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Chemistry 1b
Oils, Earth and Atmosphere…read more

Slide 2

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Cracking Crude Oil
· Long-chain hydrocarbons thick, gloopy liquids which aren't much use. So,
most of the long molecules produced from fractional distillation are turned into
smaller ones by cracking
· Some of the products are useful as fuels e.g. petrol
· It also produces substances such as ethene- needed for making plastics
· It's a thermal decomposition reaction (breaking molecules down by heating
1. Heat long hydrocarbon chain to vaporise it
2. Vapour is passed over a powdered catalyst (aluminium oxide) 400-700 °C
3. Long-chain molecules split apart on the surface of the specks of the catalyst
4. Most of the products are alkanes (saturated) and alkenes (unsaturated
· ^Alternatively, mix the vapour with steam at a very high temperature)…read more

Slide 3

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· Hydrocarbons that have a double bond between two of the Carbon
atoms in their chain
· Unsaturated because they can make more bonds
· General Formula CnH2n
1. Ethene C2H4 2. Propene C3H6
· Test by adding substance to bromine water. An alkene decolourises it
so it turns from orange to colourless. This is because the double bond
has opened up and formed bonds with bromine…read more

Slide 4

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· Ethene (C2H4) can be hydrated with steam (H2O) in a presence of a catalyst to
make ethanol
· Cheap process because ethene is fairly cheap and not much of it is wasted.
However, it comes from a non-renewable source- crude oil which could start
running out very soon. This means using ethene to make ethanol will become
very expensive
· The alcohol in beer and wine etc. is not made by ethene but fermentation. The
raw material is sugar which is converted into ethanol using yeast.
Sugar Carbon Dioxide + Ethanol
· This process needs a lower temperature and simpler equipment
· The raw material is a renewable source
· The ethanol can be used as quite a cheap fuel in countries which don't have oil
reserves to make petrol…read more

Slide 5

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Using Alkenes to make Polymers
· Most useful- polymerisation joining together lots of small alkene
molecules (monomers) to form very large molecules called polymers
(pressure and a catalyst used)
· Many ethene molecules can be joined up to produce poly(ethene)
· Physical properties depend on what it's made from e.g. polyamides are
usually stronger than poly(ethene)
· Physical properties depend on: temperature and pressure:
-poly(ethene)- 200 °C and 200 atmospheres- flexible & low density
-poly(ethene)- 60 °C and little atmospheres with a catalyst- rigid & dense…read more

Slide 6

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Polymer Uses
· Light, stretchable polymers such as low density poly(ethene) are used
to make plastic bags. Elastic polymer fibres are used to make LYCRA
fibre for tights
· Waterproof coatings for fabrics are made of polymers
· Dental polymers- resin tooth fillings.
· Polymer hydrogel wound dressings- keep wounds moist
· Biodegradable packaging materials made from polymers and
· Memory foam is an example of a smart material. It's a polymer that
gets softer as it gets warmer e.g. memory foam mattresses…read more

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