NOVEMBER 2001 INTERNATIONAL GCSE - Weebly9dwebsite.weebly.com/uploads/3/0/7/8/3078174/chem_paper_2_ms.pdf · november 2001 international gcse mark scheme maximum mark : 80 syllabus/component

NOVEMBER 2001

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK : 80

SYLLABUS/COMPONENT : 0620/2

CHEMISTRY(CORE)

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Page 1 of 4 Mark Scheme Syllabus PaperIGCSE Examinations – November 2001 0620 2

1 (a) Any two properties e.g. high melting point / boiling point / form coloured compounds / formcomplex ions / variable valency / hard / dense / (good) catalysts [2]IGNORE (elements) are coloured

(b) (i) Universal / full range indicator paper / solution;NOT: pH paper

indication of a (correct) colour change [2]colour change without first point / universal indicator = 0NOT: using pH meter / pH probeNOT: litmus or its colour change

(ii) pH6 [1]

(iii) charged atom (or group of atoms) / charged particle [1]ALLOW: atom with more / less electronsNOT: element in its oxidised stateNOT: charge on elementNOT: imbalance in charge

(iv) 2 [1]

(c) magnesium, zinc, iron, nickel [1]

(d) add sodium hydroxide / aqueous ammonia;white precipitate;soluble in excess [3]

[Total 11]

2 (a) C [1]

(b) B [1]

(c) D [1]

(d) (i) D [1]

(ii) irregularly arranged / no fixed pattern / randomly arranged / scattered;IGNORE: far apart, etc

moving randomly / rapidly / freely [2]

(e) two or more (different) elements / atoms chemically combined / bonded (both different [2]atoms + ‘bonded’ or equivalent needed for 2 marks molecules formed by more than 1 type of atom bonded = 1any reference to mixture = 0

(f) (i) sodium loses electron(s) (from outer shell);chlorine gains electron(s) (in outer shell);one electron gained by Cl / lost by sodium;complete electron shells formed / 8 electrons in both ions OWTTE; [4]an electron transfers from Na to Cl = 3

(ii) 58.5 (2 marks)1 mark for correct extraction of data but incorrect answer [2]IGNORE: units

[Total 14]

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3 (a) 5 [1]

(b) atomic / proton number [1]

(c) 6 [1]

(d) any element up to and including group 5 in this period:ALLOW symbols [1]

(e) (i) 2 atoms (in molecule); [1]

several / a few / atoms / small clusters of atoms covalently bonded [2](both a few atoms and covalent bonding needed for 2)several / a few atoms / small clusters of atoms bonded = 1no mention of bonding = 0

(ii) 2 (Cl2) [1][Total 8]

4 (a) carbon dioxide [1]

(b) catalyst / definition of catalyst;from living organism / biological substance / protein [2]NOT: natural substance / organic / an organism

(c) distillation / distilling;

some idea about process of distillation e.g. using a condenser / boiling andcondensing;NOT: heating and cooling

idea of one liquid coming off / condensing / evaporating first / more readily ORimplication of different boiling points [3]

(d) correct displayed or graphical formula for ethanol including O-H bond [1]

(e) (i) addition [1]

(ii) speed up rate of reaction [1]NOT: alters rate of reaction

(iii) ethene [1]

(iv) 100ºC [2]100 / 100º = 1 mark< or > 100ºC = 0incorrect units = 0

(f) fuel / solvent / cleaning fluid / in (alcoholic) drinks / for making named organicsubstance (e.g. esters / carboxylic acids) / sterilizing agent / any other suitable use [1]

(g) carbon dioxide; water [2][Total 15]

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5 (a) element + contains only one sort of atom (BOTH NEEDED) [1]ALLOW: contains only carbonNOT: contains carbon

(b) covalent [1]

(c) (i) 25 [1]

(ii) C13H10N2 [1]

(iii) 14 [1]

(d) diamond;use of diamond e.g. cutting / drilling tools / jewellery;

graphite;use of graphite e.g. pencil leads / lubricant / tennis racquets / golf clubs / as anelectrode, etc [4]

(e) (i) carbon monoxide [1]

(ii) CO [1][Total 11]

6 (a) oxidised; reduced [2]

(b) (i) fizzing / bubbles / effervescence / iron dissolves / mixture gets warm / green solutionformed [1]NOT: gas given off

(ii) word filter or filtration needed somewhere (can be as filter funnel);

diagram of apparatus with filter funnel and filter paper (or stated in words);

aluminium oxide on filter paper;NOT: residue

some indication that iron chloride solution goes through filter paper [4]NOT: filtrate

(c) exothermic [1]

(d) welding / cutting metals [1]NOT: to melt things

[Total 9]

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7 (a) 2.8% [1]

(b) evaporate some of the water [1]NOT: heat the water

(c) decreases [1]

(d) anode / positive (electrode) / carbon (electrode) / graphite (electrode) [1]

(e) conducts electricity [1]NOT: inert

(f) is a liquid [1]

(g) sodium hydroxide; hydrogen [2]

(h) 1950-1960 [1]

(i) (i) addition; polymerisation [2]

(ii) does not conduct electricity / non-conductor [1][Total 12]

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June 2003

INTERNATIONAL GCSE

MARKING SCHEME

MAXIMUM MARK: 80

SYLLABUS/COMPONENT: 0620/02

CHEMISTRY

(Core Paper 2)

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Page 1 Mark Scheme Syllabus Paper

IGCSE EXAMINATIONS – June 2003 0620 2

© University of Cambridge Local Examinations Syndicate 2003

1 (a) (i) Fe/Cu ALLOW Zn [1](ii) C/N/S/F/Cl/Br [1](iii) O/S [1](iv) C [1](v) Li/Na/K ALLOW F [1](vi) CU/Zn/Br/Kr [1]

(b) argon - light bulbs;chlorine - kills bacteria;carbon - as lubricant;helium - in balloons [4]

(c) (i) covalent [1](ii) BrF5 ALLOW F5Br [1](iii) ions/charged particles;

NOT: particlesnot free to move in solid/free to move in molten/liquid state [2]

2 (a) drop small tube in acid/loosen string/idea of mixing zinc and acid/let go ofcottonALLOW: cut the string [1]NOT: heat (the acid)NOT: pull the string

(b) (i) correct plotting including 0-0 point ( �1 per omission or error) [2](ii) best curve drawn and to go through origin [1](iii) no more gas produced/reaction finished;

all zinc reacted/used up [2]

(c) graph drawn with faster initial rate and starting at 0-0;ALLOW: straight line as initial rateends up at 55 cm3 [2]

(d) (i) 2 (HCl) [1](ii) zinc chloride [1](iii) 136 [1]

IGNORE units

(e) substance containing only one type of atom/substance which cannot be brokendown to any other substance by chemical means [1]NOT ‘can’t be split’ aloneNOT is a pure substance

3 (a) (i) evaporation/vaporisation/boiling [1](ii) freezing/solidification [1]

NOT: fusion(iii) condensing/condensation/liquefaction [1]

(b) 2nd box ticked [1]

(c) A;energy needed to overcome forces between molecules/idea of energy input/taking in heat [2]

(d) (i) chlorine [1](ii) bromine [1](iii) sodium chloride [1]

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(e) (i) diffusion [1]NOT: Brownian motion

(ii) ammonium chloride [1]NOT: ammonia chloride

(iii) ammonia diffuses or moves faster/HCl diffuses or moves slower/ammonia haslower mass/HCl higher mass/molecules of HCl and ammonia move at differentspeeds [1]NOT: ammonia evaporates faster/HCl evaporates more slowly

(f) neutralisation/acid base [1]NOT: exothermicNOT: addition

(g) (i) thermometer [1](ii) reference to the solid or melting point of the solid is needed for the mark.

boiling point of water too low to get solid to melt/boiling water cannot get to155°C [1]NOT: boiling point of water is only 100°C/boiling point of water too low.NOT: water boils off first

(iii) so that the liquid is the same temperature throughout/no hot or cold spots/sothe tube is the same temperature as the thermometer/so heat can circulate inall places [1]ALLOW: so that temperature of liquid is balancedNOT: to keep temperature constant

4 (a) (i) breaking down of molecules substances using heat [1](ii) substance which speeds up a reaction [1]

NOT: alters/changes rate of reactionNOT: speeds up and slows down rate

(b) ethene/ethylene [1]NOT: formula

(c) (i) paraffin [1](ii) 4000g/4kg [1]

(correct unit needed)(iii) C2H4; H2 [2]

(d) (i) two units polymerised with continuation bonds at either end and hydrogenatoms drawn [1]ALLOW: �CH2CH2CH2CH2 �

ALLOW: � [ �CH2CH2 � ] � n

ALLOW: � [ �CH2 � ] � n

(ii) addition (polymerisation) [1]

5 (a) (sodium) hydroxide/ammonia; → green/grey green; [2]silver nitrate; → yellow; [2]ALLOW: lead nitrate NOT: creamALLOW: bubble chlorine → grey/black (precipitate)silver nitrate; → white: [2]barium chloride/nitrate; → white; [2]ALLOW: lead acetate

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(b) filtration/filtering or diagram of correct apparatus for filtration (filter paper mustbe present on diagram)NOT: decantingsodium chloride through filter paper/shown on diagram;NOT: filtrate through filter paperevaporate off water from sodium chloride/suitable diagram [3]ALLOW: distilling off water

(c) different atoms/elements(chemically) joined/bonded/combined (both points needed)(reference to mixtures = 0 unless qualified enough in time frame e.g. a mixtureof elements which are then chemically combined) [1]

(d) (i) chlorine/Cl2 [1](ii) sodium/Na [1]

6 (a) potassium/magnesium/aluminium [1]

(b) they did not have electricity/did not know about electrolysis/did not know themetal existed [1]NOT: did not have the right technology

(c) (i) indication that bubbles produced rapidly or quickly/slower than magnesium butfaster than zincOR number of bubbles produced intermediate between magnesium and zinc; [1]uranium dissolved slower than magnesium but faster than zinc/dissolves atmedium rate etc. [1]

(ii) atoms of same element with different mass number/different number ofneutrons/different nucleon number [1]NOT: compounds/molecules with different mass number

