Flashcards
AQA Chemistry GCSE - Unit 2a - Oils, Earth and Atmosphere
Cards in this deck (33)
- 1what are the conditions needed for cracking?long chain hydrocarbons are heated and vaporised
passed over powdered catalyst (aluminium oxide)
temperature are 400°C to 700°C
the long chain molecules split apart on the surface of the catalyst - 2what are alkenes?hydrocarbon chains
double bond between two carbons
unsaturated - the double bonds can open up and create two more bonds
CnH2n - 3how do you test for alkenes?add the substance to bromine water
alkene will decolourise the bromine water, orange to colourless
this is because it opens up the double bond - 4how can ethene create ethanol?react ethene with steam in the presence of a catalyst to create ethanol
- 5what are the pros and cons of creating ethanol from ethene?pros = ethene is cheap/ little waste
cons = ethene is produced from crude oil which is a non-renewable resource/ this will eventually make ethanol very expensive - 6how can ethanol be made from a renewable resource?fermenting sugar creates ethanol
sugar is dissolved
then reacted with yeast
allowed to respire anaerobically - 7what are the pros and cons of creating ethanol from a renewable resource?pros = lower temperature needed/ simpler equipment/ renewable - sugar crops grown everywhere/ used as easy alternative to petrol
cons = needs to be distilled to concentrate it/ needs to be purified/ increases food prices - less land - 8how can alkenes become polymers and what are the conditions needed?polymerisation - many short chain monomers joined to create a long chain polymer - needs a catalysts
the physical properties depend on the temperature and pressures used - 9what are the uses of polymers?low density poly(ethene) used for plastic bags
elastic polymer fibres used for tights
waterproof coatings
dental polymers in resin tooth fillings
corn-starch can be added to polymers to make them bio-degradable - 10what are the issues with polymers?they are not generally bio-degradable - don't rot
most are buried in landfill
as crude oil is used up, the price of crude oil will rise - we will have to eventually chose between plastics and fuel - 11how can plant oils be extracted?water is vaporised beneath the plant
as the steam rises, it takes the natural oils with it
it passes through a tube where is cools and condenses
the oils don't mix with the water and float on top and are therefore tapped off - 12what advantages do vegetable oils have?high energy content - we get lots of energy from eating it
lots of nutrients - fatty acids
higher boiling point - cook food faster
the flavours are soluble in the oil and the oil therefore carries the flavour and intensifies it - 13what are saturated oils?long chain molecules with lots of carbon atoms, with double bonds between some carbon atoms
- 14what does polyunsaturated mean? what does monounsaturated mean?polyunsaturated = contains more than one double carbon bond
monounsaturated = contains a single double carbon bond - 15how do you make an oil harder? what are the conditions needed?hydrogenation
reacting it with hydrogen in the presence of a nickel catalyst and 60°C - 16what are the advantages of hydrogenating an oil?gives it a longer shelf life
spreadable (like margarine) if partially hydrogenated
more useful in baking - 17what are the issues with oils and partially hydrogenated fats?partially hydrogenated fats lead to trans-fats which increase cholesterol
saturated fats increase the amount of cholesterol in the blood which blocks arteries and causes heart disease
cooking food in oil makes it more fattening - 18what is an alternative use for emulsions other than food?moisturising lotions - smooth texture makes it easy to rub into the skin
- 19how do emulsifiers work?the emulsifier has molecules with a head which is hydrophilic and a tail which is hydrophobic - the tail dissolves into the oil droplets and the head dissolves into the water bonding the two. Heads repel each other to prevent the droplets from gathering
- 20what are the pros and cons of emulsifiers?pros = emulsions don't spread out and therefore have a long shelf life/ food can then be lower in fats but have the same texture
cons = many people have allergies to emulsifiers (e.g. egg) - 21what was Wegener's theory of Continental Drift? Why did he think this?there had once been a super continent (Pangea) that broke apart forming today's continents, and are still drifting
Africa and South America's coastlines appeared to fit together
the same fossils were found in different countries either side of the oceans - 22why was Wegener not believed?he believed that the continents were ploughing through the sea bed as a result of tidal waves and earth's rotation
he'd used inaccurate data which made his calculations far off
he wasn't a proper scientist - he studied astronomy - 23what is the structure of the earth?crust - rock - very thin (5km to 50km)
mantle - flowing solid - thicker
core - iron and nickel - thickest - 24what is the structure of the crust? how does the mantle affect the movement?the crust is made up of large plates that float on the mantle
radioactive processes in the mantle cause convection currents which cause movement - 25how do earthquakes occur?when a plate moves very suddenly this causes an earthquake
- 26why can't we predict earthquakes and volcanoes?plates move very suddenly - can't predict
very few clues - even then we won't know when they'll move, only that they will
there are plenty of false alarms of mini tremors and mini-eruptions (molten rock rises to the surface creating a bulge) - 27what was the first phase of the atmosphere?earth's surface was mainly molten as temperature were extremely high
volcanoes kept erupting giving off carbon dioxide, water vapour, methane and ammonia
as the earth cooled, the water vapour condensed forming oceans - 28what was the second phase of the atmosphere?green plants and algae grew and used carbon dioxide in photosynthesis
oceans absorbed the carbon dioxide
carbon dioxide was locked up within sedimentary rocks and fossil fuels - 29how did carbon dioxide become locked up in rocks and fossil fuels?plants and basic marine organisms died and fell in layers, where they were compressed and formed sedimentary rock and fossil fuels, trapping the carbon and hydrocarbons inside the plants and animals - causing them to be 'locked up'
- 30what was the third phase of the atmosphere?build up of oxygen killed of organisms which couldn't tolerate oxygen, but more complex organisms evolved
oxygen created the ozone layer which blocks the sun's harmful rays and enabled more complex organisms to evolve (us) - 31what is the theory of primordial soup?that the earth's atmosphere was originally made up of nitrogen, hydrogen, ammonia and methane
lightening struck causing chemical reactions to occur including the creation of amino acids
amino acids -> organic matter -> organisms - 32how can we fractionally distil air?air is filtered to remove dust
cooled to -200°C to create a liquid
water vapour condenses and is removed
carbon dioxide freezes and is removed
left over air is heated slowly in the column
oxygen and argon come out together so the process is repeated for them - 33what impact does carbon dioxide levels have on the environment?increase in carbon dioxide leads to global warming
oceans naturally store carbon dioxide however lots of carbon dioxide makes them acidic killing organisms and plants - also, in the future they won't be able to absorb any more
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- Questions from Unit 1b of GCSE AQA Chemistry.
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