GCSE Chemistry C1
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- Created by: Ruqayya Iqbal
- Created on: 01-06-17 18:59
What does an emulsifier contain?
Hydrophilic head-bonds to water. Hydrophobic tail-bonds to oil
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What happens when you shake oil and water with an emulsifier?
The oil forms droplets, surrounded by a coat of emulsifier, with the hydrophilic head facing outwards
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Why do foods have to be cooked?
Improve taste and texture. Easier to digest. Kill off microbes with high temperature. Make food edible and remove poison
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Why do protein molecules change shape when you heat them?
The energy from cooking breaks some of the cooking bonds in the protein and allows the molecule to take a different shape. Change is irreversible. Denaturing
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What is the chemical reaction that takes place in potatoes?
Each potato cell is surrounded by a rigid cell wall made of cellulose. Cooking potato ruptures the cell wall and makes starch grains inside cell to swell and spread. This makes the potato softer and easier to digest
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What is thermal decomposition?
This is when a substance breaks down into simpler substances when heated
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What is the thermal decomposition of sodium hydrogencarbonate?
Sodium hydrogencarbonate -> sodium carbonate + carbon dioxide + water
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How is carbon dioxide detected through lime water?
Carbon dioxide turns limewater cloudy when it's bubbled through
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Explain the process of esterification?
Acid + Alcohol -> Ester + Water
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How is an ester made?
The acid is added to alcohol and heated. The condenser stops the gas from escaping and helps to cool it down, so it can react more. The condenser allows the reaction to go on for longer
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What properties does a perfume need?
Easily evaporates. Non-toxic. Doesn't react with water. Doesn't irritate the skin. Insoluble in water
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Properties of Solids?
Particles don't move-all solids keep definite shape. Particles vibrate more, the hotter the solid becomes. Strong forces of attraction between particls
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Properties of Liquids?
Particles free to move-tend to stick together. Liquids don't keep definite shape, but same volume. Particles move faster when liquid is heated
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Properties of Gases?
No force of attraction between particles-free to move. Don't keep definite shape or volume. Hotter the gas gets the faster particles move
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Explain the process of evaporation?
Fast-moving particles at the surface will overcome the forces of attraction from the other particles and escape
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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 for you to smell them. Particles have weak attractions between them, so only need very little heat energy to make the perfume evaporate
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Explain the process of dissolving?
When you add a solid to a liquid the bonds holding the solute molecules together break, and the molecules mix with the molecules in the liquid- forming a solution
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What is a solute?
Solid. The substance being dissolved
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What is a solvent?
Liquid. The liquid it's dissolving in
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What is a solution?
The mixture of a solute and a solvent that does not separate out
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What does a substance being soluble and insoluble mean?
Soluble- it will dissolve. Insoluble- it will not dissolve
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Why is nail varnish insoluble in water?
The attraction between nail varnish molecules is stronger than the attraction between nail varnish and water molecules. Attraction between water molecules is also stronger
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Why is nail varnish soluble in acetone?
Attraction between acetone molecules and nail varnish molecules is stronger than the attraction holding the two substances together
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What does paint contain?
Solvent-thins the paint, so easier to spread. Binding Medium-liquid that holds the pigment together- goes solid + sticks the pigments to surface. Pigment-gives colour
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What don't colloids separate out?
They don't separate out because the particles are too small. They don't settle out at the bottom
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What is paint?
Paint is a colloid where particles are mixed and dispersed with particles of a liquid but are not dissolved
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How does a water-based emulsion dry?
Solvent evaporates, leaving binder and pigment as thin solid film. Thin layer of emulsion paint dries quickly
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Why are emulsion paints ideal for painting inside walls?
Emulsion paints are fast-drying and don't produce harmful fumes
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How do oil paints dry?
Solvent evaporates and oil is oxidised by oxygen in air, before it turns solid
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Why are oil paints ideal for painting outside doors + metalwork?
They are glossy, waterproof and hard-wearing. They produce harmful fumes
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What are thermochromic pigments?
Thermochromic pigments change colour or become transparent when heated or cooled
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How do phosphorescent pigments glow in the dark?
They absorb natural or artificial light and store the energy in their molecules. This energy is released as light over time
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Why are phosphorescent pigments safer than radioactive paints?
