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Alkanes, Alkenes and Polymers

Alkanes, Alkenes and Polymers. CHEMISTRY 2. GCSE Additional Science. Chapter 9. The alkanes are hydrocarbons (they contain carbon and hydrogen only).… they are represented by the formula C n H (2n+2) where n = 1,2,3,4 etc. Fractional distillation. in an oil refinery.

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Alkanes, Alkenes and Polymers

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  1. Alkanes, Alkenes and Polymers CHEMISTRY 2 GCSE Additional Science Chapter 9

  2. The alkanes are hydrocarbons (they contain carbon and hydrogen only).… they are represented by the formula Cn H(2n+2) where n = 1,2,3,4 etc. Fractional distillation in an oil refinery CRUDE OIL H H H H H H H H H H H H H H H H C H H C C C C C C C C C C H H H H H H C C C C H H H H H H H H H H H H H H H H Hydrocarbons ALKANES The lines represent covalent bonds where electrons are shared GCSE Additional Science Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10 Pentane C5H12 Chapter 9 There are only single bonds between the carbon atoms in alkanes so they are called saturated hydrocarbons. Apart from burning, they are unreactive.

  3. H H H H H H H H H H H H H H H H H H C C C C C C C C C C C C C C C C H H C C H H H H H H H H H H H H H H H H H H H H Notice the double bond. This makes ethene reactive, and it is described as an unsaturated hydrocarbon. Ethene can be used to make poly (ethene) or polythene. H H C C H H Cracking Cracking is the term used when a saturated hydrocarbon molecule is heated in the presence of a catalyst in order to break it down into smaller units – smaller alkanes (which burn better) and alkenes (which can be used to make other chemicals, such as polymers). Cracking GCSE Additional Science Decane C10H22 Octane C8H18 Chapter 9 + Ethene C2H4

  4. H H H H H H H H H H H H H H H H H H H H H H C C C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H Making Polymers The name of the small molecule used to make a polymer is a monomer. The monomer ethene forms an addition polymer (a polymer made up of similar monomers) called polythene [poly(ethene)] GCSE Additional Science Ethene C2H4 Poly(ethene) (C2H4)n Chapter 9 Note that one of the bonds in the double bond has broken allowing the ethene molecule to join the others to form the polymer.

  5. H H H H H H H H H H Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H F F F F F F F F F F F F F F F F F F F F F F C C C C C C C C C C C C C C C C C C C C C C Cl H F F F F F F F F F F F F F F F F F F F F F F C C H H Polymers we use often Poly(tetrafluoroethene) Monomer tetrafluoroethene C2F4 Poly(tetrafluoroethene) PTFE (C2F4)n PTFE is inflammable and it’s used as a non-stick coating for saucepans and frying pans. Poly(chloroethene) GCSE Additional Science Chapter 9 Monomer chloroethene C2H3Cl Poly(chloroethene) PVC (C2H3Cl)n PVC is strong and light. It’s used for buckets, window frames and doors.

  6. Thermoplastics and thermosets Thermoplastics is the name given to plastics that melt when heated. They are used to make bowls, buckets and clingfilm. Thermosets is the name given to plastics that do not soften when heated. They are used to make saucepan handles and electrical fittings. The difference:- GCSE Additional Science Thermoplastics Thermosets Chapter 9 Thermoplastics are long chains with weak bonds between them. These chains slip easily over each other, which explains why they melt when heated gently. The chains are connected by cross-links within a thermoset. A lot of heat energy is needed to break these cross-links, so they do not soften (melt) when heated.

  7. Made from a non-renewable resource Traps and kills Animals when it’s litter Light Do not corrode Use less energy to make than traditional materials Easy to mould into different shapes Many are non-biodegradable Creates rubbish and pollution Must recycle them to maintain clean environment Suitable for a wide variety of uses Advantages and Disadvantages of Polymers Cheap Advantages Disadvantages Polymers GCSE Additional Science Water doesn’t affect them Strong for their weight Chapter 9

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