C1.6 Plant Oils And Their Uses

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GCSE Chemistry (C1) Mind Map on C1.6 Plant Oils And Their Uses, created by killthemoment on 07/24/2014.

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C1.6 Plant Oils And Their Uses
1 C1.6.2 Emulsions
1.1 Oils do not dissolve in water. They can be used to produce emulsions. If oil and water are shaken together, tiny droplets of one liquid spread through the other liquid, forming a mixture called an emulsion.
1.1.1 Emulsions are thicker than oil or water and have many uses that depend on their special properties. They provide better texture, coating ability and appearance, for example in salad dressings, ice creams, cosmetics and paints. There are two main types of emulsion: oil droplets in water (milk, ice cream, salad cream, mayonnaise); water droplets in oil (margarine, butter, skin cream, moisturising lotion). If an emulsion is left to stand, eventually a layer of oil will form on the surface of the water. Emulsifiers are substances that stabilise emulsions, stopping them separating out. Egg yolk contains a natural emulsifier. Mayonnaise is a stable emulsion of vegetable oil and vinegar with egg yolk. Emulsifier molecules have two different ends: a hydrophilic end - 'water-loving' - that forms chemical bonds with water but not with oils and a hydrophobic end - 'water-hating' - that forms chemical bonds with oils but not with water. The hydrophilic 'head' dissolves in the water and the hydrophobic 'tail' dissolves in the oil. In this way, the water and oil droplets become unable to separate out.
2 C1.6.1 Vegetable Oils
2.1 Some fruits, seeds and nuts are rich in oils that can be extracted. The plant material is crushed and the oil removed by pressing (olive oil) or in some cases by distillation (sunflower oil). Water and other impurities are removed.
2.1.1 Vegetable oils are important foods and fuels as they provide a lot of energy and nutrients. Vegetable oils have higher boiling points than water and so can be used to cook foods at higher temperatures than by boiling. This produces quicker cooking and different flavours but increases the energy that the food releases when it is eaten.
3 C1.6.3 Saturated And Unsaturated Oils
3.1 Vegetable oils that are unsaturated contain double carbon–carbon bonds. These can be detected by reacting with bromine water, turning the liquid from orange to colourless.
3.1.1 Saturated vegetable fats are solid at room temperature, and have a higher melting point than unsaturated oils. This makes them suitable for making margarine, or for commercial use in the making of cakes and pastry. Unsaturated vegetable oils can be ‘hardened’ by reacting them with hydrogen, a reaction called hydrogenation. During hydrogenation, vegetable oils which are unsaturated are reacted with hydrogen gas at about 60ºC in the presence of a nickel catalyst. Hydrogen adds to the carbon–carbon double bonds. The hydrogenated oils have higher melting points so they are solids at room temperature, making them useful as spreads and in cakes and pastries.
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