CH2 - Solid Structures

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  • CH2 - Solid Structures
    • Giant Ionic Lattices
      • Number of 'nearest neighbours' is the co-ordination number.
        • Caesium Chloride, Cs+Cl-
          • Cs+ ion is larger than the Cl- ion, so more Cl- ions can fit around each Cs+ ion.
          • Cl- co-ordination number = 8
          • Cs+ co-ordination number = 8.
          • Crystal co-ordination number = 8:8 ratio.
      • Properties of Ionic Compounds
        • High melting and boiling points.
          • Strong ionic bonds (electrostatic attractions between oppositely charged ions).
            • Large amount of heat energy is needed to break them.
        • Water Soluble
          • Positively charged metal ions form strong attractions with the polar O of the water.
          • Negatively charged non-metal ions form strong attractions with the polar H of water.
          • The attractions overcome the hydrogen bonds between the water molecules and therefore the compound dissolves.
        • Conducting electricity when molten or aqueous.
          • Ions are not free to move in the solid state.
          • Melting or dissolving in water overcomes the ionic bonds.
            • The ions become free to move and therefore carry a charge.
    • Giant Covalent Substances
      • Diamond
        • Clear
        • Lustre
        • No intermolecular forces.
      • Graphite
        • Opaque
          • Black
        • Hexagonal layers.
          • Layered on top of one another.
          • Weak intermolecular forces between each layer of graphite.
    • Simple Covalent Substances
      • Iodine
        • Crystalline (solid) at room temperature.
        • Gentle warming causes it to undergo sublimation.
          • Changes state from a solid to a gas without melting first.
      • NH3
      • CH4
    • Smart Materials
      • Shape Memory Polymers
        • Softens when heated, so can be softened or deformed.
        • Remains in changed state when cooled.
        • When reheated, original shape is 'remembered'.
          • Shape Retention.
        • E.G. Medical Sutures.
      • Thermochromic Pigments
        • Change colour (reversibly) when temperature changes.
        • E.G. T-Shirts or Mugs
      • Shape Memory Alloys
        • Pseudo-elasticity (appear to be plastic).
        • Exhibit shape retention memory.
        • E.G. Deformable glasses frames.
        • E.G. Surgical plates for joining surgical fractures.
        • E.G. Thermostats for electrical devices.
      • Photochromic Pigments
        • Contain molecules that change colour when exposed to light.
          • Particularly UV light.
        • Light breaks a bond in the molecule so that it rearranges itself into a molecule with a different colour.
        • E.G. Lenses of sunglasses.
        • Original colour returns when the light source is removed.
      • Hydrogels
        • Cross-linked polymers that have the ability to absorb or expel water when subjected to certain stimuli.
          • E.G. Temperature or pH.
        • E.G. Nappies or Artificial Muscles.
    • Nano Materials
      • Other Forms of Carbon
        • Carbon Nano Tubes
          • Single layer of graphite rolled into a tube.
          • Fullerene type arrangement where the ends of the tubes are closed.
          • 10,000 times thinner than a human hair.
          • Extremely strong.
          • May have the same adverse properties as asbestos fibres.
      • Nano Particles
        • Range  size from 1nm to 100 nm.
          • 1nm = 0.000000001m
        • When materials are made Nano-sized they have significantly different properties to the material in bulk.
        • Drawback - Is there enough known about Nano-particles before they can be widely used.
          • Could they be a risk to environmental health?
            • E.G Nano-particles in the water supply.
            • E.G If Nano-particles passed through our skin and have adverse biological effects?
        • Nanoparticles of Silver
          • Anti-bacterial
            • Wound/burn dressings.
          • Anti-viral
            • Sterilising sprays for operating theatres.
          • Anti-fungal
            • Interior surfaces of fridges.
    • Metallic Lattices
      • Metals can be described as "an array of positive ions in a sea of delocalised electrons".
        • Attraction of positive ions for the delocalised electrons is the metallic bond.
          • Metallic bonds are generally strong.
            • This is why metals have generally high melting and boiling points.
          • E.G. Magnesium (Group 2 metal)
            • The electrostatic attraction is 2+.
              • Therefore the electrostatic attraction is greater than the electrostatic attraction of group 1 metals.
              • Therefore group 2 metals have higher melting and boiling points than group 1 metals.
  • Sodium Chloride, NA+Cl-
    • Na+ co-ordination number = 6
    • Number of 'nearest neighbours' is the co-ordination number.
      • Caesium Chloride, Cs+Cl-
        • Cs+ ion is larger than the Cl- ion, so more Cl- ions can fit around each Cs+ ion.
        • Cl- co-ordination number = 8
        • Cs+ co-ordination number = 8.
        • Crystal co-ordination number = 8:8 ratio.
    • Cl- co-ordination number = 6
    • Crystal co-ordination number = 6:6 ratio.
  • Tetrahedral shape atoms.
    • 3D lattice.
    • Diamond
      • Clear
      • Lustre
      • No intermolecular forces.
    • Each carbon atom is connected to another carbon atom.
      • Extremely hard to break apart.
  • It is a volatile substance.
    • It vaporises easily.
    • Iodine
      • Crystalline (solid) at room temperature.
      • Gentle warming causes it to undergo sublimation.
        • Changes state from a solid to a gas without melting first.
  • Conduct electricity
    • Makes them suitable as connectors in micro electronic circuits.
    • Carbon Nano Tubes
      • Single layer of graphite rolled into a tube.
      • Fullerene type arrangement where the ends of the tubes are closed.
      • 10,000 times thinner than a human hair.
      • Extremely strong.
      • May have the same adverse properties as asbestos fibres.

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