Chemistry - C1.5 - Products from Oil

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C1.5.1 - Cracking Hydrocarbons

  • Cracking - breaking large hydrocarbon molecules down into smaller molecules, done in two ways: heating mixture of hydrocarbon vapours and steam to high temperatures or passing hydrocarbon vapours over a hot catalyst
  • During cracking thermal decomposition reactions produce mixture of smaller molecules - some are alkanes - saturated hydrocarbons - and are more useful as fuel as they're smaller
  • Alkenes - unsaturated hydrocabons - are also formed, they are unsaturated as they have fewer hydrogen atoms than alkanes with the same no of carbon atoms - they have double bonds -> more reactive than alkanes, react with bromine water - orange->colourless
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C1.5.2 - Making Polymers from Alkenes

  • Plastics made from polymers - many small molecules (monomers) joined together, reaction to make a polymer called polymerisation - double bond breaks and joins to other carbon atoms making a long chain
  • Many ethene molecules join to form polyethene/polythene and propene molecules form polypropene
  • Many plastic bags, bottles, containers and toys are made from alkenes
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C1.5.3 - New and Useful Polymers

  • Polymers can be designed to make materials with special properties used for packaging, clothing and medical applications
  • Polymer materials have been developed to be used as fillings instead of mercury, light-sensitive polymers used in plasters so they can be removed easily (two layers, bottom one unsticks when exposed to light), hydrogels are polymers that trap water so used in dressings - let body heal in moist, sterile conditions
  • Shape-memory polymers - smart polymer, return to original shape when temperature or other conditions change - eg. stitching wounds - changes shape when heated to body temperature - tightens then can dissolve
  • Fibres in fabrics coated in polymers to be waterproof and breathable
  • Plastic drink bottles recycled to make polyester fibres for clothing or filling for pillows and duvets
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C1.5.4 - Plastic Waste

  • Most polymers aren't biodegradable - plastic waste isn't broken down when left in the environment, unless disposed of properly it gets everywhere - it's unsightly, harms wildlife, takes up landfill space
  • Biodegradable plastics are being used more and broken down by mircroorganisms which break down when coming in contact with soil
  • Non-biodegradable plastics - cornstarch added, microorgansims break down cornstarch so plastic breaks down to small pieces to be mixed with soil or compost
  • Biodegradavle plastics - sometimes made from plant material - eg. polymer made from cornstarch to make biodegradable food packaging
  • Some plastics can be recycled but many different types of plastic make sorting difficult
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C1.5.5 - Ethanol

  • C2H6O or C2H5OH - shows the OH group in the molecule = alcohol
  • Can be made by sugar plant fermentation using yeast - enzymes in the yeast produce C2H6O and CO2 from sugar
  • Can be made from hydration of ethene - reacted with steam at high temperatures with catalyst (ethene obtained from crude oil by cracking)
  • Fermentation - renewable, done at room temperature, only produces dilute aqueous solution of ethanol - must be separated by fractional distillation to produce pure ethanol
  • Produced from ethene - non-renewable (crude oil), runs continuously, produces pure ethanol, needs high temperatures
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