(iii) indication of use for energy – nuclear power stations/nuclear energy [1]ALLOW: atomic/nuclear bombsNOT: curing cancer/medical usesNOT: ‘for fuel’

(d) magnesium oxideALLOW: MgO [1]

(e) (i) idea of mixture of (different) metals [1](ii) alloys harder/stronger/decreased malleability/increased toughness/increased

corrosion resistance/heat or electrical resistance increased [1]NOT: increase in melting pointNOT: cheaperNOT: improving properties

(f) removes oxygen from zinc oxide [1]ALLOW: definition of reduction involving oxidation numbers/electron transfer

(g) (i) reversible reaction [1]ALLOW: equilibrium

(ii) 76-80% [1]

(h) (i) correct electronic structure of Mg (2.8.2) on diagram [1](ii) loses two electrons/loses its valence electrons = 2

forms Mg2+ ion = 1loses electron(s) = 1 [2]forms Mg2+ ion by losing electrons = 2

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June 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY

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Chemistry - June 2004 0620 02

© University of Cambridge International Examinations 2004

1 (a) B, C, F (all needed); [1] Only contain one type of atom [1] NOT: contain one kind of molecule NOT: cannot be split using chemical means (b) C [1] (c) (i) B [1] (ii) any gas with diatomic molecules e.g. chlorine, hydrogen, hydrogen chloride [1] (d) (i) F [1]

(ii) pencil ‘leads’/in pencils/lubricant/in electrical conductors/for electrodes/ in tennis racquets/in golf clubs/hockey sticks etc [1] (e) (i) substance containing 2 or more different atoms combined/bonded/joined (both parts needed for mark) [1] ALLOW: elements (chemically) combined (ii) methane [1] (f) (i) 8 electrons round chlorine and bonded pair with dot and cross = 2 [2] ALLOW: all dots or all crosses Correct number of electrons but bonded pair not clearly on overlap = 1 NOT: molecules other than hydrogen chloride (ii) covalent [1] (iii) blue litmus; [1] (litmus) turns red [1] (iv) pH2 [1] (v) 2 [1] (vi) magnesium chloride [1] NOT: formula Total = 17 2 (a) insoluble particles/solids/dirt trapped/caught on stones; [1] NOT: filter reacts with insoluble impurities NOT: impurities unqualified Water passes through/filtered OWTTE [1] (b) (i) kill bacteria/germs, disinfect water OWTTE [1] (ii) neutralises acidity/water [1] ALLOW: reacts with acids in water (iii) calcium hydroxide [1] NOT: formula (iv) neutralising acid soils/neutralising acidic (industrial) waste/making bleaching powder/removing acidic gases/in Solvay process/in recovery of ammonia/making limewater/in water softening/for making plaster/for making mortar/controlling soil acidity [1] NOT: neutralising acids unqualified NOT: making cement

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(c) (i) 100; [1] °C (conditional on 100) [1] (ii) anhydrous cobalt chloride/anhydrous copper sulphate (or correct colours); [1] NOT: cobalt chloride/copper sulphate unqualified Turns pink/blue (respectively) [1] (iii) any suitable e.g. washing/cleaning/drinking/cooking [1] (d) B [1] (e) ethanol [1] NOT: alcohol (f) potassium hydroxide; hydrogen [1] NOT: symbols Total = 15

3 (a) means of measuring gas volume e.g. gas syringe/measuring cylinder (must be graduated); [1] flask/test tube/vessel with calcium carbonate + acid leading to syringe etc IGNORE: lack of reference to closed system (unless drawing incorrect) [1]

record volume on gas syringe/measuring cylinder/measure how much carbon dioxide given off [1]

at various time intervals/at a particular time [1] OR flask/vessel with calcium carbonate and hydrochloric acid in flask (1) measure its mass at beginning of experiment (1) measure mass of flask and contents during reaction (1) at specific time(s) (1) (b) (i) faster/greater/speeds up [1] (ii) slower/less [1] (iii) faster/greater/speeds up [1] (c) (i) add aqueous sodium hydroxide; [1] white precipitate; [1] insoluble in excess [1] (incorrect reagent = 0) ALLOW: flame test - brick red (d) (i) high in the reactivity series/very reactive [1] (ii) 2 electrons in outer shell; [1] inner shells correct as 2.8.8 [1] Total = 13

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4 (a) ethanol - solvent ethene - polymer bitumen - roads [3] (b) ethanol [1] (c) (i) C [1] (ii) A [1] (iii) B [1] (iv) D [1] (d) (i) (compound) containing only carbon and hydrogen [1] NOT: it contains carbon and hydrogen (ii) has only single bonds/ has general formula CnH2n+2 [1] NOT: it is saturated Total = 10 5 (a) chlorine, argon, potassium, bromine, iodine [1] ALLOW: symbols (b) chlorine, potassium, argon, bromine, iodine [1] ALLOW: symbols (c) 2

nd box down ticked [1]

(d) chlorine, bromine, iodine (all 3 needed) [1] ALLOW: symbols (e) (i) potassium/K [1] (ii) argon/Ar [1] (f) 1

st and 4

th boxes ticked (1 mark each) [2]

(g) (i) high (boiling point) [1] (ii) conducts/is high [1] (h) potassium loses an/one electron/loses outer shell [1] chlorine gains an/one electron/outer shell becomes complete [1] ALLOW: (for 1 mark) potassium loses two electrons + chlorine gains two electrons ALLOW: e.g. 2.8.8.1 → 2.8.8 for first mark Any indication of sharing electrons = 0 Total = 12

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6 (a) carbon monoxide [1] (b) iron oxide loses oxygen/it loses oxygen/oxidation number of iron decreases [1] ALLOW: iron gains electrons Answer must refer to the iron/iron oxide - therefore: NOT: carbon monoxide gains oxygen NOT: oxygen lost in the reaction NOT: iron loses oxygen (c) 3; 2 (one mark each) [2] (d) (i) oxidise the impurities/oxidise Si or P or C/burn off the impurities [1] NOT: get rid of impurities NOT: slag formation (ii) exothermic [1] (iii) is/floats above the molten iron [1] (iv) calcium oxide [1] (v) stronger/harder/not brittle/less easily corroded ORA e.g. iron rusts [1] NOT: less corrosive (e) any 3 of: high melting/boiling points; have coloured compounds (NOT: they are coloured); have high densities; form complex ions; elements/compounds are good catalysts; form ions with different charges/variable oxidation states [3] (f) alloys [1]

Total = 13

Grand Total = 80

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November 2004

INTERNATIONAL GCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY (Core Theory)

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IGCSE – November 2004 0620 2


1 (a) increases; some comment that the trend is irregular/only approximate e.g. potassium (or sodium) do not follow the trend/boiling point of sodium high/boiling point of potassium too low [2] (b) allow 670-714oC (actual = 686oC) [1] (c) allow 0.260-0.300 (nm) (actual = 0.272 nm) [1] (d) slower (than sodium)/less rapid/gently etc. ALLOW: slow [1] (e) any three properties from: conduct (heat/electricity); malleable; ductile; shiny; sonorous ALLOW: solid at room temperature NOT: strong; high melting/boiling points; high density [3] (f) (i) sodium hydroxide [1] (ii) lighted splint: pops/explodes/squeaky sound [2] (2nd mark CONDITIONAL on 1st) (g) (i) proton(s) [1] (ii) isotope(s) [1] (iii) 3 [1] (iv) any suitable use e.g. radioactive tracer/cancer therapy/sterilising medical equipment [1] ALLOW: kills bacteria NOT: X-rays 2 (a) A + D [1] (b) C + E [1] (c) C5H10 [1] (d) correct formula for 1,2 – dibromoethane showing all atoms and bonds [1] ALLOW: correct dot and cross diagram

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(e) (i) 5 and 6 [1] (ii) respiration [1] (iii) decreases it/slows it ALLOW: ethane breaks down [1] NOT: stops it (iv) diffusion [1] (v) removes the ethene/blows the ethene away/reduces the amount of ethene OWTTE [1] ALLOW: dilutes ethene (vi) biological/protein/description of protein; NOT: an organism/a bacterium/natural catalyst catalyst/description of catalyst [2] (f) (i) chromatography [1] (ii) S [1] (iii) R + T [1] 3 (a) measuring cylinder ALLOW: burette/volumetric pipette [1] NOT: pipette; cylinder (b) so that all the (sulphuric) acid reacted/used up [1] NOT: ensure that reaction is complete (c) carbon dioxide/gas given off [1] NOT: there is a reaction (d) filter funnel; filter paper; beaker underneath [3] -1 mark if at least two parts not correctly labelled If no filter paper = 0 If filter paper shown flat at top of funnel, max =1 (if at least two labels are correct) (e) filtrate [1] (f) evaporate/boil off (some off) the water/allow to crystallise in a warm place/leave in a warm place; NOT: evaporate solution/evaporate nickel sulphate NOT: heat (alone) unless qualified dry with filter paper/pick out crystals and dry; [2] NOT: heat/warm to dry

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(g) (i) 7H2O [1] (ii) equilibrium/reversible reaction [1] NOT: goes back to original form/state NOT: goes two ways (iii) add (a little) water [1] 4 (a) nitrogen [1] (b) (i) oxygen; water. [2] NOT: symbols (ii) carbon and hydrogen ALLOW: symbols [1] (iii) alkanes [1] (c) incomplete combustion (of hydrocarbons/fuels)/insufficient oxygen for combustion [1] NOT: lack of oxygen (d) (i) 2 + 2 [1] (ii) any suitable e.g. breathing difficulties/irritation of throat/irritation of lungs/damage to lungs/watering eyes etc [1] NOT: causes lung diseases ALLOW: suitable affects of acid rain if clearly stated that NO2 dissolves in

water first NOT: kills organisms/animals NOT: affects lungs/eyes etc. (e) (i) burning coal ALLOW: burning fossil fuels [1] (ii) addition of oxygen [1] ALLOW: removal/loss of electrons (iii) 98 [1] (iv) iron sulphate/iron(II) sulphate; NOT: iron(III) sulphate hydrogen [2] (v) erodes them/wears them away [1] ALLOW: answers involving relevant chemical reactions (e.g. calcium carbonate + acid) in context NOT: corrodes NOT: deteriorates NOT: cracks them/destroys them

