Held together by many strong electrostatic forces. A lot of energy is needed to break many strong ionic bonds. When ionic compounds melted, ions free to move so can conduct electricity.
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Simple molecules
Held together by strong covalent bonds. Low melting points due to weak intermolecular forces. Those with the smallest molecules have weakest intermolecular forces. Don’t conduct electricity as no overall charge.
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Giant covalent structures
(macromolecules) every atom in structure is joined to several other atoms by strong covalent bonds. V. high melting points as takes enormous amount of energy to break down the lattice.
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Diamond + graphite
Diamond- form of carbon, reg 3-d giant structure. Each carbon bonded to 4 others making hard and transparent. Graphite form of carbon atoms covalently bonded to 3 other carbon atoms.
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Graphite
One electron from each carbon= delocalised, these delocalised electrons allow graphite to conduct heat & electricity. Weak intermolecular forces between layers so can slide over each other easily.
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Fullerenes
large molecules formed of hexagonal rings of carbon atoms. Rings join together to form cage-like shapes with different no.s of C atoms, some of which nano-sized. Scientists finding applications for fullerenes(lubricants,catalysts,drug delivery in bod
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Giant metallic structures
Metal atoms arranged in layers. When force applied layers can slide so metal bends or stretched in new shape so useful for making wires, rods etc.
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Alloys
mixtures of metals or metals mixed with other elements , different sized atoms distort layers in metal structure making more difficult to slide over each other. This makes alloys harder than pure metals.
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Shape memory alloys
can be bent or deformed but when heated return to original shape, can be used for braces.
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Properties of polymers
depends on the monomers used to make it and conditions we use to carry out the reaction. Poly(propene) made from propene + softens at higher temp than poly(ethene) which is made from ethene.
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Thermosoftening polymers
Example – Poly(ethene). Made up of individual polymer chains tangled together. When heated it becomes soft + hardens again when cools, means it can be heated into mould and reheated to mould again.
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Bonding in thermosoftening polymers
Forces between polymer chains weak, when heated, the weak intermolecular forces broken so polymer becomes soft, when polymer cools, intermolecular forces bring polymer molecules back together so polymer hardens.
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Thermosetting polymers
do not melt or soften when heated, these polymers set hard when first moulded because strong covalent bonds form cross-links between polymer chains, strong bonds hold polymer chains in position.
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Nanoscience -– nano particles few nanometres in size
Contain a few hundred atoms arranged in particular way. Nanotechnology uses nanoparticles as v. efficient catalysts, sun screens + deodorants. However unpredictable consequences for health + environment
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Other cards in this set
Card 2
Front
Held together by strong covalent bonds. Low melting points due to weak intermolecular forces. Those with the smallest molecules have weakest intermolecular forces. Don’t conduct electricity as no overall charge.
Back
Simple molecules
Card 3
Front
(macromolecules) every atom in structure is joined to several other atoms by strong covalent bonds. V. high melting points as takes enormous amount of energy to break down the lattice.
Back
Card 4
Front
Diamond- form of carbon, reg 3-d giant structure. Each carbon bonded to 4 others making hard and transparent. Graphite form of carbon atoms covalently bonded to 3 other carbon atoms.
Back
Card 5
Front
One electron from each carbon= delocalised, these delocalised electrons allow graphite to conduct heat & electricity. Weak intermolecular forces between layers so can slide over each other easily.
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