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CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the October/November 2013 series 0620 CHEMISTRY 0620/11 Paper 1 (Multiple Choice), maximum raw mark 40 Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.
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Page 1: 0620 CHEMISTRY - maxpapers.commaxpapers.com/wp-content/uploads/2012/11/0620_w13_ms_all.pdf · 0620/11 Paper 1 (Multiple Choice ... Page 2 Mark Scheme Syllabus Paper IGCSE – October/November

CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/11 Paper 1 (Multiple Choice), maximum raw mark 40

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

Page 2: 0620 CHEMISTRY - maxpapers.commaxpapers.com/wp-content/uploads/2012/11/0620_w13_ms_all.pdf · 0620/11 Paper 1 (Multiple Choice ... Page 2 Mark Scheme Syllabus Paper IGCSE – October/November

Page 2 Mark Scheme Syllabus Paper

IGCSE – October/November 2013 0620 11

© Cambridge International Examinations 2013

Question Number

Key Question Number

Key

1 B 21 D

2 B 22 C

3 A 23 A

4 A 24 D

5 D 25 B

6 C 26 D

7 A 27 B

8 A 28 B

9 D 29 B

10 D 30 C

11 D 31 A

12 D 32 C

13 D 33 B

14 B 34 B

15 A 35 B

16 D 36 C

17 B 37 D

18 D 38 C

19 A 39 D

20 A 40 C

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/12 Paper 1 (Multiple Choice), maximum raw mark 40

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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Page 2 Mark Scheme Syllabus Paper

IGCSE – October/November 2013 0620 12

© Cambridge International Examinations 2013

Question Number

Key Question Number

Key

1 B 21 A

2 B 22 B

3 A 23 D

4 D 24 A

5 A 25 C

6 C 26 B

7 A 27 A

8 D 28 B

9 A 29 B

10 D 30 C

11 D 31 C

12 D 32 D

13 D 33 B

14 D 34 B

15 B 35 B

16 A 36 D

17 D 37 C

18 A 38 D

19 B 39 C

20 D 40 C

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/13 Paper 1 (Multiple Choice), maximum raw mark 40

Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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Page 2 Mark Scheme Syllabus Paper

IGCSE – October/November 2013 0620 13

© Cambridge International Examinations 2013

Question Number

Key Question Number

Key

1 D 21 D

2 C 22 C

3 A 23 A

4 B 24 D

5 C 25 A

6 D 26 B

7 B 27 B

8 A 28 A

9 D 29 C

10 B 30 C

11 B 31 A

12 A 32 B

13 D 33 D

14 D 34 D

15 A 35 B

16 D 36 B

17 B 37 A

18 D 38 C

19 A 39 C

20 D 40 B

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/21 Paper 2 (Core Theory), maximum raw mark 80

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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© Cambridge International Examinations 2013

1 (a) (i) nitrogen [1] (ii) sulfur [1] (iii) iodine [1] (iv) helium [1] (v) nickel [1] (vi) iodine [1] (b) substance containing only 1 type of atom / substance which cannot be broken down further by chemical means [1] (c) Any 3 of: [3] conducts electricity / conducts heat / conducts shiny / lustrous ductile / can be drawn into wires malleable / can be shaped ALLOW: high boiling point / high melting point / solid at room temperature ALLOW: rings when hit / sonorous [Total: 10] 2 (a) (i) pair of bonding electrons [1] 8 electrons around chlorine and no additional electrons around hydrogen [1] (ii) covalent because has shared (pair of) electrons [1]

ALLOW: low melting point / low boiling point / it is a gas / doesn’t conduct electricity / both non-metals

(b) pH 2 [1] (c) (i) calcium chloride [1] carbon dioxide [1] water [1] NOTE: do not allow formulae (ii) 2 [1] calcium chloride [1]

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(d) (i) values from 215 to 245 (s) [1] (ii) 22 (cm3) [1] (iii) Any 2 of: [2] temperature / mass of magnesium / particle size of magnesium / surface area of

magnesium [Total: 13] 3 (a) 1 mark each correct answer [4] carbon / hydrogen

hydrogen (if carbon given for first marking point) / carbon (if hydrogen given for first marking point)

similar functional (b) (i) H H │ │ H – C – C – O – H [2] │ │ H H H H │ │ H – C – C – OH (for 1 mark) │ │ H H (ii) carbon dioxide [1] water [1] (c) (i) COOH ringed [1] (ii) 7 [1] (iii) foodstuffs / drinks / cosmetics / water [1]

IGNORE: generalised answers e.g. kitchen / cleaning [Total: 11]

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4 (a) Any 4 of: [4] both contain carbon atoms both have covalent bonding both are giant structures / lattices both contain rings / have hexagonal patterns / rings of 6 atoms in diamond, atoms arranged tetrahedrally in graphite, atoms arranged in layers flat rings in graphite bent rings in diamond all bonds same length in diamond

graphite has some longer bonds / weaker bonds in diamond, each C atom joined to 4 others in graphite, each C atom joined to 3 others (b) lime water; [1] turns milky / cloudy / white ppt [1] 2nd mark dependent on correct reagent (c) poisonous / kills you / toxic [1]

ALLOW: harmful / higher level answers referring to combining with haem IGNORE: causes respiration problems / damages lungs (d) oxygen removed from iron oxide [1]

ALLOW: oxidation number of iron decreases / iron gains electrons / CO becomes oxidised / oxygen adds to CO

(e) limestone [1] air [1] [Total: 10] 5 (a) filter paper / chromatography paper [1] solvent / alcohol / other suitable solvent [1] NOT: leaves / pigments in solvent (b) X drawn on base line [1] (c) chromatography [1] (d) (i) 2nd box down ticked / aqueous nickel(II) sulfate [1] (ii) nickel [1] (iii) cathode [1]

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(e) protection from corrosion / make it less reactive / make it unreactive [1] better appearance / more shiny [1] (f) (i) 6H2O [1] (ii) reversible reaction / equilibrium reaction / reaction goes both ways /

reaction goes backwards as well (as forwards) [1] IGNORE: reaction goes backwards / it is the reverse reaction (iii) add water (to white nickel(II) chloride) / hydrate (white nickel(II) chloride) [1] [Total: 12] 6 (a) Any 4 of: [4]

in steam, molecules are far apart

in water, molecules are close together in steam, molecules are moving very fast in water, molecules are moving slowly / sliding over each other in steam more randomness in arrangement of molecules NOTE: molecules are further apart in steam (than in water) = 2 marks NOTE: molecules move faster in steam (than in water) = 2 marks NOTE: for molecules the word particles can be used NOT: implication of particles ‘apart’ in liquids (b) (i) substance which dissolves another / it dissolves a solute / substance which dissolves a

solute / it dissolves something; [1] (ii) ethanol [1] IGNORE: alcohol (c) endothermic [1] (d) 1st box ticked /aqueous ammonium chloride [1] (e) (i) LiOH on right [1] 2 on left (mark dependent on LiOH being correct) [1] (ii) 20 g [1] [Total: 11] 7 (a) (i) copper [1] (ii) (copper is) better electrical conductor / iron is worse conductor [1] IGNORE: copper is a good conductor

