Chemistry - Using Plant Oils

This is for an AQA GCSE paper and has four sub-sub topics which are:

1. Vegetable Oils and Biodiesel          2. Emulsions            3. Hardening Vegetable Oils         4. Oils and Fats in Our Diets

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Vegetable Oils and Biodiesel - Extracting Oils

When plants photosynthesise they produce glucose which can converted to starch or vegetable oils or is used for respiration. We can use the oils for food and fuel.

We extract these oils but only some are worthwhile, olives, rapeseed seeds and sunflowers. After harvesting plans are seived to remove substances that can cause damage to machinery. The plant materials are then crushed to form a mixture of plant oils and plant materials.

To separate the oil from plant material press into the mixture so that oil and water is released. They separate into two layers. The water is then drained and the oil is filtered, then heated to get rid of the other impurities such as the remaining water and bacteria or by the oil dissolving in a solvent that can then be easily separated, this is by using distillation so only the oil remains.

Biodiesel is a biofuel and can be used for fueling vehicles, alone or blended with ordinary diesel. It is converted into a biodiesel by reacting it with methanol and sodium hydroxide. Biodiesel molecules contain oxygen ions so produces less carbon monoxide and less sulphur dioxide.

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Oil and water do not dissolve into one another so are immiscible.

When oil and water are shaken vigorously it forms an emulsion but they are not stable mixtures. To make it more stable we can add an emulsifier.

One end of the emulsifier is hydrophilic, head, one is hydrophobic, tail (water-loving and water-hating). 

Emulsions are more viscous than the original water or oil and used for:

  • Non-drip emulsion paint (the paint will stay on the brush but can spread on the walls easily)
  • Skin cream  and in food, such as mayonnaise and ice-cream (they make you look and better).
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Hardening Vegetable Oils

Some oils are saturated, which means, because of strong bonds, they have a high melting point, making them a solid in room temperature. The rest are unsaturated and have low melting points and making them a liquid at room temperature.

It can be tested to see whether it is an alkene or alkane use bromine water test.

The unsaturated fats can now be converted to unsaturated by adding hydrogen and hardening them (hydrogenation).

To perform hydrogenation hydrogen must be added with 60 degrees over a nickel catalyst.

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Oils and Fats in Our Diets

Oils and fats are a good supply of nutrients however too much is harmful because they raise thee level of your cholesterol which blocks our arteries and a risk of heart disease.

Food oils are useful too fry food as they have a much higher boiling point.

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sorry but the cards need to be short and snappy

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