Radioactive paints gave out atomic radiation. Phosphorescent pigments were developed as a much safer alternative
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What is polymerisation?
The formation of polymers when lots of small molecules called monomers join. This needs a high pressure and a catalyst
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What are unsaturated compounds?
Molecules with at least one double covalent bond between carbon atoms. Alkenes
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What are saturated compounds?
Molecules with no double bond between carbon atoms. Alkanes
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What is addition polymerisation?
Lots of unsaturated monomer molecules can open up their double bonds and join together to form polymer chains
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What does addition polymerisation involve?
It involves the reaction of many unsaturated monomer molecules to form a saturated polymer
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How can you recognise a polymer?
Long chain. Pattern repeating every two carbon atoms. Two brackets on the end with extended bonds through them. N after brackets
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What happens if the plastic is held by weak intermolecular forces?
The polymer chains will be free to slide over each other. Plastic can be stretched easily. Low melting point
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What happens if the plastic is held by strong intermolecular forces?
Rigid. Can't be stretched as the crosslinks hold the chains firmly together
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Properties of nylon?
Tough. Lightweight. Keeps water out. Keeps ultraviolet light out
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Disadvantages of nylon?
Doesn't let water vapour pass through. This means sweat condenses and makes the wearer wet and uncomfortable. Material isn't breathable
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Properties of GoreTex?
Same as nylon but is also breathable. It is worn by active outdoor people. Water vapour from sweat can pass through the membrane but rainwater cannot
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What is GoreTex made from?
PTFE. The holes in PTFE are too small for water to pass through but are big enough for water vapour to pass through
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How are GoreTex fabrics made?
By laminating PTFE onto nylon to produce a stronger fabric
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Advantages and disadvantages of polymers not being biodegradable?
A- they're not broken down by micro-organisms, so they don't rot. D- it is difficult to get rid of polymers
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What are the environmental issues with the use of existing polymers?
Disposal of non-biodegradable polymers mean landfill sites get filled quickly- waste of land. Burning waste plastics produces sulfur dioxide. Disposal wastes the crude oils used to make polymers. It is hard to recycle out different polymers
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What new types of polymers are scientists developing?
Polymers that dissolve. Biodegradable polymers
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What is a hydrocarbon?
A compound of carbon and hydrogen atoms only
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What are alkanes?
Alkanes are hydrocarbons that have single covalent bonds only
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What are alkenes?
Alkenes are hydrocarbons that have double covalent bonds between carbon atoms
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Why are alkenes more reactive then alkanes?
Their double bonds can open up and join onto things. They can form polymers by opening up double bonds to link in a long chain
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How can you tell the difference between an alkene and an alkane?
Bromine is used. When an alkene is added to orange bromine water, it turns colourless. An alkane won't decolourise the bromine water
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How do bromine and alkene form a new compound?
By an addition reaction. A dibromo compound forms which is colourless
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Why are fossil fuels a finite resources?
Because they are no longer being made, or being made extremely slowly
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Why are fossil fuels non-renewable?
Because they are being used up faster than they are being formed
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What difficulties are associated with the finite nature of crude oil?
All the readily extractable resources will be used up in the future. Finding replacements
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What is crude oil?
Crude oil is a mixture of many types of oil, which are all hydrocarbons
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How is crude oil formed?
It is formed from the buried remains of plants and animals-fossil fuel. With high temperature and pressure, the remains turn to crude oil, which can be drilled up
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Fractional distillation column?
LPG. Petrol. Naptha. Paraffin. Diesel. Oil. Bitumen
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Describe the temperature gradient in the column?
Its hot at the bottom (bitumen) and gets gradually cooler towards the top
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What is bitumen?
Crude oil is heated at the bottom of a fractionating column. Oil that doesn't boil sinks as a thick liquid to the bottom-bitumen. High melting point
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Why does bitumen have a high boiling point?
The longer hydrocarbons have high boiling points. The shorter hydrocarbons have lower boiling points
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What occurs as the hydrocarbon molecule increases?
Boiling point increases. Less flammable. More viscous. Less volatile
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Why can crude oil be separated?
Because the hydrocarbons in different fractions have differently sized molecules
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How is crude oil separated?