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(iii) does not conduct (electricity) [1] (iv) lead [1] (v) stronger / has more strength [1] IGNORE: tougher / harder / less malleable (vi) lead [1] (b) (i) zinc [1] (ii) (zinc) hydroxide [1] ALLOW: error carried forward from wrong metal in part (b)(i) (c) C,B,D,A [1] (d) CuCl2 [1] ALLOW: Cl2Cu (e) positive electrode: chlorine [1] negative electrode: copper [1] ALLOW: 1 mark for chlorine and copper reversed (f) chlorine / Cl2 [1] [Total: 13]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/22 Paper 2 (Core Theory), maximum raw mark 80

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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1 (a) (i) ammonia [1] (ii) methane [1] (iii) ammonium chloride [1] (iv) water [1] (v) calcium carbonate [1] (vi) copper(II) sulfate [1] (b) substance which contains two (or more) elements chemically combined (or bonded) / two

different atoms bonded (or combined or joined) / different atoms bonded [1] ALLOW: a substance containing two (or more) elements which cannot be separated by

physical means (c) CO2 on right [1] 2(O2) [1] NOTE: second mark dependent on first mark [Total: 9] 2 (a) zinc → magnesium → calcium → sodium [2] NOTE: 1 mark if one pair incorrectly placed / metals in reverse order (b) magnesium chloride [1] hydrogen [1] (c) ion [1] (d) 1 electron in outer shell [1] 8 electrons in middle shell [1] (e) (i) correct method of collection i.e. upturned measuring cylinder over water or (gas) syringe [1] workable apparatus and closed system [1] flask or test tube labelled AND measuring cylinder or syringe labelled [1] ALLOW: flask / test tube / syringe / measuring cylinder not joined up (ii) Any three of: [3] increase concentration (of hydrochloric acid) / use concentrated acid increase temperature / heat up reaction use smaller lumps of zinc / add a catalyst [Total: 13]

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3 (a) distillation [1] ALLOW: (fractional) distillation (b) (round-bottomed) flask [1] thermometer [1] condenser [1] ALLOW: condensing tube (c) 1 mark each: lower boils condenses [3] (d) (i) chloride / Cl– [1] (ii) K+ / potassium [1] (iii) Mg2+ [1] SO4

2– [1] [Total: 11] 4 (a) 1 mark each: [4] poly(ethene) → it has a very long chain ethene → it decolourises bromine water methane → it is the main constituent of natural gas ethanoic acid → it contains a –COOH functional group (b) (i) substance containing carbon and hydrogen only [1] (ii) it has a double bond [1] (c) monomers [1] (d) (i) addition of oxygen / increase in oxidation number / loss of electrons [1] ALLOW: removal of hydrogen (ii) glucose (on left) [1] ALLOW: sugar carbon dioxide (on right) [1] [Total: 10]

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5 (a) Any three of: [3] alloy is a mixture / alloy is a combination of metal with another metal / of metals / of a metal

with a non-metal IGNORE: mixed with another substance / alloying alters property of metal / makes metal stronger / makes metal more corrosion resistant / makes metal harder / ALLOW: reduces rusting ONLY if iron / steel mentioned IGNORE: lasts longer / durable ALLOW: answers from diagram ALLOW:: higher level answers e.g. layers in metals slide over each other easily / layers in

alloy do not slide as easily

(b) (i) 1 mark each: [2] 3rd box and 5th box ticked (ii) 1 mark for method and 1 mark for why it works: [2]

painting / tinning / galvanising / covering with plastic / chromium / greasing / (electro)plating (1)

IGNORE: covering / coating (unqualified) prevents air (or oxygen) and water coming into contact with iron (1) OR

galvanising / coating with zinc / putting block of named reactive metal on surface (1) metal reacts instead of iron / metal more reactive than iron (1) ALLOW: sacrificial protection (c) (i) substance which speeds up reaction / increases rate of reaction [1] (ii) (damp) red litmus paper [1] ALLOW: universal indicator turns blue [1] ALLOW: (concentrated) hydrochloric acid (1) white fumes (1) (iii) Any two of: [2]

replacement of nitrogen / nitrates / potassium / phosphorus (taken up by plants)

plants take up nitrogen / potassium / phosphorus / nitrates from soil / nitrogen (or potassium or phosphorus) needed by plants (fertiliser) adds extra nitrogen / potassium / phosphorus / nitrates (to replace this) increase plant growth / plants grow better / plants grow faster / better yield

IGNORE: for plant growth / for healthy plants make more (plant) protein

[Total: 12]

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6 (a) Any three of: [3] evaporates or evaporation (from garlic) / idea of change from liquid to gas / movement of particles / atoms / molecules / diffusion / particles (in garlic smell) collide (with

air particles) / spreading out or mixing up of particles / atoms / molecules / random / disorderly (movement of particles / atoms / molecules) / ALLOW: particles move from high(er) to low(er) concentration (b) (i) C6H10S2 [1] (ii) (one) more sulfur atom in A / B has 1 sulfur atoms but A has 2 [1] same number of C and H atoms / molecule otherwise the same / [1] (c) (i) 18 [1]

(ii) atoms of same element with different number of neutrons / atoms with same number of protons and different numbers of neutrons / atoms differing only in number of neutrons / elements with same number of protons and different number of neutrons / elements with same proton number but different nucleon (or mass) number [1]

number of protons + neutrons (in an atom) [1] (iii) coal; oxidised; dioxide; water; [4] (iv) pits surface/ idea of (chemical) weathering / (chemical) erosion [1]

ALLOW: damages building / eats away the building / dissolves building / wears away the building / surface disintegrates / surface crumbles

IGNORE: destroys buildings / cracks the building / corrosion acid (rain) reacts with carbonate / limestone / neutralisation [1] REJECT: burns carbonate / melts carbonate [Total: 15] 7 (a) (i) (limestone added): A [1] (waste gases exit): B [1] (ii) CO2 [1] (iii) 15 (g) [1] (b) (i) harder / slower to decompose down Group / (ease) decreases down Group /

easier to decompose up Group / ease increases up Group / thermal stability increases down Group / thermal stability decreases up Group [1]

