Cambridge Assessment International Education

Cambridge International General Certificate of Secondary Education

CHEMISTRY 0620/42
Paper 4 Theory (Extended) March 2019
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the March 2019 series for most Cambridge
IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 9 printed pages.

© UCLES 2019 [Turn over

Pg 01 of 349
0620/42 Cambridge IGCSE – Mark Scheme March 2019
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

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Question Answer Marks

1(a) chlorine / argon 1

1(b) sodium 1

1(c) argon 1

1(d) sulfur 1

1(e) aluminium 1

1(f) silicon 1

1(g) chlorine 1

Question Answer Marks

2(a) 4
number of electrons electronic charge on
protons structure particle

11 10 2,8 M4 1+ / +1(1)

M1 18(1) 18 M3 2,8,8(1) 0

M2 9(1) 10 2,8 1-

2(b)(i) element 1
EITHER (substance) made of atoms with the same atomic number / number of protons / proton number

OR a substance that cannot be split up / broken down into two or more simple(r) substances by chemical means

2(b)(ii) M1 6 protons in all three rows(1) 2

M2 6,7 and 8 neutrons(1)

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Question Answer Marks

3(a) gas / gaseous 1

3(b) M1 1 shared pair of electrons(1) 2

M2 6 non-bonding electrons on each atom to complete an octet(1)

3(c) 2Na + F2 → 2NaF 2

M1 NaF anywhere(1) M2 equation fully correct(1)

3(d) chlorine less reactive than fluorine ORA 1

3(e)(i) PbF2 1

3(e)(ii) covalent 1

3(e)(iii) giant ionic lattice 1

3(e)(iv) M1(It or lead(II) fluoride) forces of attraction between ions / ionic bonds(1) 3

M2(tetrafluoromethane) forces of attraction between molecules(1)

M3 ionic bonds stronger than attractive forces between molecules / ionic bonds need more energy to break than attractive
forces between molecules(1)

3(f)(i) not all the bonds are single bonds 1

3(f)(ii) M1 bromine / bromine water(1) 2

M2 turns colourless / decolourises(1)

3(f)(iii) 1

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Question Answer Marks

3(f)(iv) 2

M1 C-C(1)
M2 each C bonded to 2 F and no other atoms + extension bonds(1)

3(f)(v) M1 CF2(1) 2
M2 CF2(1)

Question Answer Marks

4(a) 4
M1 increases(1) No change

M2 increases(1) M3 decreases(1)

decreases M4 decreases(1)

4(b) M1 Suitable metal e.g. magnesium / any carbonate / any base(1) 3

M2 suitable observation e.g. insoluble base / insoluble carbonate / metal dissolve or disappear or metal / carbonate bubbles(1)

M3 balanced equation fully correct(1)

4(c)(i) proton donor 1

4(c)(ii) ionises / dissociates partially or incompletely 1

4(d)(i) M1 heat(1) 2

M2 catalyst / concentrated sulfuric acid(1)

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Question Answer Marks

4(d)(ii) M1 Correct ester linkage(1) 3

M1 and M2 whole molecule fully correct(2)

M3 methyl ethanoate (1)

4(d)(iii) ethyl methanoate 1

Question Answer Marks

5(a)(i) fractional distillation 1

5(a)(ii) carbon monoxide is toxic/poisonous 1

5(b) • 80 4

• 5

• 10

• 240

5(c)(i) TiCl4 + 2Mg → Ti + 2MgCl2 1

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Question Answer Marks

5(c)(ii) TiCl4 + 4Na → Ti + 4NaCl 1

5(c)(iii) magnesium burns in air or oxygen OR reacts with air or oxygen / argon is unreactive or inert 1

5(d)(i) M1 / 2 3
bubbles / fizzing / effervescence(1)

M1 / 2 (magnesium or solid) dissolves / disappears / forms solution(1)

M3
Mg + 2HCl → MgCl2 + H2(1)

5(d)(ii) filtration 1

5(d)(iii) titanium is below hydrogen in the reactivity series ORA 1

OR titanium less reactive than hydrogen ORA
OR titanium coated with an oxide layer

5(e)(i) hydrogen 1

5(e)(ii) Heat until magnesium chloride is molten and electrolyse 1

Question Answer Marks

6(a) M1 Transition element has higher melting point / high boiling point ORA(1) 2
M2 Transition element has higher density ORA(1)

6(b) good conduction of heat or electricity OR malleability OR ductility 1

6(c) 1 mark each for any two of: 2

• catalyst
• more than one or different or variable oxidation state / oxidation number / valency
• coloured compounds / coloured ions

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Question Answer Marks

6(d) from blue(1) to pink(1) 2

6(e)(i) M1 oxygen(1) 2
M2 water(1)

6(e)(ii) zinc / Zn 1

6(f) M1 magnesium above iron / steel in the reactivity series ORA / magnesium more reactive than iron / steel ORA(1) 2
M2 copper below iron / steel in the reactivity series ORA / copper less reactive than iron ORA(1)

6(g)(i) Fe2O3 + 2H3PO4 → 2FePO4 + 3H2O 2

M1 FePO4 anywhere(1) M2 The whole equation correct(1)

6(g)(ii) iron(III) phosphate acts as a barrier which prevents contact between iron and water or air / oxygen 1

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 Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education

CHEMISTRY 0620/41
Paper 4 Theory (Extended) May/June 2019
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2019 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and
some Cambridge O Level components.

This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 9 printed pages.

© UCLES 2019 [Turn over

Pg 10 of 349
0620/41 Cambridge IGCSE – Mark Scheme May/June 2019
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

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Question Answer Marks

1(a) number of protons (1) 2

protons in the nucleus (of an atom) (1)

1(b)(i) 12p 12n 12e (1) 2

12p 14n 12e (1)

1(b)(ii) isotope(s) 1

1(b)(iii) same number of electrons (1) 2

(same number) of electrons in the outer shell (1)

1(c) 9 Be
4 4

any element symbol with a single negative charge (1)

use of Cl (1)

use of 3717 (1)

1(d) 2 8 3 (1) 2

2 8 8 (1)

Question Answer Marks

2(a) 80(°C) (1) 1

2(b) horizontal line from end of graph at minute 9 to minute 11 (1) 1

2(c) energy is used to break bonds / overcome attraction (1) 2

between molecules (1)

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Question Answer Marks

2(d) vibrations (1) 2

increase (1)

2(e) melting point decreases (1) 2

boiling point increases (1)

2(f) decrease from 120 °C to 80 °C and horizontal line at 80 °C (1) 2

decrease from horizontal line to finish at 20 °C at 8 mins (1)

Question Answer Marks

3(a) roast zinc blende (in air) (1) 5

2ZnS + 3O2 → 2ZnO + 2SO2 (1)

add/react with coke (1)

ZnO + C → Zn + CO OR 2ZnO + C → 2Zn + CO2 (1)

(zinc is) distilled (1)

3(b) brass 1

3(c) form coloured compounds / ions (1) 2

act as catalysts (1)

3(d)(i) anhydrous copper(II) sulfate 1

3(d)(ii) white (1) 2

blue (1)

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Question Answer Marks

3(e)(i) 4KI + 2CuSO4 → 2CuI + I2 + 2K2SO4 (2) 2

3(e)(ii) 1+ 1

3(e)(iii) gains electron(s) 1

3(e)(iv) KI / potassium iodide / iodide (ions) / I– 1

Question Answer Marks

4(a)(i) proton donor 1

4(a)(ii) (CH3COOH) ⇌ CH3COO– (1) + H+ (1) 2

4(b)(i) any two from: 2

• faster rate of fizzing
• solid dissolves quicker / disappears quicker / gets smaller quicker
• fizzing stops quicker
• dissolving stops quicker

4(b)(ii) any three from: 3

• temperature
• volume (of acid)
• concentration (of acid)
• mass / amount (of CaCO3)
• particle size / surface area (of CaCO3)

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Question Answer Marks

4(c) 50.0 4
M1 mol of HCl = 2.00 × = 0.1(00) mol (1)
1000

M1
M2 mol of MgCO3 = = 0.1(00) / 2 = 0.05(00) (1)
2

M3 Mr of MgCO3 = 84 (1)

M4 mass of MgCO3 = M3 × M2 = 84 × 0.05(00) = 4.2(0)g (1)

4(d)(i) to remove the acid / make sure all the acid is used up / no acid is left over 1

4(d)(ii) to make sure all the filtrate / MgCl2 / salt goes through / no MgCl2 left behind 1

4(d)(iii) evaporation mark (1) 3

the starting of crystallisation mark (1)

drying the crystals mark (1)

4(e)(i) a solid (1) 2

which forms when two solutions are mixed / reacted / added (1)

4(e)(ii) (silver) nitrate (1) 3

BaCl2 + 2AgNO3 → 2AgCl + Ba(NO3)2

formulae (1)

balance(1)

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Question Answer Marks

5(a) CnH2n (1) 1

5(b) C5H10 (1) 1

5(c) E (1) 2

it has the longest carbon chain (1)

5(d) A (1) 2

it has the lowest Mr (1)

5(e) orange to colourless (1) 2

structure of 1,2-dibromobutane (1)

5(f)(i) structure of propan-1-ol (1) structure of propan-2-ol (1) 2

5(f)(ii) steam (1) 3

catalyst (1)

one other condition: either 60 atm pressure OR 300 °C (1)

5(g)(i) addition 1

5(g)(ii) poly(but-1-ene) 1

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Question Answer Marks

5(g)(iii) M1 2 C atoms (only) with a single bond between them linked to the continuation bonds shown 3

M2 correct repeat unit showing one C2H5 / CH2CH3 side chain attached to one of the C atoms in M1

M3 correct use of ‘n’

5(g)(iv) CH2 1

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 Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education

CHEMISTRY 0620/42
Paper 4 Theory (Extended) May/June 2019
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2019 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and
some Cambridge O Level components.

This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 10 printed pages.

© UCLES 2019 [Turn over

Pg 19 of 349
0620/42 Cambridge IGCSE – Mark Scheme May/June 2019
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

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Question Answer Marks

1(a) methane 1

1(b) oxygen 1

1(c) aluminium oxide 1

1(d) oxygen 1

1(e) methane 1

1(f) silicon(IV) oxide 1

Question Answer Marks

2(a)(i) M1 protons (are the same) / 11 protons (1) 3

M2 electrons (are the same) / 11 electrons (1)
M3 neutrons (are different) / 11,12,13 neutrons (1)

2(a)(ii) same number of protons and electrons (1) 1

2(a)(iii) M1 same number of electrons (1) 2

M2 (same number of) electrons in outer shell (1)

2(a)(iv) (they all have) 1 more proton than electrons / 11 protons and 10 electrons 1

2(b)(i) diamond / graphite / graphene 1

ANY TWO

2(b)(ii) carbon monoxide 1

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Question Answer Marks

3(a)(i) covalent 1

3(a)(ii) forces of attraction between molecules 1

AND
are weak / need a small amount of energy to break

3(a)(iii) no moving or flowing or mobile charged particles or ions or electrons 1

3(b)(i) P4 + 5O2 → P4O10 2

M1 all formulae correct (1)
M2 equation correctly balanced (1)

3(b)(ii) redox / combustion 1

3(c) P4O10 + 12NaOH → 4Na3PO4 + 6H2O 2

M1 Na3PO4 (1)
M2 equation completely correct (1)

3(d) M1 3 pairs of bonding electrons (1) 2

M2 only 1 lone pair on P (1)

3(e)(i) proton / H+ / hydrogen ion acceptor 1

3(e)(ii) 2NH3 + H2SO4 → (NH4)2SO4 2

M1 (NH4)2SO4 (1)
M2 equation completely correct (1)

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Question Answer Marks

4(a) water / natural gas / hydrocarbons 1

4(b) 4
effect on the rate of the effect on the percentage of methanol in the
reverse reaction equilibrium mixture

M1 increases(1) no change

increases M3 decreases(1)

M2 decreases(1) M4 decreases(1)

4(c)(i) any 2 from: 2

• same or similar chemical properties or reactions (1)
• (same) general formula (1)
• (consecutive members) differ by CH2 (1)
• same functional group (1)
• common (allow similar) methods of preparation (1)
• physical properties vary in predictable manner / show trends / gradually change
OR
example of a physical property variation i.e. melting point / boiling point / volatility (1)

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Question Answer Marks

4(c)(ii) M1 4

(1)

M2 propan-1-ol (1)
M3

(1)
M4 propan-2-ol (1)

4(c)(iii) structural isomers / structural isomerism 1

4(d)(i) ethyl methanoate 1

4(d)(ii) M1 methanoic acid (1) 2

M2 ethanol (1)

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Question Answer Marks

4(d)(iii) 2

M1 correct displayed ester linkage (1)

M2 whole molecule fully correct (1)

Question Answer Marks

5(a) M1 0.0025 / 2.5 × 10–3 (moles of H2SO4) (1) 3

M2 0.0025 / 2.5 × 10–3 (moles of CuSO4y5H2O) (1)
M3 0.625(g) (1)

5(b) some copper(II) sulfate remains in solution / some copper(II) sulfate does not form crystals 1
OR
some of the crystals decomposed
OR
some crystals lost in transfer

5(c) M1 no more bubbling / fizzing / effervescence (1) 2

M2 solid or powder stops dissolving (1)

5(d) M1 (lumps have) smaller surface area OR powder has larger surface area (1) 2
M2 (lumps have) fewer collisions per unit time / less collision frequency OR powder has more collisions per unit time / more
collision frequency

5(e) copper(II) oxide or copper(II) hydroxide 1

5(f) filtration 1

5(g)(i) M1 containing the maximum amount of dissolved solute / no more solute can dissolve (1) 2
M2 at any given temperature (1)

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Question Answer Marks

5(g)(ii) when crystals form on a glass rod withdrawn from solution / on a sample of solution placed on microscope slide etc. 1

5(g)(iii) (heating to dryness) would remove water of crystallisation 1

Question Answer Marks

6(a) M1 solid (1) 2

M2 black (1)

6(b)(i) M1 colourless (1) 2

M2 to brown / orange / yellow (1)

6(b)(ii) Cl2 +2KBr → 2KCl + Br2 2

OR
Cl2 +2Br– → 2Cl – + Br2
M1 all formulae (1)
M2 equation balanced correctly (1)

6(c) M1 two ticks for Cl2 / KI, Br2 / KI (1) 2

M2 three crosses for Br2 / KCl, I2 / KCl and I2 / KBr (1)

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Question Answer Marks

7(a)(i) M1 Ni / Nickel (1) 2

M2 (it) loses or donates electrons (1)

7(a)(ii) redox 1

7(b) M1 Pb → Pb2+ + 2e(–) / (1) 2

M2 Ag+ + e(–) → Ag (1)

7(c) most reactive nickel / Ni 1

lead / Pb
least reactive silver / Ag

7(d) nickel has 2

M1 higher density (1) ORA
nickel has
M2 higher melting point / boiling point (1) ORA

7(e) solutions of nickel compounds are coloured ORA 1

7(f)(i) M1 electrolyte aqueous or solution of named nickel salt (1) 3

M2 anode impure nickel (1)
M3 cathode pure nickel (1)

7(f)(ii) nickel produced at cathode under the liquid surface (1) 1

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 Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education

CHEMISTRY 0620/43
Paper 4 Theory (Extended) May/June 2019
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2019 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and
some Cambridge O Level components.

This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 9 printed pages.

© UCLES 2019 [Turn over

Pg 29 of 349
0620/43 Cambridge IGCSE – Mark Scheme May/June 2019
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

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Question Answer Marks

1(a) 3
particle where found in an atom relative mass relative charge

electron orbiting nucleus 1/1840 –1

proton (in the) nucleus 1 +1

neutron in the nucleus 1 0 / nil

1(b) M1 electrons 18 3
M2 neutrons 24
M3 protons 20

Question Answer Marks

2(a) difference: M1 (number of) neutrons 3

similarities: M2 (number of) protons

M3 (number of) electrons

2(b)(i) M1 same number of electrons 2

M2 (same number of) electrons in outer shell

2(b)(ii) Mg + 2 HCl → MgCl2 + H2 2

M1 MgCl2 as product

M2 fully correct equation

2(b)(iii) M1 Test: lighted / burning splint 2

M2 Result: (squeaky) pop

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Question Answer Marks

2(c) M1 (lattice of) positive ions / cations 3

M2 (delocalised / sea of) electrons

M3 attraction / attract between positive and negative

2(d)(i) M1 magnesium ion 3

second shell shown containing 8 electrons shown as X

M2 oxide ion
second shell shown containing 8 electrons, two as X and six as z

M3 charges:
magnesium ion as 2+ and oxide as 2-

2(d)(ii) strong forces of attraction (between oppositely charged ions) 1

2(d)(iii) ions / Mg2+ and O2– / anions and cations can move (throughout the structure) 1

Question Answer Marks

3(a)(i) any two from: max 2

• low melting point or low boiling point
• soft
• low density

3(a)(ii) any one from: max 1

• fizz / bubbles
• moves
• floats
• melts / forms a ball
• gets smaller / disappears

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Question Answer Marks

3(b) mass sodium azide = 260 (g) 4

• Moles N2 = (144 / 24 =) 6
• Moles NaN3 = (6 × 2 / 3 =) 4
• Mr NaN3 = 65
• (4 × 65 = ) 260

3(c) M1 (sodium oxide) basic 2

M2 (silicon dioxide) acidic

3(d)(i) N3– 1

3(d)(ii) M1 state symbols on right correct (s) then (aq) 2

M2 (Pb(NO3)2 +) 2 (NaN3) → (Pb(N3)2 +) 2NaNO3

3(d)(iii) M1 filter 2

M2 wash with water

3(e) M1 49.5 / 12 7.2 / 1 43.3 / 14 3

OR
4.125 7.2 3.093 .

M2 1.33 : 2.33 : 1 OR 4 : 7 : 3

M3 C4H7N3

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Question Answer Marks

4(a)(i) inert / unreactive / does not react with chlorine 1

4(a)(ii) bubbles / fizzing / effervescence 1

4(a)(iii) M1 increases 2
M2 (solid) copper deposited

4a(iv) M1 colour fades / becomes pale(r) / becomes colourless / becomes lighter 2

M2 copper (ions) removed (from solution)

4(a)(v) M1 species oxidised: chloride (ions) / Cl – 2

M2 explanation: loss of electrons / increase in oxidation state

4(b)(i) M1 spoon as cathode 4

M2 (pure)silver as anode

M3 aqueous silver nitrate as electrolyte

M4 Ag+ + e– → Ag

4(b)(ii) any one from: max 1

• Improves appearance
• prevent / resist corrosion / oxidation
• antibacterial

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Question Answer Marks

5(a)(i) ethyl ethanoate 1

5(a)(ii) correct structure of ethyl ethanoate showing all bonds 1

5(b) M1 right hand energy level lower than left hand side energy level 3

M2 reactants and product positions identified

M3 energy change shown as approximately vertical line indicating gap between reactants and products with arrow head
pointing from reactant to products. Arrow needs to be labelled

5(c) M1 (a substance which) increases the rate of a reaction 2

M2 without being used up (at the end) OR unchanged (chemically) at the end OR without changing mass

5(d) M1 particles / molecules in explanation 4

M2 (particles) move faster / more energy

M3 more collisions per second or greater collision rate

M4 more of the (colliding) molecules / particles have sufficient energy (activation energy) to react / more of the collisions have
sufficient energy (activation energy) to react

5(e)(i) M1 less ester 2

M2 equilibrium moves left and because forward reaction is exothermic

5(e)(ii) M1 more ester 2

M2 (equilibrium moves right) to replace water

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Question Answer Marks

6(a)(i) M1 contain hydrogen and carbon 2

M2 only

6(a)(ii) M1 (Reagent): Bromine (water / solution) 3

M2 (Result with hydrocarbon A): becomes colourless / decolourised
M3 (Result with hydrocarbon B): no change / stays orange

6(b) 1

6(c)(i) addition 1

6(c)(ii) 1

6(c)(iii) M1 CO on right 2
M2 2n O2 2n(CO)

6(d) 2

M1 –NH2 group drawn as displayed on one end

M2 carboxylic acid group drawn as displayed on the other end

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 Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education

CHEMISTRY 0620/41
Paper 4 Theory (Extended) October/November 2019
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2019 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 9 printed pages.