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5 (a) (i) increases growth/increases crop yield [1] NOT: for plant growth/helps growth/provides nutrients for growth/ makes them grow faster/better (ii) potassium/K/K+ [1] (iii) phosphate [1] (b) add (aqueous) sodium hydroxide; and aluminium foil/Devarda’s alloy; warm/test with red litmus/smell gas; ammonia produced/pungent smell/litmus turns blue [4] (4th mark only allowed if reagents correct) (warm gains no credit unless reagents correct) OR add iron(II) sulphate; and concentrated: sulphuric acid; brown ring (where the two layers meet) (c) (i) neutralisation/acid-base ALLOW: exothermic [1] (ii) NH3 [1] (d) 2nd and 4th boxes ticked (1 each) [2] 6 (a) 3rd box down ticked [1] (b) (i) breaking down/decomposition of a substance/compound using electricity [1] NOT: separation of ions using electricity (ii) negative/cathode [1] (iii) graphite ALLOW: carbon/platinum [1] NOT: copper (c) (i) electron [1] (ii) (acidify with nitric acid) add silver nitrate solution; white precipitate [2] (d) 2 [1] (e) (i) 2550 [1] (ii) 3.6% [1]

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(f) (i) unsaturated; catalyst; saturated [3] (ii) any suitable use e.g. fuel/specific reductions (e.g. alkenes (to alkanes)/Haber process) [1] ALLOW: in balloons/airships/rockets ALLOW: in making hydrochloric acid ALLOW: in oxy-hydrogen blowpipe NOT: making water/making margarine

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June 2005

IGCSE

MARK SCHEME

MAXIMUM MARK: 80


CHEMISTRY (Core Theory)

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IGCSE – JUNE 2005 0620 2


1 (a) (i) A [1] (ii) B + E [1] (iii) A + C [1] (iv) B [1] (v) B + E [1] (b) (i) graphite [1] NOT: charcoal (ii) diamond/buckminsterfullerene [1] NOT: graphite (but ALLOW: ecf from part (i) (c) NaI [1] ALLOW: Na+

I-

NOT: Na+ + I- (d) compound (no mark) because two different (types of) atoms joined/bonded etc. [1] ALLOW: two different elements bonded NOT: atoms together Total = 9 2 (a) filtering/filtration [1] NOT: distillation, NOT: decanting (b) litmus turns pink/red [1] NOT: orange (c) (i) steel [1] (ii) water [1] NOT: steam (iii) copper/iron [1] (iv) natural gas [1] NOT: methane (d) methane [1] (e) 100o C (100 = 0) [1] (f) (i) calcium/Ca2+ [1] (ii) e- [1] ALLOW: e NOT: electron (g) (i) carbon dioxide + water [1] ACCEPT: correct formulae

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IGCSE – JUNE 2005 0620 2


(ii) carbon monoxide [1] NOT: CO Total = 12 3 (a) random arrangement; far apart. [2] (b) pH9 [1] (c) (i) NH3/H3N [1] (ii) covalent [1] (iii) weak forces between particles OR molecules/weak intermolecular forces [1] (d) (i) H2SO4 [1] (ii) nitrogen; soil [2] (e) Any 3 from:

ammonia evaporates from (ammonia) solution; diffusion; particles/molecules of ammonia/gases are in constant movement/ move freely; ALLOW: move fast NOT: particles of ammonia solution move freely NOT: move from high to low concentration movement of particles/molecules is random. [3] NOT: ammonia spreads out;

(f) (i) the air [1] ALLOW: atmosphere (ii) 2 (NO2) [1] (iii) reversible reaction [1] ALLOW: equilibrium (iv) exothermic/heat given out [1] Total = 16 4 (a) monomers [1] (b) does not have a double bond/only contains single bonds/has a single C – C bond [1] NOT: has a single bond NOT: it is saturated NOT: no spare bonds (c) displayed/graphical formula correct [1] ALLOW: correct dot and cross diagrams (d) (i) breaking down of long-chained hydrocarbons/formation of smaller hydrocarbons from larger [1]

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IGCSE – JUNE 2005 0620 2


(ii) high temperature [1] ALLOW: heat (catalyst alone = 0) (iii) C8H18 [1] ALLOW: other sensible combinations 2(C2H4) + C6H14 (e) (i) H2 [1] (ii) any 2 of:

temperature gradient in fractionation column; smaller/lighter molecules (rise) higher in column OR smaller/lighter molecules more easily vaporised OR e.g. referring to larger/heaver molecules ALLOW: hydrocarbons in place of molecules NOT: lighter/heavier fractions different fractions condense at particular heights in column/fractions condense when temperature falls below their boiling points [2] ALLOW: different fractions have different boiling points/condense at different temperatures

(iii) petrol: fuel (for cars)/other suitable use [1] NOT: for cars etc. lubricating fraction: lubricating oils/waxes/polishes/other suitable use [1] NOT: for planes etc.

Total = 11 5 (a) (i) molecule containing 2 atoms [1] ALLOW: element containing 2 atoms (ii) whether it is solid, liquid or gas (all 3 needed) [1] (b) (i) gas; liquid; solid (all 3 = 2 marks; 2 correct = 1 mark) [2] (ii) red/brown/orange or combination of these [1] (iii) 130-210 (o C) (actual = +184 o C) [1] (c) iodine + potassium chloride (1 each) [2] (d) (i) 8 electrons in each shell + atoms joined no bonding electrons = 1 [2] IGNORE: inner shell electrons if correct (incorrect inner shell electrons = 1 max) (ii) water purification OR treatment/killing bacteria etc./bleaching agent (for paper)/

making refrigerants/making organic chlorine compounds (named)/making solvents/extracting titanium/detinning scrap tinplate/making hydrochloric acid/extraction of bromine from seawater/other suitable use [1]

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IGCSE – JUNE 2005 0620 2


(e) (i) A [1] (ii) C [1] (iii) it contains ions; which can move/are free to move (OWTTE) [2] reference to electrons = 0 (f) (i) Period 6 [1] (ii) 85 [1] (iii) atoms with (same number of protons and) different number of neutrons/ different mass number/different nucleon number [1] NOT: molecules with… ALLOW: elements with…. (iv) 125 [1] Total = 19 6 (a) (i) iron + sulphuric acid → iron sulphate + hydrogen [2] -1 per error/omission NOT: iron(III) sulphate NOT: hydrogen sulphate (ii) lighted splint; pop/small explosion etc. [2] (consequential marking) (b) (i) cathode [1] (ii) allows conduction (of electricity)/allows charges or ions to flow through the solution [1] (iii) gains layer of copper/coated with copper NOT: gets bigger [1] decreases in size/gets smaller/loses copper etc. [1] ALLOW: the copper dissolves NOT: breaks up/flakes off (iv) aqueous sodium hydroxide; light blue ppt; insoluble in excess OR aqueous ammonia; light blue ppt; soluble in excess/forming dark blue solution [3] (consequential marking) (c) to make them attractive/makes them shiny/protects the iron so it does not rust/does

not corrode OR oxidise easily/less reactive than iron [1] NOT: chromium is unreactive etc. NOT: other properties of chromium e.g. hard NOT: corrosive (d) iron > chromium > copper [1] Total = 13

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the November 2005 question paper

0620 CHEMISTRY

0620/02 Paper 2 (Core Theory)

Maximum mark 80

This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the

Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the

Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session.

• CIE will not enter into discussion or correspondence in connection with these mark schemes.

CIE is publishing the mark schemes for the November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

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IGCSE – NOVEMBER 2005 0620 2


1 (a) (i) N [1] (ii) N/O/F/Cl/Br [1] (iii) Br [1] (iv) He/Ne/Ar/Kr [1] (v) C [1] (vi) He/C/N/O [1] (vii) N [1] (b) (i) light bulbs/lamps/other suitable uses [1] (ii) balloons/other suitable uses [1] (iii) in oxygen tents in hospitals/oxyacetylene welding/other suitable uses [1] (c) (i) 8 electrons in outer shell; all other electrons correct i.e. 2,8 [2] (ii) full outer shell/outer shell cannot gain or lose electrons/stable electronic configuration with 8 electrons in outer shell [1] TOTAL 13 2 (a) NaCl [1] (b) evaporation of the water [1] (c) 3rd box down ticked [1] (d) (aqueous) silver nitrate; white precipitate [2] (e) (i) calcium sulphate [1] (ii) 136 [1] (iii) 2H2O [1] (iv) hydration [1] (v) H2SO4; 2 [2] (vi) heat (constantly) given out when anhydrite reacts with water [1] (f) 4th box ticked [1] TOTAL 13

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3 (a) suitable graduated apparatus for gas collection; flask + reactants + closed system; correct labels (at least 2) [3] (b) (i) substance which speeds up the rate of a reaction [1] (ii) X; slope or gradient greatest/produced most gas in named time interval below 70s [2] (iii) same amount of hydrogen peroxide used/all conditions kept the same [1] (iv) very high melting or boiling points/high densities/form coloured compounds/form ions with different charges owtte [2] (c) particles (of hydrogen peroxide) move faster; greater frequency of collisions [2] (d) (i) enzymes are from living things/enzymes can be denatured/enzymes specific for one reaction/enzymes are proteins [1] (ii) D [1] TOTAL 13 4 (a) 2 from calcium/magnesium/sodium;

they are metal oxides/oxides of (reactive) metals are basic [2]

(b) (i) nitrogen dioxide; sulphur dioxide [2] (ii) nitrogen dioxide: from car exhausts;

sulphur dioxide: from burning fossil fuels [2]

(c) (i) carbon dioxide [1]

(ii) high temperature (ALLOW: heat) NOT: catalysis on its own [1]

(d) (i) too reactive/above C in reactivity series owtte [1]

(ii) 2; CO2 [2]

(iii) removal of oxygen from a compound/addition of electrons ALLOW: addition of hydrogen [1] TOTAL 12

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5 (a) methane [1]

(b) A and B [1] (c) (i) C [1]

(ii) correct displayed formula = 2 correct displayed formula but not O – H bond = 1 [2]

(iii) heated with steam; suitable catalyst [2]

(d) (i) D [1] (ii) bromine (water); decolourised [2] (e) (i) ethanoic acid [1]

(ii) litmus; goes red/pH paper or meter; below7/bubbles of gas when

added to a carbonate [2]

TOTAL 13 6 (a) aluminium oxide [1]

(b) ions must be free to move [1]

(c) (i) graphite/carbon [1]

(ii) to the cathode/negative electrode; Al ions are positive/positive ions are attracted to negative electrode [2]

(d) decreased; cryolite; electrical [3]

(e) (i) aluminum has a low density [1]

(ii) low(er) electrical conductivity [1] (iii) it is stronger (than aluminum) [1]

(iv) ceramic [1]

(f) (i) lightweight [1]

(ii) add sodium hydroxide; white ppt; soluble in excess [3] OR add aqueous ammonia; white ppt; insoluble in excess

TOTAL 16

GRAND TOTAL 80

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MARK SCHEME for the May/June 2006 question paper

0620 CHEMISTRY

0620/02 Paper 2, maximum raw mark 80

These mark schemes are published as an aid to teachers and students, to indicate the requirements of the examination. They show the basis on which Examiners were initially instructed to award marks. They do not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the

Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session.

• CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2006 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

9Dwebsite.tk



IGCSE – May/June 2006 0620 02


1 (a) Substance containing only 1 type of atom/substance which cannot be broken down to any other substance by chemical means [1]

(b) B [1] (c) A + D (both needed) [1] (d) (i) C [1] (ii) carbon [1] (iii) drill bits/ for cutting OWTTE [1] (e) Any 3 of: conducts heat/conducts electricity/malleable/ductile/sonorous/shiny NOT: silvery/high melting OR boiling points [3]

(f) (i) alloy(s) [1] (ii) mild steel → car bodies; stainless steel → chemical plant; aluminium → aircraft ALLOW car bodies; copper → electrical wiring [4] [Total: 14] 2 (a) respiration [1] (b) (i) CH4; O2 (1 mark each) [2] (ii) fuel OWTTE [1] (iii) arrangement: random/not regularly arranged/not ordered/widely spaced OWTTE; motion: moving/random; [2] (iv) alkane(s) [1] (v) C2H6 box – 2nd from left ticked [1] (c) C [1] (d) (i) the bacteria NOT: living things/plants/animals [1] (ii) speeding up of a chemical reaction by a specific substance [1] (e) phosphorus; nitrogen (1 each) [2] [Total: 13]

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3 (a) (i) D [1] (ii) A + C (both needed) [1] (iii) B [1] (iv) E [1] (v) C [1] (b) sharing; chlorine; low; diamond; strong [5] (c) (i) 2 electrons paired and two atoms shown [1] (ii) lighted splint; pops/explodes OWTTE [2] [Total 13] 4 (a) (i) hydrogen; [1] (ii) ethene [1] (iii) carbon dioxide [1] (b) (add) bromine water/aqueous bromine ALLOW: bromine: with ethene – decolourises OWTTE; with methane – no reaction/remains orange/brown OWTTE [3] (c) (i) (addition) polymerisation [1] (ii) 4th box from left (last one) ticked [1] (d) cracking ALLOW thermal decomposition [1]

(e) (i) test: add (red) litmus paper; goes blue [2] (ii) 17 [1] (f) sulphur dioxide formed; harmful effect of sulphur dioxide e.g. acid rain/breathing difficulties/ kills fish/leaf drop on trees etc [2] ALLOW: carbon dioxide; global warming ALLOW: carbon monoxide; poisonous [Total: 14]

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5 (a) (i) filtration/description of filtration [1] (ii) weakly acidic/2nd box down ticked [1] (b) (i) from the limestone/ from the underlying rocks [1] (ii) carbon dioxide; water (1 each) [2] (c) (i) carbonate/CO3

2– [1] (ii) 20 mg (unit must be present) [1] (iii) nitrate/NO3

– [1] (iv) (aqueous) sodium hydroxide/other suitable hydroxide/ammonia; red-brown/ brown; precipitate [3] IF: ‘soluble in excess’ minus 1 mark (d) carbon dioxide higher (in soil air); nitrogen higher (in soil air); oxygen lower (in soil air); [3] (e) correct formula with all atoms and bonds [1] [Total: 15] 6 (a) haematite; ALLOW other correct named ores [1]

(b) (i) 2:2 [1] (ii) poisonous ALLOW: answers related to reducing oxygen carrying capacity of blood/effect on haem etc [1] (c) (i) iron oxide + carbon monoxide → iron + carbon dioxide [1] (wrong oxidation number(s) = 0)

(ii) reduction [1] (d) (i) (thermal) decomposition [1]

(ii) any suitable e.g. making cement [1] (iii) slag [1]

(e) (i) manganese [1]

(ii) acidic [1] (iii) 6% [1]

[Total: 11]

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MARK SCHEME for the October/November 2006 question paper

0620 CHEMISTRY

0620/02 Paper 2 (Core Theory), maximum raw mark 80

This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began.

All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated.

Mark schemes must be read in conjunction with the question papers and the report on the examination. The grade thresholds for various grades are published in the report on the examination for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses.

• CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2006 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

9Dwebsite.tk



IGCSE - OCT/NOV 2006 0620 02

© UCLES 2006

1 (a) C [1]

(b) (i) 2;2 (both needed) [1]

(ii) 2 from: floats on water/on surface; moves (on surface); forms a ball/melts; disappears/dissolves ALLOW: spits/explodes (at end of reaction) [2] NOT: reacts violently

(iii) blue; solution is alkaline/sodium hydroxide/ (NaOH) is alkaline [2] ALLOW: (solution) is basic/is a base

(iv) 2nd and 3rd boxes ticked (1 each) [2]

(c) faster/more reactive OWTTE (than potassium) [1]

(d) (i) atoms of same element/same number of protons with different number of neutrons/different mass numbers [1]

NOT: elements/compounds with different mass numbers

(ii) 11 [1]

(iii) 19 [1]

(iv) energy/nuclear fuel/nuclear power plants NOT: nuclear weapons/unqualified fuel [1]

[Total: 13]

2 (a) CO2 [1]

(b) (i) reduced; metal; endothermic [3]

(ii) carbon [1]

(iii) limewater; turns cloudy/milky/goes white [2]

(c) add(aqueous) sodium hydroxide; light blue ppt; insoluble in excess [3] OR add aqueous ammonia; light blue ppt; soluble in excess/giving dark blue solution

(d) (i) correct diagram (2,4) [1]

(ii) (period) 2 [1]

(e) (i) alkane(s) [1]

(ii) ethane [1]

[Total: 14]

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IGCSE - OCT/NOV 2006 0620 02

© UCLES 2006

3 (a) ring around OH group only [1]

(b) unsaturated because it contains (C=C) double bonds (both points needed) [1]

(c) carbon dioxide; water [2]

(d) (i) condenser [1]

(ii) 100oC (unit needed) [1]

(iii) it is above the water/floats on water [1]

(e) (i) on the origin line and directly below the spots [1]

(ii) 4 [1]

(iii) beaker with paper placed correctly and solvent level below the origin line and both solvent and origin line labelled [1]

(iv) random movement of molecules/molecules move anywhere [1] NOT: molecules move from higher to lower concentration

(v) correct formula for ethanol showing all atoms and bonds ALLOW: OH group shown without bond [1]

(vi) 2nd and 4th boxes ticked [1]

[Total: 13]

4 (a) substance containing different atoms bonded/ joined etc [1]

(b) treating acid soils/making plaster/any other specific reasonable use NaCl; CaCO3; in blast furnace/for making iron/making lime/any other specific reasonable use; ammonium nitrate; N = 2, H = 4, O = 3; [6]

(c) 80 [1]

[Total: 8]

5 (a) it is (very) reactive/near top of reactivity series [1]

(b) gives off bubbles rapidly; dissolves quickly; [2]

(c) for cutting/welding/for oxyacetylene blow torch [1]

(d) (i) 2H2O [1]

(ii) neutralization [1]

(e) (i) burette [1]

(ii) starts alkaline/stated alkaline pH; pH decreases/to stated lower pH [2] NOT: becomes more acid

[Total: 9]

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IGCSE - OCT/NOV 2006 0620 02

© UCLES 2006

6 (a) PbBr2 [1] (b) giant; ionic [2] (c) (i) B [1] (ii) platinum [1] (iii) ions can move/so it can conduct electricity NOT: ions are free [1] (iv) bromine; lead [2] (d) (i) Br2 [1] (ii) orange/brown/red-brown: NOT yellow [1] (iii) bromine is more reactive than iodine/bromine is higher in the activity series than

iodine (must be comparison) ALLOW: ideas about stronger bonding in NaBr [1] (e) (i) correct formula showing all atoms and bonds [1] (ii) D [1] [Total: 13] 7 (a) A + D (both needed); reason: high melting point/coloured chlorides/coloured compounds [2] NOT: properties of transition elements not shown in the table (b) iron sulphate [1] (c) idea of measuring volume of gas/amount of gas; in measuring cylinder/tube; idea of measuring (volume of gas) with time/time intervals; [3] (d) (i) doubling concentration doubles rate/rate proportional to concentration = 2

increasing concentration increases rate/speed = 1 [2] (ii) slower/decreases [1] (iii) slower/decreases [1] [Total: 10] [TOTAL: 80]

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0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began.


Mark schemes must be read in conjunction with the question papers and the report on the examination.

• CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2007 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

9Dwebsite.tk




© UCLES 2007

1 (a) ALLOW: correct names / correct formulae (i) B [1] (ii) E [1] (iii) D [1] (iv) E [1] (v) C [1] (vi) B + C [1] (vii) A + F [1] (b) (i) car exhausts / from vehicles [1] ALLOW: from metal smelting NOT: from factories / from natural causes e.g. volcanoes NOT: from fuels if unqualified (ii) damage to brain / nervous system (in children) [1] ALLOW: mental damage / poisonous / toxic / lung irritant NOT: harmful / lung cancers / poisonous to lungs / makes you ill / respiratory diseases / lung problems etc. (c) forms sulphur dioxide / acid rain [1] ALLOW: sulphur burns to form acid rain REJECT: carbon monoxide / dioxide causes acid rain = 0 REJECT: sulphur causes acid rain = 0 effect of acid rain [1] e.g. chemical erosion / chemical weathering / corrodes metals / damages trees [or plants] / kills trees [or plants] / damages limestone buildings / damages or kills plants [or animals] in lakes NOT: harmful / makes soils acidic / corrodes limestone [or buildings] / pollutant REJECT: global warming / affects ozone layer

[Total: 11]

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© UCLES 2007

2 (a) nitrogen / N2; oxygen / O2 [2] (b) (i) carbon dioxide / CO2 [1] (ii) water / H2O [1] (iii) O2 on left; correct balance [2] (c) (i) (Period) 3 [1] (ii) noble gases / inert gases [1] ALLOW: group 0 / 8 (iii) correct electronic structure of argon 2.8.8 [1] (iv) inert / doesn’t react / prevents (tungsten) filament from burning [1] ALLOW: implication that argon produces light after excitation by electric current (discharge tubes) NOT: argon produces light when it reacts NOT: argon lights up (v) 22 [1] (d) 169 [1] IGNORE: units (e) (i) XeF4O (atoms in any order) [1] (ii) covalent [1] NOT: double and single bonding

[Total: 14]

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© UCLES 2007

3 (a) (i) 2 on both sides (NOTE: only one mark) [1] (ii) comes from water / water won’t run out / water renewable resource [1] NOT: arguments about pollution NOT: easily made / renewed REJECT: found in air and water (iii) exothermic [1] (b) carbon dioxide / CO2; water / H2O [2] (c) 1 mark for each correct fraction; [2] correct use linked to each specific fraction [2] (if fraction incorrect mark cannot be given for use) Examples:

Fraction Use

Refinery gas NOT: methane / natural gas

fuel (alone or qualified) ALLOW: for heating / cooking

Naphtha feedstock for chemicals / making specific chemicals e.g. ethane

Paraffin / kerosene oil stoves / heating / aircraft fuel / feedstock for chemical industry ALLOW: for cooking NOT: fuel alone

Diesel fuel in cars / fuel for diesel engines / central heating fuel NOT: fuel alone

Fuel oil fuel for ships and power stations NOT: fuel alone

Lubricating fraction lubricants / waxes / polishes

Bitumen / residue roads / sealing roofs

(d) (i) breaking down of (larger) hydrocarbon molecules into smaller ones / making alkenes from larger alkanes [1] (idea of large hydrocarbons to smaller ones) ALLOW: breaking down petroleum fractions / hydrocarbons / alkanes NOT: decomposing unless qualified

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© UCLES 2007

(ii) high temperature [1] ALLOW: heat REJECT: heat and burn catalyst OR high pressure [1] ALLOW: aluminium oxide / silicates; IGNORE: incorrect name of catalyst NOT: high pressure (Catalyst + high pressure = 1 mark maximum) (iii) correct structure of ethene [1] All atoms and bonds must be shown

[Total: 13] 4 (a) (i) substance which speeds up (rate of) reaction [1] NOT: slows rate of reaction (ii) transition elements / transition metals [1] NOT: specific metals / named metals (b) (i) axes correctly labelled with time on horizontal axis and use of full grid [1] ALLOW: V for volume and t for time correct plotting of points (-1 per error / omission) [2] Penalise 110 cm3 points only once smooth line going through all points [1] (ii) line steeper at start; [1] ending up at same level [1] NOT: ending up after 50 mins NOT: joining previous line before 50 minutes (iii) all zinc used up / hydrochloric acid is in excess [1] ALLOW: zinc and hydrochloric acid have completely reacted NOT: reaction finished / completed / HCl completely reacted (c) (i) (speed would be) faster / rate increases [1] (comparative needed) NOT: takes less time / reacts more (ii) (speed would be) slower / rate decreases [1] (comparative needed) NOT: takes more time / reacts less (d) (i) zinc chloride [1] (ii) lighted splint / light the gas; [1] pops / explodes etc. [1]

[Total: 14]

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© UCLES 2007

5 (a) electron [1] (b) any two of: conducts electricity / conducts heat / shiny / malleable / ductile / sonorous [2] NOT: high density / high melting point / high boiling point / hard ALLOW: solid if qualified by mercury as exception (c) 4th box down ticked [1] (d) aqueous sodium hydroxide; [1] (light) blue ppt; [1] insoluble in excess [1] OR aqueous ammonia; (light) blue ppt; soluble in excess / forming (dark) blue solution (e) electrical wiring / water pipes / cooking utensils / coinage / any other sensible specific use [1] NOT: for wires / for pipes

[Total: 8]

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© UCLES 2007

6 (a) potassium chloride; [1] bromine [1] (b) iodine lower in group / less reactive than chlorine / iodine less good oxidising agent [1] ALLOW: bond between potassium and chlorine is too strong for iodine to react (c) (i) gas; [1] grey / black; [1] ALLOW: purple black NOT: brown / brown-black / purple (ii) ALLOW range of -200 to -90 (actual = -188); [1] ALLOW range of 1.6 to 4.0 (actual = 3.12) [1] (d) (i) 9 [1] (ii) 7 [1] (e) any suitable use e.g. in swimming pools/ water purification / disinfectant / kills germs / kills bacteria / bleaching agent (for paper) / extraction of titanium / de-tinning scrap tinplate etc. [1] ALLOW: making named chemicals e.g. making hydrochloric acid / making halogenoalkanes / making CFCs / making carbon tetrachloride NOT: sewage treatment / cleaning

[Total: 10]

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© UCLES 2007

7 (a) it is below the electrolyte [1] (b) graphite [1] (c) A [1] (d) aluminium is too reactive / a very reactive metal / above carbon in the reactivity series [1] NOT: because carbon won’t remove the oxygen from the oxide / won’t reduce the oxide / won’t react (e) (i) the aluminium oxide / the electrolyte [1] (ii) CO2 [1] (iii) carbon is released as carbon dioxide / carbon dioxide is a gas [1] NOT: it’s getting oxidised / reaction between carbon and oxygen (f) 530 (kg) [1] (g) molten; ions [2]

[Total: 10]

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0620 CHEMISTRY






9Dwebsite.tk



IGCSE – October/November 2007 0620 02

© UCLES 2007

1 (a) sulphur dioxide [1] ALLOW: SO2/sulphur/S (b) carbon dioxide [1] ALLOW: CO2

(c) carbon monoxide [1] ALLOW: CO (d) water [1] ALLOW: H2O (e) calcium oxide [1] ALLOW: CaO/calcium/Ca (f) calcium oxide and sodium oxide [1] ALLOW: correct formulae or calcium and sodium (g) both bonds shown by dot and cross [1] ALLOW: dot and cross anywhere along the bonding line (h) P2O3 [1] ALLOW: 2P2O3

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© UCLES 2007

2 (a) (i) monomers [1] (ii) alkenes [1] (iii) contains (carbon-carbon) double bonds [1] ALLOW: can add on extra hydrogen substance containing hydrogen and carbon only [1] (iv) bromine water/acidified potassium permanganate [1] no reaction/stays orange/nothing [1] (bromine) decolourised/goes colourless [1] (b) addition/additional [1] ALLOW: ethene/alkene (c) (i) any two of: chloride/hydrogencarbonate/nitrate/sulphate [1] ALLOW: correct formulae (ii) calcium/Ca2+/Ca [1] (iii) 40 (mg) [1] (iv) chloride/Cl

– [1] (v) nitrate/NO3

– [1] (vi) e–/e [1] (d) 2nd box down ticked [1] (e) (i) condenser/condensing tube [1] (ii) beaker [1] (iii) it is different/boiling point (in flask) is higher/pure water is lower [1] (f) any two of: bacteria or soil particles are larger than gaps in limestone/ water particles are smaller than gaps in limestone/ particles/bacteria or soil (particles) are larger than water molecules idea of bacterial or soil particles trapped above the limestone/ idea of filtration [2] ALLOW: particles/bacteria or soil (particles) are larger than water molecules

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© UCLES 2007

3 (a) aluminium – aircraft bodies; potassium – very soft; platinum – electrodes; iron – extracted from haematite; [4] (b) any two of: fizzing or bubbles/ iron disappears or dissolves/ solution becomes coloured/green [2] NOT: gets warm/iron changes colour/precipitate formed (c) (i) mixture; iron; harder/stronger/more brittle or other suitable comment [3] ALLOW: hard/strong (ii) any alloy e.g. brass/bronze [1] (iii) any two methods e.g. galvanising/painting/covering with oil/sacrificial protection (or description)/ plating with another metal [2] NOT: unspecified ‘coating’

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© UCLES 2007

4 (a) increases (at first) ALLOW: becomes acidic; then decreases/becomes less acidic [2] NOT: reference to pH values/ends up alkaline

(b) (i) any two of: sweet is acidic/ saliva only produced gradually or saliva not present at first (so pH goes down at first)/ saliva neutralises the acid ALLOW: neutralises the sweet/ as more saliva produced more acid neutralised/ [2] (ii) neutralisation [1]

(c) (i) -OH group circled [1] (ii) carboxylic (acid) [1] (iii) CH3CO2H/CH3COOH/correct displayed formula [1] ALLOW: C2H4O2

(d) (i) gas given off/carbon dioxide given off [1] IGNORE: wrong gas (ii) filter funnel and filter paper; ALLOW: just filter paper cone calcium citrate/precipitate shown in funnel and filtrate below [2] (if no labels max 1 mark) (iii) to remove (excess) lemon juice [1] ALLOW: to remove impurities (iv) evaporate (off water)/boil off some of the water and leave [1] ALLOW: leave solution in warm place/on the windowsill NOT: ‘heat’ without suitable qualification (v) microorganisms [1]

5 (a) (i) removal of oxygen from compound/electron gain/decrease in oxidation number [1] ALLOW: addition of hydrogen (ii) copper [1] (iii) idea of electric circuit; bulb lights/meter gives reading [2] NOT: electrolysis/melt the substance to see if it conducts

(b) (i) hydrocarbons (in coal)/the coal [1] ALLOW: from the damp cotton wool (ii) close together/randomly arranged NOT: further apart than in a solid moving (from place to place/randomly)/random movement [2]

