M1. (a) both bars correct height (to better than half a square) 1 mark for both

Transcription

1 Chemistry C Higher Mark Scheme M. (a) both bars correct height (to better than half a square) mark for both both bars correctly labelled (w.r.t. relative heights if these incorrect) for mark a lot less / much less / 8 times less (converse must specify coal) gains mark (c) ideas that at high temperatures (produced when fuels burn) nitrogen and oxygen from air / atmosphere combine / react or nitrogen from air / atmosphere oxidises for mark each (d) ideas that coal produces most carbon dioxide / more CO than gas / oil because coal is (mostly) carbon gas produces less carbon dioxide than coal / oil oil and gas also contain hydrogen / contain more hydrogen atoms than carbon atoms / also produce water any three for mark each 3 (e) sulphur for mark [9] Page

2 M. (a) (i) H + O H O *both circled correct for mark A + O A O 3 all circled correct for mark idea that: must end up with the same number of atoms as at the start any each otherwise matter is shown to be lost/gained for mark won t show correct amount of each element/compound [4] ## (a) Compound A has fewer C atoms or Compound B has fewer H atoms Compound A has C = C/double bond or Compound A is unsaturated each for mark (accept converse i.e compound B has not...) Compound A is reactive or can be used to make many substances or can be used in polymerisation/making plastics/named plastic or can be used as a fuel any one for mark [3] M4. (a) nitrogen and oxygen both required either order Page

3 (i) any two from (atmosphere) is now cooler water vapour has condensed to form sea(s) / ocean(s) any two from has dissolved in / reacted with seawater has formed carbonates (evolution of green) plants removed by photosynthesis has formed fossil fuels (c) (i) 5 accept any date in the Triassic period 5 9 (mya) do not credit 90 (mya) on different (tectonic) plates or answer refers to African and South American plates (movement) due to convection currents in the mantle due to energy / heat from the core or due to radioactivity [9] M5. (a) (i) convection (currents) accept (currents) which move the plates less dense (molten) rock / magma rises / moves up Page 3

4 or more dense (molten) rock / magma falls / moves down heat (is transferred / conducted) to the mantle / crust (resulting from natural) radioactive processes (in the core) or radioactivity accept radiation provided there is no contradiction as in, for example, radiation from the Sun or fission do not credit fusion any two from (formation of fold) mountains or deformation(s) hot springs do not credit just springs (oceanic) ridges (oceanic) trench(es) rift(s) seismic waves subduction or recycling of rocks tsunami(s) do not credit tidal waves volcano(es) or volcanic activity / sill(s) dyke(s) lava flow(s) [6] M6. (a) C=C do not accept C H 4 four Hs only, two attached to each carbon Page 4

5 credit CH CH for two marks C 3H 8 + 5O 3CO + 4H O two correct formulae LHS can be in either order two correct formulae RHS can be in either order correctly balanced, consequential marking allowed for 0 O [5] ## (a) either any two points () each from * (surface) below 00 C (the surface) below the boiling point of water * (allowed the) condensation (of water vapour) accept (rate of) condensation greater than (the rate of) evaporation * from the atmosphere accept from the air or condensed water (vapour) () was pulled by gravity into depressions () or idea of impervious sea bed or from comets (which crashed on the Earth) () ice (from these) melted () any two processes () each from * dissolving in (sea) water * (taken in during) photosynthesis accept taken in by algae or plants Page 5

6 formation of carbonate(s) or calcium carbonate or chalk or calcite accept formation of shells or bones or corals [4] M8. (a) (i) do not credit CH 3CH 3 do not credit C H 4 (iii) burn or react with oxygen or combustion or oxidation accept react with chlorine (iv) bubble each gas through (test tube containing) bromine water accept add bromine (water to gas collected) or burn ethene decolourises it or turns the brown colourless accept ethene burns with smoky flame Page 6

7 do not accept makes it go clear ethane does not affect it or leaves it brown accept ethane burns with clear flame note carefully the spelling of ethene and ethane both the correct name and use are required for the mark poly (ethene) or polythene; any soft or pliable plastic article or any suitable harder plastic item accept polyethene or polyethylene [7] M9. (a) hydrocarbon thermal decomposition / cracking (c) (i) making polymers / poly(e)thene accept plastic (bags) fuel [4] M0. (a) any two mark each burning / combustion fossil fuels or (locked up) carbon accept fuel / named fuel Page 7

8 oxygen used any three from produces (calcium) carbonate which is insoluble produces (calcium) hydrogencarbonate which is soluble photosynthesis releases oxygen 3 [5] M. (a) (i) X and Y both needed (iii) Z X unsaturated / alkenes / those with double (C = C) bonds [4] M. (a) B because it contains more of the light fraction) Quantitative answer e.g. B has 30%, A has 0% / 0% more /.5 times more Page 8

