C2- material choices

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  • C2- material choices
    • all materials are made up of chemicals (groups of atoms bonded together
      • Natural
        • wood, paper, cotton (plants). wool, silk etc (animals)
    • material properties
      • melting point- most pure chemicals have unique. solid goes to liquid
      • stiffness- force taken to bend a material
      • hardness- how difficult to cut into
      • density- how much mass in a specified volume
      • strength- how good a material is at resisting a force (can be flexible and strong)
    • possible uses
      • plastics- hard, stiff and low density
      • rubber- strong but soft and flexible eg car tyres
      • nylon- soft, flexible, high tensile strength eg rope
    • properties depend on the materials its made from- suitability should be assessed
    • crude oil- mixture of hydrocarbons- when heated smaller chain molecules split from rest and longer chain molecules stay together- fractional distilation- refining
      • Hydrocarbons- strong covalent bonds between atoms, weak intermolecular forces
      • polymerisation is where high pressure is used to joing small chained molecules to make longer molecules- eg inn milk cartons
      • this means you can change molecular chain length to get different properties- thats why plastics have different properties
      • forces between polymer chains determine polymer strength
        • weak forces- slide over each other, low melting point and easy to stretch
        • strong forces- dont slide over each other and so high melting point and more rigid
      • polymer modififcation
        • change chain lenght- longer means more rigid and higher melting point
        • crosslinks- chemically bond chains together, stronger and higher melting point
        • plasticisers- reduces friction between chains, softer and easier to shape.
        • make more crystaline- straight chains with no branches, fit closer, higher density, higher melting point
    • nanotechnolo-gy is a branch of technology dealing with the making and use of nano particles
      • can occur naturally- combustion (particulates) and sea spray
      • have different properties to their regular sized counterparts
      • silver- anti-bac properties. also some can be added to sports equipment to strengthen without adding weight
      • dont know long term effects- must be clearly labelled on producst


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