1. Tuesday, 13 November 2018
Unsaturated Oils
L.O: To know some of the health effects of using different oils and fats in foods. To be able to explain why hardened vegetable oils are useful (higher).

2. RECIPE TO DISTILL PLANT MATERIAL
Starter
Fill the gaps in the recipe to distill plant material.
RECIPE TO DISTILL PLANT MATERIAL
You will need:
Heat source (e.g. Bunsen Burner)
Distillation Kit
Plant Material
Water
Method
Heat the plant material until the oils that are in it evaporate.
Collect the vapour and cool it down so that it condenses back into pure liquid oil.
Boil water to make steam, then pass this down a pipe and over the plant material.
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Bunsen Burner
Plant
Cool
Condenses
Pure liquid
Plant material
Evaporate
Steam

3. What are unsaturated oils?
Oils and fats contain long-chain molecules with lots of carbon atoms.
They can be either saturated or unsaturated.
What are unsaturated oils?

4. Unsaturated oils contain double bonds between some of the carbon atoms in their carbon chains.
Saturated fats don't contain any carbon-carbon double bonds.
Bonding

5. Types of unsaturated fat
Monounsaturated fats contain one C=C double bond somewhere in their carbon chains.
Polyunsaturated fats contain more than one C=C double bond.

6. Testing for unsaturated oils
You can test for unsaturation using bromine water. Bromine water is orange, but it will decolourise when you add an unsaturated oil to it.
Can you remember where else we’ve seen this test?
Testing for alkenes.
Why do we use the same test?
Because unsaturated oils are alkenes.
Top tip: If an exam question asks you to give the result of the bromine water test, make sure you only use the words decolourised or colourless. Don't say ‘clear' or ‘transparent' — you won't get the mark.

7. Hydrogenation of unsaturated oils
Unsaturated vegetable oils are liquid at room temperature.
They can be hardened by reacting them with hydrogen in the presence of a nickel catalyst at about 60 °C.
This is called hydrogenation. The hydrogen adds to the double-bonded carbons, opening out the double bonds.
For example:
Hydrogenating the unsaturated hydrocarbon ethene makes the saturated hydrocarbon ethane.

8. Hydrogenated oils
Hydrogenated oils have higher melting points than unsaturated oils, so they're more solid at room temperature.
This means that they can be used as spreads — many margarines are made from hydrogenated vegetable oils.
You could even make margarine castles!

9. Hydrogenated oils
Hydrogenated oils are used in the food industry for baking cakes and pastries. The oils are a lot cheaper than butter and they keep longer — this makes the products cheaper and gives them a long shelf life.

10. Hydrogenated oils
The more you hydrogenate an oil, the more saturated fat it will contain and the harder it will become. Fats are often only partially hydrogenated so that they don't become too solid.

11. For example: MargarineH
For example: Margarine
Margarine is usually made from partially hydrogenated vegetable oil — turning all the double bonds in vegetable oil to single bonds would make margarine too hard and difficult to spread.
Hydrogenating most of them gives margarine a nice, buttery, spreadable consistency.

12. Vegetable Oil and Health
Vegetable oils tend to be unsaturated, while animal fats tend to be saturated.
In general, saturated fats are less healthy than unsaturated fats, as saturated fats increase the amount of cholesterol in the blood, which can block up the arteries and increase the risk of heart disease.
Unsaturated fats like olive oil reduce the amount of blood cholesterol.
Cooking food in oil, whether saturated, unsaturated or partially hydrogenated, makes it more fattening. That's why it's healthier to use cooking methods that don't involve oil.

13. Vegetable Oil and Health
Vegetable oils tend to be unsaturated, while animal fats tend to be saturated.
In general, saturated fats are less healthy than unsaturated fats, as saturated fats increase the amount of cholesterol in the blood, which can block up the arteries and increase the risk of heart disease.
Unsaturated fats like olive oil reduce the amount of blood cholesterol.
Cooking food in oil, whether saturated, unsaturated or partially hydrogenated, makes it more fattening. That's why it's healthier to use cooking methods that don't involve oil.

14. Recalling Facts
What is the difference between a saturated oil and an unsaturated oil?
Describe a test that you could do to find out if an oil is unsaturated.
[Higher] Unsaturated vegetable oils can be hydrogenated to harden them.
Give the catalyst and the temperature used for this reaction.
Give one use of hydrogenated vegetable oils.
Explain why unsaturated fats are healthier than saturated fats.

15. Applications
Tip: Remember, hydrogenating oils gets rid of double bonds.
The melting points of two samples of sunflower oil are shown in the table. One has been hydrogenated and the other has not.
Which sample is the hydrogenated oil? Explain your answer.
Which sample will contain a higher proportion of unsaturated fat?
What would you expect to see if bromine water was added to sample Y? Explain your answer.

16. Recalling Facts – Answers
An unsaturated oil contains double bonds between some of the carbon atoms in its carbon chain. A saturated oil doesn't contain any carbon-carbon double bonds.
Add some bromine water to the oil. If the mixture turns colourless then the oil is unsaturated.
nickel, 60 °C
E.g. spreads / margarines / baking cakes and pastries
Saturated fats increase the amount of cholesterol in the blood, which can block up the arteries and increase the risk of heart disease. Unsaturated fats reduce blood cholesterol.
Remember, unsaturated fats are the good ones and saturated fats are the bad ones. Don't get them mixed up.

17. Application – Answers
Sample X, because hydrogenated oils have higher melting points than unsaturated oils.
Sample Y - Hydrogenating oils gets rid of double bonds. The natural oil will have more double bonds than the hydrogenated oil, so it will also have a higher degree of unsaturation.
The bromine water would be decolourised because sample Y contains unsaturated fats.