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© UCLES 2007

6 (a) proton number/atomic number/number of + charges in nucleus [1] (b) they have the same (relative) atomic mass [1] (c) noble gases/group 0/group 8/group 18/rare gases [1] (d) any 3 differences e.g. no atomic numbers shown/ no relative atomic masses shown/ (Newlands’) groups are horizontal or periods are vertical/ no block for transition elements/ Co and Ni appear to be in with halogens or other similar discrepancies/ some elements not in correct order of molar masses/ more elements in modern table/ no man made elements/ any other suitable difference [3] (e) (i) layers slide over each other/layers flake off easily/forces between layers weak [1] NOT: weak forces between carbon atoms (without any further details) (ii) no weak bonds/only strong bonds [1] ALLOW: giant structure/lattice of covalent bonds 7 (a) methane water copper [1] (b) silver – conducts/yes; sodium chloride – soluble; sulphur – insoluble; copper sulphate – no; [4] (c) (i) graphite/platinum [1] (ii) chlorine/Cl2 NOT Cl; hydrogen/H2 NOT H [2] ALLOW: 1 mark for chlorine and hydrogen at incorrect electrodes (iii) anode [1] (iv) in solid ions cannot move/fixed in place; in aqueous solution ions move [2]

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0620 CHEMISTRY






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© UCLES 2008

1 (a) (i) B/calcium carbonate/CaCO3 [1]

(ii) E [1]

(iii) C/carbon dioxide/CO2 [1]

(iv) D/ethane [1] (b) bromine water/bromine [1] decolourises/turns colourless [1] NOT: turns clear ALLOW: (acidified) potassium manganate(VII); turns colourless (2 marks) IGNORE: original colour of bromine/potassium manganate(VII) (c) calcium carbonate [1] NOT: CaCO3 (d) lubricant/2nd box down ticked [1] IF: more than one box ticked = 0 (e) substance containing more than one type of atom different atoms ALLOW: more than one type of element/two elements bonded/joined/(chemically) combined/combination [1] Both parts needed. IF: word mixture appears = 0 (f) covalent [1] NOT: single bonding [Total: 10] 2 (a) calcium carbonate [1] (b) any 4 from: • statue becomes (chemically) eroded; ALLOW: statue becomes corroded/amount of limestone reduced NOT: destroys limestone/limestone melting/damages the statue • iron pins corroded/eroded/eaten away OWTTE • acid rain; • caused by burning fossil fuels; • sulphur dioxide formed/from sulphur in fossil fuels; ALLOW: nitrogen dioxide formed/from car exhausts • sulphur dioxide dissolves to form acid; ALLOW: nitrogen dioxide dissolves to form acid • sulphuric acid in air ALLOW: nitric acid in air • acid reacts with limestone/carbonate/statue/iron/pins NOT: (unqualified) acid reacts [4]

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© UCLES 2008

(c) iron/pin(s) corrode/rust/eaten away/erode/oxidises [1] ALLOW: iron pins dissolve away ALLOW: iron/pins react with (acid) in air NOT: iron pins have reacted/weak and break NOT: it/the arm has rusted

(d) (i) atoms (of same element) with different number of neutrons/atoms with different numbers of nucleons but same number of protons/ same elements [1]

ALLOW: atoms with same atomic number but different mass number (ii) –/negative [1] 0/no charge [1] +/positive [1] IGNORE: numbers in front of – or + (iii) 56 [1] ALLOW: 30 + 26 (e) any suitable use e.g. measuring thickness of paper/detecting leaks in pipes (ALLOW: checking leakage for suitable substances e.g. water/oil) /sterilization of surfaces/making electricity/power stations/ [1] NOT: medical uses (f) iron + nitric acid → iron nitrate + hydrogen [1] IGNORE: oxidation numbers unless incorrect/dilute (nitric acid) NOT: heat on either side of equation/equation without arrow ALLOW: = for arrow [Total: 13] 3 (a) Cl

–/chloride [1] (b) sulphate [1] IGNORE: oxidation numbers (c) potassium + sodium (both needed for the mark) [1] ALLOW: K+ and Na+/K and Na (d) sodium chloride [1] ALLOW: NaCl ALLOW: salt (e) any two of: calcium/magnesium/potassium/sodium [2]

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(f) (i) 3 (rd period) [1] (ii) single bonding pair [1] 6 non-bonding electrons in each atom [1] IGNORE: incorrect inner electrons (g) any 2 of: [2] • distillation removes dissolved ions/ salts; ALLOW: distillation removes only the water/extracts water/solvent IGNORE: reference to impurities without qualification • filtration doesn’t remove dissolved ions/salts; ALLOW: filtration can’t remove very small particles OWTTE ALLOW: filtration only removes large particles IGNORE: filtration removes solids IGNORE: reference to impurities • filtration does not remove bacteria/germs; • distillation removes/kills bacteria/germs IGNORE: cost/speed arguments [Total: 11] 4 (a) any suitable e.g. as a coolant/for specific named reactions e.g. making ethanol from

ethene/making sulphuric acid [1] ALLOW: as a solvent ALLOW: to make hydroelectricity/electricity NOT: (unspecified) making chemicals NOT: to drink/wash, etc. (b) any two of: [2] • sand has very fine/small spaces (between the grains) (idea of small spaces) • water/small molecules/small particles can pass through; (idea of small molecules going through) • water molecules are small/water is a liquid; (water molecules small/liquid) • (large) particles cannot pass through spaces/are trapped by sand/blocks particles/ (idea of particles not getting though/trapping by sand) NOT: by filtering NOT: filter takes out the smaller molecules in water IGNORE: references to absorbing/impurities (c) add sodium hydroxide; [1] white ppt/milky ppt/white solid (both white and ppt/solid needed); [1] soluble in excess/gives colourless solution in excess [1] OR add (aqueous) ammonia; white ppt; insoluble in excess/does not redissolve (d) to kill bacteria/germs [1] ALLOW: antibacterial/kills harmful organisms NOT: dissolves bacteria ALLOW: to stop bacteria growing

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(e) (i) chlorine + potassium bromide → potassium chloride + bromine [2] (–1 for each error or omission including no arrows/heat on left) (ii) it/iodine is less reactive than bromine/iodine lower in the reactivity series than bromine

ORA [1] NOT: iodine lower in the reactivity series than bromide

NOT: iodine lower in the reactivity series than potassium bromide/iodine can’t displace bromine

NOT: its not reactive enough/lower in the Periodic Table (f) (i) exothermic [1] (ii) ionic [1] (iii) sodium (atom) loses an electron [1] chlorine (atom) gains an electron [1] [sodium (atom) gives an electron to chlorine = 2] IGNORE: incorrect number of electrons/ reference to charges NOTE: any reference to sharing electrons = 0] [Total: 14] 5 (a) hydrogen/H2 [1] NOT: H (b) (i) to ensure all the (sulphuric) acid reacted [1] NOT: to ensure it reacted (ii) filtration/filter ALLOW: decanting/pouring off the solution [1] NOT: distillation/evaporation of sulphuric acid (c) evaporate water/evaporation/leave in a warm place; [1] ALLOW: heat/boil then allow solution to cool/heat then evaporate NOT: not heat/boil (to get the crystals) NOT: crystallisation/allow to crystallise; dry crystal on filter paper [1] ALLOW: filter off crystals and allow to dry (d) (i) sulphuric acid + magnesium carbonate/hydroxide/oxide or magnesium + a less reactive metal sulphate [1] NOT: magnesium + sulphuric acid (since in question) (ii) sulphuric acid + magnesium carbonate → magnesium chloride + water + carbon dioxide/ sulphuric acid + magnesium hydroxide → magnesium chloride + water/ sulphuric acid + magnesium oxide → magnesium chloride + water or e.g. magnesium + copper sulphate → magnesium sulphate + copper [1] ALLOW: correct answer(s) in either parts (i) or (ii) ALLOW: correct symbols equations

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(iii) contaminants might harm health/may make you ill/cause side effects [1] ALLOW: medicine would not work as well/might cause health problem IGNORE: contain contaminants/poisonous/kills you IGNORE: medicine would not work NOT: decrease the effect (unless specified of what i.e. of the medicine) (e) 6 (g) [1] IF: unit incorrect = 0 (f) 97.5 (%) [1] [Total: 10] 6 (a) (i) (group of) molecules/compounds with similar boiling points/group of molecules/

compounds which distil at same place in the fractionating column [1] (ii) fuel gas [1] ALLOW: methane (iii) Any two of: • temperature gradient in column/column hotter at bottom/column colder at top; • different fractions have different boiling points ALLOW: separated according to their boiling points/each fraction forms at a different

temperature • molecules condense/turn from gas to liquid at different heights in the column; • molecules condense/turn to liquid when temperature drops below their boiling point; ALLOW: molecules condense at their boiling point; • smaller molecules move further up the column ORA larger molecules/molecules with higher boiling point condense lower in the column

or smaller molecules/molecules with lower boiling point condense higher in column = 2 [2]

(iv) oil stoves/aircraft (fuel)/(fuel for) lamps [1] NOT: fuels for power stations/for burning/starting fires road (surfacing)/(tar for) roofing [1] ALLOW: paint NOT: tar without qualification

(b) (i) breaking down of larger molecules/hydrocarbons/converting large molecules into small molecules/large chains to small chains [1]

IGNORE: conditions NOT: implication of reacting with something else NOT: breaking larger substances to smaller NOT: breaking high fractions to low fractions (ii) C12H26 [1] ALLOW: other correctly balanced combinations within reason e.g. C10H22 + 2C2H4 or with

3 species

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(c) (i) speeds up rate of reaction [1] ALLOW: alters/changes rate of reaction (ii) reversible (reaction)/equilibrium (reaction)/reaction can go both ways [1] IGNORE: exothermic/endothermic (iii) fermentation [1] (iv) turns red/pink; [1] bubbles/ effervescence/fizzes [1] IGNORE: temperature changes/ppt/neutralises NOT: gas/carbon dioxide formed [Total: 13] 7 (a) Any 2 of: • crystals dissolve • water molecules colliding with crystal • diffusion • movement of ions NOT: copper particles/copper atoms/copper molecules NOT: particles slide over each other • movement of water molecules/water particles • movement is random [movement of (unspecified) particles = 1 maximum] NOT: movement of water/copper sulphate/crystals NOT: particles spread out IGNORE: movement from high to low concentration [2] (b) arrangement: regular [1] ALLOW: particles close together/linear/in lines/lattice/closely packed motion: none/vibrating [1] NOT: does not move a lot (c) suitable container with filter paper dipping into labelled solvent; [1] spot above solvent level [1] IF: metal ion where the solvent should be = 0 marks (d) (i) cathode [1] (ii) pure foil: gets further copper deposit/increases in thickness/gets less shiny [1] ALLOW: gets heavier/mass increases ALLOW: Cu2+ + 2e– → Cu (ignore wrong balance) impure foil: copper removed/decreases in thickness/appears cleaner [1] ALLOW: gets lighter/decreases in mass/dissolves/is corroded ALLOW: Cu → Cu2+ + 2e– NOT: wears away NOT: disappears [Total: 9]

