earth and atmosphere

earth and atmosphere

1. cracking crude oil

   • cracking = thermal decomposition (breaking molecules down by heating them)
   • 1) heat long chains to vaporize
     • 2)vapour passes over powdered catalyst at 400-700oc
       • 3) the long chain molecules 'crack' on the surface of the catalyst
       • catalyst = aluminium oxide
   • products are ALKENES and ALKANES

2. alkenes and ethanol

   • alkenes all have a double carbon bond
   • the double bond can open allowing the carbons to bond with other things
   • the test for an alkene is browmine water. if an alkene is present the bromine water turns clear
   • ethanol can be made by reacting ethene with steam
   • ethanol can also be made by fermentation of sugar with yeast
     • sugar -> carbon dioxide + ethanol

3. using alkenes to make polymers

   • polymerisation = joining lots of small alkene molecules which are called monomers to make larger long chain molecules called polymers
     • e.g. ethene molecules can be joined to gether to make polyethene (polythene)
   • properties:light, stretchable, not biodegradable, cheaper than most metals
     • tooth fillings, plastic bags, lycra, memory foam matress

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