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08/04/2023
Formation of oil and gas
1) Layers of dead sea _____ settle on the seabed.
2) Layers of __________ rock build up on top.
3) The heat and ________ from these rocks, along with the absence of ______, mean that oil and gas are formed over ______ of years.
Words – sedimentary, millions, oxygen, creatures, pressure
08/04/2023Hydrocarbons and crude oil
Longer chains
mean…
1. Less ability to flow
2. Less flammable
3. Less volatile
4. Higher boiling
point
Incre
asin
g le
ng
th
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Ethane
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
08/04/2023
Fractional distillationCrude 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
08/04/2023
CrackingShorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:
Butane
Ethane
Ethane
For example, this bond can be
“cracked” to give two of these:
08/04/2023Cracking
This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst
1) Carbon dioxide causes the _________ effect
2) Sulphur dioxide causes _____ _____
3) Plastics are not _____________
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:
08/04/2023
AlkanesAlkanes 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).
08/04/2023
AlkenesAlkenes are different to alkanes; they contain DOUBLE COVALENT bonds. For example:
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.
ALK
AN
ES
ALK
EN
ES
08/04/2023
Monomers and Polymers
Ethene
Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics…
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
08/04/2023
Another way of drawing it…Instead of circles, let’s use letters…
Ethene
C C
HH
HH
C C
HH
HH
Ethene
H
C C
H
HH
H
C C
H
HH
Poly(e)thene
General formula for addition polymerisation:
C Cn C C
n
e.g. C Cn
H CH3
HH
C Cn
H CH3
HH
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