© UCLES 2019 [Turn over

Pg 38 of 349
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PUBLISHED

Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific
content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these marking
principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question
as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be
limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade
descriptors in mind.

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Question Answer Marks

1(a)(i) K+ 1

1(a)(ii) Cr3+ 1

1(a)(iii) Ca2+ 1

1(a)(iv) Br- 1

1(a)(v) SO42- 1

1(b) (compound / salt) on wooden splint or (nichrome / platinum) wire (1) 2

into (roaring) Bunsen flame (1)

1(c) Mg3(PO4)2 1

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Question Answer Marks

2(a) atoms with same number of protons or atoms of the same element or atoms with same atomic number (1) 2
atoms with different number of neutrons or atoms with different mass number or atoms with different nucleon number (1)

2(b)(i) 18 1

2(b)(ii) gain of two electrons 1

2(b)(iii) Ca / calcium 1

2(c)(i) l ..g ..g. 1

2(c)(ii) vanadium (V) oxide or vanadium pentoxide (1) 2

450 (°C) (1)

2(c)(iii) SO3 + H2SO4 → H2S2O7 (1) 2

H2S2O7 + H2O → 2 H2SO4 (1)

2(d)(i) (it causes) acid rain 1

2(d)(ii) test – (aqueous) potassium manganate (VII) (1) 2

(purple to) colourless (1)

2(e) 29.1 / 23 40.5 / 32 30.4 / 16 or 1.2(65) 1.2(65) 1.9 (1) 3

1:1:1.5 (1)
Na2S2O3 (1)

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Question Answer Marks

3(a) malleable / conduct electricity / conduct heat 1

3(b) water and oxygen / air 1

3(c)(i) (zinc is) more reactive than iron 1

3(c)(ii) Fe3+ (1) 2

accept / take / gain electrons (1)

3(d) (add a) named acid (1) 3

(add a) named alkali (1)
disappears / dissolves in both (1)

Question Answer Marks

4(a)(i) cobalt carbonate 1

4(a)(ii) lead iodide 1

4(b) 2 AgNO3 + Na2CO3 → Ag2CO3 + 2 NaNO3 2

formula of silver carbonate correct (1)
fully correct equation (1)

4(c) Pb2+ + 2 I– → PbI2 2

Pb2+ and I– on left of equation (1)
fully correct equation (1)

4(d) (nitric) acid reacts with / removes carbonate ions 1

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Question Answer Marks

5(a)(i) addition 1

5(a)(ii) CH2 1

5(a)(iii) 2

one C=C (1)

fully correct structure (1)

5(b)(i) (compounds / molecules with) the same molecular formula (1) 2

different structural formulae (1)

5(b)(ii) 2

(1)

(1)

5(b)(iii) H2O and CO or C formed (1) 2

2 C4H10 + 9 O2 → 8 CO + 10 H2O (1)

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Question Answer Marks

6(a) correct final answer = 0.072(0) 3

M1 moles HCl = 0.0036(0)

M2 moles Na2CO3 = 0.0018(0) (M1 / 2)
M3 concentration Na2CO3 = 0.072 (M2 / 0.025)

6(b) 0.002(00) 1

6(c)(i) 720(.09) 1

6(c)(ii) (it contains) ions (1) 2

(ions) are able to move (1)

6(c)(iii) magnesium is not inert 1

6(b)(iv) bromine / Br2 1

6(b)(v) H+ and e(–) on LHS (1) 2

fully correct, i.e.: 2H+ + 2e– → H2 (1)

7(a) C6H12O6 → 2CO2 + 2C2H5OH (1) 5

any three from

• anaerobic
• 30 °C
• yeast
• glucose aqueous

fractional distillation (of aqueous ethanol) (1)

7(b) (energy to break bonds) = 4728 (1) 3

(energy released by making bonds) = 6004 (1)
–1276 (1)

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Question Answer Marks

7(c)(i) speeds up a (chemical) reaction (1) 2

not used up or unchanged (at end) (1)

7(c)(ii) 4 electrons in double bond between C and O (1) 3

all single bonds correct (1)
C and O each have 8 electrons in outer shell, all H have 2 electrons in outer shell (1)

7(c)(iii) (attractive) forces between molecules weaker in ethanal 1

7(d)(i) moves right (1) 2

fewer moles / molecules (of gas) on right (1)

7(d)(ii) (reaction is faster) because more collisions per second (1) 2

particles / molecules closer together or more particles / molecules per unit volume (1)

7(d)(iii) moves left (1) 2

(forward) reaction is exothermic or backward reaction is endothermic (1)

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 Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education

CHEMISTRY 0620/42
Paper 4 Theory (Extended) October/November 2019
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2019 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 9 printed pages.

© UCLES 2019 [Turn over

Pg 47 of 349
0620/42 Cambridge IGCSE – Mark Scheme October/November 2019
PUBLISHED

Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific
content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these marking
principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question
as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be
limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade
descriptors in mind.

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Question Answer Marks

1(a) fluorine / F 1

1(a)(ii) hydrogen / H 1

1(a)(iii) vanadium / V 1

1(a)(iv) sulfur / S 1

1(a)(v) phosphorus / P 1

1(a)(vi) magnesium / Mg 1

1(a)(vii) chlorine / Cl 1

1(b)(i) potassium / K 1

1(b)(ii) calcium / Ca 1

1(c)(i) gydrogen / H 1

1(c)(ii) 2H2 + O2 → 2H2O 2

water as product from reaction of hydrogen and oxygen (1)
balanced (1)

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Question Answer Marks

2(a) 78 1

2(b) fractional (1) 2

distillation (1)

2(c) acid rain 1

2(d) nitrogen and oxygen (from the air) react (in the engine) (1) 2
(due to) high temperatures (1)

2(e) nitrogen (1) 3

carbon dioxide (1)
platinum (1)

2(f) CH4 + 1½O2 → CO + 2H2O 2

CO and H2O as products and methane as reactant (1)
rest of the equation (1)

2(g)(i) A photosynthesis (1) 2

B respiration (1)

2(g)(ii) – –O– –O– –O– 2

two –O– link between three ‘blocks’ (1)

three complete units with continuation bonds (1)

2(g)(iii) acid (and heat) (1) 2

enzymes (ignore names) (1)

2(g)(iv) chromatography 1

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Question Answer Marks

3(a)(i) ⇌ 1

3(a)(ii) pressure 100–300 atmospheres / atm (1) 5

temperature in range 330 to 500 oC (1)
iron (catalyst) (1)
species: N2 + 3H2 ⇌ 2NH3 (1)
fully correctly equation (1)

3(a)(iii) water / steam or methane / natural gas 1

3(b)(i) proton acceptor 1

3(b)(ii) Contact (process) 1

3(b)(iii) 2NH3 + H2SO4 → (NH4) 2SO4 2

(NH4) 2SO4 (1)
rest of the equation (1)

3(c)(i) iron(II) hydroxide 1

3(c)(ii) any two from: 2

• it (iron(II) hydroxide) is oxidised
• to form iron(III) (hydroxide) / (oxide)
• by (iron(II) hydroxide reacting with) air / oxygen

3(c)(iii) (green ppt) Remains 1

3(d)(i) mol of NH3 = 4.8(0) / 24 = 0.2(0) (1) 3

mol of O2 = 0.2 × 5 / 4 = 0.25 (1)
mol of O2 = 0.25 × 24 = 6.(0) (1)

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Question Answer Marks

3(d)(ii) M1 Bonds broken 4

[4 × 3 × 391] + [5 × 498]
= 4692 + 2490 = 7182
M2 Bonds formed
[4 × 587] + [12 × 464]
= 2348 + 5568 = 7916
M3 Energy change = 7182 – 7916 = –734
M4 = M3 / 4 = –734 / 4 = –183.5

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Question Answer Marks

4(a) electrons (1) 4

electrons (1)
Cu2+ (ions) (1)
Br– (ions) (1)

4(b)(i) platinum 1

4(b)(ii) chlorine 1

4(b)(iii) 2H+(aq) + 2e– → H2(g) 3

H+ + e– on left hand side (1)
rest of equation (1)
state symbols of (aq) → (g) (1)

4(b)(iv) increases 3
(sodium) hydroxide is formed
(sodium) hydroxide is an alkali

4(c)(i) arrow (anywhere) going from Zn → Cu 1

4(c)(ii) reading would decrease (1) 2

Fe less reactive than Zn (1)
OR
difference in reactivity (between Fe and Cu) is smaller

4(c)(iii) Ag less reactive than Cu 1

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Question Answer Marks

5(a)(i) ultraviolet light 1

5(a)(ii) CH4 + Cl 2 → CH3Cl + HCl 1

5(a)(iii) substitution 1

5(a)(iv) NaCl 1

5(b) all bonding pairs correct (1) 2

H atoms have 2 electrons and C and O atoms have 8 electrons (1)

5(c)(i) methyl propanoate 1

5(c)(ii) water 1

5(c)(iii) molecular formula = C4H8O2 (1) 3

correct ester link showing all atoms and all bonds (1)
rest of molecule (1)

5(c)(iv) (acid) catalyst 1

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 Cambridge Assessment International Education
Cambridge International General Certificate of Secondary Education

CHEMISTRY 0620/43
Paper 4 Theory (Extended) October/November 2019
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2019 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This syllabus is regulated for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 10 printed pages.

© UCLES 2019 [Turn over

Pg 56 of 349
0620/43 Cambridge IGCSE – Mark Scheme October/November 2019
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range
may be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

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Question Answer Marks

1(a) 2
particle charge relative mass

electron M1 –1

neutron M2 0 M3 1

proton M4 1
(1) (1)
Mark by column

1(b) 6
number of number of number of
symbol
electrons neutrons protons

M1 13 (1)

M2 10 (1) M3 13 (1)

M4 19
9 (1)
M5 F (1)
M6 – (1)

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Question Answer Marks

2(a) F 1

2(b) I 1

2(c) F (1) 3
H (1)
I (1)

2(d) G (1) 2

good conductor when solid (1)

2(e) D (1) 3

high melting point (1)

non-conductor of electricity when solid or liquid (1)

2(f) E (1) 2

only conducts when liquid / conducts when liquid but not when solid (1)

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Question Answer Marks

3(a) bauxite 1

3(b)(i) improves conductivity / better conductor (1) 2

lower (operating) temperature (1)

3(b)(ii) positive: 2O2– → O2 + 4e– (1) 2

negative: Al 3+ + 3e– → Al (1)

3(b)(iii) anodes or carbon react with oxygen (1) 1

(form) carbon dioxide (1)

3(c)(i) Mg(s) + Cu2+(aq) → Cu(s) + Mg2+(aq) 2

ionic equation correct (1)

state symbols (1)

3(c)(ii) any two from: 2

• solid dissolves / disappears
• blue colour of solution fades OR paler solution OR
colour of solution disappears OR becomes colourless solution
• pink or orange or brown AND solid

3(c)(iii) unreactive coating of aluminium oxide 1

3(d) 2Al + Fe2O3 → 2Fe + Al2O3 2

Fe2O3 and Al2O3 both correct (anywhere) (1)

Equation completely correct (1)

4(a) P4 1

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Question Answer Marks

4(b)(i) P4 + 6Cl2 → 4PCl3 2

formulae correct (1) equation balanced (1)

4(b)(ii) 3 bonding pairs and 1 lone pair on P (1) 2

six non-bonding electrons on 3 chlorine atoms (1)

4(c)(i) method 1 3

• (bond breaking) = 1221 or (326 × 3) + 243 (1)

• (bond forming) = 1630 or (326 × 5) (1)
• energy change = –409 kJ (1) negative sign essential

OR

method 2 (ignoring 3 P–Cl bonds on both sides)

• bond breaking = 243 .(1)
• bond forming = 652 or 326 × 2 (1)
• energy change = –409 kJ (1) negative sign essential

4(c)(ii) exothermic AND energy released when bonds form is greater than energy absorbed to break bonds 1

OR exothermic AND overall energy change has a negative sign

4(d) fewer OR less molecules OR moles + on right OR in product (1) ORA 2

equilibrium shifts to the right (1)

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Question Answer Marks

4(e) any two numbers correct (1) 2

equation fully balanced (1)

Ca3P2 + 6H2O → 3Ca(OH)2 + 2PH3

4(f)(i) NH4+ 1

4(f)(ii) PH4I 1

4(g) Ca3(PO4)2 1

4(h)(i) 93.94 / 31 and 6.06 / 1 2

OR 3.03 and 6.06
OR 1 : 2 ratio (1)

PH2 (1)

4(h)(ii) P2H4 1

Question Answer Marks

5 M1 5 moles of calcium nitrate (1) 4

M2 10 moles ammonium nitrate (1) or ecf M1 × 2

M 3 Mr of ammonium nitrate = 80

M4 800 g or ecf M2 × M3

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Question Answer Marks

6(a) strong = exists entirely as ions in solution / fully dissociated 100% dissociated in solution (1) 2

acid = proton donor (1)

6(b) 50.0 (cm3) 1

6(c)(i) yellow flame 1

6(c)(ii) solid dissolves / disappears (1) 2

blue solution (1)

6(d)(i) white precipitate 1

6(d)(ii) Ba2+(aq) + SO42–(aq) → BaSO4(s) 2

correct ionic equation (1)

state symbols (1)

Question Answer Marks

7(a) carbon-carbon double bond / C = C 1

7(b)(i) 3 1

7(b)(ii) 2

(1)

but-2-ene (1)

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Question Answer Marks

7(b)(iii) CH2 (1) 2

CH2 (1)

7(c) (broken down by) hydrolysis (1) 6

acid (used to break down) (1)

enzymes (used to break down) (1)

chromatography (used to separate) (1)

locating agent / (view under) UV light (used to detect) (1)

measure Rf (values) or retention factor / compare with standards (used to identify) (1)

7(d)(i) Nylon / Kevlar 1

7(d)(ii) water 1

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) March 2020
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the March 2020 series for most Cambridge
IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

This document consists of 9 printed pages.

© UCLES 2020 [Turn over

Pg 66 of 349
0620/42 Cambridge IGCSE – Mark Scheme March 2020
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

© UCLES 2020 Page 3 of 9

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PUBLISHED

5 ‘List rule’ guidance (see examples below)

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided
• Any response marked ignore in the mark scheme should not count towards n
• Incorrect responses should not be awarded credit but will still count towards n
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form, (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

© UCLES 2020 Page 4 of 9

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Question Answer Marks

1(a) distillation (1) 2

fractional (1)

1(b) naphtha (1) 2

bitumen (1)

1(c)(i) any two from: 2

methane ethane propane

1(c)(ii) 2C4H10 + 13O2  8CO2 + 10H2O 2

CO2 and H2O as products (1)
correct equation (1)

1(c)(iii) carbon monoxide 1

1(d)(i) kerosene is more viscous 2

gasoline is more flammable

1(d)(ii) kerosene has molecules with a longer carbon chain 1

1(e) hydrogen + oxygen  water 1

Question Answer Marks

2(a)(i) bauxite 1

2(a)(ii) breakdown by (the passage of) electricity (1) 2

of an ionic compound in molten / aqueous (state) (1)

2(b)(i) cryolite 1

2(b)(ii) less CO2 emission 1

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Question Answer Marks

2(b)(iii) Al3+ + 3e–  Al 4

any positive Al species gaining electron(s) (1)
correct species and balance (1)
2O2–  O2 + 4e–
any negative O species losing electron(s) (1)
correct species and balance (1)

2(b)(iv) anodes or carbon / graphite react with oxygen / O2 (1) 2

(form) carbon dioxide (1)

2(c)(i) amphoteric 1

2(c)(ii) aluminium sulfate (1) Al2(SO4)3 (1) 2

2(c)(iii) water 1

2(c)(iv) 2Al(OH)3  Al2O3 + 3H2O 2

species (1) balance (1)

2(c)(v) aluminium carbonate (1) 2

aluminium nitrate (1)

Question Answer Marks

3(a) selenium / Se 1

3(b) Ca has 2 and Cl has outer electrons 7 (1) 5

Ca (atoms) lose electrons (1)

Cl (atoms) gain electrons (1)

Ca2+ (ions) (1)

Cl– (ions) (1)

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Question Answer Marks

3(c)(i) any number in the range 72 – 129°C 1

3(c)(ii) attraction increase (1) 2

between molecules (1)

3(c)(iii) 3 P – Cl dot cross bonds (1) 3

2 (only) non-bonding electrons to make an octet on P (1)
6 (only) non-bonding electrons to make an octet on each Cl (1)

3(d)(i) constant concentrations (1) 2

rate of forward reaction = rate of reverse reaction (1)

3(d)(ii) increased temperature: 4

(equilibrium) shifts to LHS (1)
(forward) reaction is exothermic (1)

increased pressure:
(equilibrium) shifts to RHS (1)
fewer moles (of gas) on RHS (1)

3(d)(iii) rate increases and particles have more energy (1) 3

more collisions (between particles) occur per second / per unit time

more (of the) particles / collisions have energy greater than activation energy
or
more (of the) particles / collisions have sufficient energy to react
or
a greater percentage / proportion / fraction of collisions (of particles) are successful

3(e) mol of LiPF6 = 3.04 / 152 = 0.02(00) (1) 3

mol of LiF = 0.02(00) × 6 = 0.12(0) (1)
mass of LiF = 3.12 g (1)

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Question Answer Marks

3(f)(i) oppositely charged ions 2

(ions) are attracted

3(f)(ii) any two from: 2

physical constants: high boiling point / melting point
conductivity: conduct (electricity) when aqueous or conduct (electricity) when molten
solubility: soluble in water

Question Answer Marks

4(a) Haber (process) (1) 2

ammonia (1)

4(b)(i) green 1

4(b)(ii) Fe2+(aq) + 2OH–(aq)  Fe(OH)2(s) 3

Fe(OH)2 (as only product) (1)
Fe2+ and 2OH– (as reactants) (1)
state symbols (1)

4(c)(i) oxidising agent 1

4(c)(ii) presence of an acid 1

4(c)(iii) lose an electron 1

4(c)(iv) colourless 1

4(d) 3+ 2
3+

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Question Answer Marks

5(a)(i) monomer 1

5(a)(ii) any hydrocarbon with one C=C bond (with both C atoms having 4 bonds) (1) 2

structure of methylpropene (1)

5(b) water is a product (when polymer is made) 1

5(c)(i) any correct amide link between any two blocks showing all atoms and all bonds (1) 3

correct orientation of 3 inter-block amide links (1)

continuation bonds (1)

5(c)(ii) nylon 1

© UCLES 2020 Page 9 of 9

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) May/June 2020
MARK SCHEME
Maximum Mark: 80

Published

Students did not sit exam papers in the June 2020 series due to the Covid-19 global pandemic.

This mark scheme is published to support teachers and students and should be read together with the
question paper. It shows the requirements of the exam. The answer column of the mark scheme shows the
proposed basis on which Examiners would award marks for this exam. Where appropriate, this column also
provides the most likely acceptable alternative responses expected from students. Examiners usually review
the mark scheme after they have seen student responses and update the mark scheme if appropriate. In the
June series, Examiners were unable to consider the acceptability of alternative responses, as there were no
student responses to consider.

