C2

C2

1. Polymers

   • Polymerisation
     • Small molecules (monomers) join to make long molecules (polymers)
       • Type of polymers depends on type of monomers
     • Can create a wide range of different materials with different uses
       • Many natural materials have been replaced with superior polymers
         • Carrier bags were made of paper
           • Now they're made of polythene
   • Molecular structure
     • Properties of materials depend on how the particles are held together
     • Natural rubber
       • Vulcanisation
         • Mass of tangled molecules
         • Atoms in chain are held together by strong covalent bonds
         • Molecules also have cross-links
           • Sulfur atoms form cross links between rubber molecules
         • Rubber becomes rigid and hard to stretch
           • Needs a high melting point as well
       • Mass of long-chain molecules
       • Atoms in the chains are held together by strong convolent bonds
         • However there are weak forces between the molecules
           • This means it has a low melting point as not a lot of energy is needed
       • The long polymer molecules can slide over each other
         • This makes the material very stretchy and flexible

2. Materials

   • Synthetic
     • Produced by chemical synthesis
     • Made as alternatives
       • Starting with materials extracted go the earths crust
     • Petrochemical industry refines crude oil
       • Only a small proportion is used though
         • The rest is used for fuels
   • Natural
     • Comes from living things
       • Cotton (plants)
       • Paper (trees)
       • Silk (spiders)
       • Wool (sheep)

3. Crude oil

   • Raw material found in earths crust
   • Mixture of hydrocarbons
     • Some have small molecules and others have longer chain molecules
   • Separated by fractional distillation
     • Hydrocarbons in a fraction have similar boiling points
   • Heated to evaporate all the hydrocarbons
     • Vapour passes into the fractioning column near the bottom
       • Fractions condense to liquids and run off once they cool below their boiling point
         • Any remaining gases leave the tower at the top
           • Used as gaseous fuels

4. Boiling point

   • All molecules have forces between them
     • Intermolecular forces
     • The longer the hydrocarbon molecules, the stronger the forces
   • Strong forces need more energy to overcome them
     • So a higher temperature is needed

5. Properties

   • Different materials have different properties
     • Different melting points
     • Rigid or flexible
     • Better suited for different uses
   • Properties affect the durability and effectiveness

6. Modifications

   • Produce changes to properties of polymers
   • Increasing the chain length makes more contact between molecules
     • Forces become stronger
   • Plasticisers
     • Small molecule that sits between molecules to force them apart
       • Forces are weaker so molecules move easily
   • Packing molecules more closely together to form crystalline polymers
     • Forces are slightly stronger
       • Polymer is stronger, denser and has a slightly higher melting point

7. Nanotechnology

   • Nanometre is one millionth of a millimetre
   • Particles can...
     • Occur naturally (sea spray)
     • Occur as an accidental result of human activity
     • Made deliberately by scientists
       • Called nanotechnology
   • Particles have different properties
     • Smaller particles so have a much larger surface area
   • Production, study and control of nanoparticules
   • Modify properties of other polymers
     • Silver nanoparticles give clothes antibacterial properties
     • Carbon nanotubes to sports equipment makes it lighter and stronger
   • Risks
     • New technology
     • Haven't been thoroughly tested
     • Possible health problems in future

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