C2.2 Structure and Properties

Giant Ionic Structures
1. Ions arranged in a lattice, with strong electrostatic forces
2. High melting/boiling points as more energy needed to break bonds
3. Solid ionic compound can not conduct electricity as they are in fixed position. Liquid, ions can move so conduct
4. Many dissolve in water. Lattice split by water molecules. Ions are free to move, form a solution, conduct
Simple Molecules
1. Covalent bonds have low melting points
2. Intermolecular forces
  1. Covalent have weak forces but strong bonds
    1. Atoms in molecule are tight together
    2. Energy between molecules is weak
3. No overall charge so no chance of conducting electricity
Giant Covalent structures
1. AKA Macromolecules
2. Diamond, graphite and silicon dioxide
3. Held by strong convalent bonds
4. Hard, high melting points,
5. Graphite has layers
6. Bonding in graphite
  1. Carbon arranged in hexagons
  2. Has delocalised electrons
    1. can conduct
7. Fullerenes
  1. Ball/cage shape
  2. Can place things inside the cage
    1. medicine?
Giant Metallic Structures
1. closely packed layers
2. Alloys are mixtures of metals, they are harder as the layers can not slide as easily
3. Explaining the properties
  1. positive ions are held together by a glue of delocalised electrons
  2. these electrons can move so allow a lattice to distort
4. Shape Memory Alloys
  1. When heated return to their original state
  2. braces and bone broken things
Properties of Polymers
1. Different Monomers
  1. monomers affect the properties of the polymer
2. Different reaction conditions
  1. High pressures and a trace of oxygen, ethene makes low density polyethene
    1. Polymer chains are Banches
  2. Catalyst at 50°C and slight pressure makes High Density Polyethene
    1. Chains are closer
3. Thermosoftening and thermosetting polymers
  1. Thermosoftening melt and untangle their chains
  2. Thermosetting do not melt as they have cross links
4. Bonding
  1. Thermosoftening is weak
Nanoscience
1. Science of the smallest of things
2. nanoparticles behave differently from the materials they are made from
3. New developements are always good but more research into problems are needed

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C2.2 Structure and Properties

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