Mark schemes should usually be read together with the Principal Examiner Report for Teachers. However,
because students did not sit exam papers, there is no Principal Examiner Report for Teachers for the June
2020 series.

Cambridge International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the June 2020 series for most Cambridge
IGCSE™ and Cambridge International A & AS Level components, and some Cambridge O Level
components.

This document consists of 9 printed pages.

© UCLES 2020 [Turn over

Pg 75 of 349
0620/41 Cambridge IGCSE – Mark Scheme May/June 2020
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

© UCLES 2020 Page 2 of 9

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

© UCLES 2020 Page 3 of 9

Pg 77 of 349
0620/41 Cambridge IGCSE – Mark Scheme May/June 2020
PUBLISHED

5 ‘List rule’ guidance (see examples below)

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided
• Any response marked ignore in the mark scheme should not count towards n
• Incorrect responses should not be awarded credit but will still count towards n
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form, (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

© UCLES 2020 Page 4 of 9

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PUBLISHED
Question Answer Marks

1(a)(i) protons 1

neutrons 1

1(a)(ii) nucleon number 1

1(a)(iii) 34 1

1(a)(iv) 2:8:8 1

1(a)(v) Al2X3 1

1(b)(i) isotopes 1

1(b)(ii) 12C 1

1(b)(iii) a mole 1

1(b)(iv) Avogadro constant 1

1(c) M1 (3 × 69) + (2 × 71) 3

349
M2 = = 69.8
5

M3 Y = Ga / gallium

1(d)(i) phosphorus / P 1

1(d)(ii) gains electrons 2

three electrons (when forming ion)

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Question Answer Marks

2(a) metallic (bonding) 1

sea of electrons 1

positive ions 1

attraction between 1

2(b)(i) Mg octet of eight dots 1

O octet of six crosses and two dots. 1

correct charges on both ions 1

2(b)(ii) 2Mg + O2  2MgO 2

M1 species
M2 balancing

2(c)(i) 2Mg(NO3)2  2MgO + 4NO2 + O2 2

M1 product species
M2 balancing

2(c)(ii) (thermal) decomposition 1

2(c)(iii) magnesium carbonate 1

magnesium hydroxide 1

Question Answer Marks

3(a) zinc blende 1

3(b)(i) reaction is reversible 2

rate of forward reaction = rate of reverse reaction

3(b)(ii) vanadium(V) oxide 1

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Question Answer Marks

3(b)(iii) increases the rate of reaction 1

3(b)(iv) particles have more energy (E) 1

rate of collisions increase 1

a higher proportion of particles have energy greater than activation energy (E > EA) 1

3(b)(v) exothermic 1

3(b)(vi) Mr of SO3 = 80 1

32 1
100 × = 40%
80

3(c) anhydrous copper(II) sulfate 2

carbon

3(d)(i) not all (C–C) bonds are single 1

3(d)(ii) C3H7OH  C3H6 + H2O 2

M1 C3H6
M2 rest of the equation

3(d)(iii) propene 1

Question Answer Marks

4(a) (damp) litmus 1

(turns) blue 1

4(b)(i) proton acceptor 1

4(b)(ii) Above pH 7 up to 11 1

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Question Answer Marks

4(b)(iii) blue precipitate 1

precipitate dissolves 1

deep blue solution remains 1

4(c)(i) neutralisation 1

4(c)(ii) Na2SO4 1

2H2O 1

4(d)(i) methyl orange 1

4(d)(ii) 25.0 3
M1 mol of NaOH = 0.0400 × = 0.001( 00 ) mol
1000

M1 0.001
M2 mol of H2SO4 = = = 0.0005 ( 00 )
2 2

1000 1000
M3 M2 × = 0.0005 × = 0.025 (mol / dm3)
20.0 20.0

allow ecf

4(d)(iii) M1 use of 40 g/mol 2

M2 40 × 0.04 = 1.6 (g/dm3)

Question Answer Marks

5(a) M1 sugar(s) 4
M2 fermentation
M3 ethene
M4 hydration
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Question Answer Marks

5(b) (acidified) potassium manganate(VII) 1

5(c)(i) (Liebig) condenser 1

5(c)(ii) arrow at the lower inlet 1

5(d)(i) methanal 1

C4H8O 1

5(d)(ii) CnH2nO 1

5(e)(i) functional group 1

5(e)(ii) M1 4 × C–H dot cross bonds and 1 C–C dot cross bond 3
M2 1 × C=O dot cross bond
M3 non-bonding electrons on O

5(f)(i) (structural) isomers 1

5(f)(ii) M1 any structure with correct valencies and formula of C3H6O 2

M2 C=O bond on second carbon (of a chain of 3)

© UCLES 2020 Page 9 of 9

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) May/June 2020
MARK SCHEME
Maximum Mark: 80

Published

Students did not sit exam papers in the June 2020 series due to the Covid-19 global pandemic.

This mark scheme is published to support teachers and students and should be read together with the
question paper. It shows the requirements of the exam. The answer column of the mark scheme shows the
proposed basis on which Examiners would award marks for this exam. Where appropriate, this column also
provides the most likely acceptable alternative responses expected from students. Examiners usually review
the mark scheme after they have seen student responses and update the mark scheme if appropriate. In the
June series, Examiners were unable to consider the acceptability of alternative responses, as there were no
student responses to consider.

Mark schemes should usually be read together with the Principal Examiner Report for Teachers. However,
because students did not sit exam papers, there is no Principal Examiner Report for Teachers for the June
2020 series.

Cambridge International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the June 2020 series for most Cambridge
IGCSE™ and Cambridge International A & AS Level components, and some Cambridge O Level
components.

This document consists of 9 printed pages.

© UCLES 2020 [Turn over

Pg 84 of 349
0620/42 Cambridge IGCSE – Mark Scheme May/June 2020
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

© UCLES 2020 Page 2 of 9

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0620/42 Cambridge IGCSE – Mark Scheme May/June 2020
PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

© UCLES 2020 Page 3 of 9

Pg 86 of 349
0620/42 Cambridge IGCSE – Mark Scheme May/June 2020
PUBLISHED

5 ‘List rule’ guidance (see examples below)

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided
• Any response marked ignore in the mark scheme should not count towards n
• Incorrect responses should not be awarded credit but will still count towards n
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form, (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a)(i) condensation 1

1(a)(ii) sublimation 1

1(a)(iii) fractional distillation 1

1(a)(iv) electrolysis 1

1(a)(v) chromatography 1

1(b)(i) N 1

1(b)(ii) O 1

1(b)(iii) Be 1

1(b)(iv) N 1

1(b)(v) Ne 1

1(b)(vi) Li 1

Question Answer Marks

2(a)(i) magnesium 2.8 (all crosses) (1) 3

fluorine 2.8 (seven dots and one cross in outer shell) (1)
Mg2+ and F-(1)

2(a)(ii) MgF2 1

2(a)(iii) heat until molten or dissolve in water (1) 2

moving ions / mobile ions (1)

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Question Answer Marks

2(b) two single bonds (1) 3

one double bond (1)
six non-bonding electrons on both F atoms and four non- bonding electrons on O atom to complete the octet in each
case (1)

2(c)(i) forces of attraction between oppositely charged ions / ionic bonds (1) 2
strong / need a lot of energy to break / weaken (1)

2(c)(ii) forces of attraction between molecules (1) 2

weak / need a small of energy to break / weaken (1)

Question Answer Marks

3(a)(i) heat in air 1

3(a)(ii) 2SO2 + O2 → 2SO3 (1) 3

450°C (1)
vanadium(V) oxide (1)

3(a)(iii) rate of forward reaction and rate of backward reaction are equal (1) 3
concentrations of reactants and products are constant (1)

3(b) concentrated sulfuric acid 1

3(c) H2S2O7 + H2O → 2H2SO4 2

3(d) Cu + 2H2SO4 → CuSO4 + SO2 + 2H2O 1

3(e) purple to colourless 1

3(f) 2NH3 + H2SO4 → (NH4)2SO4 2

3(g)(i) barium nitrate / barium chloride 1

3(g)(ii) Ba2+(aq) + SO42-(aq) → BaSO4(s) 2

formulae (1) state symbols (1)

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Question Answer Marks

4(a) substance that speeds up a reaction / increases rate (1) 2

unchanged (chemically) at the end OR not used up OR lowers activation energy OR provides alternative pathway (1)

4(b) rate decreases (1) 4

particles further apart / less particles per unit volume (1)
fewer collisions per unit time / lower collision frequency (1)
reaction stops because all hydrogen peroxide is used up

4(c) steeper gradient (1) 2

reaches same volume of oxygen (1)

4(d) particles gain kinetic energy / particles move faster (1) 3

greater number of collisions with activation energy (or more) / greater number of particles with activation energy (or
more) / greater number of particles with energy required for reaction (1)
more collisions are successful / more collisions are fruitful / more collisions lead to reaction (1)

4(e) 48.0 3
M1 moles of oxygen = or moles of oxygen = 0.002 (1)
24 000
M2 moles of hydrogen peroxide = M1 × 2 or moles of hydrogen peroxide = 0.004 (1)
M3 concentration = M2 × 40 = 0.16 mol / dm3 (1)
allow ECF

4(f) 2KClO3 → 2KCl + 3O2 2

ALL formulae correct (1)
balancing (1)

Question Answer Marks

5(a) breakdown of an ionic compound when molten or in aqueous solution (1) 2

(using) electricity / electric current / electrical energy (1)

5(b) platinum / graphite 1

5(c) 2H+ + 2e → H2 1

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Question Answer Marks

5(d) Na+ H+ Cl - OH- 2

all four (2) 3 or 2 (1)

5(e) H+ and Cl - are discharged / removed (1) 2

Na+ and OH- remain (1)

Question Answer Marks

6(a)(i) substitution 1

6(a)(ii) ultraviolet light / ultraviolet radiation 1

6(a)(iii) 2

6(b)(i) only one product / double bond becomes single bond / two molecules join (to make one molecule) 1

6(b)(ii) (energy required to break bonds =) 854 (1) 3

(energy given out when bonds form =) 1025 (1)
overall energy change 854 – 1025 = –171 (1)

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Question Answer Marks

6(c)(i) alkene (1) 3

alcohols / alkanols (1)
carboxylic acids/alkanoic acids (1)

6(c)(ii) turns colourless / decolourised (1) 2

bubbles / fizzing / effervescence (1)

6(d)(i) 2
COOH CH2OH

C C

H H
C–C (1)
each C bonded to –CH2OH / –COOH and H with no other atoms + extension bonds (1)

6(d)(ii) polyester 1

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) May/June 2020
MARK SCHEME
Maximum Mark: 80

Published

Students did not sit exam papers in the June 2020 series due to the Covid-19 global pandemic.

This mark scheme is published to support teachers and students and should be read together with the
question paper. It shows the requirements of the exam. The answer column of the mark scheme shows the
proposed basis on which Examiners would award marks for this exam. Where appropriate, this column also
provides the most likely acceptable alternative responses expected from students. Examiners usually review
the mark scheme after they have seen student responses and update the mark scheme if appropriate. In the
June series, Examiners were unable to consider the acceptability of alternative responses, as there were no
student responses to consider.

Mark schemes should usually be read together with the Principal Examiner Report for Teachers. However,
because students did not sit exam papers, there is no Principal Examiner Report for Teachers for the June
2020 series.

Cambridge International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the June 2020 series for most Cambridge
IGCSE™ and Cambridge International A & AS Level components, and some Cambridge O Level
components.

This document consists of 10 printed pages.

© UCLES 2020 [Turn over

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PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

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5 ‘List rule’ guidance (see examples below)

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided
• Any response marked ignore in the mark scheme should not count towards n
• Incorrect responses should not be awarded credit but will still count towards n
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form, (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a)(i) D 1

1(a)(ii) C 1

1(a)(iii) C 1

1(a)(iv) B 1

1(a)(v) D AND E or A 1

1(a)(vi) C 1

1(a)(vii) A or E 1

1(a)(viii) H 1
H O H
H C C C H
H H H

1(b) donate or lose protons 2

does not fully ionise / partially ionises / forms an equilibrium mixture

Question Answer Marks

2(a)(i) reversible reaction 1

2(a)(ii) hydrocarbons (reacting with steam) 1

2(b) [increasing pressure] increases yield 2

[increasing temperature] decreases yield

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Question Answer Marks

2(c) (particles) have more energy OR (particles) move faster 3

more collisions per second OR greater collision rate
more (of the) particles OR collisions have sufficient energy / activation energy to react OR a greater percentage /
proportion / fraction of collisions are successful

2(d)(i) N / NH3 2
change in oxidation state of N from –3 to +2 / increase in oxidation number / gain in oxygen / loss of electrons

2(d)(ii) 75 1

2(d)(iii) (it could react with rain water to) form nitric acid / acid rain 1

2(d)(iv) (Mr of HNO3 =) 63 (1) 4

20 (1)
5 (1)
120 (dm3) (1)

2(e) • horizontal product energy line at lower energy level than reactant 3
• label of product
• correct direction of vertical arrow – arrow must start level with reactant energy and finish level with product level
and one arrow head ONLY

Question Answer Marks

3(a)(i) same number of electrons 2

same electronic configuration

3(a)(ii) 3
number of electrons number of neutrons number of protons
35 Cl
17 17 18 17
37 Cl –
17 18 20 17

3(b)(i) displacement / redox 1

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Question Answer Marks

3(b)(ii) iodine is less reactive than bromine 1

3(c) magnesium ion has an outer shell with eight crosses 3

chloride ion has an outer shell with seven dots and one cross
chloride has a charge of 1– and magnesium has a charge 2+

3(d) energy needed to break bonds = 436 + 243 = 679 3

energy released when bonds formed = 2 × 432 = 864
energy change = 679 – 864 = – AND 185

Question Answer Marks

4(a) (filtration:) remove solids from water / remove insoluble substances 2

(chlorination:) sterilises / kill microbes / prevent illness

4(b)(i) white to blue 2

4(b)(ii) higher boiling point / greater than 100°C 1

4(c)(i) more than one spot 1

4(c)(ii) 0.8 (circled) 1

4(c)(iii) use a locating agent 1

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Question Answer Marks

5(a) 3
particle particle type of
separation arrangement motion

solid touching

liquid random

gas random

5(b) condensing 1

5(c) evaporation 2
diffusion

Question Answer Marks

6(a)(i) 2, 2, 4, 1 1

6(a)(ii) thermal decomposition 1

6(b) • add aqueous sodium hydroxide 3

• then (reduction with) aluminium (foil) (and warm)
• (ammonia gas produced which) turns damp red litmus blue

Question Answer Marks

7(a) breakdown of a molten / or aqueous ionic compound by the passage of electricity 2

7(b) bauxite 1

7(c)(i) it is above carbon in the reactivity series / more reactive than carbon 1

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Question Answer Marks

7(c)(ii) any one from: 1

• aluminium oxide has high melting point / cryolite has lower melting point than aluminium oxide
• using cryolite reduces costs / expensive to melt aluminium

7(c)(iii) oxygen 1

7(c)(iv) Al 3+ + 3e −  Al 2

7(d) any two related to use as electricity cables: 2

• ductile / malleable
• conducts (electricity)
• low density
• protective oxide layer

7(e)(i) iron + water + oxygen  (hydrated) iron oxide 2

7(e)(ii) any two from: 2

• act as catalysts
• variable oxidation numbers
• form coloured compounds / coloured ions
• higher melting point
• higher density
• harder

Question Answer Marks

8(a)(i) 1

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Question Answer Marks

8(a)(ii) 2

8(a)(iii) water 1

8(b) non-biodegradable / running out of space / toxic / leaching 1

8(c) (complex) carbohydrate / protein 1

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) October/November 2020
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2020 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 10 printed pages.

© UCLES 2020 [Turn over

Pg 103 of 349
0620/41 Cambridge IGCSE – Mark Scheme October/November 2020
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a)(i) hydrogen / carbon 1

1(a)(ii) silicon 1

1(a)(iii) aluminium 1

1(a)(iv) iron 1

1(a)(v) aluminium 1

1(a)(vi) oxygen 1

1(b)(i) metal higher in reactivity series / metal more reactive (than iron) / allow named metal e.g. magnesium or zinc (1) 2

zinc corrodes/oxidises/reacts in preference to iron (1)

1(b)(ii) any barrier method e.g. painting 1

Question Answer Marks

2(a) zinc blende 1

2(b)(i) ZnO + C → Zn + CO 1
or
2ZnO + C → 2Zn + CO2

2(b)(ii) chemical change: reduction (1) 2

explanation: oxygen is lost (1)

2(b)(iii) aluminium is more reactive than carbon 1

2(b)(iv) electrolysis 1

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Question Answer Marks

2(c) exists as layers (1) 3

(alloy) contains different sized (copper) atoms (1)

makes it more difficult for layers (of atoms) to slide over each slip/shift other (1)

Question Answer Marks

3(a)(i) 2 → 2 + 2 1

3(b) 75(%) 1

3(c) test: (damp red) litmus paper (1) 2

result: (litmus goes) blue (1)

3(d)(i) diffusion 1

3(d)(ii) particles move from an area of high to low concentration 2

particles move randomly

3(d)(iii) CO2 molecules are heavier (than NH3) 1

3(e)(i) lower temperature: (rate of reaction) slower (1) 2

higher pressure: expensive/specialist equipment

3(e)(ii) catalyst 1

3(f)(i) proton acceptor 1

3(f)(ii) any value greater than 7 up to 12 1

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Question Answer Marks

4(a) 21 1

4(b)(i) fractional (1) 2

distillation (1)

4(b)(ii) (different) boiling point 1

4(c) 2 double bonds (1) 2

whole molecule correct (2 pairs of lone pairs on each O) (1)

4(d) increase in (concentrations of) carbon dioxide 3

(carbon dioxide is) greenhouse gas/greenhouse effect

contributes to climate change/global warming

4(e) photosynthesis 1

Question Answer Marks

5(a)(i) breakdown by (the passage of) electricity (1) 2

of an ionic compound in molten/aqueous (state) (1)

5(a)(ii) they do not react 1

5(a)(iii) negative electrode: hydrogen (gas) (1) 2

positive electrode: oxygen (gas) (1)

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Question Answer Marks

5(a)(iv) H+ + e(–) as the only species on the left (1) 2

equation fully correct (1)

2H+ + 2e(–) → H2 (scores 2)

5(b)(i) S + O2 → SO2 1

5(b)(ii) rate of forward reaction is equal to rate of reverse reaction (1) 2

constant concentration (of reactants and products) (1)

5(b)(iii) exothermic / heat / energy is released / surroundings warm up 2

products have lower energy than reactants / ORA

5(c) water / H2O 1

5(d) (Mr =) 98 2
(0.75 × 98 =) 73.5

Question Answer Marks

6(a)(i) alkanes 1

6(a)(ii) one mark each for any two of: 2

• same chemical properties
• same functional group
• same general formula
• (consecutive members) differ by CH2
• common (allow similar) methods of preparation
• physical properties vary in predictable manner / show trends / gradually change OR example of a physical property
variation i.e. melting point / boiling point / volatility (1)

6(b) 3.01 × 1023 (molecules) 1

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Question Answer Marks

6(c)(i) HCl 1

6(c)(ii) 1

6(c)(ii) substitution 1

6(d)(i) from: orange (1) 2

to: colourless (1)

6(d)(ii) contains no double bonds/ethane only contains single bonds 1

6(e)(i) 2

(1) (1)

6(e)(ii) C2H4 1

6(f)(i) (C = 85.7, H = 14.3, Mr 112) 2

85.7 14.3
C= = 7.14 H = = 14.3 (1)
12 1
(ratio = 7.13 : 14.3 = 1 : 2)
CH2 (2)

6(f)(ii) C8H16 1

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Question Answer Marks

7(a)(i) sugar or C6H12O6, is renewable / sustainable 1

7(a)(ii) slow(er) process 1

7(b)(i) ethanoic acid 1

7(b)(ii) oxidation 1

7(c)(i) ethyl methanoate 1

7(c)(ii) 1

7(d) ethanol: (forces of attraction) between molecules (1) 2

sodium chloride: (force of attraction) between positive and negative ions/ionic bonding (1)

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) October/November 2020
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2020 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 9 printed pages.

