Alkenes
- Created by: izzygreenxoxo
- Created on: 07-04-17 14:46
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- Alkenes
- Alkenes and Ethanol
- Alkenes have a C=C double bond
- Unsaturated - can make more bonds if double bond opens up
- First two alkenes - ethene and propene
- General formula - Cn H2n
- H H \ / C = C / \ H H
- Ethane reacts with steam to make ethanol
- Cheap
- Ethane is cheap and not much is wasted
- However ethane is from crude oil which is non-renewable so could run out - become expensive
- Ethanol can be made from renewable sources
- Fermentation for alcohol in beer and wine
- Raw material - sugar - converted using yeast
- Process at lower temperatures and with simpler equiptment than using ethene
- Sugar is renewable - can be grown in poor countries
- Cheap fuel in countries that can't get petrol
- Ethanol made this way - not very concentrated
- Needs to be purified to use
- Fermentation for alcohol in beer and wine
- Alkenes have a C=C double bond
- Using Alkenes to Make Polymers
- Polymerisatio-n
- Most useful thing alkenes do
- Join lots of small alkene molecules to form very large molecules
- Many ethene molecules join to form polyethene
- H H \ / C = C / \ H H
- ---->
- H H H | | | - C - C - C - | | | H H H
- etc.
- ---->
- H H H | | | - C - C - C - | | | H H H
- H H \ / C = C / \ H H
- Different polymers - different physical properties
- Depend on what it is made of
- Affected by what temp andpressure it was made at
- Polyethene - 200*C and 2000 atm - flexible + low density
- Polyethene - 60*C and few atm with a catalyst - rigid and dense
- Different polymers have different uses
- Light, stretchable - polyethene - plastic bags
- Elastic polymers - tight material
- New uses always developed - waterproof coatings for tights
- Dental polymers - fillings
- Polymer hydrogel wound dressing - keep wound moist
- Memory foam - smart material - polymer that gets soft as it gets warmer
- Polymers are cheap
- Don't break down easily by microorganisms
- Difficult to get rid of - still be there for years if in landfill sites
- Should re-use before recycling
- Will increase in price as crude oil runs out
- Polymerisatio-n
- Alkenes and Ethanol
- H H \ / C = C / \ H H
- ---->
- etc.
- ---->
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