ALLOW: the more reactive the metal, the higher the decomposition temperature (ii) ALLOW: values from 1000 to 2000 (oC) (actual = 1360

oC) [1] (c) (i) neutralise acidic soils / neutralise acidic lakes / making mortar / making calcium hydroxide / making limewater / whitewash [1]

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(ii) basic [1] IGNORE: alkali / metal (iii) 56 [1] (d) (calcium) too reactive / (calcium) above carbon in reactivity series [1] ALLOW: very reactive / high reactivity / more reactive than carbon [Total: 10]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/23 Paper 2 (Core Theory), maximum raw mark 80

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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1 (a) (i) aluminium [1]

(ii) calcium and iron [1]

(iii) lithium [1]

(iv) silver [1]

(v) aluminium [1]

(b) Any 2 of: [2]

reacts with acids rusts / reacts with water and oxygen / reacts with water and air reacts with steam reacts with oxygen reacts with chlorine acts as a catalyst any other suitable e.g. reacts with nitrates of less reactive metal

(c) calcium oxide added / lime added [1] oxygen / air (blown into molten iron) [1] [Total: 9]

2 (a) Any five of: [5]

nucleus in centre of atom protons and neutrons in nucleus / protons and neutrons in centre of atom

electrons outside the nucleus / idea of electrons in shells outside the centre of atom 2 protons 2 electrons 2 neutrons (in commonest isotope) protons positively charged electrons negatively charged neutrons have no charge

(b) airships / blimps / balloons / diving / lasers / any other suitable [1]

(c) 223 [2] Xe =131, O =16, F = 19 (for 1 mark)

(d) (i) (room temperature): gas [1] (-200

oC): liquid [1]

(ii) has two atoms [1] IGNORE: F2 / Cl2 (unqualified) / reference to same atoms or different atoms

[Total: 11]

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3 (a) 2 electrons in outer shell [1] 8 electrons in middle two shells [1]

(b) calcium chloride [1]

(c) (i) 27 cm3 [1]

(ii) lower initial gradient [1] ends up at same volume of gas [1]

(iii) temperature: goes faster / increases [1] hydrochloric acid: goes slower / decreases [1]

(d) (i) decomposition [1]

(ii) limewater [1] ALLOW: calcium hydroxide solution

turns milky / cloudy / white ppt [1] 2nd mark dependent on first being correct

(e) (i) calcium nitrate [1] water [1]

(ii) neutralise acidic soils / neutralise acidic lakes / making mortar / making calcium hydroxide / making limewater / whitewash [1]

ALLOW: making cement / making lines on roads (or games pitches) /

in steel making

(iii) exothermic [1]

[Total: 15]

4 (a) Bunsen burner / source of heat [1] ALLOW: heating / heat

(b) X at ‘space’ at top of test tube [1]

(c) speed up the reaction / increase rate of reaction / make reaction go faster [1]

(d) C4H8 / 2C2H4 [1]

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(e) (i) decolourises / goes colourless [1] IGNORE: goes clear

(ii) B [1]

(iii) 4th box ticked (polymerisation) [1] (f) (i) C7H16 [1] (ii) substance containing carbon and hydrogen only [1] (g) carbon dioxide [1] water [1] ALLOW: correct formulae [Total: 11] 5 (a) 3rd and 5th boxes ticked (sugar and water) (1 mark each) [2] (b) (fractional) distillation [1] IGNORE: fractionation (c) O-H at right [1] ALLOW: OH (d) octanol [1] (e) from ethene and steam [1] ALLOW: from ethene and water AND any two of: [2]

high temperature / heat / stated temperature between 150 and 1000

oC catalyst / phosphoric acid high pressure / stated pressure between 50-100 atm

NOTE: allow sulfuric acid (1) dilute with water (1) heat (1) [Total: 8] 6 (a) (i) reversible reaction / equilibrium reaction / reaction can go both ways [1] IGNORE: products go to reactants / it is a reverse reaction (ii) add water to white copper sulfate / add water to anhydrous copper sulfate ALLOW: add water to CuSO4 [1] turns it blue [1]

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(iii) melt it / turn it to liquid [1] dissolve it in water / make a solution of it [1] ALLOW: add water (b) (i) floats on top (of the mixture) / it is on top (of the mixture) [1] (ii) S gains oxygen / it gains oxygen / S turns to SO2 [1] ALLOW: it / sulfur increases in oxidation number ALLOW: it / sulfur loses electrons (iii) cathode: C [1] electrolyte: D [1] [Total: 9] 7 (a) 112 (oC) [1] liquid [1] (b) arrangement: go from regularly to irregularly arranged / become more irregularly

arranged / go from regular to random [1] ALLOW: idea of becoming less packed / less arranged / not so close together (but not implication of particles being apart from each other) NOTE: do not allow implication of particles being ‘apart’ in solid motion: start moving / start sliding over each other / go from no movement to movement / go from just vibrating to moving (over each other) [1]

ALLOW: idea of greater movement (c) Any three of: [3]

(crystal) dissolves / idea of dissolving

particles (in crystal) become separated / solvent molecules get in between particles / mixing of particles / spreading out of particles diffusion movement of particles (in solution) random (movement of particles) particles collide

ALLOW: particles move from concentrated to dilute solution [Total: 7]

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8 (a) Any 2 of: [2] compound has constant composition but mixture has variable composition

compound cannot be separated into different components (by physical means) but mixture can (be separated) / only the mixture can be separated ALLOW: elements are chemically combined in compound but not in mixture

compound has properties different from elements it contains but mixture has the properties of the substances within it ALLOW: compounds have sharp melting point (or boiling point) and mixture does not

energy change when compound formed but no (or very small) energy change when mixture formed

(b) Any two of: [2]

filtration / salts move to the clay pot and insoluble particles (remain) in the bowl large particles (or insoluble particles) caught by leaves the salts dissolve in the water / the salts are soluble (dissolved) salts pass or through) the (holes in the) leaves /

IGNORE: salts pass through holes in the bowl (c) (i) sodium carbonate [1] (ii) chloride / Cl

- [1] IGNORE: chlorine (iii) K+ [1] SO4

2- [1] (d) 2 (NaCl) [1] (e) electrons / an electron [1] IGNORE: negative charge [Total: 10]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/31 Paper 3 (Extended Theory), maximum raw mark 80

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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© Cambridge International Examinations 2013