© UCLES 2020 [Turn over

Pg 113 of 349
0620/42 Cambridge IGCSE – Mark Scheme October/November 2020
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a)(i) A (1) 2
H (1)

1(a)(ii) B 1

1(a)(iii) D 1

1(a)(iv C and G OR C and E 1

1(b) F (1) 2
third / outer shell is being filled before second shell is full; second shell has 6 electrons: it should have 8 electrons (1)

1(c) 12 1

1(d)(i) H– 1

1(d)(ii) aluminium / Al 1

Question Answer Marks

2(a) HNO3 1

2(b)(i) to make sure all the (sulfuric) acid reacts 1

2(b)(ii) no (more) fizzing (1) 2

(FeCO3) stops dissolving or a solid remains / is visible (in the mixture) (1)

2(b)(iii) rinse the residue (with distilled water) 1

2(b)(iv a solution that can dissolve no more solute (1) 2

at the specified temperature (1)

2(b)(v) iron(II) oxide / iron(II) hydroxide 1

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Question Answer Marks

2(c) mass of FeSO4 = 152 (1) 3

mass of H2O = 278 – 152 = 126 (1)
mol of H2O = 126 / 18 and x = 7 (1)

2(d)(i) precipitation 1

2(d)(ii) cream precipitate 1

2(d)(iii) Ag+(aq) + Br–(aq)  AgBr(s) 3

AgBr (as only product) (1)
Ag+ and Br– (as reactants)(1)
state symbols(1)

2(e) M1 mol of NaCl = 2.34 / 58.5 = 0.04(00) 3

M2 mol of Cl 2 = M1/2 = 0.04(00)/2 = 0.02(00)
M3 0.02(00) × 24000 = 480 (cm3)

2(f)(i) ions (1) 3

(ions) are fixed (in a lattice) (1)
ions are mobile (1)

2(f)(ii) chlorine 1

2(f)(iii) oxidation (1) 2

electrons are lost (1)

2(f)(iv) dissolve it (in water) 1

Question Answer Marks

3(a) any two from: 2

• shiny / lustrous
• conduct electricity
• conduct heat

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Question Answer Marks

3(b) low(er) density (1) 2

low(er) melting points (1)

3(c)(i) hydrogen 1

3(c)(ii) hydroxide / OH– 1

3(c)(iii) 2Na + 2H2O  2NaOH + H2 2

NaOH (as a product) (1)
rest of equation (1)

3(d)(i) galvanising 1

3(d)(ii) prevents water or / and oxygen reaching iron 1

3(d)(iii) zinc more reactive (than iron) (1) 2

zinc corrodes / oxidises / reacts in preference to iron (1)

Question Answer Marks

4(a) hydrocarbon 1

4(b)(i) (only) one product is formed 1

4(b)(ii) 2

3 single bonded C atoms

entire molecule correct

4(b)(iii) orange (1) to colourless (1) 2

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Question Answer Marks

4(b)(iv structure of but-1-ene 2

structure of but-2-ene

4(c) C3H8 + Cl 2  C3H7Cl + HCl 2

HCl as product
rest of equation

Question Answer Marks

5(a)(i) presence of an acid 1

5(a)(ii) oxidation 1

5(a)(iii) all single bonding dot and cross pairs correct (1) 3
double C=O bond dot and cross pairs are correct (1)
Complete diagram is correct (1)

5(b) partial (dissociation) (1) 6

full / 100% (dissociation) (1)
both acid colours (1)
HCl indicating a lower pH acid colour than CH3COOH (1)
fizzing OR dissolving / disappearing in both (1)
either observation happens quicker with HCl (1)

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Question Answer Marks

5(c)(i) water 1

5(c)(ii) acid (catalyst) 1

5(c)(iii) any one alcohol group on a molecule (1) 2

structure of propan-2-ol (1)

5(d)(i) the atoms / group of atoms which give (any molecule its) chemical properties 1

5(d)(ii) C3H5O2 1

5(d)(iii) Mr of HO–CH2–CH2–OH = 62 (1) 2

%ge = 100 × 32/62 = 52% (1)

5(d)(iv) any correct ester link between any two blocks showing all atoms and all bonds (1) 2

correct orientation of 3 inter-block ester links and continuation bonds (1)

5(d)(v) Terylene 1

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) October/November 2020
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2020 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 12 printed pages.

© UCLES 2020 [Turn over

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PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

© UCLES 2020 Page 3 of 12

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PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) iron(III) oxide 1

1(b) nitrogen dioxide 1

1(c) ammonia 1

1(d) silver 1

1(e) carbon monoxide 1

1(f) anhydrous cobalt(II) chloride 1

Question Answer Marks

2(a) 11 1

2(b) 38 1

2(c) 2,8,8 1

2(d)(i) B, C and E 1

2(d)(ii) A 1

2(d)(iii) D 1

2(d)(iv) B and C 1

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Question Answer Marks

3(a) triple bond (1) 2

diagram completely correct (1)

3(b)(i) METHOD 1 2
liquid air (1)
fractional distillation (1)

METHOD 2
hydrogen
burns in air (to remove the oxygen and then scrub out the carbon dioxide)

3(b)(ii) (pressure) 200 atmospheres (1) 5

(temperature) 450 °C (1)

iron catalyst (1)

N2 + 3H2 → 2NH3 (1)

equilibrium / reversible (1)

3(c)(i) substance that speeds up a reaction / increases rate (1) 2

unchanged (chemically) at the end

OR not used up

OR lowers activation energy (1)

3(c)(ii) gain of oxygen / loss of hydrogen / electron loss / increase in oxidation state (oxidation number) 1

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Question Answer Marks

3(c)(iii) 4
effect on the rate of the effect on the equilibrium
forward reaction yield of NO(g)

increase (1) decrease (1)

increase (1) decrease (1)

3(d) 4NO2 + O2 + 2H2O → 4HNO3 2

all formulae (1)
equation fully correct(1)

3(e) (Mr of NH4NO3 =) 80 (1) 2

35% (1)

Question Answer Marks

4(a) sulfur dioxide 1

4(b)(i) Any two from 2

(coke)
• releases heat or releases energy(when it reacts with oxygen or burns in air) / (acts as a) fuel / increases temperature (in
the furnace) / heats (the furnace) / source of energy

(coke)
• reduces zinc oxide / is a reducing agent / converts zinc oxide to zinc / removes oxygen from zinc oxide

(coke)
• (reacts with oxygen) to produce carbon monoxide / reacts with carbon dioxide to form carbon monoxide

• carbon monoxide reduces zinc oxide / converts zinc oxide to zinc / removes oxygen from zinc oxide

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Question Answer Marks

4(b)(ii) ZnO + CO → Zn + CO2 1

OR

2ZnO + C → 2Zn + CO2

OR

ZnO + C → Zn + CO

4(b)(iii) temperature inside furnace is above / higher than 907 (°C ) 1

OR temperature is above / higher than the boiling point (of zinc) ORA

OR 1200 (°C) is above / higher than the boiling point (of zinc) ORA

OR 1200 (°C) is above / higher than 907 (°C) ORA

4(b)(iv) condensation / condensing 1

4(c)(i) zinc 1

4(c)(ii) (a solution containing the) maximum amount of solute dissolved / no more solute can dissolve (1) 2

at a given temperature (1)

4(c)(iii) one mark for each of any two from: 2

• zinc oxide
• zinc hydroxide
• zinc carbonate

4(d)(i) heat again and weigh again / repeat steps 2 and 3 (1) 2

until mass is constant (1)

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Question Answer Marks

4(d)(ii) (moles of MgSO4 = ) 0.005 / 5 × 10-3 (1) 4

mass of water = 0.63 g (1)

moles of water = 0.63 ÷ 18 = 0.035 / 3.5 × 10–2 (1)

(x = 0.035 ÷ 0.005 ) = 7 (1)

Question Answer Marks

5(a) become more reactive down the group ORA (1) 1

5(b)(i) one mark each for any two of: 2

• floats
• dissolves / disappears / melts
• moves
• bubbles / fizzes / effervesces
• lilac flame

5(b)(ii) 2K + 2H2O → 2KOH + H2 2

all formulae (1)
equation fully correct (1)

5(c)(i) Cl2 + 2KI → 2KCl + I2 2

OR Cl2 + 2I– → 2Cl – + I2

all formulae (1)

equation fully correct (1)

5(c)(ii) brown / black 1

5(d)(i) breakdown by (the passage of) electricity (1) 2

of an ionic compound in molten or aqueous (state) (1)

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Question Answer Marks

5(d)(ii) heat until it melts / heat to or above melting point 1

5(d)(iii) Na+ + e → Na 1

5(e)(i) one mark for each of any two from: 2

• (chromium has) high melting point ORA
• (chromium forms) coloured ions / coloured compounds ORA
• (chromium has) variable valency / variable oxidation state / variable oxidation number ORA
• catalytic behaviour ORA

ORA ALLOW group 1 or sodium if stated

• no colour or white or colourless ions or compounds
• fixed valency / +1 charge only or one oxidation state / forms one chloride
• low melting point
• doesn’t behave as a catalyst

5(e)(ii) one mark for each of any two from: 2

• (chromium / sodium) conducts electricity
• (chromium / sodium) compounds are soluble (in water)
• (chromium / sodium) form hydrated salts / form hydrated compounds

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Question Answer Marks

6(a)(i) compounds with the same molecular formula (1) 2

different structural formula (1)

6(a)(ii) 4

diagram (1) diagram (1)

ethanoic acid (1) methyl methanoate (1)

6(b)(i) 1

6(b)(ii) condensation 1

6(b)(iii) 2

1 for each correct functional group

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Question Answer Marks

6(c) 2

one correct linkage fully displayed (1)

the whole structure fully correct (1)

6(d)(i) proteins 1

6(d)(ii) amino acids 1

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) March 2021
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the March 2021 series for most Cambridge
IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

This document consists of 10 printed pages.

© UCLES 2021 [Turn over

Pg 134 of 349
0620/42 Cambridge IGCSE – Mark Scheme March 2021
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

© UCLES 2021 Page 3 of 10

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PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a)(i) E 1

1(a)(ii) A 2
I

1(a)(iii) D 2
G

1(a)(iv) F 1

1(a)(v) H 1

1(v)(i) G and I 1

1(v)(ii) A 1

1(v)(iii) B 1

1(b) same proton number 2

different neutron number

Question Answer Marks

2(a) chlorine 1

2(b) fluorine 1

2(c)(i) random motion of molecules / particles 1

2(c)(ii) hydrogen 2

lowest (relative) molecular mass

2(d)(i) 78 1

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Question Answer Marks

2(d)(ii) argon / Ar 1

2(d)(iii) carbon dioxide 1

2(d)(iv) fractional (1) 2

distillation (1)

Question Answer Marks

3(a)(i) Haber 1

3(a)(ii) reversible / equilibrium 1

3(a)(iii) 450 °C (1) 2

200 atm (1)

3(a)(iv) iron / Fe 1

3(a)(v) equilibrium shifts / moves in forwards direction (1) 2

fewer molecules / moles (of gas) on RHS (1)

3(a)(vi) particles have more energy (1) 3

more collisions (between particles) occur per second / per unit time (1)

a greater percentage / proportion / fraction of collisions (of particles) are successful / have energy above activation
energy / have energy equal to activation energy (1)

3(b) 2NH3 + H2SO4  (NH4)2SO4 2

(NH4)2SO4 (1) correct equation (1)

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Question Answer Marks

4(a) Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g) 3

ZnCl2 or H2 as a product (1)
correct equation (1)
states (1)

4(b) to make sure all the (hydrochloric) acid reacts 1

4(c) filtration 1

4(d) a solution that can dissolve no more solute (1) 2

at a given temperature (1)

4(e) solubility (of ZnCl2 / solids) decreases (as temperature decreases) 1

4(f) zinc oxide 2

zinc carbonate

4(g) Ca will also react with water 1

4(h)(i) neutralisation 1

4(h)(ii) 0.100 × 25 / 1000 = 0.0025(0) (1) 5

0.0025 × 2 = 0.005(00) (1)

0.005 × 1000 / 20 = 0.25(0) (1)

Mr = 40 (1)

0.25 × 40 = 10.(0) (1)

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Question Answer Marks

5(a) R and U only 2

5(b) aqueous bromine (1) 2

turns colourless / decolourises (1)

5(c)(i) but-2-ene 1

5(c)(ii) structure of methyl propene 1

5(d)(i) C12H26 1

5(d)(ii) P, R and U 2

5(e) steam (1) 3

catalyst (1)

One other condition (1):

either 60 atm or 300 °C

5(f)(i) oxidation 1

5(f)(ii) potassium manganate(VII) 1

5(g)(i) ester 1

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Question Answer Marks

5(g)(ii) name = methanol structure = 4

name = butanoic acid structure =

5(g)(iii) C5H10O2 1

Question Answer Marks

6(a) monomers 1

6(b)(i) any hydrocarbon with one C=C bond (with both C atoms having 4 bonds) (1) 2
structure of but-2-ene (1)

6(b)(ii) addition 1

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Question Answer Marks

6(c)(i) protein 1

6(c)(ii) 3

any correct amide link between any two blocks showing all atoms and all bonds (1)
identical orientation of both inter-block amide links including terminal groups with correct orientation (if shown) (1)
continuation bonds on polymer (1)

6(c)(iii) hydrolysis (1) 1

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) May/June 2021
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2021 series for most Cambridge
IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

This document consists of 10 printed pages.

© UCLES 2021 [Turn over

Pg 144 of 349
0620/41 Cambridge IGCSE – Mark Scheme May/June 2021
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) Haber (process) 1

1(b) fractional distillation 1

1(c) electrolysis 1

1(d) filtration 1

1(e) hydrolysis 1

1(f) chromatography 1

Question Answer Marks

2 Mg: 12 and 13 (1) 5

Cu2+: 29 and 27 (1)
37(above)
and17(below) (1)
Cl (1)
1– (1)

Question Answer Marks

3(a) 2K + Cl2 → 2KCl 2

Cl2 on left hand side (1)
equation fully correct (1)

3(b) K outer shell with 8 crosses (1) 3

Cl outer shell with 7 dots and 1 cross (1)
+ and – (1)

3(c)(i) breakdown by (the passage of) electricity (1) 2

of an ionic compound in molten or aqueous (state) (1)

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Question Answer Marks

3(c)(ii) (anode) chlorine 1

(cathode)potassium

3(d)(i) 2H+ + 2e(–) → H2 2

H+ and e(–) on left hand side (1)
equation fully correct (1)

3(d)(ii) chlorine 1

3(d)(iii) potassium hydroxide (1) 1

3(e) one shared pair of electrons and 6 non-bonding electrons on each chlorine atom 1

3(f)(i) liquid (1) 2

BOTH melting point is below –75 oC AND boiling point is above –75 oC

OR
BOTH –75 oC is higher than –101 oC / melting point AND lower than –35 oC / boiling point

OR
–75 oC is between melting point or –101 oC and boiling point or –35 oC

3(f)(ii) ionic bonds in KCl (1) 3

attraction between molecules in Cl2 (1)
weaker attraction (between particles) in Cl2 ORA (1)

Question Answer Marks

4(a) the rate of forward reaction equals the rate of the reverse reaction (1) 2
concentrations of reactants and products are constant (1)

4(b)(i) (increased pressure) nitrogen dioxide particles or molecules (forced) closer together 1
OR
same number of nitrogen dioxide particles or molecules in a smaller volume

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Question Answer Marks

4(b)(ii) fewer number of gas moles or molecules on left hand side or reactant side (of the equation) ORA 1

4(c)(i) shifts to the right 1

4(c)(ii) increase / faster (1) 2

increase / faster (1)

Question Answer Marks

5(a) (add) water (to both salts) (1) 5

dissolve both salts / make solutions (1)
filter (lead(II) iodide)(1)
wash (residue of lead(II) iodide) with water AND dry e.g. with filter paper / description of washing and drying (1)
Pb(NO3)2 + 2 NaI → 2NaNO3 + PbI2
OR Pb2+ + 2I– → PbI2 (1)

5(b)(i) glowing splint (1) 2

relights / rekindles (1)

5(b)(ii) 2ZnO(s) and 4NO2(g) (1) 2

12H2O(g) (1)

5(c)(i) heat again and weigh again / repeat steps 2 and 3 (1) 2
until mass is constant (1)

5(c)(ii) 0.005 (1) 4

0.9 (1)
(0.9 ÷ 18 =) 0.05 (1)
(0.05 ÷ 0.005 =) 10 (1)

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Question Answer Marks

6(a)(i) hematite 1

6(a)(ii) air 1

6(a)(iii) slag / calcium silicate 1

6(a)(iv) any two from: 2

• (coke)
releases heat (when it reacts with oxygen or reacts in air)
OR (acts as a) fuel
OR increases temperature (in the furnace) / heats (the furnace)
OR source of energy

• (coke or carbon monoxide)

reduces iron oxide
OR is a reducing agent
OR converts iron oxide to iron /
removes oxygen from iron oxide

• (coke)
reacts with oxygen to form carbon monoxide
OR reacts with carbon dioxide to form carbon monoxide

6(b) S22- or S- 1

6(c)(i) any two from: 2

• (iron forms) coloured compounds
• (iron has) variable oxidation states
• (iron acts as a) catalyst

6(c)(ii) any two from: 2

• (iron is) good conductor of electricity
• (iron) forms a basic oxide
• (iron salts are) soluble (in water)

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Question Answer Marks

6(d)(i) magnesium is more reactive than iron / steel ORA (1) 2

iron is not oxidised

OR
iron does not lose electrons

OR
magnesium loses electrons more easily than or in preference (to iron) ORA

OR
magnesium is oxidised more easily or reacts with oxygen more easily or corrodes more easily or in preference (to iron)
ORA (1)

6(d)(ii) copper is less reactive than iron / copper is lower in the reactivity series than iron ORA 1

Question Answer Marks

7(a) 48.65 / 12 8.11 / 1 43.24 / 16 (1) 3

OR evaluation
4.05 8.11 2.7(0)

divide all by smallest

OR 1.5 : 3 : 1
OR 6 : 3 : 2 (1)

C3H6O2 (1) ALLOW symbols in any order

7(b) (Mr of CH4O = 32) 1

CH4O (1)

7(c)(i) CnH2nO2 1
OR
CnH2n+1 COOH

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Question Answer Marks

7(c)(ii) butanoic acid (1) 3

fully displayed carboxylic acid group (1)

correct structure of butanoic acid showing all atoms and bonds (1)

7(c)(iii) homologous series 1

7(d)(i) brown to colourless 1

7(d)(ii) C9H20 (1) 2

2C3H6 (1)

7(d)(iii) addition 1

7(d)(iv) 2

any one repeat unit (1)

both repeat units fully correct (1)

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) May/June 2021
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2021 series for most Cambridge
IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

This document consists of 9 printed pages.

