Structure and Properties

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  • Structure and Properties
    • Giant ionic structures
      • Strong electrostatic forces hold the ions together
        • High melting and boiling points
      • When an ionic compound has been melted the ions are free to move around
        • Some dissolve in water because water breaks up the compound
          • Can carry a charge
      • Can't conduct electricity when solid because the ions aren't free to move around
    • Simple molecules
      • Covalently bonded
      • E.g. Carbon Dioxide
      • Weak intermolecular forces between molecules
        • Low melting and boiling points
          • Gases at room temperature
            • Like hydrogen, chlorine and ethene
      • No charge - don't conduct electricity
    • Giant covalent structures
      • Form many covalent bonds
      • High melting points
        • A lot of energy needed to break down the lattice
      • Macromolecules
      • Diamond
        • Regular 3 dimensional structure
        • Carbon atoms covalently bonded to three others
        • Makes diamond hard and transparent
        • Similar to silica
      • Graphite
        • Carbon atoms covalently bonded to 3 others
        • Giant flat two-dimensional layers formed
          • Weak intermolecular forces
            • Allow the layers to slide over each other
        • Delocalised electron allows graphite to carry a charge
      • Fullerenes
        • Large molecules formed of hexagonal rings of carbon
        • Form cage like shapes with different numbers of carbon atoms (some are nano sized)
        • Many applications - drug delivery, lubricants, catalysts
    • Giant metallic structures
      • Arranged in layers
        • When a force is applied, the layers can slide over each other
        • Can be bended without breaking
        • Makes them useful in wires and sheet materials
      • Alloys are stronger because the different sized atoms distort the layers, making it difficult for them to slide over each other
      • Shape memory alloys
        • When heated return to their original shape
        • Used in bakes
    • Properties of polymers
      • Depends on the monomer and conditions made in
        • High density polythene is made using a catalyst and high pressure
          • Stronger
        • Low density polythene made in the presence of oxygen
      • Thermosoftening
        • Individual polymer chains tangeled together
        • Heated to mould into shape and can be remoulded by heating it again
      • Thermosetting
        • Don't melt at high temperatures
        • Cross links between polymer chains
        • Set hard when first moulded
    • Nanoscience
      • Particles in the nano range
      • Used in cosmetics
      • Long term effects are unknown
      • Long term effects unknow
      • Could get into the air and our bides
      • A nanometer is 10-9m
      • Large surfacearea

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