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C3 Structure and Bonding (Nanoparticles (Particulate Matter (PM) (Coarse…

- - - - particles can be atoms, molecules or ions
      - particles vary in size
      - particles can contain many atoms
      - particles are not solid or spherical
  - - - solid melt to liquid
        
        solid particles vibrate faster
        
        energy transferred to break forces
        
        particles break away from fixed positions
      - liquids freeze into solids
        
        particles become closer together
        
        stronger forces formed between particles
    - - liquid boils to gas
        
        some surface particles escape before boiling point is reached (evaporation)
        
        energy transferred to substance
        
        liquid particles move around faster
      - gas condenses to liquid
        
        energy transferred from substance to surroundings
        
        particles slow down
    - - heating/cooling curves
      - temperature changes pause at the melting and boiling points as energy is transferred to break or form forces
  - - - particles vibrate
      - fixed arrangement
      - particles close together
    - - particles slide over eachother
      - random arrangement
      - particles close together
    - - particles move very quickly
      - random arrangement
      - particles far apart
      - compressed easily
- - - - only outer shell of electrons involved in bonding shown
  - - - forces act in all directions
      - between oppositely charged ions
      - holds ionic compounds together
      - needs lots of energy to overcome
        
        high melting and boiling points
        
        solids at room temperature
    - - ions are free to move
      - ions can carry a charge through the liquid
      - water molecules can split up the lattice
- - - - each shared pair of electrons is a covalent bond
      - atoms achieves stable electronic structure of a noble gas
      - shared pairs of electrons strongly attracts the two atoms, holding them together
        
        covalent bonds only act between the 2 atoms bonded
    - - the outer energy shells
      - the outer electrons in a dot and cross diagram
      - the number of covalent bonds in displayed formula
      - 3D ball and stick model
      - 2D ball and stick model
      - Limitations
        
        most models do not show actual shape of the molecule. i.e. 3D ness
        
        All electrons are identical but dot and cross diagrams show electrons from different atoms differently
        
        Electrons are shown in fixed positions, but they constantly move
        
        in giant structures, diagrams only reflect a tiny fraction of the structure in its simplest ratio
        
        bonds are not sticks between the particles
    - - strong covalent bonds within each molecule
      - weak intermolecular forces / forces of attraction between separate molecules
        
        easy to overcome
        
        intermolecular forces increase with the size of the molecules
        
        larger molecules have higher melting and boiling points
        
        Polymers have very large covalent molecules
        
        Polymers are solids at room temperature
    - - because there is no overall charge on the simple molecules in a compound
        
        neutral molecules can't carry an electrical charge
      - except for acids
        
        reacts with the water to from aqueous ions
  - - - high melting and boiling points
        
        lots of energy required to overcome many strong bonds
      - insoluble in water
      - hard
        
        except graphite
      - do not conduct electircity
        
        except graphite
    - - form of carbon
      - every atom has 4 covalent bonds
        
        rigid covalent structure
        
        no free electrons
    - - each carbon atom has 3 strong covalent bonds
        
        each atom has 1 delocalised electron
        
        moves freely along layers
        
        conducts heat and electricity
      - forms layers of hexagonal rings
        
        weak intermolecular forces between layers
        
        layers slide easily
      - soft and slippery
      - form of carbon
    - - silicon and oxygen covalently bonded
- - - - shaped like footballs, rugby balls, doughnuts, onions, cones or tubes
    - - but also have pentagonal or heptagonal rings
    - - first discovered fullerene
      - contains 60 carbon atoms
      - spherical shape
    - - very thin cylinders
        
        high length : diameter ratio
      - high tensile strength
        
        reinforcing composite materials
      - delocalised electrons
        
        high conductivity
        
        used in electronics
    - - drug delivery to body
      - lubricant
      - catalyst
        
        large SA : volume ratio
  - - - one atom thick
      - hexagonal rings
    - - useful in electronics
    - - low density
      - useful in composite materials
- - - - metals form crystals
    - - electrons move freely throughout the lattice
        
        quickly transfers electrical charge and thermal energy
        
        metals are good conductors
      - 'lattice of positive ions in a sea of delocalised electrons'
      - holds the giant structure together
        
        strong electrostatic attraction between -ve electrons and +ve ions
        
        forces extends in all directions
        
        lots of energy to overcome forces
        
        metals have high melting and boiling points
    - - atoms are the same size
      - layers can slide over each other easily
      - malleable and ductile
        
        malleable as when stuck, metal ions can slip past one another, as the delocalised electrons shifts to another atom
  - - - more difficult for layers to slide
      - alloys are harder than pure metal
    - - returns to original shape after being bent
      - used in braces
- - - - 0.1µm - 2.5µm
      - (PM 2.5)
    - - 2.5µm - 10µm
      - dust
      - (PM 10)
    - - 1µm = 1 x 10⁻⁶ m
    - - pollutants
      - pollen
      - dust
  - - - more reactive than normal sized particles
        
        smaller quantities needed
      - high proportion of atoms exposed at surface
      - effective as catalysts
  - - - deodrants
      - face creams
      - absorbed deeper into skin
      - sun creams
        
        more effective
    - - drug delivery in body
        
        carbon nanocages
      - wound dressings
        
        silver nanoparticles protect against bacteria
    - - nanowires improve capacity and speeds
  - - - breathing in tiny particles could damage lungs
      - nanoparticles could enter bloodstream
      - unpredictable effects on cells
    - - nanoparticles entering atmosphere or water
      - affect aquatic life
        
        nanoparticles accumulating in organisms
    - - large surface area
      - very reactive