Chemistry C1

Name the four types of additives and their purpose?
Food Colours - appetising appearance; Flavour Enhancers - to bring out the flavour of a food without adding any flavour of its own; Antioxidants - preserve food; Emulsifiers - help oil and water blend together in salad cream and ice cream
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What is an emulsion?
A mixture of oil and water where droplets of one liquid are suspended into another.
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What is an emlsifier?
Something that prevents two liquids in an emulsion from separating out. A molecule which has one end attracted to water and the other attracted to oil.
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Which is the hydrophillic end?
The end that is attracted to water.
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Which is the hydrophobic end?
The end that is attracted to oil.
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How does an emulsifier work?
The hydrophillic end bonds to water molecules and the hydrophobic end to oil. When you shake the oil and water together with emulsifier, the oil forms droplets surrounded by a coating of emulsifier with the hydrophillic part facing outwards. ....
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Other oil droplets are repelled by the hydrophilic part of the emulsifier so the water molecules won't latch on and the emulsion won't separate out.
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Five reasons why we cook food?
Better taste, better texture, easier to digest, poisonous when raw, the high temperatures kill microbes which cause disease.
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What happens to protein when cooked?
Protein molecules change shape when heated. The energy from cooking breaks some of the chemical bonds in the protein and this allows the molecules to change shape. This gives the food a more edible texture - denaturing/irreversible.
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Why are potatoes easier to digest when cooked?
Each potato cell is surrounded by a rigid cell wall made of cellulose which humans can't digest. Cooking the potaoto breaks down the cell walls and makes the starch inside the cells spread out which makes the potato softer and easier to digest.
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What is thermal decomposition?
When a substance breaks down into two or more simpler substances when heated.
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Word equation for the thermal decomposition of baking powder?
sodium hydrogencarbonate = sodium carbonate + carbon dioxide + water
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Symbol equation for thermal decomposition of baking powder?
2NaHCO3 = Na2CO3 + CO2 + H2O
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Why is baking powder used to make cakes?
The carbon dioxide produced makes the cake rise.
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How do you check carbon dioxide has been produced?
Carbon dioxide can be detected by using limewater. When CO2 is bubbled through limewater the limewater becomes cloudy.
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How to make an ester?
Heat a carboxylic acid ((an acid built around one or more carbon atoms)) with an alcohol - esterification.
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Equation for esterification?
Acid + Alcohol = Ester + Water
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Describe the esterification method?
Mix 10cm3 of a carboxylic acid such as ethanoic acid with 10 cm3 of an alcohol such as ethanol. Add 1cm3 of concentrated sulfuric acid to the mixture and warm gently for five minutes. Tip the mixture into 150cm3 of sodium carbonate solution..........
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..................
(to neutralise the acids) and smell carefully by wafting the smell towards your nose. The fruity smelling product is the ester.
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Five properties of perfumes and why they are necessary?
Easily evaporates-so it can be smelt; non-toxic-can't posion skin; doesn't react with water-so it can't react with sweat; doesn't irritate skin-couldnt be applied; insoluble in water-can't wash off
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One reason for animal testing?
To check they won't damage humans.
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One reason against animal testing?
It is wrong to cause suffering to animals just to test the safety of a cosmetic item especially when the results might not be conclusive.
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Describe the structure of the particles in a solid? [7 Brief Points]
Strong forces of attraction; fixed position; regular lattice arrangement; particles dont move; definite shape and volume; don't flow; particles vibrate
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What happens when a solid is heated?
The particles vibrate more so the solid expands slightly. Eventually the solid would melt and become a liquid.
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Describe the structure of the particles in a liquid? [6 Brief Points]
Some force of attraction; free to move but tend to stick together; no definite shape; flow to fill the bottom of a tub; keep the same volume; constantly move with random motion
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What happens if a liquid is heated?
The particles move faster and the liquid expands slightly. Eventually it will boil and become gas.
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Describe the structure of a gas? [8 Brief Points]
No force of attraction; free to move; travel in straight lines; only interact when they collide; dont keep a definite shape or volume; always fill a containe; they exert pressure when bouncing off walls; move constantly with random motion
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What happens if a gas is heated?
The particles move faster and the gas either expands or the pressure increases.
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How do we smell stuff? (Evaporation)
When a liquid is heated the heat energy goes to some particles which makes them move faster. Some faster than others. Fast particles at the surface overcome the forces of attraction and escape and receptors in the nose pick up the chemical.
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What is volatility?
How easily a liquid evaporates.
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Why do perfumes need to be volatile?
So they can evaporate enough to be able to smell them.
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Why do the particles in a perfume have week forces of attraction?
So it is easier for the particles to overcome it and escape. Only very little heat energy is needed to make the perfume evaporate.
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Other cards in this set

Card 2

Front

What is an emulsion?

Back

A mixture of oil and water where droplets of one liquid are suspended into another.

Card 3

Front

What is an emlsifier?

Back

Preview of the front of card 3

Card 4

Front

Which is the hydrophillic end?

Back

Preview of the front of card 4

Card 5

Front

Which is the hydrophobic end?

Back

Preview of the front of card 5
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