Chemistry C2

All topics from OCR 21st century science textbook.

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  • Created by: ameliaG72
  • Created on: 14-05-14 19:46
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  • C2- Material Choices
    • Made from?
      • Every material is a chemical or mixture of chemicals
        • Examples: ceramic-bricks, wall tiles and plates, metals- vehicles, high-rise buildings and jewellery, polymers- packaging and protective clothing.
      • Obtain materials from: living or non-living things
        • Examples: cotton, wool, leather and wood
    • Properties
      • Key properties are: melting point, tension strength, compression strength, stiffness, hardness and density.
      • manufactures want best quality materials for their products.
    • Crude Oil
      • crude oil is liquid and a mixture of hydrocarbon molecules of different lengths
      • Oil companies use fractional distillation to separate the oil
      • Fractionating tower does this: oil is heated in furnace- evaporates and moves up the tower, fractions condense at different levels.
      • Small molecules have low boiling points and rise to the top of the tower
      • Big molecule compounds have high boiling points and condense at the bottom of the tower
      • Uses of crude oil: fuels, lubricants and raw materials.
    • Polymers
      • Are very long molecules, formed when small molecules called monomers join together. This is polymerisation
      • 4% of crude oil is used to produce synthetic materials, these do not occur naturally.
      • Synthetic materials have replaced natural materials, e.g. ropes are now made using polypropene instead of sisal or using nylon instead of cotton
    • Polymer Properties
      • Properties depend on how molecules are arranged and held together
      • Example: Wax has shorter molecules than polythene. Polythene is stronger, long molecules are tangled and difficult to separate. polythene melts at higher temps as stronger forces of attraction.
      • Changing properties: Longer chains- stronger, adding cross links- stronger, harder, less flexible, adding plasticisers- softer, more flexible, increasing crystallinity by lining up polymer molecules- stronger and denser
    • Nanotechnology
      • is the use and control of tiny structures
      • Nanoparticles are same size as some molecules and 1 to 100 nanometres across
      • Nanoparticles have diffrent properties to larger molecules mainly due to bigger surface area: volume ratio
      • Nano particles occur: naturally in sea spray, by accident when fuels burn, by design e.g. silver in medical dressings and socks or adding to plastics to make them stronger
      • May be health risks, some people think they should be studied more before full usage.

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