polymers and giant covalent structures -
. polymers are lots of small molecules linked together to make a long chain that has repeating sections
. they have large intermolecular forces holding the molecules together, so alot of energy is needed to break these bonds (stronger than simple covalent bonds)
. usually solids at room temp due to the strong intermolecular forces
. the intermolecular forces are weaker than covalent and ionic bonds, so polymers have lower boiling points than ionic and covalent structures
. instead of drawing out the long chain, they’re drawn with the smallest repeating part inside the bracket with a ‘n’ on the outside to indicate that it repeats many times
. to find molecular formula: write out formula in brackets with the added n to show it repeats many times = (c4h2)n
. polyethene is an example of a polymer
. all atoms in a giant covalent structure are covalently bonded - strongly
. very high melting and boiling points due to strong covalent bonds - lots of energy needed to break the bonds
. don’t conduct electricity as they have don’t contain charged particles -not even molten apart from some exceptions such as graphite
- main examples - diamond, graphite and silicon dioxide
diamond features - made up of carbon atoms each with 4 strong covalent bonds to other carbon atoms - this makes it very hard, the strong bonds give it a high melting and boiling point as the bonds need lots of energy to overtake, it contains free electrons or ion (charged particle) so doesn’t conduct electricity
graphite features - made up of hexagonal layers of covalently bonded carbon atoms, each with only 3 covalent bonds, the bonds are strong giving it a high melting and boiling point, there are no covalent bonds between the layers, so it’s soft as the layers can slide over each other making it a good lubricating material, only 3 out of 4 of carbons outer electrons are covalently bonded so it has one free one, meaning graphite can conduct electricity and thermal energy
graphene - one layer of graphite, the sheet of carbon atoms is one atom thick, its two- dimensional and contains free/ delocalised electrons like graphite so it can conduct electricity throughout the whole structure meaning it can be used in electronics, network of bonds makes it strong and it’s very light so can be added to composite materials as it adds strength but not weight
fullerenes
molecules of carbon, either shaped like hollow spheres (buckminister) or narrow tubes
they can be used to cage other molecules so are useful in transporting drugs into the body
they have a very large surface area, meaning they make good industrial catalysts, as catalysts can be attached to them
can be good lubricating materials
made up of hexagons but can contain pentagons and heptagons
buckminister fullerene is shaped like a hollow sphere and was the first fullerene to be discovered
nanotubes are tiny carbon cylinders
nanotubes can be used in nanotechnology (which uses very small materials), they have a high tensile strength (they can be stretched far without breaking)
nanotubes can conduct electricity and thermal energy
they can be used to strengthen materials without adding much weight e.g tennis racket frames
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Studied by 4 people
