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Revision OCR C1

Chemistry Revision65

Why should carbon dioxide and methane be prevented from entering the atmosphere? They are greenhouse gases that cause global warming and can cause the polar ice caps to melt and sea levels rise.
What are the main gases that cause global warming? co2 and methane
How is a polymer made? Many monomers join together to form a long chain. The double bonds are broken in the monomer units and addition polymerisation takes place.
What are the conditions needed for polymerisation? High pressure and a catalyst
What do all monomers have? A double bond
What polymer is made from ethene molecules? Polyethene
What is the difference between an alkene and an alkane? Alkene contains a double bond - it is unsaturated. Alkanes are saturated (no double bond)
How can you test for an alkene? Use bromine water
What happens to bromine water in the presence of an alkene? The orange bromine water becomes colourless
What happens to bromine water in the presence of an alkane? The orange bromine water stays orange
What does the bromine water do to the alkene? It breaks the double bond and forms a dibromo alkane
What are the usefufproperties of-polystyrene? Light weight, absorbs shock and insulates
What are the useful properties of polypropene? Strong and flexible
What is Goretex? A material made from nylon and PTFE.
What are the special properties of Goretex? It is waterproof, breathable and windproof
Why does Goretex let sweat out but not rain in? The sweat particles are small enough to fit through the material but water particles are too big.
Name 2 uses of polymers in healthcare. Plasters, contact lenses and fillings.
How do the intermolecular bonds between the polymer chains affect the properties? Weak bonds means that the polymer will stretch and stronger bonds means that the polymer will be rigid.
What are the properties of a shape memory polymer? . When they are heated or cooled, they return to their original shape when have been deformed.
What are the advantages of recycling polymers? less fuels used, less energy used, reduced carbon dioxide emissions, less landfill sites used.
What changes happen when food is cooked? Texture improved, taste improved, microbes killed.
What happens to proteins when they are cooked? The protein molecules become denatured.
What happens to potatoes when they are cooked? The cell walls are broken and the potato softens. The starch grains burst and make the potato easier to digest.
Why is baking powder used in cooking? To make cakes rise.
What is an emulsifier? An additive that is used to stop two components like oil and water separating - it holds them together.
How does an emulsifier work? It has a hydrophilic head and hydrophobic tail. The hydrophilic end is attracted to the water and the hydrophobic end bonds to the oil .
How do smells reach our noses? The molecules diffuse and sensors on the inside of your nose pick it up and send a message to your brain. .
Why is it important that a perfume evaporates easily? So that it reaches our noses
Why is it important that a perfume is non-toxic? So that it doesn't poison us
Why is it important that a perfume does not react with water? So that it does not react with our sweat
Why is it important that a perfume is insoluble in water? So that it is not easily washed off
What is the equation for making an ester? Alcohol + acid >>> ester + water
What does volatile mean? Something that evaporates easily.
Why are some substances volatile? Because they have weak attractions between the molecules and they are easily overcome
What does soluble mean? A substance that dissolves in a liquid
What is a solute? The substance dissolved in a solution.
Why does water not dissolve nail varnish? The forces of attraction between the nail varnish and·water molecules is weaker than the forces of attraction between 2 nail varnish molecules and two water molecules.
What 3 substances does paint contain? Binding agent, solvent and pigment
What does the solvent do? It thins the paint making it easier to spread.
What does the binding agent do? It sticks the pigment to the surface
What happens when paint dries? The solvent evaporates and the colloid reacts with oxygen in the air
What is the solvent in emulsion paint? Water
What is a colloid? A mixture of tiny particles suspended in a liquid - they are too small to settle out.
What are thermochromic paints? Paints that change colour with changing temperature.
What are phosphorescent paints? Paints that absorb energy and re-emit the energy as light over a Iong period.
Why are radioactive paints dangerous? They can cause cancer.