© UCLES 2021 [Turn over

Pg 154 of 349
0620/42 Cambridge IGCSE – Mark Scheme May/June 2021
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) Na or Mg or Al 1

1(b) Mg 1

1(c) S 1

1(d) S 1

1(e) Al 1

1(f) Ar 1

1(g) Si 1

1(h) Al 1

1(i) Cl 1

1(j) Cl 1

Question Answer Marks

2(a)(i) isotopes 1

2(a)(ii) mark by row 3

107Ag 109Ag+

p 47 47

n 60 62

e 47 46

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Question Answer Marks

2(a)(iii) average / mean 3

12C

12

2(a)(iv) 50(%) 1

2(b) HNO3 1

2(c)(i) yellow precipitate 1

2(c)(ii) Ag+(aq) + vI–(aq) → AgI(s) 3

AgI (as only product) (1)
Ag+ and I– (as only reactants) (1)
state symbols (1)

2(d) aluminium (1) 2

ammonia (1)

2(e) photochemical 1

2(f)(i) any named alkane 1

2(f)(ii) name of organic product derived from 2(f)(i) (1) 2

hydrogen chloride / HCl (1)

Question Answer Marks

3(a) (thermal) decomposition 1

3(b) 84 (1) 4
12.6 / 84 = 0.15(00) (1)
0.15(00) / 2 = 0.075(00) (1)
0.075(0) × 24.0 = 1.8 (1)

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Question Answer Marks

3(c) Ca(OH)2 (1) 2

CaCO3 (1)

Question Answer Marks

4(a) electrolyte 1

4(b)(i) 4OH– → 2H2O + O2 + 4e– 2

balance of charge (1)
rest of equation (1)

4(b)(ii) (OH–(aq) ions) lose electrons 1

4(c) fizzing 1

4(d) 2H+ + 2e– → H2 2

species correct (1)
fully correct equation (1)

4(e)(i) fizzing (1) 2

green gas (1)

4(e)(ii) (litmus turns) blue and alkali / base forms (1) 2

Sodium hydroxide / NaOH (forming) (1)

4(f) platinum 1

Question Answer Marks

5(a)(i) 6Li + N2 → 2Li3N 2

N2 as reactant (1)
rest of equation (1)

5(a)(ii) new octet of 8 electrons consisting of 5 crosses and 3 dots in second shell (1) 2
charge of 3– (1)
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Question Answer Marks

5(b)(i) bonds broken [945 + (3 × 160)] = 1425 (1) 3

bonds formed (2 × 3 × 300) = 1800 (1)
energy change = M1 – M2 = 1425 – 1800 = –375 (1)

5(b)(ii) Answer must reflect answer in 5(b)(i) 1

exothermic
and
more energy released (in bond formation) than used/taken in (in bond breaking)

5(b)(iii) N with 1 bonding pair with each F (1) 3

2 non-bonding dots for N (1)
6 non-bonding crosses for F (1)

5(c) ionic bonds in Li3N (1) 3

attraction between molecules in NF3 (1)
weaker attraction (between particles) in NF3 ORA (1)

5(d)(i) rfm of NH4NO3 = 80 (1) 2

mass of N = 2 × 14 = 28 and percentage N = 100 × 28 / 80 = 35% (1)

5(d)(ii) fertiliser 1

5(d)(iii) calcium hydroxide 1

5(e)(i) proton acceptor 1

5(e)(ii) 7 < × ⩽ 11 1

Question Answer Marks

6(a)(i) carboxylic acid 1

6(a)(ii) any correct displayed ester link between any two blocks showing all atoms and all bonds (1) 3
correct orientation of three displayed inter-block ester links with correct orientation (1)
continuation bonds on polyester (1)

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Question Answer Marks

6(a)(iii) water 1

6(b)(i) two blocks linked by –O– 1

6(b)(ii) acid (and heat) (1) 2

enzymes (ignore names) (1)

6(b)(iii) chromatography 1

6(c)(i) fermentation 1

6(c)(ii) C6H12O6 → 2C2H5OH + 2CO2 2

C2H5OH (1)
rest of equation (1)

© UCLES 2021 Page 9 of 9

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) May/June 2021
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2021 series for most Cambridge
IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level components.

This document consists of 9 printed pages.

© UCLES 2021 [Turn over

Pg 163 of 349
0620/43 Cambridge IGCSE – Mark Scheme May/June 2021
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

© UCLES 2021 Page 4 of 9

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PUBLISHED
Question Answer Marks

1(a) polymerisation 1

1(b) fractional distillation 1

1(c) fermentation 1

1(d) distillation 1

1(e) electrolysis 1

1(f) chromatography 1

1(g) filtration 1

Question Answer Marks

2 B: 5 and 6 (1) 5
Cl –: 18 and 18 (1)
54 and 24 (1)
Cr (1)
3+ (1)

Question Answer Marks

3(a) 2Na + F2 → 2NaF 2

F2 (1)
equation fully correct (1)

3(b) Na outer shell with 8 crosses (1) 3

F outer shell with 7 dots and 1 cross (1)
Na+ and F− (1)

3(c)(i) breakdown by (the passage of) electricity (1) 2

of an ionic compound in molten / aqueous (state) (1)

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Question Answer Marks

3(c)(ii) oxygen 2
hydrogen

3(d)(i) (anode) fluorine (1) 2

(cathode) sodium (1)

3(d)(ii) Na+ + e(–) → Na 1

3(e) one shared pair of electrons and 6 non-bonding electrons on each fluorine atom 1

3(f)(i) liquid (1) 2

BOTH melting point is below –195 °C and boiling point is above –195 °C
OR –195 °C is in between melting point and boiling point / –220 °C and –188 °C (1)
OR
BOTH –195 °C is higher than –220 °C / melting point AND lower than –188 °C / boiling point

3(f)(ii) ionic bonds in NaF (1) 3

attraction between molecules in F2 (1)
weaker attraction (between particles) in F2 ORA (1)

Question Answer Marks

4(a) the rate of forward reaction equals (the rate of the) reverse reaction (1) 2
concentrations of reactants and products are constant (1)

4(b)(i) same number of gas moles on both sides of the equilibrium / same number of gas molecules on both sides of the 1
equilibrium

4(b)(ii) iodine particles or molecules (forced) closer together / same number of iodine particles or molecules in a smaller volume 1

4(c)(i) shifted to the left 1

4(c)(ii) decrease / slower (1) 2

decrease / slower (1)

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Question Answer Marks

5(a) add zinc carbonate to sulfuric acid until 5

• it stops dissolving
OR
• no more effervescence (1)
filter (zinc carbonate) (1)
evaporation of filtrate to form dry crystals (1)
ZnCO3 + H2SO4 → ZnSO4 + CO2 + H2O
CO2 product in equation (1)
rest of equation correct (1)

5(b)(i) acidified aqueous potassium manganate(VII) (1) 2

purple to colourless (1)

5(b)(ii) 2 FeSO4.7H2O (1) 2

14 H2O (1)

5(c)(i) heat + weigh + repeat (1) 2

until mass is constant (1)

5(c)(ii) M1 0.02 (1) 4

M2 0.72 (1)
M3 M2 ÷ 18 = 0.72/18 = 0.04 (1)
M4 M3 ÷ M1 = 0.04 ÷ 0.02 = 2 (1)

Question Answer Marks

6(a)(i) limestone 1

6(a)(ii) (molten) iron 1

6(a)(iii) coke / carbon / carbon monoxide 1

6(a)(iv) (reaction between) coke / carbon and oxygen 1

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Question Answer Marks

6(a)(v) nitrogen (1) 2

carbon dioxide (1)

6(b)(i) zinc sulfide 1

6(b)(ii) condensation/condensing 1

6(c) brass 1

6(d)(i) any two from (copper has): 2

• high density
• high melting point
• variable oxidation states

6(d)(ii) any two from (copper): 2

• good conductor of electricity
• forms a basic oxide
• soluble salts

Question Answer Marks

7(a) 11.63 / 1 69.77 / 12 18.6 /16 2

Or evaluation
11.63 5.81 1.16
Or ratio
10 : 5 : 1 (1)

C5H10O (1)

7(b) (Mr of CH2O =) 30 (1) 2

C2H4O2 (1)

7(c)(i) structural isomers 1

7(c)(ii) carboxylic acids 1

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Question Answer Marks

7(c)(iii) name of ester, corresponding to C3H6O2: ethyl methanoate or methyl ethanoate (1) 3
correctly displayed ester linkage (1)
fully correct displayed formula corresponding to C3H6O2 and matching named ester (1)

7(c)(iv) displayed formula of propanoic acid (1) 2

propanoic acid (1)

7(d) Step 1: 4
cracking (1)
C10H22 → C2H4 + C8H18 (1)

Step 2:
(catalytic) addition (1)
C2H4 + H2O → C2H5OH (1)

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) October/November 2021
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2021 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 11 printed pages.

© UCLES 2021 [Turn over

Pg 172 of 349
0620/41 Cambridge IGCSE – Mark Scheme October/November 2021
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range
may be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a)(i) hydrogen 1

1(a)(ii) sodium 1

1(a)(iii) iron 1

1(a)(iv) aluminium 1

1(a)(v) zinc or copper 1

1(a)(vi) iron 1

1(b)(i) zinc blende 1

1(b)(ii) bauxite 1

1(c) protective oxide layer 1

1(d) Any 2 from 3 2

• zinc
• iron
• copper

1(e)(i) copper 1

1(e)(ii) zinc sulfate 1

1(e)(iii) M1 particles have more energy 3

M2 More collisions (between particles) occur per second / per unit time

M3 A greater percentage / proportion / fraction of collisions (of particles) are successful / have energy above activation
energy / have energy equal to activation energy

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Question Answer Marks

1(e)(iv) Any 2 from 3: 2

• use a catalyst
• use smaller granules
• increase concentration

Question Answer Marks

2(a)(i) isotopes 1

2(a)(ii) 1 mark for each correct row 3

63Cu 65Cu2+

p 29 29

n 34 36

e 29 27

2(a)(iii) M1 = (70 × 63) + (30 × 65) or [ ( 4410) + (1950) ] or 6360 (1) 2

M2 = M1 / 100 = 63.6 (1)

OR

M1= (0.7(0) × 63) + (0.3(0) × 65) or [ (44.1(0) ) + (19.5(0)) ] (1)

M2 = 63.6 (1)

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Question Answer Marks

2(b)(i) M1 white (1) 2

M2 to (light) blue (1)

2(b)(ii) 5H2O 1

2(b)(iii) heating 1

2(b)(iv) M1 boiling point (1) 2

M2 is 100 °C

OR

M1 freezing point (1)

M2 is 0 °C (1)

2(c)(i) blue precipitate 1

2(c)(ii) Alternative suggestion: 3

M1 Cu(OH)2 (as only product) (1)
M2 Cu2+ and 2OH– (as reactants) (1)
M3 state symbols (1)

2(d) M1 188 4

M2 4.7 / 188 = 0.025(0)

M3 0.025(0) × 2 = 0.05(0)

M4 0.05(0) × 24.0 = 1.2

2(e) 2NaNO3 → 2NaNO2 + O2 2

NaNO2 (1)
rest of equation (1)

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Question Answer Marks

3(a)(i) 2Cl – → Cl 2 + 2e– 2

Cl 2 (1)
rest of equation (1)

3(a)(ii) Oxidation AND lose electrons 1

3(b) effervescence (of colourless gas) 1

3(c) 2H+ + 2e– → H2 2

H+ + e as only species on LHS (1)
rest of equation fully correct (1)

3(d)(i) 1 1

3(d)(ii) M1 increase (1) 2

M2 H+ ions being removed (1)

3(e) M1 cathode: silver / grey solid (1) 2

M2 anode: bubbles of orange / brown gas (1)

3(f) M1 inert (1) 2

M2 conducts electricity (1)

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Question Answer Marks

4(a) (4FeCuS 13O2) → 2Fe2O3 + 4CuO + 8SO2 2

Fe2O3 and CuO as a product (1)
Equation fully correct (1)

4(b)(i) M1 rate of forward reaction = rate of reverse reaction (1) 2

M2 concentration of reactants and products are constant (1)

4(b)(ii) M1 450 °C (1) 2

M2 1-2 atm (1)

4(b)(iii) vanadium(V) oxide 1

4(b)(iv) increase rate of reaction 1

4(b)(v) M1 equilibrium shifts to left hand side (1) 2

M2 forward reaction is exothermic (1)

4(c) C6H12O6 → 6C + 6H2O 2

H2O (1)
balance (1)

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Question Answer Marks

5(a) homologous series 1

5(b) CnH2n 1

5(c)(i) orange to colourless 1

5(c)(ii) (only) one product is formed 1

5(c)(iii) C4H8 + Br2 → C4H8Br2 2

C4H8Br2 (1)
equation fully correct (1)

5(c)(iv) (poly) but-2-ene 1

5(c)(v) but-1-ene (1) 2

structure of but-1-ene

(1)

5(d)(i) C2H4O 1

5(d)(ii) 2C3H7COOH + Na2CO3 → 2C3H7COONa + H2O + CO2 2

C3H7COONa (1)
equation fully correct (1)

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Question Answer Marks

5(d)(iii) methyl butanoate (1) 3

ester link (1)

rest of structure (1)

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) October/November 2021
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2021 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 11 printed pages.

© UCLES 2021 [Turn over

Pg 183 of 349
0620/42 Cambridge IGCSE – Mark Scheme October/November 2021
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range
may be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) 1 mark for each correct row 3

State touching random regularly

movement arranged

Gas ✔

Liquid ✔ ✔

Solid ✔ ✔

1(b)(i) boiling happens at a specific temperature (1) 2

boiling has bubbles (1)

1(b)(ii) condensation (1) 2

sublimation (1)

1(c) one horizontal line level with Y (1) 2

two separate decreases before and after horizontal line (1)

1(d)(i) dissolving 1

1(d)(ii) precipitation 1

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Question Answer Marks

2(a)(i) strong 1

2(a)(ii) 2H+ + SO42– 2

H+ (1) correct equation (1)

2(a)(iii) pink / red 1

2(b)(i) ZnCO3(s) + 2HNO3(aq) → 2

Zn(NO3)2(aq) + H2O(l) + CO2(g)
reactant states (1) product states (1)

2(b)(ii) M1 125 4
M2 2.5 / 125 = 0.02(00)
M3 0.02(00) × 2 = 0.04(00)
M4 0.04(00) × 1000 / 20 = 2(.00)

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Question Answer Marks

3(a) 1 mark for each correct row 3

Name Relative mass Relative charge

Proton 1 +1

Neutron 1 0

Electron 1 / 1840 –1

3(b) 5
Particle Number of Number of Number of
protons neutrons electrons
32 S 16 16 16
16

39 K+ 19 20 18
19

79 Br– 35 44 36
35

M1 = row 1 (1) M2 = row 2 (1) M3 =Br (1)

M4 = 7935 (on left of any symbol) (1) M5 = charge (on any symbol) (1)

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Question Answer Marks

4(a) M1 E of making bonds > breaking bonds 3

M2 bond making releases energy

M3 bond breaking requires energy

4(b)(i) M1 exothermic mark 3

horizontal line below energy level to R.H.S. of reactants line
and
labelled COCl 2(g) (1)

M2 activation E mark
activation energy ‘hump’ with upward arrow labelled A / activation energy (1)

M3 energy change mark

one downward arrow labelled ΔH
and
energy change starting from E level of reactants and finishing at E level of products (1)

4(b)(ii) increases rate of reaction 1

4(c)(i) equilibrium shifts to right hand side (1) 2

fewer moles (of gas) on right hand side (1)

4(c)(ii) equilibrium shifts to left hand side (1) 2

(forward) reaction is exothermic (1)

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Question Answer Marks

4(d) M1 bond energy in making bonds 3

= [(2 × 400) + 745] = 1545 (kJ mol–1)

M2 use of total E change

–230 = [240 + E(C≡O)] – 1545
OR
[240 + E(C≡O)] = –230 + 1545 = (+1315)

M3 E(C≡O)
= [–230 + 1545] – 240 = 1075 (kJ mol–1)

4(e) M1 all single bonding dot and cross pairs correct 3

M2 double C=O bond dot and cross pairs are correct
M3 complete diagram is correct

Question Answer Marks

5(a) metallic (1) 4

(lattice of) positive ions (1)
sea of / delocalised / mobile electrons (1)
attraction between positive ions and electrons (1)

5(b)(i) malleability / malleable 1

5(b)(ii) (particles) slide (over each other) 1

5(b)(iii) unreactive 1

5(c) high(er) density 2

high(er) melting points

5(d)(i) Na – yellow (1) 4

K – lilac (1)
colourless solution (1)
clear idea of increased reactivity in both reactions (1)

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Question Answer Marks

5(d)(ii) hydrogen 1

5(d)(iii) potassium hydroxide 1

5(d)(iv) any number in the range 7< pH ⩽ 14 1

5(d)(v) 4Na + O2 → 2Na2O 2

Na2O (1) correct equation (1)

5(e)(i) N2 + 3H2 → 2NH3 2

species (1) correct equation (1)

5(e)(ii) 450 °C (1) 2

200 atm (1)

Question Answer Marks

6(a) CnH2n+1OH (1) 1

6(b) not all atoms are C or H 1

6(c)(i) C2H4 1

6(c)(ii) glucose 1

6(d) C2H5OH + 3O2 → 3H2O + 2CO2 2

species (1) correct equation (1)

6(e)(i) C3H5O2 1

6(e)(ii) any one ester link (1) 2

rest of molecule (1)

6(e)(iii) water 1

6(f)(i) carboxylic acid 1

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PUBLISHED
Question Answer Marks

6(f)(ii) structure of ethanedioic acid 1

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) October/November 2021
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2021 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 11 printed pages.

