Chemistry Module 1

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How do additives improve food quality?
Food colours make it look nicer / Flavour enhancers bring out taste without adding any / Antioxidants preserve food / Emulsifiers help oil and water blend together
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What is an emulsion?
When one liquid is suspended in another
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How do emulsifiers prevent water and oil separating out?
When water, oil and emulsifiers are mixed, the tail is attracted and bonds to the oil and the head bonds to the water. The heads on all oil droplets repel each other and constantly bond with water molecules. This prevents the oil ever separating out
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What is the structure of an emulsifier?
The emulsifier molecule has a hydrophilic head and hydrophobic tail.
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Why do some foods have to be cooked?
Better taste and texture / Easier to digest / Kills off dangerous microbes / Some foods re poisonous when raw
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Why do we have to cook meat and eggs?
The energy from cooking breaks some of the chemical bonds in the protein and allows the molecule to take a different shape. This gives the food a more edible texture. The change is irreversible as it is denaturing
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Why do we have to cook potatoes?
Each potato cell has a rigid cell wall made of cellulose. Humans can't digest cellulose so we cook potato to rupture the cell walls and eat the contents. Also the starch grains swell and spread making potato softer, more flexible and easier to digest
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Why is baking powder used in baking cakes?
When thermally decomposed, one of baking powder's products is CO2 - this makes the cake rise
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What is the word equation for the thermal decomposition of baking powder?
Sodium Hydrogencarbonate ----(heat)----> Sodium Carbonate + Carbon Dioxide + Water
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What is the balanced symbol equation for the thermal decomposition of baking powder?
2NaHCO3 ----(heat)----> Na2CO3 + CO2 + H2O
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What is the equation for making an ester?
Acid + Alcohol ---> Ester + Water
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What is a carboxylic acid?
An acid built around one or more carbon atoms
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What properties does perfume have to have?
Quite volatile / Non-toxic / Doesn't react with water - otherwise it will react with sweat / Doesn't react with skin - otherwise it couldn't be worn directly on skin / Insoluble in water - otherwise it would wash off every time someone got wet
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What are the moral issues with cosmetics being tested on animals?
Makes sure that the product won't harm humans / It's wrong to cause an animal suffering just to test the safety of a cosmetic and the results may not be conclusive also ------ Animal testing has been banned in the EU due to concerns on animal welfare
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How and why are perfumes very volatile?
The liquid particles in perfume have weak attractions with each other. When a little heat is added, the particles have enough energy to overcome this attraction and so evaporate. Perfumes are volatile so they can evaporate easily and be smellt
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What is the definition of a solution?
A mixture of a solute and solvent that doesn't separate out
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Why doesn't nail varnish dissolve in water?
The attractions between nail polish particles are very strong compared to nail varnish and water. The attraction between water particles are also strong in comparison to water and nail varnish. The two substances are more attracted to themselves
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Why does mail varnish dissolve in acetone?
The attraction between acetone and nail varnish is stronger than the attraction between their own substance.
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What makes up paint?
Pigments - gives colour / Binding Medium - liquid that carries pigment and holds them together / Solvent - thins paint making it easier to spread
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What is a colloid?
A colloid consists of really tiny particles of one substance dispersed within another substance. The particles can be solid, liquid or gas. Colloids don't separate out because the particles are so small and so they don't settle at the bottom
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What is an emulsion paint made out of?
The solvent is water and the binding medium is usually acrylic or vinyl acetate polymer
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How does emulsion paint dry?
The solvent evaporates leaving behind the binder and pigment as a thin solid film. They are fast drying and don't produce harmful fumes - good for indoors
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What is an gloss and artist's oil paint made out of?
The binding medium is oil and the solvent is an organic compound that'll dissolve oil
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How does oil-based paint dry?
The solvent evaporates and then the oil is oxidised by oxygen in the air before it turns solid. These paints are glossy, hard-wearing and waterproof but produce harmful fumes - suitable for outdoor use
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What is special about thermochromic pigments?
They change colour or become transparent when heated or cooled
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What can thermochromic pigments be used for?
Babies' bath toys or spoon as a safety feature / Drink mugs so you know when their too hot / Mood rings / Can be mixed with paint and be used on novelty mugs
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How do phosphorescent pigments work?
They absorb artificial or natural light and store the energy in their molecules. This energy is released as light over a period of time
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What are the uses of phosphorescent pigments?
Glow-in-the-dark hands on clocks and watches / traffic or emergency exit signs / toys and novelty decorations
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What was used instead of phosphorescent pigments but has been discontinued?
