1. Formation of oil and gas
21/03/2012
1) Layers of 2) Layers of 3) The heat and ________ from
dead sea _____ __________ these rocks, along with the
settle on the rock build up on absence of ______, mean that oil
seabed. top. and gas are formed over ______
of years.
Words – sedimentary, millions, oxygen, creatures, pressure

2. Hydrocarbons and crude oil
21/03/2012
Crude oil is a mixture of HYDROCARBONS
(compounds made up of carbon and hydrogen).
Some examples:
H H
Longer chains mean…
Increasing length
H C C H
H H 1. Less ability to flow
Ethane
2. Less flammable
H H H H
H C C C C H 3. Less volatile
H H H H
4. Higher boiling point
Butane

3. Fractional distillation
21/03/2012
Crude oil can be separated by fractional distillation. The oil is evaporated
and the hydrocarbon chains of different lengths condense at different
temperatures:
Fractions with
low boiling
points condense
at the top
Fractions with
high boiling
points condense
at the bottom

4. Cracking
21/03/2012
Shorter chain hydrocarbons are in greater demand because
they burn easier. They can be made from long chain
hydrocarbons by “cracking”:
Butane
Ethane
For example, this bond
can be “cracked” to give
two of these:
Ethane

5. Cracking
21/03/2012
This is a THERMAL DECOMPOSITION reaction,
with clay used as a catalyst
Cracking is used to produce plastics such as polymers and polyethanes. The
waste products from this reaction include carbon dioxide, sulphur dioxide
and water vapour. There are three main environmental problems here:
1) Carbon dioxide causes the _________ effect
2) Sulphur dioxide causes _____ _____
3) Plastics are not _____________

6. Alkanes
21/03/2012
Alkanes are SATURATED HYDROCARBONS. What does this
mean?
HYDROCARBONS are molecules that are made up of
hydrogen and carbon atoms
SATURATED means that all of these atoms are held
together by single bonds, for example:
Ethane Butane
Alkanes are fairly unreactive (but they do burn well).

7. Alkenes
21/03/2012
Alkenes are different to alkanes; they contain DOUBLE
COVALENT bonds. For example:
ALKANES
ALKENES
Ethane Ethene
Butane Butene
This double bond means that alkenes have the potential to join
with other molecules – this make them REACTIVE. We can
test for alkenes because they turn bromine water colourless.

8. Monomers and Polymers
21/03/2012
Here’s ethene again. Ethene is called a
MONOMER because it is just one small
molecule. We can use ethene to make
plastics…
Ethene
Step 1: Break the double bond
Step 2: Add
the molecules
together:
This molecule is called POLYETHENE,
and the process that made it is called
POLYMERISATION

9. Another way of drawing it…
21/03/2012
Instead of circles, let’s use letters…
H H H H H H H H
C C C C C C C C
H H H H H H H H
Ethene Ethene Poly(e)thene
General formula for addition polymerisation:
n C C C C
n
H CH3 H CH3
e.g. n C C C C
H H H H n