C2 - Material Choices (b)

C2 - Material Choices

Crude Oil
1. Mixture of hydrocarbons
  1. Molecules that are made of a chains of carbon and hydrogen atoms only.
  2. Varying chain length
2. Properties
  1. As the length of the hydrocarbon changes the properties also change.
    1. When supplied heat the smaller molecules receive enough energy to overcome the weak intermolecular forces
      1. Low mpt and bpt
    2. Longer chains need more energy
      1. Higher mpt and bpt
  2. Bonds in crude oil
    1. Strong covalent bonds between the carbons and hydrogens of the molecule
    2. Weak intermolecular molecular forces of attraction between molecules
Uses of Crude Oil
1. Separated by fractional distillation
  1. 1. Most of the hydrocarbons in crude oil are used to make fuels.
    2. Some are sued to make new compounds
      1. Plastics, medicines, fertilisers and food
      2. Chemical synthesis
2. The petrochemical industry refines crude oil to produce fuels and lubricants.
3. It also produced raw materials that can be used to make synthetic chemicals
4. Some less useful hydrocarbons can be reacted with hydrogen so that they split into more useful hydrocarbons
Polymers
1. Polymerisation
  1. Plastics are formed when lots of small molecules (monomer) join together to make a very long molecule (polymer)
    1. Carbon based
    2. Formed under high pressure
2. Properties
  1. Polymers made from varying monomers have different properties
    1. Strong and rigid
      1. HDPE
        Used to make milk bottles
    2. Light and stretchable
      1. LDPE
        Plastic bags and water bottles
    3. Strong and Durable
      1. PVC
        Rigid
        Window frames and piping
        Stretchy
        Synthetic leather
    4. Impact resistant and soft
      1. Polystyrene
        Packaging
    5. Heat resistant
      1. Melamine resin and polypropene
        Plastic Kettles
3. Replacing natural materials
  1. Synthetic fibres are replacing cotton, wool and silk
    1. Lighter, more durable, water-resistant and often cheaper
  2. Rigid PVC has replaced wood as a material for window frames
    1. Weather-resistant, strong, durable, no painting
Structure and Properties of Polymers
1. Properties
  1. Depend on molecular arrangement
  2. Density
    1. Polymers packed together tightly = high density
    2. Polymer chains are spread out = low density
2. Forces
  1. Weak forces
    1. Free to slide over each other
    2. Easily stretched
    3. Low mpt.
  2. Strong forces
    1. Inflexible
    2. higher mpt.
    3. Cross links prevent free movement
      1. Crosslinks are chemical bonds
3. Modification
  1. Increase chain length
    1. Stronger
  2. Cross-linking
    1. Stronger, stiffer, more heat resistance
  3. Plasticisers
    1. Softer and easier to shape
    2. Work by reducing intermolecular forces
  4. Crystallinity
    1. Made more crystalline
      1. Strighter chains with no branches
      2. Higher density
      3. Stronger and have higher mpt.
B

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	Creado por nicole_j_baldwin hace casi 11 años