The forces between the molecules are intermolecular forces and are broken during boiling. The molecules of the liquid separate from each other as molecule of gas
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What is the result of large molecules having strong forces of attraction?
A lot of energy is needed to break the forces between the molecules. These fractions have high boiling points
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What is the result of small molecules having weak attractive forces?
Easily separated as less energy is needed to break the forces between the molecules. These fractions have low boiling points
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What problems does transporting oil cause?
Oil slicks can damage birds' feathers and cause their death. Clean-up operations use detergents that can damage wildlife
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What political problems are related to the extraction of crude oil?
The UK is dependent on oil and gas from politically unstable countries. Oil-producing nations can set high prices and cause problems for the future supply of non-oil producing nations
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What is there to consider when choosing the best fuel?
Toxicity. Energy. Availability. Cost. Use. Pollution. Storage
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What is cracking?
Cracking turns large alkane molecules into smaller alkane and alkene molecules- thermal decomposition need heat and a catalyst
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How does cracking help manufactures?
Allows them to match supply with demand. Petrol and Kerosene are cracked into smaller molecules because there is more demand
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What conditions are needed for cracking?
400*-700*. Aluminium oxide is the catalyst used
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When does complete combustion occur?
When a fuel burns in plenty of oxygen. More energy is released. Clear blue flame. hydrocarbon + oxygen -> carbon dioxide + water
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What happens when there is not enough oxygen?
Incomplete combustion.Carbon monoxide and carbon produced. Smoky yellow flame
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Phase 1 of the evolution of the atmosphere?
Earths surface was molten-cooled and thin crust formed. Volcanoes kept erupting releasing carbon dioxide, steam and ammonia- degassing. Early atmosphere was CO2 and water vapour
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Phase 2 of the evolution of the atmosphere?
CO2 dissolved into oceans. Green plants photosynthesised- removed CO2 and produced O2. O2 built up and CO2 removed. Nitrogen produced by ammonia reacting with oxygen and by denitrifying bacteria. Nitrogen being made but not removed
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Phase 3 of the evolution of the atmosphere?
Build up of O2 killed organisms- allowed evolution of organisms that made use of oxygen. Oxygen formed ozone layer which blocked harmful rays and enabled more complex organisms to survive. No CO2 remained
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What is the present composition of the Earth's atmosphere?
78% nitrogen. 21% oxygen. 0.0035% carbon dioxide
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Carbon Cycle?
Respiration, combustion and decay of plants and animals add carbon dioxide to the air and removes oxygen. Photosynthesis removes carbon dioxide and adds oxygen.
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How have humans affected the composition of air?
More people are respiring, giving out more carbon dioxide.Increased energy consumption from burning of fossil fuels, releases more carbon dioxide. More deforestation-less photosynthesis so less carbon dioxide removed
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What do fossil fuels release when burnt?
Carbon dioxide. Sulfur dioxide. Nitrogen oxide. When these gases mix they fall as acid rain.
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What does acid rain damage?
Causes lakes to be acidic and many plants and animals die. It kills trees and damages limestone buildings and ruins stone statues. Makes metals corrode
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What is photochemical smog?
Photochemical smog is a type of air pollution caused by sunlight acting on oxides of nitrogen. These oxides combine with oxygen to produce ozone. Causes breathing difficulties, headaches and tiredness
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When is carbon monoxide produced?
When petrol is burnt without enough oxygen-incomplete combustion. Prevents blood from carrying oxygen- leads to fainting, a coma or death
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Why is it important to control atmospheric pollution?
Because of the effects it has on people's health, the natural environment and the built environment
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How do catalytic converters on vehicles reduce the amount of carbon monoxide and nitrogen oxide in atmosphere?
A reaction between carbon monoxide and nitric oxide takes place on surface of catalyst. the two gases formed are natural components of air- nitrogen and carbon dioxide
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Other cards in this set
Card 2
Front
What happens when you shake oil and water with an emulsifier?
Back
The oil forms droplets, surrounded by a coat of emulsifier, with the hydrophilic head facing outwards
Card 3
Front
Why do foods have to be cooked?
Back
Card 4
Front
Why do protein molecules change shape when you heat them?
Back
Card 5
Front
What is the chemical reaction that takes place in potatoes?
Back
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