C1 A 3

Revision notes on the products of rocks (crude oil) for GCSE Chemistry.

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  • Created on: 12-04-08 15:57
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C1a. ­ Products from rocks
3. Crude oil
C1a 3.1 ­ Fuels from crude oil
Crude Oil is a mixture of many different compounds.
A mixture contains two or more elements or compounds
that are not chemically bonded together.
Crude oil straight out of the ground is not much use. It has
too many substances in it, with all different boiling points.
We use distillation to separate the mixtures in crude oil.
Crude oil mainly contains carbon and hydrogen. These are
known as hydrocarbons. Most hydrocarbons in crude oil are
alkanes.
Formula = CnH2n+2
We describe alkanes as being saturated hydrocarbons. This
means they contain as many hydrogen atoms as possible in
each molecule. We cannot add anymore.
C1a 3.2 ­ Fractional distillation
The smaller a hydrocarbon the more useful it is.
The smaller chain of hydrocarbon has a lower boiling point.
The smaller chain of hydrocarbon is more runny. It isn't as
viscous as the longer chains of hydrocarbon.
The smaller chain of hydrocarbon is more flammable.
At room temperature, small hydrocarbons are gases, the
ones in with between five or twelve carbon atoms are
liquids, and large hydrocarbons are solids.
We separate crude oil into fractions using fractional
distillation.
It is fed into a tall tower (fractionating tower) as hot
vapour. The tower is kept very hot at the bottom and much
cooler at the top, so the temperature decreases going up
the column. The gases in the column condense when they
reach their boiling points, and the different fractions are
collected at different levels.
C1a 3.3 + 3.4 ­ Burning fuels and Cleaner fuel
When fuels burn they all produce carbon dioxide and water.
Carbon dioxide is a greenhouse gas and it causes global
warming. As well as producing these hydrocarbons they
produce other substances as well. These include Sulfur
Dioxide, Nitrous Oxide, Carbon Dioxide and Carbon Monoxide.
Sulfurdioxide is the substance that has caused us major
problems. This is because this gas is poisonous and it
causes acidic rain.
Sulfur dioxide can also cause engine corrosion.

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Changing the conditions in which we burn fuels may change
the products that are made. For example when a car engine
does not have enough oxygen to burn the fuel we get
incomplete combustion. Instead of all the carbon in the fuel
turning to carbon dioxide we get carbon monoxide as well.
Carbon monoxide is a poisonous gas which is bad for your
health. It is bad for you because it replaces the oxygen in
your blood.…read more

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