Topic 2 - bonding, structure and the properties of matter

• Nanoparticles


  Particles 1-100 nanometers across, containing a few hundred atoms
• Particle sizes


  • Nanoparticles (1-100 nm)
  • Fine particles (PM2.5, 100-2500 nm)
  • Coarse particles (PM10, 1x10^-5 m - 2.5x10^-6 m)
• Coarse particles are often referred to as dust
• As the side of a cube decreases by a factor of 10


  The surface area to volume ratio increases by a factor of 10
• Nanoparticles


  Involve fullerenes
• Nanoparticles


  • They have different properties to the 'bulk' chemical they're made from, due to their high surface area to volume ratio
  • Smaller quantities may be needed to be effective compared to normal particle sizes
• Nanoparticles with different properties to bulk

  • Fullerenes have different properties to big lumps of carbon
• Uses of nanoparticles


  • Good catalysts due to high surface area to volume ratio
  • Produce highly selective sensors
  • Stronger, lighter building materials (nanotubes)
  • New cosmetics (no white marks)
  • Lubricant coatings (reduce friction)
  • Small electrical circuits (nanotubes conduct electricity)
• There are some concerns that nanoparticles may be toxic to people, as they may be able to enter the brain from the bloodstream and cause harm
• The three states of matter


  Solid, liquid and gas

  
• Melting and freezing


  Take place at the melting point
• Boiling and condensing


  Take place at the boiling point
• Particle theory


  • Can help to explain melting, boiling, freezing and condensing
  • The amount of energy needed to change state depends on the strength of the forces between the particles
  • The nature of the particles involved depends on the type of bonding and the structure of the substance
  • The stronger the forces between the particles the higher the melting point and boiling point of the substance
• Limitations of the simple particle model include that there are no forces, all particles are represented as spheres, and the spheres are solid
• State symbols


  Solid (s), liquid (l), gas (g), aqueous (aq)

  
• Ionic compounds


  • Have regular structures (giant ionic lattices)
  • Have strong electrostatic forces of attraction in all directions between oppositely charged ions
  • Have high melting and boiling points
  • Conduct electricity when melted or dissolved in water, but not when solid
• Small molecules


  • Usually gases or liquids with low boiling and melting points
  • Have weak intermolecular forces between the molecules
  • Larger molecules have higher melting and boiling points
  • Don't conduct electricity
• Polymers


  • Have very large molecules
  • Atoms in the polymer molecules are linked by strong covalent bonds
  • Intermolecular forces between polymer molecules are relatively strong, so they are solids at room temperature
• Giant covalent structures


  • Are solids with very high melting points
  • All atoms are linked by strong covalent bonds that must be overcome to melt or boil
• Giant covalent structures


  • Diamond, graphite, silicon dioxide
• Metals


  • Have giant structures of atoms with strong metallic bonding
  • Most have high melting and boiling points
  • The layers of atoms can slide over each other, so metals can be bent and shaped
• Alloys


  • Made from 2 or more different types of metals
  • The different sized atoms distort the layers in the structure, making it harder for them to slide over each other, so alloys are harder than pure metals
• Metals as conductors


  • Good conductors of electricity because the delocalised electrons carry electrical charge
  • Good conductors of thermal energy because energy is transferred by the delocalised electrons
• Diamond


  Each carbon is joined to 4 other carbons covalently
• Diamond


  • Very hard
  • Has a very high melting point
  • Does not conduct electricity
• Graphite


  Each carbon is covalently bonded to 3 other carbons, forming layers of hexagonal rings which have no covalent bonds between the layers
• Graphite


  • The layers can slide over each other due to no covalent bonds between the layers, but weak intermolecular forces
  • Soft and slippery
• Graphite


  One electron from each carbon atom is delocalised
• Graphite


  • Similar to metals because of its delocalised electrons
  • Can conduct electricity - unlike Diamond, because the delocalised electrons can move
• Graphene


  Single layer of graphite
• Graphene


  • Has properties that make it useful in electronics and composites
  • Very strong because atoms within its layers are very tightly bonded
  • Elastic because the planes of atoms can flex relatively easily without the atoms breaking apart
• Fullerenes


  Molecules of carbon atoms with hollow shapes
• Fullerenes


  • Based on hexagonal rings of carbon atoms, but may also contain rings with five or seven carbon atoms
  • The first fullerene to be discovered was Buckminsterfullerene (C60), which has a spherical shape
• Carbon nanotubes


  Cylindrical fullerenes with very high length to diameter ratios
• Carbon nanotubes


  • Their properties make them useful for nanotechnology, electronics and materials
• Uses of carbon-based materials


  • Can be used as lubricants, to deliver drugs in the body and catalysts
  • Nanotubes can be used for reinforcing materials, for example tennis rackets
• Coarse particles (PM10)


  Diameters between 1 x 10-5 m and 2.5 x 10-6 m, often referred to as dust
• Conductor


  A material which contains charged particles which are free to move to carry electrical or thermal energy
• Covalent bond


  A shared pair of electrons between two non-metals
• Diamond


  • A giant covalent structure which is made up of carbon atoms each of which form four covalent bonds with four other carbon atoms