1 (a) uranium / plutonium / thorium [1] (b) graphite / carbon [1] (c) platinum / titanium / mercury / gold [1] NOT: carbon / graphite (d) helium [1] (e) nitrogen / phosphorus [1] (f) argon [1] ACCEPT: any ion 2 + 8 + 8 e.g. K+ etc. (g) tellurium [1] ACCEPT: correct symbol [Total: 7] 2 (a) Any three of: iron is harder iron has higher density ACCEPT: heavier or potassium lighter iron has higher mp or bp iron has higher tensile strength or stronger iron has magnetic properties [3] NOTE: has to be comparison, e.g. iron is hard (0) but iron is harder (1) NOT: appearance e.g. shiny ACCEPT: comparative statements relating to potassium (b) potassium hydrogen (1) and potassium hydroxide (1) zinc hydrogen (1) and zinc oxide (1) copper no reaction (1) [5] [Total: 8]

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3 (a) (i) fractional distillation [1] (liquid) air [1] (ii) cracking / heat in presence of catalyst [1] of alkane / petroleum [1] to give an alkene and hydrogen [1]

OR: electrolysis (1) named electrolyte (1) hydrogen at cathode (1)

OR: from methane (1) react water / steam (1) heat catalyst (1) only ACCEPT: water with methane or electrolysis (b) (i) the pair with both graphs correct is C [1] NOTE: mark (b)(ii) independent of (b)(i) (ii) high pressure favours side with lower volume / fewer moles [1] this is RHS / product / ammonia [1] %NH3 / yield increases as pressure increases [1] the forward reaction is exothermic [1] exothermic reactions favoured by low temperatures [1] %NH3 / yield decreases as temperature increases [1] ACCEPT: reverse arguments (iii) increases reaction rate [1] ACCEPT: reduces activation energy [1] OR: decreases the amount of energy particles need to react OR: economic rate at lower temperature so higher yield [Total: 14] 4 (a) (i) (mass at t =0) – (mass at t = 5) [1] NOTE: must have mass at t = 5 not final mass (ii) fastest at origin slowing down between origin and flat section gradient = 0 where gradrient = 0 three of above in approximately the correct positions [2] (iii) 3 correct comments about gradient = [2] 2 correct comments about gradient = [1] 1 correct comment about gradient = [0] [2] (b) start at origin and smaller gradient [1] same final mass just approximate rather than exact [1]

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(c) (i) smaller surface area [1] lower collision rate [1] (ii) molecules have more energy [1] collide more frequently / more molecules have enough energy to react [1] (d) number of moles of HCl in 40 cm3 of hydrochloric acid, concentration 2.0 mol / dm3 = 0.04 × 2.0 = 0.08 [1] maximum number of moles of CO2 formed = 0.04 [1] mass of one mole of CO2 = 44 g [1] maximum mass of CO2 lost = 0.04 × 44 = 1.76 g [1] [Total: 15] 5 (a) (i) have same molecular formula / both are C5H12 [1]

they have different structural formulae / different structures [1] (ii) CH3-CH2-CH=CH-CH3 / any other correct isomer [1] (b) (i) CH2-(Br)-CH2Br [1] NOT: C2H4Br2 dibromoethane [1] NOTE: numbers not required but if given must be 1, 2 (ii) CH3-CH2-CH3 [1] NOT: C3H8

propane [1]

(iii) CH3-CH2-CH2-CH2-OH / CH3-CH2-CH(OH)-CH3 [1] butanol [1] numbers not required but if given must be correct and match formula (c) (i) CH3-CH=CH-CH2-CH3 [1] CH3-CH=CH-CH3 [1] (ii) pink / purple [1] colourless [1] NOT: clear (d) -CH2-CH(CN)-CH2-CH(CN)- correct repeat unit CH2-CH(CN) [1] COND: at least 2 units in diagram [1] continuation [1] [Total:16]

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6 (a) (i) (attractive force between) positive ions [1] and (negative) electrons [1] opposite charges attract ONLY [1] electrostatic attraction ONLY [1] (ii) lattice / rows / layers of lead ions / cations / positive ions [1] NOT: atoms / protons / nuclei can slide past each other / the bonds are non-directional [1] (b) (i) anhydrous cobalt chloride becomes hydrated [1] ACCEPT: hydrous (ii) carbon dioxide is acidic [1] sodium hydroxide and calcium oxide are bases / alkalis [1] (iii) Any two of: water, calcium carbonate and sodium carbonate [2] ACCEPT: sodium bicarbonate (c) number of moles of CO2 formed = 2.112 / 44 = 0.048 [1] number of moles of H2O formed = 0.432 / 18 = 0.024 [1] x = 2 and y = 1 NOT: ecf from this line formula is 2PbCO3.Pb(OH)2 / Pb(OH)2. 2PbCO3 [1] [Total:12] 7 (a) (i) hydrogen (atoms) replaced by (atoms) of a different element e.g. chlorine [1] NOT: substitute (ii) light required [1] (b) exothermic reaction gives out energy [1] endothermic reaction absorbs takes in energy [1] (c) bonds broken energy C-H +412 Cl-Cl +242 total energy +654 [1] bonds formed energy C-Cl –338 H-Cl –431 total energy –769 [1] energy change –115 [1] negative sign indicates exothermic [1] [Total: 8]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/32 Paper 3 (Extended Theory), maximum raw mark 80

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October / November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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© Cambridge International Examinations 2013

1 (a) C and F [1] (b) A [1] (c) B [1] (d) D [1] (e) E [1] (f) A and D [1] [Total: 6] 2 (a) (i) two atoms per molecule [1] (ii) 7e in outer shell or level / same number of outer electrons / need to gain one electron [1] (iii) different number of energy levels / different number of electrons [1] (iv)

halogen solid, liquid or gas at room temperature

colour

chlorine

gas yellow / yellow green / green

bromine liquid brown / red-brown / orange-brown

not: red / orange

iodine solid black / grey / silver-grey / purple / violet

NOT: blue-black

NOTE: one mark for each vertical column [2] (b) correct formula, AsF3 [1] 3nbps and 1bp around all 3 fluorine atoms [1] 3bps and 1nbp around arsenic atom [1] (c) (increased) light increases / causes forward reaction / light causes AgCl reacts with CuCl [1] (increased) light increases the amount of silver (and so darkens glass) [1] decrease in light reverses reaction / uses up silver / silver reacts (and so reduces darkness)[1] [Total: 11]