© UCLES 2021 [Turn over

Pg 194 of 349
0620/43 Cambridge IGCSE – Mark Scheme October/November 2021
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range
may be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) oxygen 1

1(b) bauxite 1

1(c) sulfur dioxide 1

1(d) ethanol 1

1(e) sodium chloride 1

1(f) ammonia 1

1(g) carbon dioxide 1

1(h) carbon monoxide 1

1(i) ammonia 1

Question Answer Marks

2(a) M1 ionic compound 2

AND either molten or aqueous(or both)(1)
M2 conducts electricity / undergoes electrolysis(1)

2(b)(i) M1 oxygen (1) 5

M2 pink / brown solid (1)

M3 copper (1)

M4 orange / brown / yellow liquid (1)

M5 bromine (1)

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Question Answer Marks

2(b)(ii) 2H+ + 2e(–) → H2 (2) 2

2(b)(iii) M1 inert (1) 2

M2 good conductor of electricity (1)

2(b)(iv) electron 1

Question Answer Marks

3(a) 267 1

3(b) (207 / 239 × 100 = ) 86.6% 1

3(c) PbS because the percentage of lead is larger in PbS or answer to (b) > 77.5% 1

3(d) PbCO3 → PbO + CO2 1

3(e) PbCO3 + 2HNO3 → Pb(NO3)2 + H2O + CO2 2

3(f)(i) M1 two double bonds (1) 2

M2 two pairs of non-bonding electrons on each oxygen and no non-bonding electrons on carbon (1)

3(f)(ii) M1 bonds between ions or ionic bonds in lead(II) oxide (1) 3

M2 attraction between molecules in carbon dioxide (1)

M3 weaker attraction (between particles) in carbon dioxide ORA (1)

3(g) M1 Mg + Pb2+ → Mg2+ + Pb (1) 2

M2 no reaction (1)

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Question Answer Marks

3(h)(i) M1 glowing splint (1) 2

M2 relights (1)

3(h)(ii) nitrogen dioxide / 1

nitrogen(IV) oxide

Question Answer Marks

4(a) 1 mark for each row 2

6 6 6

6 6 7

4(b) diamond and graphite 1

4(c)(i) M1 (22 ÷ 44 =) 0.5 (moles) (1) 2

M2 3.01 × 1023(1)

4(c)(ii) 1.505 × 1023 1

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Question Answer Marks

5(a)(i) too many colour changes 1

5(a)(ii) Any acid-base indicator, e.g. methyl orange or phenolphthalein 1

5(b) M1 repeat without indicator using same volumes OR remove indicator by adding charcoal or carbon and filtering (1) 5

M2 evaporate / heat / warm/

boil/leave in hot place (1)

M3 until most of the water is gone / some water left /

saturation(point) /
crystallisation (point) /
evaporate some of the water (1)

M4 cool /
leave to crystallise(1)

M5 description of drying (1)

5(c)(i) yellow flame 1

5(c)(ii) M1 solid dissolves / disappears(1) 2

M2 blue solution(1)

5(c)(iii) white precipitate 1

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Question Answer Marks

6(a) M1 (a substance that) speeds up a reaction / increases the rate of a reaction (1) 2

M2 unchanged chemically at the end (1)

6(b)(i) oxygen gas escapes 1

6(b)(ii) M1 rate decreases 2

OR
rate / reaction is fastest at the start (1)

M2 reaction stops or
rate = zero (1)

6(c)(i) M1 (particles) have more kinetic energy / particles move faster(1) 3

M2 more collisions per unit time (1)

M3 more particles have energy greater than or equal to activation energy

OR
more particles have sufficient energy to react
OR
A greater percentage or greater proportion or greater fraction of collisions have sufficient energy to react
OR
A greater percentage or greater proportion or greater fraction of collisions have energy greater than or equal to activation
energy
OR
A greater percentage or greater proportion or greater fraction of collisions are successful (1)

6(c)(ii) M1 steeper gradient from start (1) 2

M2 levels off at the same mass (1)

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Question Answer Marks

7(a) 1 for each for any 2 of: 2

• (same) general formula

• similar chemical properties
• (consecutive members) differ by CH2
• same functional group
• common (allow similar or same) methods of preparation
• physical properties and vary in predictable manner or show trends or
gradually change
OR example of a physical property variation, e.g.
melting points increase
boiling points increase
volatility decreases

7(b)(i) cracking 1

7(b)(ii) → C2H4 + C4H10 (2) 2

7(b)(iii) C2H4 + H2O → C2H5OH 1

7(b)(iv) hydration / addition 1

7(b)(v) 1 mark for ANY 1 of: 1

• 300 °C
• 60 atmospheres
• H3PO4

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Question Answer Marks

7(c) 1 mark each for any 2 of: 2

• carbohydrates are renewable

• fossil fuels are non-renewable OR fossil fuels conserved
• lower temperature OR lower energy
• hydration is equilibrium meaning lower yield
• lower pressure (used)

7(d)(i) substitution 1

7(d)(ii) addition 1

7(d)(iii) 2

M1 any one repeat unit with extension bonds (1)

M2 both units fully correct (1)

7(e) 1 mark for each functional group fully correct (2) 2

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Cambridge IGCSE™

CHEMSITRY 0620/42
Paper 4 Theory (Extended) February/March 2022
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the February/March 2022 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 9 printed pages.

© UCLES 2022 [Turn over

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PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a × 10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) nitrogen 1

1(b) sodium 1

1(c) iron 1

1(d) silicon 1

1(e) chlorine 1

1(f) cobalt 1

1(g) chlorine 1

1(h) copper 1

1(i) oxygen 1

1(j) zinc 1

Question Answer Marks

2(a) MgCO3(s) + 2HCl(aq) → MgCl2(q) + H2O(l) + CO2(g) 1

2(b) eight crosses in second shell of Mg 3

7 dots and 1 cross in third shell of both Cl
2+ charge on Mg and – charge on both Cl ions on correct answer line

2(c) C atom double bonded to 2 O atoms 2

4 non-bonding e- on each O and no non-bonding e– on C and both octets complete

2(d)(i) gradient (of line) decreases 1

2(d)(ii) concentration of particles (of acid) decreases 2

lower rate of collisions of particles

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Question Answer Marks

2(d)(iii) a new line steeper than printed line and starts at origin and levels off earlier than printed line 2
levels off at the same volume

2(e) M1 mol HCl = 0.400 × 25.0 / 1000 = 0.01(00) 3

M2 mol CO2 = M1 / 2 = 0.0100 / 2 = 0.005(00)
M3 volume CO2 = M2 × 24000 = 120 (cm3)

Question Answer Marks

3(a) nitrogen (from air) and oxygen (from air) react 2

react due to high temperatures (of engine)

3(b) acid rain 1

3(c)(i) (thermal) decomposition 1

3(c)(ii) HCNO 1

3(c)(iii) (damp red) litmus 2

(litmus) turns blue

3(d)(i) 6NO2 8NH3 7N2 2

either 6NO2 or 8NH3
all three balanced

3(d)(ii) (nitrogen) loses oxygen 1

3(d)(iii) reduction and oxidation occur 1

3(e) Mr urea = 60 2
135 × 60 = 8100 and g to kg conversion = 8.1(00) kg

3(f)(i) carbon monoxide 1

3(f)(ii) carbon dioxide and nitrogen 1

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Question Answer Marks

4(a)(i) arrow going from Zn to Fe 1

4(a)(ii) Zn → Zn2+ + 2e– 2

Zn as only reactant and Zn2+ as only product
correct equation

4(b)(i) any metal above zinc in reactivity series 1

4(b)(ii) any metal below iron in reactivity series 1

4(c)(i) hydrogen and oxygen 1

4(c)(ii) water 1

4(d)(i) electrolysis 1

4(d)(ii) mobile ions 1

4(e)(i) hydrogen 3
chlorine
sodium hydroxide

4(e)(ii) sodium 1

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Question Answer Marks

5(a)(i) cracking 1

5(a)(ii) C10H22 → 4C2H4 + C2H6 3

C10H22 as only reactant
formulae of ethene and ethane as only products
correct equation

5(b)(i) hydrogen chloride 1

5(b)(ii) ultraviolet light 1

5(c)(i) (only) one product is formed 1

5(c)(ii) M1 Bond energy in breaking bonds 4

= [(4 × 410) + 610 + 240] = 2490 (kJ / mol)

M2 Use of total E change to find bond energy of C2H4Cl2

= M1 + 180 = 2490 + 180 = 2670 (kJ / mol)

M3 Determination of total C–Cl bond energy

= M2 – [(4 × 410) + 350] = 2670 – 1990 = 680 (kJ / mol)

M4 Determination of each C–Cl bond energy

= M3 / 2 = 680 / 2 = 340 (kJ / mol)

Question Answer Marks

6(a)(i) homologous series 1

6(a)(ii) Same functional group 1

6(a)(iii) general (formula) 1

6(a)(iv) 7 1

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Question Answer Marks

6(b) fractional 2
distillation

6(c)(i) propanoic acid 2

structure of propanoic acid

6(c)(ii) methanol 1

6(d)(i) structural isomers 1

6(d)(ii) ethyl butanoate 2

butyl ethanoate

6(e)(i) any correct displayed ester link between any two blocks showing all atoms and all bonds 3
correct orientation of three displayed inter-block ester links with correct orientation
continuation bonds on polyester

6(e)(ii) condensation 1

6(e)(iii) terylene 1

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) May/June 2022
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2022 series for most
Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 12 printed pages.

© UCLES 2022 [Turn over

Pg 214 of 349
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PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

 the specific content of the mark scheme or the generic level descriptors for the question
 the specific skills defined in the mark scheme or in the generic level descriptors for the question
 the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

 marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
 marks are awarded when candidates clearly demonstrate what they know and can do
 marks are not deducted for errors
 marks are not deducted for omissions
 answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

 The response should be read as continuous prose, even when numbered answer spaces are provided.
 Any response marked ignore in the mark scheme should not count towards n.
 Incorrect responses should not be awarded credit but will still count towards n.
 Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
 Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) carbon dioxide 1

1(b) aluminium oxide 1

1(c) ethanol (1) 2

carbon dioxide (1)

1(d) ethanol 1

1(e) oxygen 1

1(f) carbon dioxide 1

1(g) nitrogen 1

1(h) diamond 1

Question Answer Marks

2(a)(i) 2
charge relative mass

–1

0 1

(1) (1)

Mark by column

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Question Answer Marks

2(a)(ii) 2
12 12 12 (1)

12 13 12 (1)

Mark by row

2(a)(iii) (they have) 2 more protons than electrons 1

OR
(they have) 2 fewer electrons than protons

OR
(they have) 12 protons and 10 electrons

2(b) Na+ or Al 3+ (1) 3

F- or O2– or N3– (1)

Ne (1)

Question Answer Marks

3(a)(i) positive ions / cations (1) 3

sea of electrons / mobile electrons / delocalised electrons (1)

attraction between positive ions and electrons (1)

3(a)(ii) electrons move / 1

electrons mobile /
electrons flow

3(b)(i) ionic 1

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Question Answer Marks

3(b)(ii) ions move / 1

ions are mobile /
ions flow

3(c)(i) pipette 1

3(c)(ii) yellow to orange 1

3(c)(iii) at least two results are within 0.2 cm3 or less 1

3(c)(iv) 0.005 / 5  10–3 (1) 3

0.0025 / 2.5  10–3 (1)

0.125 (1)

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Question Answer Marks

4(a)(i) S + O2 → SO2 1

4(a)(ii) (temperature) 450 °C (1) 4

(pressure) 1–2 atmosphere(s) (1)

vanadium(V) oxide catalyst (1)

2SO2 + O2 ⇌ 2SO3 (1)

4(a)(iii) SO3 + H2SO4 → H2S2O7 1

4(a)(iv) water 1

4(b)(i) 2 bonding pairs as one dot and cross each (1) 2

2 lone pairs on S (and no additional electrons on Hs) to complete the outer shell on S and both Hs (1)

4(b)(ii) 2H2S + SO2 → 3S + 2H2O 1

Question Answer Marks

5(a) the rate of forward reaction equals the rate of the reverse reaction (1) 2

concentrations of reactants and products are constant (1)

5(b) reaction too slow (1) 2

yield of ethanoic acid too low (1)

5(c) 3
increases (1)

decreases (1) decreases (1)

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Question Answer Marks

5(d) cobalt (1) 2

transition element (1)

5(e) CnH2n+1COOH 1

5(f) COOH fully displayed (1) 2

whole molecule completely correct (1)

5(g)(i) methyl butanoate 1

5(g)(ii) butanoic acid (1) 2

methanol (1)

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Question Answer Marks

5(h) C 48.65 / 12 3
H 8.11 / 1
O 43.24 / 16
OR
4.05:8.11:2.70 (1)

fractions shown dividing all by smallest

OR
1.5:3:1
OR
3:6:2 (1)

C3H6O2 (1)

5(i) C4H8O2 1

Question Answer Marks

6(a)(i) zinc blende 1

6(a)(ii) heat( zinc sulfide) strongly in air / roast in air 1

6(a)(iii) carbon or carbon monoxide 1

6(a)(iv) the temperature in the furnace is above or higher than the boiling point of zinc 1
OR
the boiling point of zinc is below or less than the temperature of the furnace

6(a)(v) condensation / condensing / condense 1

6(b)(i) no bubbles 1
or
no fizzing
or
no effervescence

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Question Answer Marks

6(b)(ii) zinc / zinc oxide / zinc hydroxide 1

6(b)(iii) (powder has) larger surface area OR lumps have smaller surface area (1) 2

(powder has) more collisions per unit time / more collision frequency
OR
lumps have fewer collisions per unit time / less collision frequency (1)

6(b)(iv) crystals (form on glass rod or microscope slide) 1

6(b)(v) ZnSO4 1

Question Answer Marks

7(a)(i) from left to right 1

caesium → rubidium→ potassium →sodium → lithium

7(a)(ii) caesium hydroxide 1

7(b) Group I element is less strong / not strong 1

ORA

OR
Group I element has low(er) density ORA

OR
Group I element is soft(er) ORA

7(c) solid 1

7(d)(i) colourless (1) 2

orange / brown / yellow (1)

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Question Answer Marks

7(d)(ii) Br – (1) 2
loses electron(s) (1)

7(e) 432(1) 3

436(1)

– 4(1)

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) May/June 2022
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2022 series for most
Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 9 printed pages.

© UCLES 2022 [Turn over

Pg 226 of 349
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PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

 the specific content of the mark scheme or the generic level descriptors for the question
 the specific skills defined in the mark scheme or in the generic level descriptors for the question
 the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

 marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
 marks are awarded when candidates clearly demonstrate what they know and can do
 marks are not deducted for errors
 marks are not deducted for omissions
 answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

 The response should be read as continuous prose, even when numbered answer spaces are provided.
 Any response marked ignore in the mark scheme should not count towards n.
 Incorrect responses should not be awarded credit but will still count towards n.
 Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
 Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) Mg 1

1(b) Ar 1

1(c) Cl 1

1(d) Si 1

1(e) P 1

1(f) Na 1

1(g) Al 1

1(h) S 1

Question Answer Marks

2(a)(i) Ca + 2H2O  Ca(OH)2 + H2 2

M1 H2 as product
M2 Fully correct equation

2(a)(ii) calcium oxide 1

2(b)(i) 7 < pH ⩽ 12 1

2(b)(ii) OH– 1

2(c)(i) carbon dioxide 1

2(c)(ii) (a solution that) can dissolve no more solute 2

at a given temperature

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Question Answer Marks

2(c)(iii) add excess (solid) calcium hydroxide (to water) 2

filter

2(c)(iv) (aqueous) sodium hydroxide 1

white ppt 2

insoluble / remains in excess

2(d)(i) burette 1

2(d)(ii) neutralisation 1

2(d)(iii) indicator 1

2(d)(iv) M1 Mol HCl = 0.0500  20.0 / 1000 = 0.001(00) 5

M2 Mol Ca(OH)2 = M1 / 2 = 0.00100 / 2 = 0.0005(00)

M3 M2  1000 / 25 = 0.0005(00)  40 = 0.02(00)

M4 Mr Ca(OH)2 = 74

M5 M4  M3 = 74  0.02 = 1.48 (g / dm3)

Question Answer Marks

3(a)(i) atom(s) of the same element 2

with different number of neutrons

3(a)(ii) 55 1

3(a)(iii) 24 protons; 28 neutrons; 21 electrons 3

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Question Answer Marks

3(b)(i) blue 2
pink

3(b)(ii) (act as) catalysts 2

variable oxidation state

3(c)(i) mobile electrons 1

3(c)(ii) malleability / malleable 1

3(d) high(er) density 2

high(er) melting points

Question Answer Marks

4(a) (pale) yellow and gas 1

4(b) Method 1 3
M1 S 25.2 / 32 or 0.78/0.79 …
and
F 74.8 / 19 or 3.93 / 3.94…

M2 ÷ both by 0.7875 = 1 : 5 or SF5

M3 (254 ÷ 127 = 2 and) S2F10

Method 2
M1 254  25.2/100 and 254  74.8 / 100 OR ‘64’ and ‘190’

M2 64 / 32 and 190 / 19

M3 (2 and 10) to give S2F10

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Question Answer Marks

4(c) N with 1 dot-cross bonding pair with each Cl 3

2 non-bonding dots for N
6 non-bonding crosses for Cl

4(d) two crosses in first shell of Li 3

7 dots and 1 cross in third shell of Cl
‘+’ charge on Li on correct answer line and ‘–‘ charge on Cl ion on correct answer line

4(e) ionic bonds in LiCl 3

attraction between molecules in NCl3

weaker attraction (between particles) in NCl3 ORA

Question Answer Marks

5(a) fermentation 1

5(b) (complete) combustion 3

C2H5OH + 3O2  3H2O + 2CO2
reactant species
fully correct equation

5(c)(i) ethene 1

5(c)(ii) addition 1

5(c)(iii) steam 2

catalyst + 60 atm or catalyst + 300 °C

5(d)(i) hydrogen 3
catalyst
high temperature

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Question Answer Marks

5(d)(ii) CnH2n+2 1

5(e)(i) potassium manganate(VII) 1

5(e)(ii) carboxylic acids 1

5(e)(iii) fully displayed formula of ethanoic acid 1

Question Answer Marks

6(a)(i) 3 1

6(a)(ii) diagram of dioic acid showing two fully displayed carboxylic acid groups on unshaded block 2

diagram of diol showing two fully displayed hydroxyl groups on shaded block

6(a)(iii) polyester 1

6(b) one 1

6(c)(i) any hydrocarbon with one C=C bond (with both C atoms having 4 bonds) (1) 3

structure of but-2-ene (1)

but-2-ene

6(c)(ii) cracking 1

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) May/June 2022
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2022 series for most
Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 11 printed pages.

