Extracting Vegtable Oils - AQA GCSE Core

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  • Created on: 03-01-12 12:35
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Extracting vegetable oils
The plant materials are crushed and pressed to squeeze the oil out. Olive oil is obtained this
way.
Sometimes the oil is more difficult to extract and has to be dissolved in a solvent.
Once the oil is dissolved, the solvent is removed by distillation, and impurities such as water
are also removed, to leave pure vegetable oil. Sunflower oil is obtained in this way.
Vegetable oils in food:
All vegetable oils have molecules that have chains of carbon atoms with hydrogen atoms
attached.
In some vegetable oils there are carboncarbon double bonds which are known as
unsaturated oils
We can use the same test as we use for testing alkenes for testing unsaturated oils.
Using plant oils:
Biodiesel is a fuel made from plant oils and can be used in any and car or van that has a diesel
engine.
It is made from oils that come from plants. Plants use photosynthesis to convert solar energy
to chemical energy. The chemical energy is released when the biodiesel is burned.
Advantages:
It is renewable, biodegradable and non toxic.
Doesn't give off as many poisonous gases.
It is carbon neutral (the amount of carbon dioxide it gives off is balanced by the amount it
absorbs).
Making Alcohol:
Alcohol is a very useful substance:
It makes an excellent solvent
Can be used as an alternative fuel
Can be made into an alcohol beverage or posh vinegar.
Methods of making it:
1) Fermentation:
Yeast is mixed with sugar and kept warm for a period of time.
The yeast uses the sugar for respiration producing Ethanol and Carbon Dioxide
Yeast + warm 45°C
C6H12O6 2C2H5OH + 2CO2
2) Reaction of ethene and steam:
Ethene is mixed with steam and passed over a at catalyst at very high temperatures.
C2H4 + H2O C2H5OH
Ethene steam ethanol
Fermentation:
Advantages:
Renewable
Very pure product
Disadvantages:
Batch process
Slow
Lots of energy to purify
Emulsions:

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It is a combination of two liquids that do not normally mix.
It works if tiny droplets of one liquid spread out throughout the other liquid.
Eg. Milk is made from tiny droplets of animal fat dispersed in water.
Emulsifiers:
They stop the two liquids separating out into two layers.
Eg: Egg yolks are a very good emulsifier. Normally oil and water don't mix but if you add egg yolks
then it stops them separating.…read more

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