C15 - Using Our Resources

• Corrosion


  The wearing down of metal, usually by oxidation
• Rusting

  1. Oxygen and water are present

  2. Iron forms iron(III) oxide (rust)
• Techniques to prevent rusting and corrosion


  • Sacrificial process (using a more reactive metal)
  • Coating with plastic
  • Coating with oil
• Alloy

  A mixture of metals with other elements
• Effects of adding other elements to metals

  • Disrupts the metallic structure
  • Makes the metal harder and less malleable
  • Changes melting/boiling point and conductivity
• Thermosoftening polymer

  Can change shape when heated
• Thermosetting polymer

  Cannot change shape when heated
• Crosslinks


  Covalent bonds between polymer chains that hold the polymer together when heated
• Ceramics


  Made from clay, a mixture of metals and non-metals like silicon and oxygen
• Properties of ceramics

  • Hard, durable, brittle, heat resistant
• Glass

  Made from silicon dioxide, limestone, and sodium carbonate
• Glass can be recycled and new glass is often made from recycled glass
• Composite

  Material made up of several elements, with a matrix and reinforcement
• Reinforced concrete


  Concrete combined with steel reinforcement
• Haber process

  1. Reaction between nitrogen and hydrogen to produce ammonia

  2. Carried out at 450C and 200 atm pressure

  3. Uses an iron catalyst

  4. Unreacted nitrogen and hydrogen recycled
• NPK fertilizers

  Fertilizers containing nitrogen, phosphorus, and potassium
• Fertilizers are important to replace minerals depleted from over-farming
• Brass is copper and zinc.
• Higher density means harder polymer.
• Haber process forward reaction is exothermic.
• Haber process

  • Hydrogen and nitrogen pumped into reactor over iron catalyst.
  • Ammonia forms and condenser separates ammonia from left over hydrogen and nitrogen.
  • Hydrogen and nitrogen pumped back into reactor
• Longer polymer chains have stronger forces of attraction between the molecules.
• Plasticisers are small molecules that are added to plastics to make them more flexible. They push the polymer molecules slightly further apart, weakening the forces between them.
• Forming ceramics

  • There is ionic bonding and covalent bonding
  • Layers are formed
  • Water molecules in wet clay get between the layers
  • Baking the clay evaporates water, and strong bonds (ionic and covalent) form between the layers
  • Higher baking temp, harder ceramic
• Nitrogen for Haber Process obtained by cooling air to become liquid and distilling for nitrogen.
• Le Chatelier's Principle

  If a change in conditions is introduced to a reaction at equilibrium, position of equilibrium will move to counteract the change.
• Factors affecting Haber Process

  • Temperature - increasing moves reaction left so low temp needed for high yield but faster temp increases rate of reaction
  • Pressure - high pressure moves reaction to the right increasing yield but expensive to maintain
  • Concentration - Ammonia produced is removed straight away to move equilibrium position right
• NPK Fertilisers

  • (N)itrogen used for production of amino acids
  • (P)hosphorous for growth, photosynthesis, respiration
  • (K) Potassium for regulating opening and closing of stomata and root development
• Making fertilisers

  • Ammonia itself can be used as a fertiliser
  • Ammonia can be reacted with acid to form salt for fertiliser
• Phosphoric acid


  H3PO4
• Nitric acid

  HNO3
• Sulphuric acid


  H2SO4
• Source of potassium

  Potassium chloride and potassium sulphate can be mined from the ground. As soluble in water, they are separated from impurities and then used directly.
• Source of phosphorous


  Comes from deposits of phosphate-containing rocks.
• How salts are made from rock and acids.

  • Nitric acid - Makes phosphoric acid and calcium nitrate. Phosphoric acid is neutralised with ammonia to make ammonium phosphate
  • Sulphuric acid - Makes single superphosphate, mixture of calcium phosphate and calcium sulphate.