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3 (a) (i) the (forward) reaction is endothermic [1] (ii) none [1] volume of reactants and products the same [1] ACCEPT: number of moles or molecules (iii) the reaction (between oxygen and nitric oxide) is exothermic [1] high temperatures push equilibrium to left / high temperatures decrease yield of products

/ low temperatures favour forward reaction [1] (iv) 4NO2 + O2 + 2H2O � 4HNO3 [2] not balanced = (1) only (v) (cost of) high amount of electricity / energy [1] (b) (i) contains more nitrogen [1] (ii) photosynthesis [1] chlorophyll is catalyst / chlorophyll absorbs light [1] carbon dioxide and water react [1] to make glucose / carbohydrates / starch / sugar / named sugar [1] [Total: 13] 4 (a) Any one of: Fe2O3 + 3C � 2Fe + 3CO 2Fe2O3 + 3C � 4Fe + 3CO2 Fe2O3 + 3CO � 2Fe + 3CO2

for correct equation (2) not balanced = (1) only any four of: coke burns to form carbon dioxide / C + O2 � CO2 this reacts with more carbon to form carbon monoxide / C + CO2 � 2CO calcium carbonate decomposes to form calcium oxide and carbon dioxide / CaCO3 � CaO +

CO2 calcium oxide / calcium carbonate reacts with silica / silicon oxide / silicon(IV) oxide (in ore)

to form calcium silicate / slag / CaO + SiO2 � CaSiO3 or CaCO3 + SiO2 � CaSiO3 + CO2 the reaction between carbon and oxygen is exothermic / produces heat / coke is used as a

fuel / the slag floats on the (molten) iron / the slag and molten iron can be run off separately [6]

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(b) (i) greenhouse effect / CO2 is a greenhouse gas [1] global warming / ice caps melting / suitable example [1] (ii) burning or combustion of charcoal produces carbon dioxide [1] trees use carbon dioxide (in photosynthesis) [1] (iii) cathode reaction Fe3+ + 3e � Fe [1] anode reaction 2O2- � O2 + 4e [2] not balanced = (1) only [Total: 13] 5 (a) because they have more than one oxidation state or valency / form ions with different

charges [1] there are two iron oxides (iron(III) oxide and iron(II) oxide) / iron forms Fe2+ and Fe3+

compounds / iron forms iron(II) and iron(III) compounds [1] (b) (i) to remove the precipitate / remove the silver(I) chromate(VI) / remove the residue [1] (ii) to remove soluble impurities / remove named soluble salt e.g. potassium nitrate / remove

reactants [1] (iii) to dry solid / to remove water [1] (c) (i) need one mole of potassium chromate(VI) for two moles of silver(I) nitrate / correct

references to mole ratio [1] (ii) mass of AgNO3 needed is 170 × 0.2 × 0.1 = 3.4g [2] NOTE: if answer given is 34 they have omitted 0.1 ALLOW: (1) ecf (iii) number of moles of AgNO3 used = 0.02 × 0.2 = 0.004 [1] number of moles of Ag2CrO4 formed = 0.002 [1] mass of one mole of Ag2CrO4 = 332g mass of Ag2CrO4 formed = 0.664g [1] NOTE: use ecf when appropriate [Total: 11]

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6 (a) (i) Cu(OH)2 � CuO + H2O [1] (ii) Rb [1] (b) (i) electron loss [1] (ii) because they can accept electrons [1] (c) (i) copper and mercury [1] (ii) add copper / mercury / metal to (named) acid and no reaction / no bubbles / no

hydrogen [1] (d) (i) Mn [1] (ii) (solution) becomes colourless / decolourises NOT: clear [1] [Total: 8] 7 (a) (i) contains only carbon, hydrogen and oxygen [1] hydrogen (atom) to oxygen (atom) ratio is 2:1 [1] ALLOW: C:H:O as 1:2:1 or Cn(H2O)n (ii) condensation [1] polymerisation [1] (b) (i) cells / micro-organisms / plants / animals / metabolic reactions [1] obtaining energy from food / glucose / nutrients [1] (ii) 2C2H5OH + 2CO2 [2] allow: C2H6O for C2H5OH not balanced = (1) only (iii) to prevent aerobic respiration / to get anaerobic respiration / to prevent ethanoic acid /

lactic acid / carboxylic acids being formed / to prevent oxidation of ethanol [1] (c) displayed formula of methyl butanoate [2] NOTE: all bonds must be shown NOTE: award (1) if error in alkyl groups but correct displayed structure of –COO– (d) (i) alcohol, e.g. glycerol, circled [1] ALLOW: if only part of glycerol molecule is circled as long as it involves an OH group (ii) saturated correct reason based on group C17H35 / all C–C bonds / no C = C bonds [1]

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(iii) salt / carboxylate / alkanoate [1] (making) soap [1] ACCEPT: detergent / washing (e) at least one correct amide linkage –CONH– [1] continuation shown at both ends of chain [1] diagram showing three (different) amino acid residues [1] [Total: 18]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/33 Paper 3 (Extended Theory), maximum raw mark 80

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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© Cambridge International Examinations 2013

1 (a) same number of protons [1] same number of electrons [1] different number of neutrons [1] (b) (i) 235U / 239Pu [1] NOTE: need symbol or name and nucleon number (ii) treating cancer / chemotherapy / radiographs / tracer studies / x–ray (scans) /

sterilise surgical instruments / diagnose or treat thyroid disorders / radiotherapy [1]

paper thickness / steel thickness / radiographs / welds / tracing / fill levels in packages / food irradiation / smoke detectors [1] ACCEPT: any other uses

(iii) Zr + 2H2O � ZrO2 + 2H2 [2] not balanced = (1) only (iv) hydrogen explodes / fire (risk) [1] (c)

if the oxide is predicted result with hydrochloric acid

predicted result with aqueous aqueous sodium hydroxide

acidic NR R

neutral NR NR

basic R NR

amphoteric R R

(1) per line [4]

[Total: 13]

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2 (a) (i) positive and negative ions [1] regular pattern / opposite charges closer than the same charge [1] (ii) so that charges cancel / ions may not have the same charge [1] (iii) Any three of:

high melting point or boiling point hard brittle soluble in water / insoluble in organic solvents conduct (electricity) in liquid state or in aqueous solution / non-conductors or poor conductor (when solid) [3]

(b) correct formula [1]

correct charges [1] 6x and 2o around oxygen [1]