Radioactive paints - these would glow for years without having to be charged up. However, they gave off doses of atomic radiation and so weren't safe. Phosphorescent pigments are a safer alternative
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What is addition polymerisation?
When lots of unsaturated monomers join together to form polymer chains
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Why do different plastics have different properties?
It depends on the intermolecular forces or bonds between each polymer chain that makes up the plastic
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What are the properties of thermosoftening plastics?
They have weak intermolecular forces between each polymer chain so the chains are free to slide over each other. This makes the plastic soft/mouldable, stretched easily and have a low boiling point
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What are the properties of thermosetting plastics?
They have strong bonds between polymer chains - possibly covalent. The plastic is rigid due to cross-linking. This also means the plastic cannot be stretched and has a high melting point
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Why is nylon (a synthetic polymer) used in clothing?
If coated with polyurethane, it becomes a tough, hard-wearing and waterproof outdoor piece of clothing which can also keep UV out
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What are the problems with using nylon for outdoor clothing?
Polyurethane doesn't allow water vapour to pass through. This means sweat can condense on the inside making it uncomfortable for the wearer. It isn't breathable
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What is an alternative to nylon?
Gor-tex has all the same properties as nylon but is breathable meaning water vapour can escape and so is comfortable for outdoor weather.
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Why is Gor-tex breathable?
The PTFE is microporous which can let water vapour through but is waterproof as the holes are too big to let water droplets through and PTFE repels water
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How is Gor-tex made?
It is made by laminating a thin layer of expanded PTFE onto another layer of fabric such as nylon or polyester to make the PTFE sturdier.
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What are the different ways of getting rid of plastic?
Bury it in a landfill site - long time to decompose / Burn it - releases toxic gases (sulfur dioxide, hydrogen cyanide, hydrogen chloride) / Reuse and recycle - sorting = difficult and expensive
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What are chemists trying produce with polymers?
Most polymers aren't biodegradable. This means plastic won't rot as it isn't broken down by microorganisms. However chemists are trying to produce polymers that biodegrade or dissolve so that they break down in landfills
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What is a hydrocarbon?
An atom made up of hydrogen and carbon atoms only
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What happens if you add an alkane to bromine water?
Nothing. The alkane is a saturated compound and so cannot react with the bromine. The bromine water will remain bright orange
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What happens if you add an alkene to bromine water?
As bromine is very reactive, it reacts with the double bond in the alkene in an addition reaction. This decolourises the bromine water turning it from orange to colorless. It forms a colourless dibromo compound
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What is fractional distillation?
It is aprocess used to separate a mixture of liquids that have different boiling points
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Explain what happens to crude oil during fractional distillation
The oil's heated to 450*C and pumped into column. It vapourises, rises, cools and condenses as the bottom hot but the top cool. Heavy fractions have HBP and condense near the bottom of the column. Light fractions have LBP and condense further up
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How do hydrocarbon properties change as the chain length increases?
As size increases, boiling point increases / volatility decreases / flammability decreases / becomes more viscous
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How come different chain lengths have different boiling points?
Intermolecular forces between each hydrocarbon molecule. As heat is supplied, smaller molecules overcome these forces easily as their forces are weaker than larger molecules. Larger chains, higher boiling points, more energy required to break forces
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What is cracking?
Taking large alkane molecules and breaking them into smaller alkane molecules and alkene molecules using heat (so is a form of thermal decomposition) and a catalyst
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Why is cracking used?
There is more demand for smaller alkane molecules such as petrol and kerosene than there is for diesel and bitumen. It also produces an alkene which can be used in polymerisation
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What is the method for cracking?
Vaporised hydrocarbons are passed over the powdered aluminium oxide catalyst at about 400-700*C. The long chains split apart or 'crack' on the surface of the bits of catalyst
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Why does cracking have to take place in hot conditions?
So that there is enough energy to break the covalent bonds holding the loong hydrocarbon chains together
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What are the problems with crude oil?
It is anon-renewable source and even though new reserves are found, it'll eventually run out. Some people think we should just use crude oil for plastics and other chemicals instead of fuel. However, this may lead to conflicts between industries
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What are the political problems with crude oil?
As it gets used up, prices will increase and countries with big stocks may keep it for itself / Countries with oil and gas will have more power than others / Countries without a lot of oil might rely on politically unstable countries - may cut us off
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What are the environmental problems with crude oil?
Oil leaks lead to huge amount of crude oil being released into the sea called big oil slicks / Oil covers bird's feathers stopping them flying and not waterproof so die of cold / Detergents are used to clean up but toxic to marine creatures
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How do detergents help clean up crude oil?