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0620 CHEMISTRY






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1 (a) metal; non-metal; non-metal; non-metal; non-metal; [5] ALLOW: named metal or non-metal or correct symbols (b) metallic character decreases (across the table)/metals on the left and non-metals on

the right [1] ALLOW: metals get less reactive (across the table)/metals conduct better across the

table) (c) (i) electrons shown in shells as 2,8,1 [1] ALLOW 2,8,1 (ii) + e/electron (on the right) [1] (d) soft; increase; lithium; basic; [4] [Total: 12] 2 (a) sulphur dioxide → combustion of fossil fuels containing sulphur; carbon monoxide → incomplete combustion of fossil fuels; ALLOW: carbon monoxide → car exhausts nitrogen oxides → car exhausts; [3] (b) (i) oxygen is added [1] ALLOW: electrons are lost (from sulphur dioxide) (ii) 21% [1] ALLOW 19-22% (iii) neutralisation [1] (iv) Any two of: crops remove nitrogen (or phosphorus or potassium) from soil/ nitrogen or essential elements etc. removed when crops harvested; fertilisers provide nitrogen or essential elements or nutrients or minerals/ fertilisers improve plant growth or yield; [2] (v) ammonium nitrate [1] NOT: ammonia nitrate/ammonium salt/nitrate salt [Total: 9]

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3 (a) (i) heating (calcium carbonate in a furnace) [1] (ii) CaCO3 → CaO + CO2 [1] (iii) neutralising (acid) soil/neutralising industrial waste [1] ALLOW: for making mortar/for making limewater NOT: for limewater (b) (i) thermometer; flask; measuring cylinder; [3] (ii) calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water (1 mark for correct reactants; 1 mark for correct products) [2] ALLOW: hydrogen chloride in place of hydrochloric acid (iii) 86s [1] ALLOW: between 81 and 90s (iv) slope of graph steeper and always above other line; graph flattens out at 80 cm3 gas; [2] (v) (speed) decreased/less/slower; (speed) increased/more/faster; [2] [Total: 13]

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4 (a) haematite (or any other correct ore) [1] NOT: iron oxide (b) (i) calcium carbonate/limestone/CaCO3 [1] (ii) C/just above the iron [1] (c) (i) 2C + O2 → 2CO 1 mark for O2; 1 mark for 2C and 2CO; [2] (ii) poisonous/toxic/kills you/deadly/suffocates you [1] NOT: harmful/causes breathing difficulties (d) 1st and 3rd boxes ticked [1] (e) Any two of: blast furnace can only be used for metals below zinc or carbon; aluminium is very reactive or high in the reactivity series or too reactive or higher then

iron in the reactivity series; carbon cannot remove oxygen from aluminium oxide/carbon cannot displace

aluminium; aluminium above carbon in reactivity series or more reactive than C = 2 marks too much heat required for carbon to remove oxygen from aluminium oxide = 2 marks [2] (f) (i) electrolysis [1] (ii) aircraft bodies/car bodies/(overhead) power cables/drinks cans/window frames etc. [1] [Total: 11]

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5 (a) (i) temperature of the water rises/heat given to the water/heat or energy given out/the thermometer reading goes up [1]

(ii) carbon dioxide + water (1 mark each) [2] (b) any two from coal/natural gas/wood/paraffin/any other suitable fuel containing carbon [2] ALLOW: named alcohols (except ethanol) NOT: alkenes/named alkenes/naphtha (c) OH/–OH [1] NOT: complete formula for ethanol (d) blue cobalt chloride (paper); turns pink or white/anhydrous copper sulphate; turns blue [2] (e) (i) painting/galvanising/covering with plastic/sacrificial protection/(electro)plating [1] ALLOW: oiling/greasing NOT: removing air/removing water (ii) contains water NOT: dissolves in water [1] (iii) Any two of: high boiling point or melting point; can act as catalyst; forms coloured compounds; high density; compounds can have variable oxidation states or have ions with different charges; [2] ALLOW: general metallic properties e.g. conducts electricity; conducts heat; ductile

etc. NOT: not very reactive [Total: 12]

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6 (a) Any two of; (group of similar organic) compounds with same chemical properties; (group of similar organic) compounds showing trend in physical properties; have same functional group; have same general formula; members differ by CH2 group; [2] ALLOW: can be made by same method (b) ethane; correct structure of ethane; [2] ALLOW: correct structure from incorrectly named alkane (c) 1st row correct structure of ethene; use e.g. for making plastics/ethanol etc.; [2] 2nd row correct structure of ethanoic acid; [1] 3rd row C2H4Br2; [1] 4th row methane; fuel; [2] (d) 188 [1] ALLOW: error carried forward from incorrect structure in the table [Total: 11]

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7 (a) (i) ions cannot move in solid; ions move when molten; [2] (ii) calcium has atoms/particles closely packed together/regularly arranged/strong

forces between particles/particles can’t move; ALLOW: calcium has high boiling point (because of strong forces between

particles) chlorine has molecules/particles randomly arranged/far apart/particles can move

easily (from place to place); [2] ALLOW: chlorine has low boiling point (because of weak forces between particles) (b) (i) chlorine; calcium; [2] ALLOW: For 1 mark: calcium and chlorine the wrong way round NOT: chloride/chloride ions (ii) graphite/carbon [1] (iii) to prevent it from reacting with the air/oxygen [1] ALLOW: does not react/prevents (other) reactions (with calcium) (iv) any noble gas [1] ALLOW: nitrogen (c) with sodium hydroxide white precipitate; insoluble in excess; [2] with ammonia no precipitate/(very slight) white precipitate [1] ALLOW: no reaction/no change [Total: 12]

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for the guidance of teachers

0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers.



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Page 2 Mark Scheme: Teachers’ version Syllabus Paper


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1 (a) (i) iron(III) oxide / iron oxide / Fe2O3; [1] ALLOW: iron (ii) lead(II) bromide / lead bromide / PbBr2; [1] NOT: lead (iii) calcium carbonate / CaCO3; [1] NOT: carbonate (iv) sodium hydroxide / NaOH; [1] ALLOW: hydroxide / OH– NOT: sodium (v) methane; [1] (b) (i) oxygen is removed (from the iron oxide); [1] ALLOW: carbon takes the oxygen from the iron oxide ALLOW: oxygen goes to the carbon / the oxygen combines with the carbon ALLOW: oxidation number of iron decreases / electrons added to iron NOT: the iron oxide loses electrons (ii) haematite; limestone; blast; slag; [4] [Total: 10] 2 (a) calcium, magnesium, iron, copper; [1] (b) bubbles produced steadily / moderately / slowly / bubbles produced faster than iron and slower than magnesium / fewer bubbles than magnesium and more than iron; [1] ALLOW: many bubbles produced but less than magnesium NOT: bubbles produced rapidly / less rapidly NOT: less bubbles than magnesium / more bubbles than iron NOT: reaction / it’s faster than iron and slower than magnesium (c) (i) magnesium floats on top of the magnesium chloride ORA / magnesium is above the magnesium chloride ORA; [1] ALLOW: magnesium is on top of the magnesium chloride ORA (ii) (magnesium) too reactive / above carbon in reactivity series / more reactive than

carbon; [1] ALLOW: magnesium is a reactive metal / magnesium is reactive ALLOW: too high a temperature needed for the extraction NOT: magnesium oxide / magnesium will not react with carbon

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(iii) to prevent magnesium reacting with the air / oxygen / nitrogen; [1] ALLOW: to stop magnesium oxidising NOT: because it is reactive NOT: to stop it reacting NOT: because inert gases are unreactive (iv) nitrogen / helium / neon / argon / krypton / xenon / radon; [1] (d) (i) structure of ethene showing all atoms and all bonds; [1] ALLOW: correct electronic structure (ii) two of: [2] (1 mark each)

• carbon monoxide + poisonous / toxic; ALLOW: carbon monoxide combines with haemoglobin / red blood cells ALLOW: carbon monoxide suffocates NOT: carbon monoxide harmful / dangerous

• hydrogen + flammable / explosive; NOT: hydrogen dangerous

• hydrogen sulfide + poisonous / toxic; ALLOW: harmful NOT: dangerous / affects breathing

• ethene + flammable;

• methane + flammable; ALLOW: explosive

(e) (i) carbon monoxide + water / steam → carbon dioxide + hydrogen; [1] ALLOW: arrow for equilibrium sign NOT: carbon oxide instead of carbon monoxide NOT: mixture of words and symbols (ii) equilibrium / reversible reaction / the reaction can go both ways / the reaction can

go backwards or forwards; [1] ALLOW: the reaction can also go backwards NOT: the reaction goes backwards (iii) add sodium hydroxide (solution) / (aqueous) ammonia; [1] (red-)brown / rusty red precipitate (both points); [1] ALLOW: solid for precipitate ALLOW: yellow-brown precipitate / orange precipitate IGNORE: references to excess ammonia / sodium hydroxide NOT: red precipitate [Total: 13]

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3 (a) (fractional) distillation; [1] ALLOW: fractionation (b) Two of: [2]

• fuel gas / refinery gas;

• naphtha;

• light gas oil / heavy gas oil / fuel oil;

• lubricating oil / lubricating fraction; (NOT: lubricant)

• bitumen; (ALLOW: residue) IGNORE: kerosene / paraffin / gasoline / petrol / diesel IGNORE: methane / named chemical compounds IGNORE: gas alone (c) oil stoves / aircraft fuel / for jet engines / for car engines; [1] ALLOW: for making more petrol ALLOW: for cooking / for heating / for lighting / for fuel (d) A and D; (both needed) [1] (e) ethane; unreactive; oxygen; water; [4] (f) saturated: has only single bonds / contains the maximum amount of hydrogen atoms