[Total: 9] 3 (a) (i) roast or heat or burn in air / roast or heat or burn in oxygen [1] need both of the above (ii) ZnO + C � Zn + CO / 2ZnO + C � 2Zn + CO2 / ZnO + CO � Zn + CO2 [1] (b) (i) ZnO + H2SO4 �ZnSO4 + H2O [1] (ii) zinc reduces / gives electrons / displaces (copper / cobalt / nickel ions) [1] forming copper / cobalt / nickel (metal which is precipitated) [1] (c) (i) Zn2+ + 2e � Zn [1] (ii) OH– � 2H2O + O2 + …..e (1) only 4OH– �2H2O + O2 + 4e [2] (iii) sulfuric acid / hydrogen sulfate [1] ACCEPT: sulfuric acid

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(d) (i) Any two of: appearance more resistant to corrosion harder (accept stronger) easier to cast [2] (ii) zinc more reactive (than iron or steel) [1] zinc loses electrons [1] electrons move (from zinc) to iron [1]

zinc reacts (with air and water) / zinc corrodes / is oxidised / forms positive ions / anodic or iron and steel don’t react (with air and water) / not oxidised / do not form ions / do not lose electrons [1]

[Total: 15] 4 (a) (i) S + O2 � SO2

or sulfur burnt / roasted / heated in air to form sulfur dioxide [1]

2SO2 + O2 2SO3 [2] unbalanced = (1) only (catalyst) vanadium(V) oxide / vanadium pentoxide [1] (temperature) 440 to 460

oC [1] (dissolve) sulfur trioxide in sulfuric acid (to form oleum) [1] ignore comments about pressure (ii) add oleum to water [1] (b) Ba(C6H13SO3)2 / (C6H13SO3)2Ba [1] (c) (i) � magnesium hexanesulfonate + hydrogen [1] (ii) � calcium hexanesulfonate + water [1] (iii) 2C6H13SO3H + Na2CO3 � 2C6H13SO3Na + CO2 + H2O C6H13SO3Na = (1) [1] remaining species correct and equation balanced = (1) [1]

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(d) (i) measure pH / add universal indicator [1] both acids have a low value / pH 0–2 / same colour / red [1] or measure rate with named reactive metal, Mg, Zn (1) both fast reactions (1) or measure rate using piece of insoluble carbonate, CaCO3 (1) both fast reactions (1) NOTE: must be insoluble for first mark or measure electrical conductivity (1) both good conductors (1) (ii) to have same concentration of H+ / one acid is H2SO4, the other is C6H13SO3H / sulfuric

acid is dibasic, hexanesulfonic is monobasic [1] (iii) a strong acid is completely ionised, [1] a weak acid is partially ionised [1] [Total: 17] 5 (a) protective / layer and of oxide [1] (b) correct repeat unit [1] continuation shown [1] (c) (i) catalyst [1] biological / protein [1] (ii) hydrochloric acid / any strong acid / any strong alkali [1] (iii) amino acids [1] (iv) chromatography [1] (v) nylon / kevlar [1] (d) (i) non-biodegradable [1] (ii) CH2=CH(C6H5) [1] [Total: 11]

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6 (a) (i) CH3–CH2–CH2–OH [1] NOT: C3H8O between 2030 and 2050 [1] (ii) C5H11OH + 7½ O2 � 5CO2 + 6H2O [1] (b) any three from: same general formula same functional group same chemical properties same methods of preparation accept consecutive members differ by CH2 [3] (c) (i) same molecular formula [1] different structures / different structural formulae [1] (ii) CH3–CH2–CH(OH)–CH3 / (CH3)3C–OH [1] (d) (i) number of moles of glucose = 72/180 = 0.4 [1] maximum number of moles ethanol = 0.8 [1] maximum mass of ethanol, Mr = 46 g, 0.8 × 46 = 36.8 g [1] or 180 (g) produces 2 × 46 = 92 (g) (1) (72 (g) produces) 72/180 × 92 (1) = 36.8 (g) (1) (ii) crack (petroleum or alkane) [1] react with water / hydrate (ethene to make ethanol) [1] conditions for cracking

(temperature) 450to 800

oC / (catalyst) zeolites / aluminosilicates / silica / aluminium oxide / alumina / china / broken pot / chromium oxide

or conditions for hydration (temperature) 300

oC / (pressure) 60 atmospheres / (catalyst) phosphoric acid [1] [Total: 15]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/51 Paper 5 (Practical), maximum raw mark 40

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October / November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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2

1 (a) table of results for Experiment 1 initial final and difference volume boxes completed correctly (1) readings to 1 decimal place (1) comparable to supervisors (1) ±2 cm [3] (b) table of results for Experiment 2 initial and final boxes completed correctly (1) difference box completed correctly (1) comparable to supervisors (1) ±5 cm3 [3] (c) colourless (1) pink / magenta (1) [2] (d) neutralisation / acid-base (1) [1] (e) 2× volume for Experiment 1 from table (1) cm3 (1) [2] allow: 1 mark for double the volume (f) (i) reacts with (1) neutralises the acid (1)

less sodium hydroxide needed (1) max [2] (ii) volume in (e) – volume added in Experiment 2 (1) e.g. 50–17

correct value (2) e.g. 33 [2] (iii) estimate based on (ii) answer to (ii) / 3 divided into 50 × 0.1 e.g. 0.5

allow: 1 mark for 0.45–0.6g [1] (g) no effect (1) reason – reaction not affected by temperature / volumes / concentrations the same (1) [2]

(h) (i) more accurate (1) than a measuring cylinder (1) not: more accurate than a burette = 0 [2] (ii) no effect / advantage (1)

not measuring temperature changes / no temperature difference (1) [2]

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3

2 (a) colourless / pale yellow (liquid) [1] not: clear

(b) (i) liquid turns yellow / red / brown (1) [1] (two) layers (1) top layer pink / purple (1) [2]

(ii) two layers / oil bubble (1) yellow (1) [2] (c) no reaction / change / precipitate (1) [1] (d) yellow (1) precipitate (1) [2] (e) brown / white (1) precipitate (1) [2] (f) yellow (1) bubbles / fizz / effervescence (1) starch turns blue / black (1) [3] not: black precipitate (g) iodine dissolves / soluble / diffuses / owtte (1) [1] not: reacts (h) organic / hydrocarbon (1) solvent (1) oil / immiscible (1) max [2] (i) iodide / not a sulfate (1) [1] not: iodine

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/52 Paper 5 (Practical), maximum raw mark 40

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October / November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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2