9 (i) heat catalyst if neither mark gained allow cracking for mark [5] M3. (a) unreactive / near bottom of reactivity series (c) carbon more reactive / higher up reactivity series very reactive / near top of reactivity series cannot use displacement methods / can only be extracted by electrolysis / had to wait discovery of electricity [4] M4. (a) any three from carbon (atom) spine / chain accept idea of backbone of carbon (atoms) surrounded by hydrogen (atoms) accept idea of only bonded to hydrogen (atoms) 3 Page 9

10 single (covalent) bonds between carbon atoms accept no double bonds saturated (hydrocarbons) (general formula) C nh n+ many small molecules/ monomers accept many unsaturated molecules or alkenes join together to form a large / long molecule / polymer [5] M5.(a) (i) bonds / pair of electrons / shared electrons for one mark saturated since it has single bonds / no double bonds / no multiple bonds / maximum number of atoms attached for one mark (iii) sensible answer (e.g. it is harmful) or better solvent could be used on expanded polystyrene or foam for one mark (i) simply writing monomers form / react to form polymers gains no mark monomers join / bond / combine / link to form polymers = mark the mark is for the idea of joining to gain the second mark the idea of the relative size of monomer and polymer is required small molecules join to form a polymer ( marks) many monomers join to form a polymer ( marks) monomers join to form a large molecule / long chain ( marks) many molecules join together ( marks) Page 0

11 for mark each polyethene / poly(ethene) / polythene don t worry too much about the exact positioning of the C6H5 at the end of the bond placement of linking bonds inside / outside brackets is not important must have n for mark each [8] M6. (a) (i) burning / breathing / respiration / fuels / food for mark each. rock is heated / subducted (owtte) / close to magma / melted. rock is decomposed / carbon dioxide released through volcanoes for mark each carbon dioxide reacts / dissolves in sea-water / dissolves in rain water insoluble carbonates / calcium carbonate are / is formed carbon dioxide turned into shells / coral / limestone / chalk / sediments also soluble hydrogencarbonates (calcium / magnesium) are formed photosynthesis by plants any three for mark each 3 Page

12 (c) (i) sea unable to absorb all the extra carbon dioxide being produced more trees being cut down / deforestation increased burning of fuels / more cars / more industry (not more people) any one for mark global warming / greenhouse effect or effects such as melting ice caps / rising sea levels / climatic change / more deserts (not changes to ozone layer) for one mark [9] M7. (i) (hot air) gives faster reaction makes coal burn faster (provides air / oxygen to help to) allow the coal to burn / helps combustion flushes out the waste / gases / carbon dioxide any one for mark decomposition of limestone yields carbon dioxide (owtte) the combustion / burning of coal produces carbon dioxide (owtte) each for mark [3] M8. (a) hydrogen and carbon for mark (i) the oil is evaporated / boiled / liquid converted to gas / vaporised oil is condensed/changed back to liquid/cooled below boiling point (not just cooled) Page

13 liquids of different boiling points condense at different levels / fractions with lower boiling points form near the top / boiling point linked to chain length or Mr each for mark 3 Assume they mean naphtha unless they say otherwise. smaller molecules /contains less atoms /lower boiling point /more volatile /less bonds to break /lower activation energy If the answer is given the opposite way around then diesel must be specified. any one for mark (iii) correct number of atoms = correct number of bonds (attached to correct atoms) = Accept diagrams which show electrons correctly. CH 3CH CH CH CH CH CH 3 = for marks [7] M9. (a) calcium carbon oxygen correct for mark 3 correct for marks Page 3

14 cement glass each for mark (c) (i) allows coal to bum / flushes out CO for mark produced by burning coal produced by decomposition of limestone each for mark (d) (i) calcium oxide + water calcium hydroxide or quicklime + water slaked lime for mark (allow composite equation from these two) to neutralise it / because it is alkaline or basic for mark [9] M0. (a) (fractional) distillation/fractionation for mark (i) cracking/decomposition for mark polymerisation/addition reaction for mark Page 4

15 (c) (Must have H atoms) for mark (d) contains only/all single bonds no double bonds contains maximum number of H atoms carbon atoms bonded to 4 other atoms (not 4 H atoms) will not undergo addition reactions any for mark (e) (n must be on (right)) = marks = marks (n on left = mark) = mark = mark Page 5

16 (Double bond loses both marks) = 0 marks OR = marks (for both a minimum of 4 carbon atoms) = mark = marks = mark = mark [7] M. (a) amount of CO (much) lower amount of O (much) higher amount of N (much) higher (owtte.) less other gases/less NH 3/less CH 4 Page 6

