using resources

• Corrosion


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


  Where iron reacts with oxygen and water from the environment to form hydrated iron oxide (rust)
• Rusting


  1. Iron atoms lose 3 electrons to become iron 3+ ions

  2. Oxygen atoms gain 2 electrons each to become oxygen 2- ions

  3. Overall reaction is a redox reaction with both oxidation and reduction
• Conditions required for rusting: iron, oxygen, and water
• Corrosion


  • Only the surface of a metal corrodes
  • Rust flakes off revealing new metal underneath, allowing further corrosion
  • Aluminium forms a protective oxide layer on the surface
• Methods to prevent iron from rusting

  • Barrier methods
  • Sacrificial methods
• Barrier methods


  Prevent oxygen and water from touching the iron
• Barrier methods


  • Painting
  • Oiling/greasing
  • Electroplating
• Sacrificial methods


  Adding a more reactive metal like aluminium or zinc to the iron, so it gets oxidised instead
• Galvanizing


  • Coating iron in a layer of zinc (barrier method)
  • If zinc coating is scratched, zinc will react instead of iron (sacrificial method)
• Life cycle assessment


  Analyzes the different stages in a product's life cycle in order to assess its impact on the environment
• Life cycle assessment stages

  1. Extracting and processing raw materials

  2. Manufacturing and packaging

  3. Using the product

  4. Disposing of the product
• Extracting and processing raw materials


  • Directly damages the local environment
  • Indirectly damages the environment due to energy use and pollutants released
• Manufacturing and packaging


  • Energy use
  • Release of pollution
  • Production of waste products
• Using the product


  • Damage done during lifetime
  • How long the product is used for
• Disposing of the product

  • Space taken up in landfill
  • Chemicals seeping out
  • Pollutants released from incineration
  • Energy used for transport
• Life cycle assessments have limitations - it's almost impossible to quantify all the different steps involved, and the complex calculations can be manipulated to support a particular company
• Potable water


  Water that's safe to drink
• Getting potable water


  1. Treating fresh water sources

  2. Desalinating seawater
• Pure water


  Contains only H2O molecules
• Impure water


  Contains other dissolved substances
• Criteria for water to be considered potable

  • Levels of dissolved substances needs to be fairly low
  • pH between 6.5 and 8.5
  • No microorganisms like bacteria or fungi
• Sources of fresh water

  • Surface water (lakes, rivers, reservoirs)
  • Groundwater (aquifers)
• Surface water


  • Easy to access, frequently replaced by rain
  • Can dry up in hot, sunny weather
• Groundwater


  • Found under the ground in permeable rock
• Treating fresh water to make it potable

  1. Filter out large solid bits

  2. Filter out smaller solid bits

  3. Sterilize to kill harmful microbes (chlorine, ozone, UV)
• Desalination


  Extracting potable water from seawater
• Desalination techniques


  • Distillation (boil seawater, collect water vapour)
  • Reverse osmosis (pass seawater through membrane, trapping ions and larger molecules)
• Desalination techniques require large amounts of energy and are expensive
• Wastewater treatment


  The process of treating wastewater to make it safe for disposal or reuse
• Desalination is used in countries with limited fresh water supplies, like in the Middle East
• Sources of wastewater


  • Domestic
  • Agricultural
  • Industrial
• Domestic wastewater


  Household waste like water from showers, sinks, and toilets
• Agricultural wastewater


  Nutrient runoff from fields and animal waste from farms
• Haber process


  1. Take hydrogen and nitrogen as reactants

  2. Feed into reaction vessel

  3. Conditions kept at 450°C and 200 atm with iron catalyst

  4. Ammonia forms but reaction is reversible

  5. Separate ammonia from unreacted gases

  6. Condense ammonia, recycle unreacted gases
• Haber process


  • One of the most important reactions in the world
  • Produces ammonia used to make nitrogen-based fertilizers
• Nitrogen is easy to acquire as 78% of air is nitrogen
• Industrial wastewater


  Wastewater from factories that make and use chemicals
• Hydrogen


  Tricky to get as has to be made from hydrocarbons like methane
• Haber process reaction is exothermic