They break the oil up into tiny droplets making it easier to disperse
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What should be considered when choosing a fuel?
Energy value / Availability / Storage / Cost / Toxicity / Ease of Use / Pollution
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What is the equation for complete combustion?
Hydrocarbon + Oxygen ----> Carbon Dioxide + Water (+ lots of energy)
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How can you show a fuel burns and produces CO2 and H2O?
A water pump draws gases from the burning fuel through apparatus. Water collects in the U-shaped tube as the ice surrounding it condenses it. The limewater at the end turns cloudy and CO2 is present
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What colour is the flame for complete combustion and what happens to the waste products?
clean blue - the room has to be ventilated as lots of CO2 is dangerous and H20 can be drained away
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How does incomplete combustion occur?
If there is a lack of oxygen whilst trying to burn something, incomplete combustion occurs and harmful products are produced
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What is the equation for incomplete combustion?
Hydrocarbon + Oxygen ---> Carbon Dioxide + Water + Carbon Monoxide + Carbon (+ energy)
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What is bad about carbon monoxide?
It is colourless, odourless and poisonous. This makes it very dangerous. Many people die a year in their sleep due to faulty gas burners so gas appliances should be regularly serviced. A clue is the soot given off from the black carbon produced
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Why is it ideal to have complete combustion?
It is less messy - no soot produced / No poisonous gases / More heat energy given out
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What was phase 1 in the evolution of the atmosphere?
Earth's surface was originally molten so any atmosphere burned away. It eventually cooled forming a thin crust but volcanoes kept erupting throwing up gases: CO2, H2O, NH3. When it settled, the atm was mostly CO2 and H20 with little oxygen
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What was phase 2 in the evolution of the atmosphere?
A lot of CO2 dissolved into oceans. Green plants evolved, removed CO2 and produced O2. O2 gradually built up and CO2 got locked in fossil fuels and sedimentary rock. N2 was put into atm: ammonia reacts O2, bacteria put it there and doesn't get used
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What was phase 3 in the evolution of the atmosphere?
Build up of O2 killed off early organisms that couldn't tolerate it. Allowed evolution of complex beings that used O2. O2 formed O3 layer blocking harmful Sun rays and enabled even more complex beings to evolve. Virtually no CO2 left
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What is the composition of the present day atmosphere?
78% Nitrogen / 21% Oxygen / 0.035% Carbon Dioxide / Noble gases (mainly argon) / Varying amounts of Water Vapour
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What is the carbon cycle?
Photosynthesis takes CO2 out of the air and adds O2. Respiration, Combustion, Decay of plants, and animals takes O2 out of the air and adds CO2.
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What are the human effects on the carbon cycle? (talk about output of CO2)
With an increasing population, more people are respiring, more fuel is required for electricity and energy per person is also increasing as more countries become industrialised, using up more fossil fuels meaning more CO2 is being added to the air
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What are the human effects on the carbon cycle? (talk about input of CO2)
As more people are born, more land is required to live on (food and shelter) and so deforestation happens at a faster rate meaning there are less plants to take CO2 out of the atmosphere
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How is acid rain caused?
When fossil fuels are burnt, sulfur dioxide (sulfur impurities) and various nitrogen oxides (nitrogen reacting with oxygen with heat from burning) are also released. These mix with clouds to form sulfuric acid and nitric acid. It then falls as rain
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What are the main causes of acid rain?
Power stations and internal combustion engines
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What are the effects of acid rain?
It causes lakes to become acidic and so many plants and animals die / Kills trees / Damages limestone buildings and ruins stone statues / Metal corrodes
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What is photochemical smog?
A type of air pollution caused by sunlight acting on nitrogen oxides. These oxides combine with oxygen in the air creating ozone. Ozone can cause breathing difficulties, headaches and tiredness
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How is carbon monoxide formed and why is it deadly?
It is formed through incomplete combustion of petrol or diesel in car engines. It's deadly because it combines with red blood cells and prevents it carrying oxygen which can lead to fainting, a coma or death
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What has happened as a cause of all these air pollutants
Lots of air pollutants makes life unhealthy and miserable and the number of respiratory cases has increased in recent years
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What does a catalytic converter do?
It is attached to motor vehicle exhaust pipes so that it can clean up exhaust fumes. It is normally made up of platinum and rhodium. 2CO + NO ---> N2 + 2CO2 Even though these aren't ideal (global warming) they're less dangerous than the reactants
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What air pollutants are there? What caused them? What is their effect?
CO2 - burning fossil fuels - greenhouse effect / CO - incomplete combustion of alkanes - poisons RBC / SO2 - powerstations - acid rain / Particulates - burning fossil fuels - breathing difficulty / NO+NO2 - road traffic, powerplants - acid rain, smog
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Card 2

Front

What is an emulsion?

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When one liquid is suspended in another

Card 3

Front

How do emulsifiers prevent water and oil separating out?

Back

Preview of the front of card 3

Card 4

Front

What is the structure of an emulsifier?

Back

Preview of the front of card 4

Card 5

Front

Why do some foods have to be cooked?

Back

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