© UCLES 2022 [Turn over

Pg 235 of 349
0620/43 Cambridge IGCSE – Mark Scheme May/June 2022
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

 the specific content of the mark scheme or the generic level descriptors for the question
 the specific skills defined in the mark scheme or in the generic level descriptors for the question
 the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

 marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
 marks are awarded when candidates clearly demonstrate what they know and can do
 marks are not deducted for errors
 marks are not deducted for omissions
 answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

 The response should be read as continuous prose, even when numbered answer spaces are provided.
 Any response marked ignore in the mark scheme should not count towards n.
 Incorrect responses should not be awarded credit but will still count towards n.
 Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
 Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Examples of how to apply the list rule
State three reasons…. [3]

A 1 Correct  F 1 Correct 
2 Correct  2 (4 responses) 2 Correct 
2
3 Wrong  3 Correct 
CON (of 3.) (discount 3)

B 1 Correct, Correct , 
G 1 Correct 
(4 responses) 2 Correct  3
(5 responses) 2 Correct 
3 Wrong ignore
3
3 Correct 
Correct ignore
CON (of 4.) ignore
C 1 Correct 
(4 responses) 2 Correct, Wrong ,  2
3 Correct ignore H 1 Correct 
(4 responses) 2 Correct 
2
3 CON (of 2.) (discount 2)
D 1 Correct 
Correct 
(4 responses) 2 Correct, CON , (discount 2)
2
(of 2.)
3 Correct  I 1 Correct 
(4 responses) 2 Correct 
2
3 Correct 
E 1 Correct 
CON (of 2.) (discount 2)
(4 responses) 2 Correct  3
3 Correct, Wrong 

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Question Answer Marks

1(a) carbon dioxide 1

1(b) iron(III) oxide 1

1(c) copper 1

1(d) carbon monoxide 1

1(e) glucose 1

1(f) carbon monoxide 1

1(g) copper 1

1(h) oxygen 1

Question Answer Marks

2(a)(i) number of protons (are the same) / 16 protons (1) 3

number of electrons (are the same) / 16 electrons (1)

number of neutrons (are different) / 16,17 neutrons (1)

2(a)(ii) number of protons is the same as (the number of) electrons 1

2(a)(iii) same number of (outer shell) electrons 1

2(b)(i) (they have) two more electrons than protons 1

2(b)(ii) P3– OR Cl– (1) 2

K+ OR Ca2+ (1)

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Question Answer Marks

3(a)(i) covalent 1

3(a)(ii) weak force(s) of attraction between molecules 1

3(a)(iii) no ions 1
OR no mobile electrons

3(b) 450 °C (1) 4

200 atmospheres (1)

iron (catalyst) (1)

N2 + 3H2 ⇌ 2NH3 (1)

3(c) 2NH4Cl + Ca(OH)2 → 2NH3 + CaCl2 + 2H2O 1

3(d) all 4 NH dot and cross bonds (1) 2

single bonding pair between N’s and two non-bonding electrons on each N and no non-bonding e on H and nitrogen octet
complete (1)

3(e)(i) proton acceptor 1

3(e)(ii) N2H4 + H2O ⇌ N2H5+ + OH– 1

Question Answer Marks

4(a) (a substance which) increases the rate of a reaction 2

remains unchanged or unaffected or without changing mass

4(b) 4
increases (1) decreases (1)

decreases (1) decreases (1)

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Question Answer Marks

4(c)(i) CnH2n+1OH 1

4(c)(ii) any 2 from: 2

 same or similar chemical properties or reactions
 (contain) the same functional group
 (consecutive members) differ by CH2
 physical properties vary in predictable manner / show trends / gradually change

4(c)(iii) 2

(1)
propan-2-ol (1)

4(d)(i) ethyl butanoate 1

4(d)(ii) ethanol (1) 2

butanoic acid (1)

4(e) C 58.82 / 12 H 9.80 / 1 O 31.37 / 16 3

OR
4.90:9.80:1.96 (1)

2.5:5:1
OR
5:10:2 (1)

C5H10O2(1)

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Question Answer Marks

4(f) C6H12O2 1

Question Answer Marks

5(a) (lattice of) positive ions (1) 3

sea of / delocalised / mobile electrons (1)

attraction between positive ions and electrons (1)

5(b) copper (1) 3

spoon (1)

(aqueous or solution) of named copper salt (1)

5(c) (0.2  50 / 1000) = 0.01 (1) 3

0.01 (1)

(250  0.01) = 2.5 (1)

5(d) solid undissolved 1

5(e) particles have less energy 3

fewer collisions (between particles) occur per second / per unit time

a smaller percentage / proportion / fraction of collisions (of particles) are successful / have energy above activation
energy / have energy equal to activation energy

5(f) copper(II) carbonate OR copper(II) hydroxide 1

5(g) filtration 1

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Question Answer Marks

5(h) (a solution that) can dissolve no more solute 2

at a given temperature

5(i) forms anhydrous (copper sulfate) 1

OR forms (white) powder

Question Answer Marks

6(a)(i) Group 1 metals do not show catalytic behaviour 2

Group 1 have fixed oxidation states

6(a)(ii) any 2 observations from: 5

 moves / floats
 dissolves / disappears
 bubbles / effervescence / fizzes
 lilac flame
 explodes
 melts / forms a spherical shape

2K(s) + 2H2O(l) →2KOH(aq) + H2(g)

KOH or H2 product (1) in equation

fully correct equation (1)

state symbols (1)

6(b) transition elements have high(er) melting point (1) 2

transition elements have high(er) density (1)

6(c)(i) colourless (1) 2

brown (1)
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Question Answer Marks

6(c)(ii) redox 1

6(c)(iii) Br2 (1) 2

(bromine) is reduced (1)

6(d) two ticks in first row (1) 2

three crosses in the other three boxes (1)

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) October/November 2022
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2022 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 10 printed pages.

© UCLES 2022 [Turn over

Pg 246 of 349
0620/41 Cambridge IGCSE – Mark Scheme October/November 2022
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

© UCLES 2022 Page 2 of 10

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) oxygen 1

1(b) carbon 1

1(c) lithium 1

1(d) nitrogen 1

1(e) neon 1

1f lithium 1

1(g) boron 1

1(h) nitrogen 1

Question Answer Marks

2(a) M1 metallic (1) 4

M2 lattice of potassium ions (1)

M3 sea of electrons (1)

M4 attraction between potassium ions and electrons (1)

2(b)(i) any two (one from each bullet point) 2

• physical constants: high boiling point / melting point

• conductivity: conduct electricity when aqueous / conduct electricity when molten
• solubility: soluble in water

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Question Answer Marks

2(b)(ii) M1 eight dots in third shell of both K (1) 3

M2 six crosses and two dots in third shell of S (1)

M3 ‘+’ charge on each K on correct answer line and ‘2–‘ charge on S ion on correct answer line (1)

2(c)(i) lilac 1

2(c)(ii) OH– 1

2(c)(iii) blue 1

2(c)(iv) M1 mol of K = 2.34 / 39 = 0.06(00) (1) 3

M2 mol of H2 = 0.06 / 2 = 0.03(00) (1)

M3 volume of H2 = 0.03  24 000 = 720 cm3 (1)

2(d)(i) hydrochloric (acid) 1

2(d)(ii) neutralisation 1

2(d)(iii) titration 1

2(e)(i) white 1

2(e)(ii) silver chloride 1

2(e)(iii) Ag+(aq) + Cl –(aq) → AgCl(s) 3

M1 AgCl (as only product) (1)

M2 Ag+ and Cl– (as only reactants) (1)

M3 state symbols (1)

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Question Answer Marks

3(a) Haber (process) 1

3(b) air 1

3(c) reversible 1

3(d) 450 (1) 2

200 (1)

3(e) Iron / Fe 1

3(f) reduced temperature: 4

M1 (position of) equilibrium moves to right-hand side (1)

M2 reaction is exothermic (1)

reduced pressure:
M3 (position of) equilibrium moves to left-hand side (1)

M4 more (gaseous) moles on left hand side (1)

3(g) M1 rate decreases and particles have less energy (1) 3

M2 less collisions (between particles) occur per second / per unit time (1)

M3 less of the particles/collisions have energy equal to or above the activation energy (1)

or
less of the particles / collisions have sufficient energy to react

or
a lower percentage / proportion / fraction of collisions (of particles)
• are successful or
• have energy equal to or above activation energy

3(h) (NH4)2SO4 1

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Question Answer Marks

4(a) CaCO3 + 2HNO3 → Ca(NO3)2 + H2O + CO2 2

M1 H2O and CO2 as product (1)

M2 rest of equation correct (1)

4(b) M1 fizzing / effervescence (1) 2

M2 solid disappears / dissolves (1)

4(c) filtrate 1

4(d)(i) M1 a solution that can contain no more solute (1) 2

M2 at a given temperature (1)

4(d)(ii) cool the solution 1

4(e)(i) anhydrous 1

4(e)(ii) M1 Mr Ca(NO3)2 = 164 (1) 3

M2 mol Ca(NO3)2 = 2.46 / 164 = 0.015(00) (1)

M3 0.015(00) / 0.015(00) = 1
0.0600 / 0.015(00) = 4 and x = 4 (1)

4(f) 2NaNO3 → 2NaNO2 + O2 2

M1 NaNO2 on the right-hand side

M2 equation completely correct

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Question Answer Marks

5(a) CnH2n 1

5(b) orange to colourless 1

5(c) addition 1

5(d)(i) M1 horizontal line below energy level to right hand side of reactants line and labelled C2H4Br2 (1) 3

M2 activation energy ‘hump’ with upward arrow labelled A from the reactants level (1)

M3 one downward arrow starting from the energy level of the reactants and finishing at the energy level of the products (1)

5(d)(ii) M1 energy needed to break bonds 3

4  C–H + C=C + Br–Br = 4  410 + 610 + 190 = 2440 (kJ) (1)

M2 energy released in making bonds

4  C–H + C–C + 2  C–Br = 4  410 + 350 + 2  290 = 2570 (kJ) (1)

M3 energy change M1 – M2 = – 130 (kJ / mol) (1)

Question Answer Marks

6(a)(i) methyl methanoate 1

6(a)(ii) CH2O 1

6(b) M1 all single bonding dot and cross pairs correct (1) 3

M2 double C=O bond dot and cross pairs are correct (1)

M3 complete diagram is correct (1)

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Question Answer Marks

6(c) M1 methanoic acid (1) 4

M2 structure of methanoic acid (1)

M3 methanol (1)

M4 structure of methanol (1)

6(d)(i) M1 same (molecular) formula (1) 2

M2 different structural formula (1)

6(d)(ii) ethanoic acid 1

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) October/November 2022
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2022 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 10 printed pages.

© UCLES 2022 [Turn over

Pg 256 of 349
0620/42 Cambridge IGCSE – Mark Scheme October/November 2022
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) 4 1

1(b) giant covalent 1

1(c) silicon dioxide 1

1(d) M1 layers 2
M2 hexagon(al) (rings of carbon)

1(e) mobile electrons 1

1(f) 60 1

1(g) limewater 1

Question Answer Marks

2(a)(i) to prevent contact with air / oxygen and / or water 1

2(b)(i) combustion 1

2(b)(ii) yellow 1

2(b)(iii) 4Na + O2 → 2Na2O 2

M1 species (1)

M2 balancing (1)

2(b)(iv) M1 eight crosses in second shell of both Na (1) 3

M2 six dots and two crosses in second shell of O (1)

M3 ‘+’ charge on each Na ion on correct answer line and ‘2–‘ charge on O ion on correct answer line (1)

2(c)(i) proton acceptor 1

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Question Answer Marks

2(c)(ii) pH 14 1

2(c)(iii) yellow 1

2(c)(iv) M1 mol Na = 0.345 / 23 = 0.015(00) (1) 5

M2 mol NaOH = M1 = 0.015(00) (1)

M3 M2  1000 / 50 = 0.015(00)  20 = 0.3(00) (1)

M4 Mr NaOH = 40(1)

M5 M4  M3 = 40 x 0.3= 12.(0) (g / dm3) (1)

2(d)(i) precipitation 1

2(d)(ii) red-brown 1

2(d)(iii) iron(III) hydroxide 1

2(d)(iv) Fe3+(aq) + 3OH–(aq) → Fe(OH)3(s) 3

M1 Fe(OH)3 (as only product) (1)

M2 Fe3+ and 3OH– (as only reactants) (1)

M3 state symbols (1)

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Question Answer Marks

3(a) zinc blende 1

3(b) strong heating in air / roasting in air 1

3(c) contact 1

3(d)(i) M1 450 (°C) (1) 2

M2 1–2 (atm) (1)

3(d)(ii) vanadium(V) oxide 1

3(d)(iii) M1 the rate of forward reaction equals (the rate of the) reverse reaction (1) 2

M2 concentrations of reactants and products are constant (1)

3(d)(iv) increased temperature: 4

M1 (position of) equilibrium moves to left-hand side (1)

M2 reaction is exothermic (1)

increased pressure:
M3 (position of) equilibrium moves to right-hand side (1)

M4 more (gaseous) moles / molecules on left-hand side (1)

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Question Answer Marks

3(d)(v) M1 rate increases and particles have more energy (1) 3

M2 more collisions (between particles) occur per second / per unit time (1)

M3 more of the particles / collisions have energy equal to or above the activation energy (1)

or
more of the particles / collisions have sufficient energy to react

or
a higher percentage / proportion / fraction of collisions (of particles) are successful / have energy equal to or above
activation energy

3(e) ammonium sulfate 1

Question Answer Marks

4(a) Mg + H2SO4 → MgSO4 + H2 1

4(b) M1 no (more) fizzing (1) 2

M2 solid stops dissolving or a solid remains / is visible (in the mixture) (1)

4(c) residue 1

4(d)(i) saturated 1

4(d)(ii) solubility (of MgSO4 / solid) decreases (as temperature decreases) 1

4(e)(i) hydrated 1

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Question Answer Marks

4(e)(ii) M1 Mr MgSO4 = 120 (1) 3

M2 mol MgSO4 = 2.40 / M1 = 2.40 / 120 = 0.02(00) (1)

M3 0.02(00) / 0.02(00) = 1
0.140 / 0.02(00) = 7 and x = 7 (1)

4(f) 2Mg(NO3)2 → 2MgO + 4NO2 + O2 2

M1 NO2 + O2 (1)

M2 equation completely correct (1)

Question Answer Marks

5(a) CnH2n+2 1

5(b) needs ultraviolet (light) 1

5(c) substitution 1

5(d) hydrogen chloride 1

5(e)(i) activation energy 1

5(e)(ii) energy (change) of reaction 1

5(e)(iii) energy of products is lower than energy of reactants 1

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Question Answer Marks

5(f) M1 energy needed to break bonds 3

6  C–H + C–C + Cl–Cl = 6  410 + 350 + 240 = 3050 (kJ / mol) (1)

M2 energy released in making bonds

5  C–H + C–C + C–Cl + H–Cl = 5  410 + 350 + 340 + 430 = 3170 (kJ / mol) (1)

M3 energy change M1 – M2 = –120 (kJ / mol) (1)

Question Answer Marks

6(a) CnH2n+1COOH 1

6(b) methanoic acid 1

6(c) CH2O2 1

6(d) M1 all single bonding dot and cross pairs correct (1) 3

M2 double C=O bond dot and cross pairs are correct (1)

M3 four non-bonding cross electrons on each O atom (1)

6(e)(i) M1 propyl methanoate (1) 3

M2 ester linkage with all atoms and all bonds (1)

M3 correct structure of propyl methanoate (1)

6(e)(ii) water 1

6(e)(iii) M1 methyl propanoate (1) 2

M2 butanoic acid (1)

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) October/November 2022
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2022 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 10 printed pages.

© UCLES 2022 [Turn over

Pg 266 of 349
0620/43 Cambridge IGCSE – Mark Scheme October/November 2022
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) 2
M1 relative M2 relative
charge mass

0 1

+1 1

1 mark for each correct column

1(b) M1 22 (1) 6

M2 17 (1)

M3 17 (1)

M4 32 and 16 (1)

M5 S (1)

M6 2 - / - 2 / --
(1)

Question Answer Marks

2(a)(i) E 1

2(a)(ii) H 1

2(a)(iii) G 1

2(b) M1 D (1) 2

M2 conducts electricity when solid (1)

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Question Answer Marks

2(c) M1 F (1) 3

M2 high melting point (1)

M3 non-conductor of electricity when solid and liquid (1)

2(d) M1 I (1) 2

M2 conducts electricity when liquid but not when solid / ONLY conducts when liquid (1)

Question Answer Marks

3(a) bauxite 1

3(b) M1 breakdown by (the passage of) electricity (1) 2

M2 of an ionic compound in molten or aqueous (state) (1)

3(c)(i) M1 improves conductivity of the electrolyte / makes the electrolyte a better conductor (1) 2

M2 lower operating temperature (1)

3(c)(ii) Al3+ + 3e– → Al 2

M1 only Al3+ + (3) e– on the left (1)

M2 equation fully correct (1)

3(c)(iii) M1 anodes or carbon react(s) with oxygen (1) 2

M2 form carbon dioxide (1)

3(d) unreactive coating of aluminium oxide (1) 1

3(e)(i) neutralises both acids AND alkalis 1

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Question Answer Marks

3(e)(ii) 2NaOH + Al2O3 → 2NaAlO2 + H2O 2

M1 NaAlO2 on the right hand side (1)

M2 equation fully correct (1)

3(f) M1 GaCl3 (1) 2

M2 Ga2(SO4)3 (1)

Question Answer Marks

4(a)(i) 4
M1 increases (1)

M2 decreases (1) M3 increases (1)

M4 increases (1)

4(a)(ii) forward reaction is endothermic 1

4(b) M1 3 dot and cross bonding pairs (1) 2

M2 All lone pairs correct.

All octets should be complete AND dots and crosses should be different on P and all Cl (1)

4(c) P4O10 + 6PCl5 → 10POCl3 2

M1 all formula correct and on the correct sides of the arrow (1)

M2 equation fully correct (1)

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Question Answer Marks

4(d) M1 H 3.66 / 1 2
P 37.80 / 31
O 58.54 / 16

OR H = 3.66 P = 1.22 O = 3.66

OR H:P:O 3:1:3 (1)

M2 H3PO3 (1)

4(e) H3PO4 (1) 1

Question Answer Marks

5(a)(i) M1 450 (1) 3

M2 1-2 (1)

M3 vanadium (V) oxide (1)

5(a)(ii) SO3 + H2SO4 → H2S2O7 1

5(a)(iii) water 1

5(b) carbon 1

5(c)(i) M1 2.5  10–3 / 0.0025 (1) 3

M2 1.25  10-3 / 0.00125 (1)

M3 20 (1)

5(c)(ii) 40 1

5(d)(i) lilac flame 1

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Question Answer Marks

5(d)(ii) Any Two from 2

• solid disappears

• blue solution

• bubbles / effervescence / fizzing

5(d)(iii) white precipitate 1

5(e) Ba2+(aq) + SO42-(aq) → BaSO4(s) 3

M1 BaSO4 on the right (1)

M2 ONLY Ba2+ and SO42- on the left (1)

M3 state symbols (1)

Question Answer Marks

6(a)(i) M1 2670 (1) 3

M2 2610 (1)

M3 (+) 60 (1)

6(a)(ii) endothermic AND energy released when bonds form is less than energy absorbed to break bonds 1

OR

endothermic AND overall energy change has a positive sign

6(b)(i) 2 1

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Question Answer Marks

6(b)(ii) M1 but-1-ene (1) 3

M2 C=C (both C atoms should have 4 bonds) (1)

M3 Displayed formula of but-1-ene (1)

6(b)(iii) CH2 1

6(c)(i) hydrolysis 1

6(c)(ii) M1 acids (1) 2

M2 enzymes (1)

6(c)(iii) M1 chromatography (1) 3

M2 locating agent (1)

M3 Rf (1)

6(d)(i) nylon 1

6(d)(ii) M1 carboxylic acid (1) 2

M2 amine (1)

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) February/March 2023
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the February/March 2023 series for most
Cambridge IGCSE™, Cambridge International A and AS Level components and some Cambridge O Level
components.

This document consists of 10 printed pages.