(that can be combined with carbon atoms); [1] ALLOW: does not have double bonds ALLOW: consists of single bonds NOT: has single bonds hydrocarbon: (compound / substance) containing hydrogen and carbon only / it has

carbon and hydrogen only; [1] REJECT: it has carbon and hydrogen molecules only / ideas of mixtures of carbon and

hydrogen [Total: 11]

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4 (a) ammonia / NH3; [1] (b) goes blue; [1] ALLOW: goes purply-blue NOT: goes blue then bleaches NOT: goes purple (c) ammonium chloride; carbon dioxide; water; [3] NOT: formulae NOT: ammonia chloride (d) (i) to replace nitrogen lost from soil; [1] ALLOW: to make (crop) plants grow better ALLOW: to make plants grow more / faster ALLOW: to improve crop yield IGNORE: to replace minerals lost from the soil / to replace nutrients (ii) more nitrogen / greater percentage of nitrogen; [1] NOT: more nitrate (iii) 80; [1] (e) oxygen / O2; [1] NOT: O (f) acid rain / effect of acid rain e.g. trees or plants die / pond animals die / fish die /

erosion of buildings / corrosion of bridges; [1] ALLOW: smog / damages buildings NOT: destroys buildings NOT: breathing difficulties / lung damage / irritation to throat / poisonous / harmful [Total: 10]

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5 (a) carbon dioxide released / gas is released / gas is formed; [1] NOT: we get carbon dioxide, calcium chloride and water (b) (i) 615 s; [1] ALLOW: in numbers in range 600–630 s (ii) X on or near the line at beginning of experiment; [1] ALLOW: on or near line up to 50 s (iii) shallower curve at initial rate; [1] starts levelling off at 100.2 g; [1] ALLOW: (beginning to) level off between 100.15 and 100.25 g (c) (i) increases / goes faster; [1] NOT: takes less time / becomes fast / reaction increases (ii) increases / goes faster; [1] NOT: takes less time / becomes fast / reaction increases (d) combustion; small; large; [3] (e) (i) respiration; [1] NOT: oxidation (ii) (substance / compound / it) speeds up / increases the rate of a reaction; [1] ALLOW: changes rate of reaction NOT: decreases the rate IGNORE: references to biological substances [Total: 12]

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6 (a) Br2; [1] (b) particles random AND roughly similar size to the one shown; [1] particles very close together or touching; [1] (c) Any three of: [3]

• bromine evaporates / liquid evaporates; (NOT: it evaporates)

• more energetic particles from liquid to vapour;

• diffusion;

• random movement of molecules / particles move everywhere / both air and bromine particles are moving;

• (bromine and air) particles get mixed up / collision of bromine and air particles; ALLOW: molecules in place of particles NOT: atoms in place of particles (d) (light) green; [1] IGNORE: yellow to reddish-brown / brown / orange / yellow-brown; [1] NOT: yellow / red (e) bromine higher in reactivity series than iodine / bromine more reactive than iodine; [1] NOT: bromide more reactive than iodide NOT: magnesium bromide more reactive NOT: bromine stronger than iodine (f) (i) NaBr; [1] ALLOW: Na+Br– NOT: multiples e.g. 2NaBr (ii) zinc bromide; [1] ALLOW: zinc(II) bromide NOT: ZnBr2 (iii) covalent; [1] NOT: single bonding (iv) A and D; (both needed) [1] (v) the ions can move / ions are mobile; [1] ALLOW: the ions are free (from each other) NOT: ions delocalised / charged particles moved REJECT: electrons and ions move [Total: 14]

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7 (a) Cl2; [1] correct balancing; [1] (b) bonding pair; [1] chlorine electrons all correct and no other electrons on hydrogen; [1] ALLOW: use of circle / dot for chlorine and cross for hydrogen IGNORE: inner electrons (c) pH1; [1] (d) hydrogen; [1] NOT: H2 (e) Any two of: [2]

• evaporate off some of the water / heat solution to crystallisation point; ALLOW: concentrate the solution NOT: boil off the water / implication that all the water is removed NOT: heat without further qualification

• leave to crystallise / leave in the warm / leave in the air / leave on a window sill / leave at room temperature;

NOT: let it cool / leave it to cool

• dry crystals with filter paper; NOT: heat / warm to dry / put in an oven (f) (i) chlorine / Cl2; [1] NOT: Cl (ii) zinc / Zn; [1]

[Total: 10]

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for the guidance of teachers

0620 CHEMISTRY


This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers.



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1 (a) bromine and fluorine / Br and F [1] (b) krypton / Kr [1] (c) nitrogen and oxygen / N and O [1] (d) 175 [1] (e) (i) basic ALLOW: metallic [1] (ii) (burning) fossil fuels / fuels containing sulfur / volcanoes ; [1] effect of SO2 on environment e.g. destroys trees / kill plants / kills animals or plants in

lakes or rivers / chemical erosion of (limestone) buildings / corrosion of metals ; ALLOW: difficulty in breathing NOT: kills plants / animal in seas / kills marine life [1] (iii) any three of: starts off high pH / pH above 7 / named pH above 7 / alkaline (pH) ; as acid added pH goes down ; neutralises / neutralisation / neutral / pH 7 ; pH ends up below 7 / named pH below 7 / acid (pH) ; [3] (iv) universal indicator paper / pH meter [1] (v) potassium nitrate ALLOW: KNO3 [1] 2 (a) compound: top box ; element: 2nd box ; ion: 5th box ; molecule: 4th box ; [4] (b) air + steel / first and last boxes ticked [1]

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(c) (i) any four of: nucleus or particles on inside and electrons on outside ; nucleus labelled ; electrons on outside labelled ; ALLOW: e for label two electrons ; protons + neutrons in nucleus + labels ; ALLOW: p for proton and n for neutron IGNORE: incorrect number of neutrons two protons ; [4] (ii) balloons / (arc) welding / (advertising) lights / growing Si or Ge crystals / making Ti or Zr /

coolant (in nuclear reactors) / wind tunnels / for divers [1] NOT: as an inert gas / in (hot) air balloons / in bulbs (iii) helium unreactive / second box down ticked [1] 3 (a) structure of ethanol with all atoms and bonds shown ALLOW: OH in place of O – H [1] (b) (i) exothermic [1] (ii) 16.2 (g) [1]

(iii) 2 (CO2) + 3 (H2O) [1] (c) any two of: (very) high melting / boiling points ; (very) high density ; ALLOW: harder form coloured compounds ; NOT: they are coloured variable oxidation numbers / can form more than one type of ion / variable valency / form complex ions ; are (good) catalysts ; ALLOW: chemical differences e.g. do not react with cold water [2]

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(d) (i) any two of: bubbles / effervescence ; copper carbonate / solid dissolves ; solution becomes coloured / solution goes green / change of colour ; NOT: wrong colour [2 (ii) aqueous / dissolved in water [1] (e) polymer ; addition ; monomers ; [3] 4 (a) any two physical properties of group I metal e.g. (fairly) low melting boiling point (for a metal) ; solid ; conducts heat or conducts electricity ; malleable ; soft ; ALLOW: ductile / shiny (when cut) NOT: hard / sonorous [2] (b) 1 [1] (c) (i) atoms of same element / same proton number with different numbers of neutrons /

different number of nucleons [1] (ii) 78 [1] (d) boiling point 500 – 680 (actual = 669) ; [1] reactivity: any idea of faster than rubidium e.g. explosion / very violent spitting ; ALLOW: more reactive / increased reaction [1] (e) CsCl [1] (f) pH 7 [1] (g) (aqueous) silver nitrate / aqueous lead nitrate ; [1] white precipitate ; (result conditional on correct reagent) [1]

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5 (a) double bond(s) ringed [1] (b) C10H16 [1] (c) red-brown / brown ; [1] to colourless / loses its colour ; NOT: becomes discoloured [1] (d) (i) A thermometer ; B condenser ; C measuring cylinder ; NOT: measuring tube [3] (ii) arrangement: random ; ALLOW: far apart [1] movement: random / rapid / move everywhere ; [1] (e) (i) idea of oxygen not in excess / carbon monoxide formed (instead of carbon dioxide) ALLOW: doesn’t burn completely / doesn’t burn as much as it could ALLOW: carbon or soot formed (instead of carbon dioxide) [1] (ii) toxic / kills you / poisonous / asphyxiation / suffocation NOT: harmful [1] (f) (i) A [1] (ii) C [1] (iii) B [1] 6 (a) decomposition [1] (b) ions must be able to move NOT: charges must be able to move REJECT: ions and electrons move = 0 [1] (c) lower melting point of the electrolyte ALLOW: helps dissolve the aluminium oxide [1] (d) B [1]

(e) anode: oxygen ; [1] cathode: aluminium ; (both aluminium and oxygen but at wrong electrodes = 1) [1]

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(f) oxygen reacts with them / oxygen reacts with carbon ; [1] ‘burns’ them away / carbon dioxide formed / gas formed ; ALLOW: the electrodes get used up [1]

(g) 3 [1] (h) aircraft body / car body / saucepans/ electricity cables / food containers / window frames /

cooking foil / other suitable uses NOT: alloys unqualified [1] 7 (a) both parts required for each mark A: yes – air and water present ; [1] B: no – no water / there is only air ; [1] C: no – coating protects / zinc protects (from air and water) / zinc corrodes instead / zinc is a sacrificial metal ; [1] (b) any three of: oxygen blown into molten iron ; to oxidise sulphur / carbon / phsophorus / silicon ; basic oxides / CaO / MgO added ; react with phosphorus and silicon ; (P and Si) removed as slag / slag formed ; [3] (c) chemical plant / surgical instruments / cutlery [1] (d) O removed (from iron oxide) / oxidation number (of iron) decreased [1] (e) iron(II) oxide + hydrochloric acid → iron chloride + water (1 for correct reactants, 1 for correct products) [2]

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Documents

NOVEMBER 2001 INTERNATIONAL GCSE - Weebly9dwebsite.weebly.com/uploads/3/0/7/8/3078174/chem_paper_2_ms.pdf · november 2001 international gcse mark scheme maximum mark : 80 syllabus/component