1 (a) table of results for Experiment 1 initial final and difference volume boxes completed correctly (1) readings to 1 decimal place (1) comparable to supervisors (1) ±2 cm [3] (b) table of results for Experiment 2 initial and final boxes completed correctly (1) difference box completed correctly (1) comparable to supervisors (1) ±5 cm3 [3] (c) colourless (1) pink / magenta (1) [2] (d) neutralisation / acid-base (1) [1] (e) 2× volume for Experiment 1 from table (1) cm3 (1) [2] allow: 1 mark for double the volume (f) (i) reacts with (1) neutralises the acid (1)

less sodium hydroxide needed (1) max [2] (ii) volume in (e) – volume added in Experiment 2 (1) e.g. 50–17

correct value (2) e.g. 33 [2] (iii) estimate based on (ii) answer to (ii) / 3 divided into 50 × 0.1 e.g. 0.5

allow: 1 mark for 0.45–0.6g [1] (g) no effect (1) reason – reaction not affected by temperature / volumes / concentrations the same (1) [2]

(h) (i) more accurate (1) than a measuring cylinder (1) not: more accurate than a burette = 0 [2] (ii) no effect / advantage (1)

not measuring temperature changes / no temperature difference (1) [2]

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2 (a) colourless / pale yellow (liquid) [1] not: clear

(b) (i) liquid turns yellow / red / brown (1) [1] (two) layers (1) top layer pink / purple (1) [2]

(ii) two layers / oil bubble (1) yellow (1) [2] (c) no reaction / change / precipitate (1) [1] (d) yellow (1) precipitate (1) [2] (e) brown / white (1) precipitate (1) [2] (f) yellow (1) bubbles / fizz / effervescence (1) starch turns blue / black (1) [3] not: black precipitate (g) iodine dissolves / soluble / diffuses / owtte (1) [1] not: reacts (h) organic / hydrocarbon (1) solvent (1) oil / immiscible (1) max [2] (i) iodide / not a sulfate (1) [1] not: iodine

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/53 Paper 5 (Practical), maximum raw mark 40

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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2

1 (a) table of results for Experiment 1 initial and final volumes and differences completed correctly (1) to 1 decimal place (1) comparable to supervisors (1) ± 2 cm3 [3] (b) table of results for Experiment 2 initial and final volumes and differences completed correctly (1) to 1 decimal place (1) comparable to supervisors (1) ± 2 cm3 [3] (c) Experiment 3 green (1) precipitate (1) brown at surface (1) max [2] (d) (i) colourless / pale green not clear to yellow / pink (1) pink / purple to colourless [1] (ii) not an acid / alkali reaction or potassium manganate is coloured / owtte not needed / would interfere (1) [1] (e) (i) experiment 2 (1) [1] (ii) experiment 2 2x volume experiment 1 [1] (iii) solution E more concentrated / stronger (1) or converse 2x as concentrated (2) [2] (f) half value from table result for experiment 2 (1) half volume of C used (1) [2] (g) advantage easy to use / quick / convenient (1) disadvantage not accurate / owtte (1) [2] (h) iron (1)(II) (1) oxidised to iron(III) / reacted with air (1) [3]

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2 (a) yellow (1) pH = 6–8 (1) with acid turns orange (1) with excess alkali yellow (1) [4] (b) blue (1) effervescence (1) / (max 1) glowing splint (1) relights/brighter (1) [3] (c) red / brown (1) precipitate (1) with acid yellow solution / dissolves (1) [3] (d) yellow (1) precipitate (1) with acid yellow solution / dissolves (1) [3] (e) turns green (1) bubbles / fizz / effervescence (1) [2] (f) reversible (1) solution returned to original colour (1) [2] (g) oxygen (1) [1] (h) transition metal (ion present) / neutral dependent on pH in (a) (1) [1]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/61 Paper 6 (Alternative to Practical), maximum raw mark 60

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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© Cambridge International Examinations 2013

1 (a) funnel (1) [1] (b) to move products through the apparatus / owtte e.g. let the gases go out (1) [1] (c) (i) limewater (1) to detect carbon dioxide (1) [2] (ii) so gas bubbles through liquid (1) [1] (d) condensation / drops (1) water (1) [2] allow: black deposit (1) soot / carbon (1) 2 (a) straight line drawn with a ruler through all points missing point at pH 5 (1) [1] (b) idea of fair test / comparability (1) [1] (c) temperature (1) [1] (d) the lower the pH the greater the % corrosion / or converse / pH 1 is most corrosive (1) [1] (e) 2.5% (1) [1] 3 (a) table of results for Experiment 1

initial, final and difference volume boxes completed correctly (1) 0.0, 38.0 difference 38.0 readings to 1dp (1) [2]

(b) table of results for Experiment 2 initial and final boxes completed correctly (1) 10.0, 29.0 difference (1) [2] (c) colourless (1) pink (1) [2] (d) neutralisation / exothermic (1) [1]

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(e) 2 × volume for Experiment 1 from table / 76 (1) cm3 (1) [2] (f) (i) reacts with the acid / neutralised (1) less sodium hydroxide needed (1) [2] (ii) volume in (e) – volume added in Experiment 2 (1) e.g. 76–19 correct value (2) e.g. 57 cm3 [2] (iii) estimate based on (ii) answer to (ii) / 3 divided into 19 × 0.1 + 0.3 = 0.4 g [1] (g) no effect (1) reason – reaction not affected by temperature (1) [2] (h) (i) more accurate (1) than a measuring cylinder (1) [2] (ii) no effect / advantage (1) not measuring temperature changes (1) [2] 4 tests on liquid L (a) colourless (liquid) [1] allow: (pale) yellow (c) no reaction / change (1) [1] (d) yellow (1) precipitate (1) [2] (e) iodine dissolves / owtte (1) [1] (f) organic (1) solvent (1) liquids do not mix (1) max [2]

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5 (a) volumes completed correctly (4), –1 each incorrect [4] time / s catalyst R catalyst S 0 0 0 30 23 16 60 34 36 90 59 51 120 66 63 150 71 69 180 72 72 (b) points plotted correctly (3) smooth curves (2) labels (1) [6] (c) result at 60s / volume 34 / third result (1) [1] (d) R (1) rate faster (1) [2] (e) sketch to left of R graph / steeper (1) to same level (1) [2] 6 mass of silica gel (1)

heat in oven > 100 ˚C (1) for specified realistic time / until turns blue (1) reweigh (1) record (1) heat in oven again to check constant mass / indication of colour change (1) calculation (1) max [6]

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/62 Paper 6 (Alternative to Practical), maximum raw mark 60

