C3.3 PROPERTIES OF MATERIALS

• how many bonds can carbon make?

  4 covalent bonds
• what are allotropes?

  different forms of the same element
• how many bonds does carbon make in DIAMOND?

  four, forming a tetrahedron
• diamond does not conduct electricity because?

  all the outer shell electrons are held in the four covalent bonds around each carbon atom, so there are no freely moving charged particles
• diamond has a very high melting point because?

  the four covalent bonds are very strong and extend in a giant lattice, so a very large amound of heat energy is needed to break the lattice.
• diamond is extremely hard and has a high density. this means what?

  useful for purposes where tough material is required

  • jewellery
  • coating blades in cutting tools
  • cutting edges in discs used to cut concrete are tipped in diamonds
  • tooling equipment are also diamond tipped
• how many bonds does carbon make in GRAPHITE?

  3, forming layers of hexagons
• why does graphite conduct electricity?

  carbon bonds to 3 other carbons, leaving one free electron per carbon atom

  • free to move and carry charge
• why is graphite soft and slippery?

  the layers are attracted to each other by weak intermolecular forces, so the layers can slide over each other
• why does graphite have a high melting point?

  strong covalent bonds
• uses of graphite?

  pencils, industrial lubricant, engines and locks, intert electrodes for electrolysis
• what is graphene?

  a single later of graphite
• how thick is graphene?

  one atom thick
• why is graphene strong?

  • unbroken pattern
  • strong covalent bonds
• why can graphene conduct electricity?

  free electrons that move along its surface
• what are fullerenes?

  a group of carbon allotropes which consist of molecules that form hollow tubes or spheres
• what was the first fullerene to be discovered?

  bickminsterfullerene
• in buckminsterfullerence, 60 carbon atoms are joined together forming 20 hexagons and 12 pentagons
• why are fullerenes useful for drug delivery systems?

  can be used to trap other moledcules by forming around the target molecule and capturing it
• what are nanotubes?

  graphene rolled into a cylinder
• properties of nanotubes:

  • high tensile strenght
  • resistant to breaking or stretching
  • conduct electricity
  • used in composites, electronics and nanotechnology
• at temperature below melting point?

  solid state
• at temperature between melting and boiling point?

  liquid state
• temperature above the boiling point?

  gas state