17 any for marks 4 points from: plants (evolved)/photosynthesis/algae take in CO give out O water vapour condensed ozone formed from oxygen less CO is produced now from volcanic activity CO from air trapped in sedimentary rocks or fossil fuels nitrogen produced by bacteria/living organisms/microbes/decay of dead organisms (not nitrifying bacteria, nitrogen fixing 4 bacteria) nitrogen produced by reaction of NH 3 with O /decomposition of NH 3 nitrogen builds up because it is unreactive (Assume answer refers to today s atmosphere) any 4 for mark each 4 [6] M. (a) the more C atoms the higher the b.pt./temperature Allow just higher. Not answer based on melting point for mark (fractional) distillation/fractionation for mark (c) must include H atoms and lines not CH 3 CH 3 for mark Page 7 [3]

18 M3. (a) C H 4 H H H H C C C H H H H Accept even if in wrong columns (c) (i) polythene or poly(ethene) addition [4] M4. (a) (i) convection currents in the mantle () driven by heat () from radioactive processes () 3 plates moving apart magma rises to fill gap forms new rock each for mark 3 Rock further from ridge is older more time for sediment to settle each for mark [8] Page 8

19 M5. (a) 95% ( mark for working) Much less carbon dioxide Much more nitrogen (c) Plants take up CO plants give out oxygen when they die trap CO in rocks and fossil fuels methane and ammonia reacted with oxygen nitrogen gas produced by reaction of oxygen and ammonia and by denitryfying bacteria formation of ozone layer any 4 for mark each 4 [8] M6. (a) A compound made from carbon and hydrogen (not mixture etc.) C 5H (e) (i) Break down by heat (iii) Speeds up reaction C 8H 6 each for mark 4 [6] Page 9

20 M7. (a) (i) heat accept increase temperature ignore pressure with a catalyst accept displayed formulae only (iii) O CO + H O ignore state symbols correct balancing accept only if reactants and products correct double bond breaks many (ethene) molecules accept many monomers bond together accept join or combine for bond Page 0

21 accept for first marks ignore unsaturated becomes saturated [0] M8. (a) mixture not compound of a metal with other element(s) / metals not of elements not of a metal with other substances steel allow stainless steel (c) stronger / increased strength / harder / less malleable / less brittle not corrosion / rusting (d) copper and zinc [5] M9. (a) fractional distillation Page

22 boiling point or use (i) mixture: compounds or elements or substances together but not chemically combined ignore references to separation compound: (different) elements or different atoms together and chemically combined ignore references to separation element: contains only one type of atom accept made of atoms which contain the same number of protons compound: contains different types of atom chemically combined chemically combined not needed here if already stated in (i) [6] M30. (a) (i) C 4H 0 + Cl C 4H 9Cl + HCl reactants products ignore incorrect balancing no state symbols required substitution / chlorination Page

23 H atoms not necessary (c) [6] M3. (a) (i) by heating pressure is neutral using a catalyst/pot/ceramic/porcelain/aluminium oxide use bromine water/(alkaline) permanganate accept bromine alkene makes bromine go colourless or lose its colour accept alkane does not change the red/orange colour of bromine not change colour/goes clear (i) either of these must show bonds at end Page 3

24 or not H on ends allow 3 instead of n not any other number poly(ethene) brackets not essential accept polythene (iii) large amount of waste polymer/poly(ethene)/polythene/litter accept large amount of crude oil or finite resource used it is not biodegradable accept it does not decompose/decay/break down it causes pollution/it creates toxic fumes when burnt are neutral not it is not recyclable [8] M3. heat released from (natural) radioactive decay causes convection (currents) in the mantle / underneath the crust do not accept in the magma [] Page 4

25 M33. (a) Quality of written communication for any two ideas sensibly stated any three from: plants take in (CO ) accept photosynthesis uses (CO ) converted to glucose / starch / carbohydrates ignore carbon compounds by itself CO locked up in fossil fuels accept coal / oil / natural gas / methane for fossil fuels CO reacts with / dissolves (sea)water accept ocean removes CO producing hydrogencarbonates accept carbonic acid producing carbonates accept named carbonates marine animals use carbonates to make shells do not accept bones forms sedimentary rocks accept limestone / chalk accept marble do not accept sediments alone 3 any two from: burning of fossil fuels or cars / industry / air travel / power stations ignore increase in population ignore more use of electricity natural processes cannot absorb all the extra CO deforestation accept less photosynthesis ignore volcanic activity accept burn trees Page 5 [6]

26 M34. (a) (i) heat (the limestone) accept decompose limestone accept heat with coke add water / slake dependent on st mark unless they say add water to the calcium oxide magnesium hydroxide + hydrochloric acid magnesium chloride + water / H O mark for each side of the equation (if a symbol equation is given then give mark for correct formulae (all) and mark for balancing) [4] M35. (a) (i) heat (the limestone) accept decompose limestone accept heat with coke add water / slake dependent on st mark unless they say add water to the calcium oxide magnesium hydroxide + hydrochloric acid magnesium chloride + water / H O mark for each side of the equation (if a symbol equation is given then give mark for correct formulae (all) and mark for balancing) [4] Page 6

27 Page 7