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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1 (a) trough / tub / beaker / bowl / waterbath / basin (1) [1] not: tray / container / dish (b) arrow to space in boiling tube above liquid in trough (1) [1] (c) to absorb / contain / store / trap / hold the alkane / liquid (1) [1] (d) idea of large surface area / catalyst / speeds up reaction (1) [1] (e) test bromine(water) (1) result colourless (1) [2] not: clear 2 (a) chromatography (1) [1] (b) 3 dots above the line and must be vertical (1) 1 dot on base-line (1) [2] allow: 1 mark for 4 dots above the base-line and must be vertical (c) interferes with results / ink spreads / ink is soluble / owtte (1) [1] (d) dyes would wash off / dissolves in propanone (1) [1] 3 (a) both masses correct 31.2 and 31.8 (1) [1] (b) all masses correct (2), –1 each incorrect 31.9, 32.2, 32.2 [2] (c) to allow air / oxygen in (1) [1] not: release / allow gas to escape (d) to make sure all calcium reacted / owtte (1) eliminate anomalies / reduce errors / reference to accuracy (1) constant mass (1) max [2] not: fair test / take average / reference to reliability (e) results table completed for mass of oxygen reacted (1) 0.21, 0.28, 0.31, 0.36 [1]

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(f) all points plotted correctly (4), –1 each incorrect straight line drawn with a ruler through all points except 0.4 g (1) [5] (g) point at 0.4 g mass calcium / 0.21 g oxygen / Experiment 4 (1) [1] (h) any evidence of extrapolation / indication (1) 0.45 g oxygen reacted (1) mass of calcium oxide = 1.15 g(1) [3] 4 (c) table of results for Experiments 1, 2 and 3 initial temperature boxes completed correctly (1) 23, 22, 21 maximum temperature boxes correctly completed (1) 26, 24, 71 temperature rises correct (1) 3, 2, 50 [3] (e) table of results for Experiments 4 and 5 initial and maximum temperature boxes completed correctly (2) 19, 21 44, 29 ` [2] all temperature rises correct in tables (1) 25, 8 [1] (f) appropriate scale for y axis (1) bars inserted at correct heights (3) –1 for any incorrect not: a line graph labels (1) [5] (g) (i) temperature rises greatest in Experiment 3 (1) (ii) magnesium is most reactive / more reactive (1) [2] (h) hydrogen (1) [1] (i) (i) copper (1) (ii) displacement / redox / exothermic (1) [2] allow: oxidation / reduction (j) solid would react slower / temperature rises would be lower / less temperature change (1) smaller / less surface area (1) [2] or same temperature (1) same mass of magnesium used (1) (k) dangerous / too reactive / explodes / owtte (1) [1]

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5 (a) colourless and smells acidic / vinegar / pungent / choking / sour (1) [1] not: strong red / orange / yellow (1) pH 1–6 (1) [2] (b) fizzes / effervescence (1)

lighted splint (1) pops (1) [3] not: glowing splint pops (c) effervescence / fizz / bubbles (1) [1] not: carbon dioxide unless limewater test described as an observation (f) organic / hydrocarbon (1) fuel / flammable (1) reducing agent (1) max [2] allow: 2 marks for alcohol / ethanol 6 x cm3 of hydrogen peroxide / solution H (1)

add MnO2 (1) method to collect gas that works (1) measurement of (total) volume of gas produced / counting bubbles in time interval (1) repeat using solution J (1) comparison / conclusion (1) max [5] ignore: reference to heat not: speed of relighting a glowing splint

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CAMBRIDGE INTERNATIONAL EXAMINATIONS

International General Certificate of Secondary Education

MARK SCHEME for the October/November 2013 series

0620 CHEMISTRY

0620/63 Paper 6 (Alternative to Practical), maximum raw mark 60

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. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October / November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

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© Cambridge International Examinations 2013

1 (a) stirring / glass rod / stirrer (1) Bunsen and / or burner (1) [2] (b) solvents (1) solution (1) [2] (c) B (1) allow: filter

C (1) [2] allow: evaporating dish / basin

(d) evaporated / lost into air owtte / turned into steam / turned into water vapour (1) [1] 2 (a) three mistakes (3) explanations (3) heat in wrong place / water should not needs to be under flask / reactants (1) be heated (1) should not pass through water (1) gas is soluble (1) collection wrong way / gas jar is the gas denser than air (1) wrong way up / gas should be collected downwards / gas should be collected in syringe (1) [6] (b) in fume cupboard / well-ventilated area (1) [1] ignore: goggles / masks etc. 3 (a) boiling points completed correctly (3), –1 each incorrect 100, 121, 134, 139, 152, 159, 166 [3] (b) points plotted correctly (3) smooth curve through all points except anomalous point (1) [4]

(c) point at 4 atmos / 139οC / 4th point (1) off curve / outlier / anomalous (1) [2] (d) extrapolation (1) value from graph (1) 168–170

unit οC (1) [3]

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(e) test (1) anhydrous copper sulfate or cobalt chloride(paper) (1)

result (1) turns blue or pink (1) [2]

ignore: original colour 4 (a) table of results for experiment 1

initial and final volumes and differences completed correctly (1) 15.7, 0.0 and 15.7 to 1 decimal place (1) [2]

allow: 2 decimal places (b) table of results for experiment 2

initial and final volumes completed correctly (1) 47.3 and 15.9 differences completed correctly (1) 31.4 [2]

(c) iron / Fe (1) (II) / 2+ (1) oxidised / reacts with air / to iron(III) (1) [3] (d) (i) colourless to pink / purple (1) [1] not: clear allow: reverse (ii) not an acid and alkali reaction / potassium manganate is coloured / owtte / indicator not

needed / a colour change already occurs / potassium manganate acts as an indicator (1) [1]

(e) (i) experiment 2 (1) [1] (ii) experiment 2 2× volume experiment 1 [1] (iii) solution E more concentrated / stronger (1) or converse 2 × as concentrated (2) [2] (f) half value from table result for Experiment 2 / 15.7 cm3 (1)

half volume of E used (1) [2] (g) advantage easy to use / quick / convenient (1)

disadvantage not accurate / owtte (1) [2]

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5 (c) no reaction / no change / no precipitate (1) [1] (d) white (1) precipitate (1) [2] (e) neutral (1) transition metal (ion) present (1) [2] (f) reversible / equilibrium / neutralisation / (1)

solution returned to original colour / solution turns back to yellow (1) [2] (g) oxygen (1) [1] 6 stated / known / same volume of hydrochloric acid (1) use of named measuring apparatus (1) addition of named indicator (1) add tablets (1) until the colour changes / pH =7 (1) take measurement (1) e.g. number of tablets repeat with other tablet (1) compare / conclusion (1) e.g. brand that uses fewer tablets is most effective allow: other correct methods including loss of mass and collection of gas max [7]