showers sinks and toilets

  goes into sewers
• Waste water (agricultural systems)


  When nutrients run off fields into rivers and animal waste from farms
• Waste water (industrial)


  Factories and chemicals
• Waste water treatment 


  Screening = removes large objects like twig or bottles

  sedimentation = sewage sets in settlement tanks where heavy mixture sinks (sludge) and effluent floats to top and go to separate tanks

  Breakdown = biological breakdown by microorganisms but effluent is in aerobic conditions and sludge is in anaerobic

  so effluent can then be released after a long time as it is safe again

  but sludge makes methane which is captured and used as energy and waste is fertiliser
• Toxic substances in waste

  Often if contains toxic chemicals extra steps are needed like adding chemicals or ultraviolet radiation
• Haber process equation


  Nitrogen + hydrogen --> ammonia + heat
• haber process


  Produces ammonia which is used to make nitrogen based fertilisers

  needs massive amounts of nitrogen (easy to get) and hydrogen (hard to get hold of)
• haber process endo or exo ?

  Exothermic
• How does haber process work?

  Feed nitrogen and hydrogen into reaction vessel

  it is in conditions at 450 degrees and 200 atmospheres and iron catalyst

  this is where reactions form ammonia but still lots of N and H

  so passes through to condenser where ammonia gas condenses to liquid and the N and H pass back to reaction vessel
• Why 450 degrees?


  Exothermic reaction = low temp to favour forward reaction = increase percentage yield

  higher rate of reaction = high temp = kinetic energy so more reactions

  so for this 450 is chosen as a compromise

  generating heat is expensive so too high is to too expensive
• Why 200 atmospheres of pressure ?

  High pressure = pushes equilibrium to right as there are fewer products than reactants

  also means more frequent collisions so more reactions

  but it is very expensive to keep a high pressure and if things go wrong it can be very dangerous

  so this is best pressure
• fertilisers

  Fertilisers are applied to soil to provide nutrients

  used to be made from animal waste but now tend to be formulated in factories
• Formulated fertilisers


  Mixture of certain chemicals in a specific ratio to create a formulated fertiliser