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Reminder from C1a
Crude oil is a mixture of hydrocarbons
It can be split into fractions
Fractions with long hydrocarbon molecules aren't very useful.
Cracking Hydrocarbons
Cracking ­ Breaking large hydrocarbon molecules into smaller ones
- Thermal decomposition
smaller hydrocarbons
hot catalyst
vapour
hydrocarbon
Heat
Done in a catalytic cracker in industry.
J.…read more

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Alkane Molecules Alkene Molecules
(reminder from first chemistry module) (Of interest in this module)
Saturated ­ Contain as many hydrogen atoms as Unsaturated ­ Contains fewer hydrogen atoms
possible
No double bonds Contains one carbon ­ carbon double bond
H H
H H
e.g.…read more

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Making Polymers from Alkenes
Monomers - Small molecules (alkenes)
Polymers - Very long hydrocarbon molecules
Addition polymerisation - Adding lots of monomers together to make a polymer.
Plastic - Made of polymers
Addition
polymerisation
Monomer Polymer
Monomer Polymer Uses
Ethene Poly(ethene) Bags, bottles
Propene Poly(propene) Crates, ropes
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Properties of Plastics
Long, tangled polymer molecules strong, flexible (bendy) plastics
H H H H H H H H
C C C C C C C C
H H H H H H H H
Strong bonds hold atoms together in a polymer
molecule
Thermosoftening Plastics Thermosetting Plastics
Weak intermolecular forces hold molecules together Strong chemical bonds hold molecules together
Soften when heated Stay hard when heated
Flexible (bendy) Rigid (not bendy)
Use when something needs to be bendy and isn't Use when something should…read more

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Useful Polymers
Properties = how something behaves/what it is like.
Different polymers different properties different uses
e.g.
clear
poly(ethene) light weight Cola
strong
Transparent (clear) Drinks bottle
New Polymers
Scientists design new polymers for new jobs.
Smart polymer ­ Properties changed by light, temperature or other changes around them
e.g.
Sticking plaster Peel top layer off.
Comes off without
Light sensitive polymer hurting
stops being sticky.
e.g.
Sew a skin wound with shape memory polymer thread.
The temperature of the skin tightens the thread
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Problems with Polymers
Non ­ biodegradable ­ Don't rot, so fill up landfill sites (rubbish dumps)
Made from oil ­ oil is running out.
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Page 8

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VEGETABLE OILS
Contain a lot of energy so .....
..... can be used ....... are
as fuels important foods
Extracted from seeds, nuts or
fruits by ...........
... pressing ......... distillation
Vegetable Oils
Contain molecules with
chains of carbon atoms, with
hydrogen atoms attached.
Unsaturated oils...
have carbon ­
carbon double
bonds (C=C)
Test to detect unsaturated oils
are usually liquids
unsaturated
oil
bromine water or colourless
iodine solution decolourised
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Extracting Vegetable Oils
Extracting Vegetable Oils by Pressing Extracting Vegetable Oils by Distillation
Plant harvested Plant harvested
Crushed Crushed
Mixed with water Mixed with water
Pressed Mixture heated
Oil and water obtained Oil and some water evaporate (turn to gas)
Oil separates from water They condense (back to liquid)
Oil collected Oil separates from water
Oil collected
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Vegetable Oils as Food
Vegetable oils have higher boiling
Food absorbs oil when
points than water, so food cooked in
cooked in it
vegetable oil..........
Higher energy content in
food
... Cooks ..... has a
faster different flavour
......... has a ........…read more

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