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Slide 1

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REVISION…read more

Slide 2

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Single covalent bonds
Saturated hydrocarbons- no spare single bonds
Don't decolourise bromine water- no spare bonds
Won't form polymers- no spare bonds
The first four alkanes (all you're expected to know
for GCSE) are:
... Methane ­CH(4)
... Ethane- C(2)H(6)
... Propane- C(3)H(8)
... Butane ­ C(4)H(10)
Alkenes have one `e'= 1 covalent
bond…read more

Slide 3

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Double covalent bonds
Unsaturated hydrocarbons- have spare C=C bonds
Will decolourise bromine water- have spare bonds
Form polymers via polymerisation
The first two alkenes (all you're expected to know
for GCSE) are:
... Ethene- C(2)H(4)
... Propene- C(3)H(6)
Double `e' for double bond…read more

Slide 4

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Long chain hydrocarbons are thick liquids
... i.e. Not useful
Cracking makes them shorter chains, which are
much more useful
For this you need a high heat and a catalyst of
finely-powdered aluminium oxide and silicon (IV)
It is important because it is used to produce more
petrol. Larger alkanes in crude oil are cracked to
produce alkanes with about 8 carbon atoms like
octane. These are the main constituents in petrol.
Petrol obtained this way is better than that gathered
by fractional distillation of crude oil.…read more

Slide 5

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They are unsaturated (have C=C bonds)
Polyunsaturated oils are the healthiest and
saturated oils are the least healthy because of what
effect they have on the cholesterol levels in the
Unsaturated oils are more viscous (runny) because
of their bonds.....
... The double bonds change the shape of the molecule
by making them an `inflexible kink' in the
hydrocarbon chain
... Kinked and less flexible chains can't pack together as
tightly as straighter and more flexible chains do. As a
result, the intermolecular forces are weaker.
... Weak intermolecular forces make oils less viscous so
unsaturated are more viscous than saturated.…read more

Slide 6

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Ethene has an addition reaction with hydrogen
at 150C using a nickel catalyst.
The product is ethane.
This is known as catalytic hydrogenation. It is
important in making margarine from vegetable
oils in palm seeds and sunflower seeds. The
vegetable oils are liquids containing C=C double
bonds, like alkenes.
During hydrogenation, some of these C=C bonds
are converted to C-C bonds by addition of
hydrogen. This change in structure turns an oily
liquid into a harder, fatty solid that can be used
to make margarine…read more

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