2908998
Description
Flashcards by RosettaStoneDecoded, updated more than 1 year ago
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Created by RosettaStoneDecoded
over 9 years ago
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| Question | Answer |
| what 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 |
| what are alkenes? | hydrocarbon chains double bond between two carbons unsaturated - the double bonds can open up and create two more bonds CnH2n |
| how 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 |
| how can ethene create ethanol? | react ethene with steam in the presence of a catalyst to create ethanol |
| what 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 |
| how can ethanol be made from a renewable resource? | fermenting sugar creates ethanol sugar is dissolved then reacted with yeast allowed to respire anaerobically |
| what 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 |
| how 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 |
| what 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 |
| what 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 |
| how 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 |
| what 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 |
| what are saturated oils? | long chain molecules with lots of carbon atoms, with double bonds between some carbon atoms |
| what does polyunsaturated mean? what does monounsaturated mean? | polyunsaturated = contains more than one double carbon bond monounsaturated = contains a single double carbon bond |
| how 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 |
| what are the advantages of hydrogenating an oil? | gives it a longer shelf life spreadable (like margarine) if partially hydrogenated more useful in baking |
| what 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 |
| what is an alternative use for emulsions other than food? | moisturising lotions - smooth texture makes it easy to rub into the skin |
| how 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 |
| what 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) |
| what 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 |
| why 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 |
| what is the structure of the earth? | crust - rock - very thin (5km to 50km) mantle - flowing solid - thicker core - iron and nickel - thickest |
| what 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 |
| how do earthquakes occur? | when a plate moves very suddenly this causes an earthquake |
| why 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) |
| what 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 |
| what 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 |
| how 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' |
| what 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) |
| what 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 |
| how 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 |
| what 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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