What are the advantages of using animals to test cosmetics? Safe for human use, do not cause life threatening illnesses
What are the disadvantages of using animals to test cosmetics? Animals are harmed, we don't need any more cosmetics, natural substances could be used, animals may not react in the same way as humans
What is a hydrocarbon? A chemical containing only carbon and hydrogen atoms
What is an alkane? A hydrocarbon where all the carbon atoms are saturated with hydrogen
What is an alkene? A hydrocarbon that contains double bonds
What is crude oil made up of? Many different sized hydrocarbons
How can the hydrocarbons be separated? Using fractional distillation
How does fractional distillation separate a mixture of hydrocarbons? The crude oil is heated and changes to a vapour. The hydrocarbons have different size molecules and so cool and condense at different temperatures/boiling points
What are the forces between molecules called? Intermolecular forces
What is the relationship between the size of the hydrocarbon and the boiling point? The bigger the molecule the greater the intermolecular forces and so the higher the boiling point. More energy is needed to break the bigger bonds.
Why is the market demand for smaller hydrocarbons higher than the demand for larger hydrocarbons? The smaller ones are easier to burn
What is cracking? Breaking down large hydrocarbons into smaller more useful hydrocarbon molecules.
How is cracking carried out? The hydrocarbon is heated and passed over a catalyst
Why is cracking used? Because the smaller hydrocarbons have a higher demand but lower supply and are more useful.
How else can the oil industry overcome the problem of high demand or small hydrocarbons? Use different crude oils, develop alternative fuels, develop ways to use the bigger hydrocarbons
What are the environmental issues associated with crude oil? Oil slicks can harm birds, pollute beaches and destroy habitats
What are the political issues associated with crude oil? The UK is dependent on oil and gas from politically unstable countries. Prices can be set high and cause issues.
What characteristics are considered when choosing a fuel? Energy value, availability, storage, toxicity, cost, ease of use, pollution caused
What is the equation for complete combustion? Methane + oxygen >>> carbon dioxide + water CH4 + 2O2 >>> CO2 + 2H2O
What is produced when there is incomplete combustion? Carbon monoxide and soot (carbon)
What colour flame is produced with complete combustion? Blue
What colour flame is produced with incomplete combustion? Yellow
Which produces the most energy - complete or incomplete combustion? Complete combustion
What are the advantages of complete combustion? Less soot, more heat, no toxic carbon monoxide produced
What is today's air a mixture of? Nitrogen, oxygen, carbon dioxide, water vapour and noble gases
What affects the levels of these gases? Combustion, respiration, photosynthesis
What are the 2 main gases in today's atmosphere? Nitrogen (78%) and oxygen (21%)
What were the main gases in the atmosphere billions of years ago? Carbon dioxide and ammonia
How was this early atmosphere formed? Gases from volcanoes produced CO2 and water
What happened to the ammonia? Formed nitrogen by reacting with rocks.
How did the nitrogen levels increase? Because of the lack of reactivity of nitrogen
Where did most of the CO2 go? Dissolved into the oceans and removed by photosynthesis of early plants and bacteria
What has caused the changes in the levels of carbon dioxide? Carbon dioxide has decreased because it is used by plants during photosynthesis, and some has been locked up inside rocks and fossil fuels some has also dissolved in the ocean
What has caused the changes in the levels of oxygen? Oxygen has increased because it is released by plants during photosynthesis
What is the word equation for respiration? Glucose + oxygen >>> water + carbon dioxide
What is the word equation for photosynthesis? Opposite of RESPIRATION.
Why have the levels of carbon dioxide increased over the past 2 centuries? Deforestation, increased population causing increased energy usage (more cars/more factories)
What is the problem with carbon monoxide gas? It is toxic and combines with red blood cells to stop oxygen being carried around the body. It can cause death.
What gases cause acid rain? Sulphur dioxide (SO2) and nitrous oxides (NOx)
What are the main causes of these gases? SO2 - burning fossil fuels (cars/factories/power stations). NOx- from car exhausts.
How can they be reduced? Using filters in factories and using catalytic converters in cars
What are the problems with nitrous oxides? They cause smog and acid rain
How do cars now control the amount of carbon monoxide and nitrous oxides? They are fitted with a catalytic converter.
What reaction takes place in a catalytic converter? Carbon monoxide + nitrogen monoxide >>> nitrogen + carbon dioxide 2CO + 2NO ~ N2 + 2CO2
What conditions ensure that this reaction takes place? High temperature in the engine and a catalyst
Why does biodiesel contribute less to global warming than fossil fuels? The plants use the carbon dioxide from the air in photosynthesis and release carbon dioxide so they are carbon neutral. Fossil fuels release new carbon dioxide and doesn't absorb any new carbon dioxide so is not carbon neutral
Created by: haifisch99