© UCLES 2023 [Turn over

Pg 276 of 349
0620/42 Cambridge IGCSE – Mark Scheme February/March 2023
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any
correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus
terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where
necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should
be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) carbon dioxide 1

1(b) 78 (%) 1

1(c) calcium oxide 1

1(d) catalytic converter 1

1(e)(i) CH4 1

1(e)(ii) lowest relative molecular mass 1

1(f) toxic 1

1(g) M1 glucose 2

M2 oxygen

1(h) M1 two dot-and-cross double bonds 2

M2 two pairs of non-bonding electrons on O and zero non-bonding electrons on C

Question Answer Marks

2(a) metallic 1

2(b)(i) lighted splint and (squeaky) pop 1

2(b)(ii) 14 1

2(b)(iii) universal indicator 1

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Question Answer Marks

2(b)(iv) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) 3

M1 NaOH as product in equation (1)

M2 fully correct equation (1)

M3 state symbols (1)

2(c)(i) isotope(s) 1

2(c)(ii) 6 7 3
Li Li+

protons 3 3

neutrons 3 4

electrons 3 2
each row ✔

2(c)(iii) M1 (6  10) + (7  90) (= 690) (1) 2

M2 690 / 100 = 6.9 (1)

2(d) M1 eight dots in third shell of both K (1) 3

M2 six crosses and two dots in second shell of O (1)

M3 ‘+’ charge on each K on correct answer line and ‘2–‘ charge on O ion on correct answer line (1)

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Question Answer Marks

3(a) nitrogen: air (1) 2

hydrogen: methane (1)

3(b)(i) enthalpy change 1

3(b)(ii) (the value of) ΔH is negative 1

3(b)(iii) M1 450 (1) 3

M2 20 000 (1)

M3 iron (1)

3(b)(iv) one mark for each of 4

decreases

decreases decreases

no change

3(b)(v) M1 kinetic energy of particles increases (1) 3

M2 frequency of collisions between particles increases (1)

M3 higher percentage / proportion / fraction of collisions / particles have energy greater than / equal to activation energy (1)

or
more of the collisions / particles have energy greater than / equal to activation energy

3(c)(i) H2SO4 1

3(c)(ii) fertiliser 1

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Question Answer Marks

3(c)(iii) M1 Mr of (NH4)2SO4 = 132 (1) 2

M2 2  14 = 28 and %N = 100  28 / 132 = 21.2% (1)

Question Answer Marks

4(a)(i) zinc 1

4(a)(ii) alloy 1

4(b)(i) ductility 1

4(b)(ii) electrons 1

4(c)(i) high melting point 1

4(c)(ii) (act as) catalysts 1

4(d)(i) water(s) of crystallisation 1

4(d)(ii) blue 1

4(d)(iii) CuSO4∙5H2O 2

M1 CuSO4 (1)
M2 ∙5H2O (1)

4(e)(i) basic 1

4(e)(ii) the oxidation number of copper is +2 1

4(e)(iii) M1 Mr of Cu(NO3)2 = 188 (1) 2

M2 = 0.0200  M1 = 0.0200  188 = 3.76 g (1)

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Question Answer Marks

4(e)(iv) M1 moles of gas formed = 0.0200  5 / 2 = 0.05(00) (1) 2

M2 volume = M1  24.0 = 0.05(00)  24.0 = 1.2(0) (1)

4(e)(v) 2Al + 3CuO → Al2O3 + 3Cu 2

M1 correct products (1)

M2 rest of equation correct (1)

Question Answer Marks

5(a) same functional group 1

5(b) carboxylic acids 1

5(c) CnH2n+1COOH 1

5(d) M1 propan-2-ol (1) 2

M2 displayed formula of propan-2-ol (1)

5(e)(i) C10H22 → C3H8 + C3H6 + C4H8 2

M1 C3H8 + C3H6 (1)

M2 rest of equation correct (1)

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Question Answer Marks

5(e)(ii) cracking 1

5(f)(i) M1 six C atoms joined by single bonds in a chain and with continuation bonds (1) 2

M2 3  CH3 at two C intervals and whole structure correctly displayed (1)

5(f)(ii) addition 1

5(g)(i) sodium propanoate 1

5(g)(ii) CH3CH2COO– 1

5(h)(i) acid 1

or

any named inorganic acid, e.g. phosphoric acid

5(h)(ii) ethyl propanoate 1

5(h)(iii) M1 displayed formula of any ester linkage (1) 2

M2 correct structure of ethyl propanoate (1)

© UCLES 2023 Page 10 of 10

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) May/June 2023
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2023 series for most
Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 12 printed pages.

© UCLES 2023 [Turn over

Pg 286 of 349
0620/41 Cambridge IGCSE – Mark Scheme May/June 2023
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

 the specific content of the mark scheme or the generic level descriptors for the question
 the specific skills defined in the mark scheme or in the generic level descriptors for the question
 the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

 marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
 marks are awarded when candidates clearly demonstrate what they know and can do
 marks are not deducted for errors
 marks are not deducted for omissions
 answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

© UCLES 2023 Page 2 of 12

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0620/41 Cambridge IGCSE – Mark Scheme May/June 2023
PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

© UCLES 2023 Page 3 of 12

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0620/41 Cambridge IGCSE – Mark Scheme May/June 2023
PUBLISHED
Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons):

 The response should be read as continuous prose, even when numbered answer spaces are provided.
 Any response marked ignore in the mark scheme should not count towards n.
 Incorrect responses should not be awarded credit but will still count towards n.
 Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be awarded
for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should be treated
as a single incorrect response.
 Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

© UCLES 2023 Page 4 of 12

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0620/41 Cambridge IGCSE – Mark Scheme May/June 2023
PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show your
working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1 and
10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

© UCLES 2023 Page 5 of 12

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Question Answer Marks

1(a) B 1

1(b) A 1

1(c) H 1

1(d) J 1

1(e) G 1

1(f) D 1

Question Answer Marks

2(a)(i) N 1

2(a)(ii) B 1

2(a)(iii) F 1

2(a)(iv) C 1

2(a)(v) Li 1

2(a)(vi) Ne 1

2(b)(i) M1 different atoms of the same element with the same number of protons(1) 2

M2 different numbers of neutrons(1)

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Question Answer Marks

2(b)(ii) M1 10  20 + 2
11 80
( = 1080)(1)

M2 (1080 ÷ 100 =) 10.8(1)

Question Answer Marks

3(a)(i) M1 Na with 2,8 all crosses(1) 3

M2 O with 2,8 outer shell with 6 dots and 2 crosses(1)

M3 + AND 2(1)

3(a)(ii) Na2O 1

3(b) M1 both bonds with 2 dots and 2 crosses(1) 2

M2 2 lone pairs
(all dots or all crosses) on both oxygen atoms completing all 3 octets(1)

3(c)(i) M1 positive ions and negative ions (1) 2

M2 strong attraction / strong bonds (1)

3(c)(ii) intermolecular forces 1

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Question Answer Marks

4(a) M1 increases the rate of reaction / 2

speeds up a reaction(1)

M2 unchanged at the end of the reaction(1)

4(b)(i) oxygen escapes from the flask or apparatus 1

4(b)(ii) concentration of hydrogen peroxide is highest at the start / particles of hydrogen peroxide are closest together at the start 1

OR

collision frequency is highest at the start

4(b)(iii) the hydrogen peroxide is used up / 1

ALL the hydrogen peroxide has reacted or decomposed

4(c) M1 kinetic energy of particles increases(1) 3

M2 frequency of collisions between particles increases(1)

M3 more or higher percentage or higher proportion or

higher fraction of particles have energy greater than / equal to activation energy

OR
more of the collisions or higher percentage or higher fraction of collisions have energy greater than or equal to activation
energy(1)

4(d) M1 (50.0  0.200 ÷ 1000 =) 0.01(1) 3

M2 0.005(1)

M3 0.16(0)(1)

4(e) no effect 1

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Question Answer Marks

4(f) 2HgO → 2Hg + O2 2

M1 all formulae correct(1)

M2 equation correct(1)

5(a)(i) M1 breakdown by (the passage of) electricity(1) 2

M2 of an ionic compound in molten or aqueous (state) (1)

Question Answer Marks

5(a)(ii) graphite is inert AND graphite conducts electricity 1

5(a)(iii) 2H+ + 2e– → H2 2

M1 H+ + e as only species on LHS(1)

M2 equation correct(1)

5(a)(iv) electrons 1

5(a)(v) ions 1

5(a)(vi) M1 oxygen(1) 2
M2 hydrogen(1)

5(b)(i) aluminium oxide 1

5(b)(ii) any two from: 2

 solvent
 lowers the operating temperature
 increases conductivity

5(b)(iii) carbon reacts with oxygen and forms carbon dioxide 1

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Question Answer Marks

5(c)(i) 2H2 + O2 → 2H2O 2

M1 all formulae(1) M2 equation correct(1)

5(c)(ii) no carbon dioxide evolved 1

OR
more efficient

Question Answer Marks

6(a)(i) 4FeS2 + 11O2 → 2Fe2O3 + 8SO2 1

6(a)(ii) iron(III) oxide 1

6(b)(i) yield of SO3 is less 1

6(b)(ii) yield of SO3 is less 1

OR

rate is less

6(c) 2NH3 + H2SO4 →(NH4)2SO4 2

M1 (NH4)2SO4 on the right (1)

M2 equation correct(1)

6(d)(i) lead(II) nitrate 1

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Question Answer Marks

6(d)(ii) Pb2+ (aq) +SO42-(aq) → PbSO4(s) 3

M1 PbSO4 on the right(1)

M2 only Pb2+ and SO42– on the left(1)

M3(aq) + (aq) → (s)(1)

6(d)(iii) M1 filter(1) 3

M2 wash (the residue or lead sulfate) with distilled or deionised water(1)

M3 description of drying(1)

Question Answer Marks

7(a)(i) needs or uses ultra violet light 1

7(a)(ii) M1 displayed formula of 1-chlorobutane(1) 2

M2 displayed formula of 2-chlorobutane(1)

7(b)(i) C4H6O3 1

7(b)(ii) M1 alkene(1) 3

M2 alcohol(1)

M3 carboxylic acid(1)

7(b)(iii) M1 turns colourless(1) 2

M2 bubbles / fizzing / effervescence(1)

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Question Answer Marks

7(b)(iv) M1 only two carbon atoms joined by a single bond and two additional bonds on each(1) 2

M2

(1)

7(b)(v) polyester 1

© UCLES 2023 Page 12 of 12

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) May/June 2023
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2023 series for most
Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 10 printed pages.

© UCLES 2023 [Turn over

Pg 298 of 349
0620/42 Cambridge IGCSE – Mark Scheme May/June 2023
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

 the specific content of the mark scheme or the generic level descriptors for the question
 the specific skills defined in the mark scheme or in the generic level descriptors for the question
 the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

 marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
 marks are awarded when candidates clearly demonstrate what they know and can do
 marks are not deducted for errors
 marks are not deducted for omissions
 answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

© UCLES 2023 Page 2 of 10

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

 The response should be read as continuous prose, even when numbered answer spaces are provided.
 Any response marked ignore in the mark scheme should not count towards n.
 Incorrect responses should not be awarded credit but will still count towards n.
 Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be awarded
for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should be treated
as a single incorrect response.
 Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

© UCLES 2023 Page 3 of 10

Pg 300 of 349
0620/42 Cambridge IGCSE – Mark Scheme May/June 2023
PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show your
working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by
the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1 and
10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Check the page above Q1(a) and assuming no relevant work is there, place ‘SEEN’ on the page
For equations, allow multiples (including fractions); ignore state symbols except Q2(f)(ii)

Question Answer Marks

1(a) D 1

1(b) C 1

1(c) H 1

1(d) B 1

1(e) C 1

1(f) G 1

Question Answer Marks

2(a) halogen(s) 1

2(b) same number of outer shell electrons 1

2(c) 3
gas

M1 pale yellow-green gas

M2 red-brown

M3 both gases

2(d)(i) nucleon number / mass number 1

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Question Answer Marks

2(d)(ii) 79Br 81Br– 3

protons 35 35

neutrons 44 46

electrons 35 36

Each row ✔

2(d)(iii) M1 79  55(%) + 81  45(%) 2

M2 7990 / 100 = 79.9

2(e)(i) Cl2 + 2KBr  2KCl + Br2 2

M1 KCl as product
M2 correct equation

2(e)(ii) chlorine less reactive than fluorine 1

2(f)(i) white precipitate 1

2(f)(ii) Ag+(aq) + Cl –(aq)  AgCl(s) 3

M1 AgCl as only product
M2 Ag+ + Cl – as only reactants (in 1 : 1 ratio)
M3 state symbols

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Question Answer Marks

3(a) contact (process) 1

3(b(i) M1 burning sulfur (in air) 2

M2 Roasting sulfide ores (in air)

3(b)(ii) M1 the rate of forward reaction equals (the rate of the) reverse reaction 2
M2 concentrations of reactants and products are constant

3(b)(iii) 450 (oC) 3

200 (kPa)

vanadium(V) oxide

3(b)(iv) 4
increases

increases increase

no change

3(b)(v) M1 kinetic energy of particles decreases 3

M2 frequency of collisions between particles decreases

M3 lower percentage / proportion / fraction of collisions / particles have energy greater than / qual to activation energy
OR
fewer of the collisions / particles have energy greater than / equal to activation energy

3(c) M1 4  2 or 8 2
M2 S + (4  –2) = –2 ∴ S = + 6

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Question Answer Marks

4(a) proton acceptor 1

4(b) alkali 1

4(c) blue 1

4(d) M1 sodium chloride 3

M2 water
M3 ammonia

4(e)(i) amphoteric (oxides) 1

4(e)(ii) aluminium oxide 1

or
zinc oxide

4(f)(i) M1 all single bonding dot and cross pairs correct 3

M2 double C = O bond dot and cross pairs are correct
M3 complete diagram is correct

4(f)(ii) 3≤ pH < 7 1

4(f)(iii)i CH3COOH ⇌ CH3COO– + H+ 3

M1 H+
M2 CH3COO–
M3 use of ⇌

4(f)(iv) H+ + OH–  H2O 1

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Question Answer Marks

4(g) M1 mol KOH = 0.0800  25 / 1000 5

= 0.002(00) / 2(00)  10–3

M2 mol H2SO4 = M1 / 2 = 0.002 / 2

= 0.001(00) / 1(00  10–3

M3 = M2  1000 / 20 = 0.001  1000 / 20

= 0.05(00) / 5.(00)  10–2

M4 = 98

M5 = 98  M3 = 98  0.05(00) = 4.9(0) (g / dm3)

Question Answer Marks

5(a)(i) substitution 1

5(a)(ii) provide activation energy 1

5(a)(iii) photochemical 1

5(a)(iv) C3H8 + Cl2  C3H7Cl + HCl 2

M1 HCl M2 equation correct

5(b)(i) it has a carbon-carbon bond which is not a single bond 1

5(b)(ii) CH3CHClCH2Cl 1

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Question Answer Marks

5(c) M1 displayed formula of propan-1-ol 4

M2 displayed formula of propan-2-ol

M3 propan-1-ol
(as either name)

M4 propan-2-ol (under displayed formula of propan-2-ol)

Question Answer Marks

6(a) ethyl butanoate 1

6(b) water 1

6(c) C3H6O 1

6(d)(i) 1 repeat unit circled 1

6(d)(ii) M1 displayed diol on correct box (unshaded) 2

M2 displayed dioic acid on correct box (shaded)

6(d)(iii) condensation 1

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) May/June 2023
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the May/June 2023 series for most
Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some
Cambridge O Level components.

This document consists of 11 printed pages.

© UCLES 2023 [Turn over

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PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

 the specific content of the mark scheme or the generic level descriptors for the question
 the specific skills defined in the mark scheme or in the generic level descriptors for the question
 the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

 marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
 marks are awarded when candidates clearly demonstrate what they know and can do
 marks are not deducted for errors
 marks are not deducted for omissions
 answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

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Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

 The response should be read as continuous prose, even when numbered answer spaces are provided.
 Any response marked ignore in the mark scheme should not count towards n.
 Incorrect responses should not be awarded credit but will still count towards n.
 Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
 Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) J 1

1(b) D 1

1(c) B 1

1(d) G 1

1(e) F 1

1(f) C 1

Question Answer Marks

2(a)(i) Al 1

2(a)(ii) Ar 1

2(a)(iii) Cl 1

2(a)(iv) Al 1

2(a)(v) S 1

2(a)(vi) Cl 1

2(b)(i) 12C 1

2(b)(ii) M1 24  85(%) + 26  15(%) 2

M2 2430 / 100 = 24.3

2(c)(i) 27 1

2(c)(ii) Aluminium / Al 1

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Question Answer Marks

3(a)(i) M1 eight crosses in second shell of Mg 3

M2 7 dots and 1 cross in second shell of F

M3 ‘2+’ charge on Mg ion on correct answer line

and ‘–‘ charge on F ion on correct answer line

3(a)(ii) MgF2 1

3(a)(iii) melting 1

3(b) M1 4 dot and cross single bonds 2

M2 3 pairs of non-bonding e on each Cl and no non-bonding e on Si

3(c)(i) molecule(s) 1

3(c)(ii) M1 covalent bonds 2

M2 strong bonds

and

giant (covalent) structure

Question Answer Marks

4(a)(i) concentration (of sulfuric acid particles) decreases 1

OR

frequency of collisions between particles decreases

4(a)(ii) all the (sulfuric) acid has reacted 1

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Question Answer Marks

4(b) M1 greater surface area (of zinc) 2

M2 frequency of collisions between (zinc and acid) particles increases

4(c) M1 mol H2SO4 = 2.00 x 25.0/1000 = 0.05(00) 3

M2 mol H2 = M1 = 0.05(00)

M3 vol H2 = M2  24 = 1.2(0)

4(d)(i) Zn + 2HCl → ZnCl2 + H2 2

M1 ZnCl2
M2 equation correct

4(d)(ii) lighted splint and (squeaky) pop 1

Question Answer Marks

5(a)(i) M1 ionic compound 2

M2 molten and / or aqueous

5(a)(ii) oxidation number (of copper) 1

5(a)(iii) fades / (becomes) colourless 1

5(a)(iv) Cu2+ + 2e → Cu 2

M1 Cu2+ and (any number of) e on left hand side

M2 equation correct

5(a)(v) OH– 1

5(b) anode dissolves 1

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Question Answer Marks

5(c)(i) M1 silver 3

M2 spoon

M3 (aqueous or solution) of silver nitrate

5(c)(ii) M1 prevent corrosion 2

M2 improve appearance

5(d)(i) M1 carbon dioxide: (increased) global warming 2

M2 carbon monoxide: toxic

5(d)(ii) needs high pressure to store hydrogen 1

Question Answer Marks

6(a)(i) air 1

6(a)(ii) methane 1

6(a)(iii) M1 450 (°C) 2

M2 200 (atm)

6(a)(iv) iron 1

6(a)(v) M1 (a substance which) increases the rate of a reaction 2

M2 remains unchanged at the end of the reaction

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Question Answer Marks

6(b)(i) temperature change: 2

M1 low(er) rate (of reaction)

pressure change:
M2 (position of) equilibrium shifts to the left hand side/ towards reactants

6(b)(ii) 4NO + 3O2 + 2H2O →.4HNO3 1

6(c)(i) CuCO3 + 2HNO3 → Cu(NO3)2 + CO2 + H2O 2

M1 Cu(NO3)2
M2 correct equation

6(c)(ii) M1 undissolved solid 2

M2 effervescence stops on addition of more copper(II) carbonate

6(d)(iii) copper(II) oxide or 1

copper(II) hydroxide

Question Answer Marks

7(a)(i) ultraviolet (light) 1

7(a)(ii) M1 displayed formula of 2

1–chloropropane

M2 displayed formula of 2–chloropropane

7(b)(i) any 2 from: 2

(same) general formula

(same / similar) chemical properties or reactions

(contain the same) functional group

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Question Answer Marks

7(b)(ii) M1 single bond between the two C atoms (and nothing on continuation bonds) 2

M2 1 CH3 group and 1 H on first carbon and 1 CH3 group and 1 H on second carbon and whole structure correct

7(c)(i) M1 structural formula of 2

propan-1,3-dioic acid

M2 structural formula of
ethan-1,2-diol

7(c)(ii) polyester 1

7(c)(iii) M1 carboxylic acids 2

M2 alcohols

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Cambridge IGCSE™

CHEMISTRY 0620/41
Paper 4 Theory (Extended) October/November 2023
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2023 series for most
Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level
components.

This document consists of 10 printed pages.

© UCLES 2023 [Turn over

Pg 319 of 349
0620/41 Cambridge IGCSE – Mark Scheme October/November 2023
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) sulfur dioxide 1

1(b) ammonia 1

1(c) xenon 1

1(d) oxygen 1

1(e) ethene 1

1(f) ammonia 1

Question Answer Marks

2(a) M1 5p and 5e (1) 2

M2 6n (1)

2(b)(i) 20% 1

2(b)(ii) M1 0.540 / 10.8 = 0.05(0) mol (1) 2

M2 0.05  6.02  1023 = 3.01  1022 (1)

2(c)(i) bauxite 1

2(c)(ii) M1 cryolite (1) 2

M2 lowers operating temperature OR improves conductivity (1)

2(c)(iii) Al3+ + 3e– → Al 2

M1 Al3+ + 3e– on the left-hand side (1)

M2 equation correct (1)

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Question Answer Marks

2(c)(iv) M1 (anodes of) carbon react with oxygen (formed at the anode) (1) 2

M2 (form) carbon dioxide (1)

2(d) M1 (good) conductor (of electricity) (1) 2

M2 low density (1)

2(e) M1 aluminium oxide layer (1) 2

M2 (oxide layer) is unreactive (1)

2(f)(i) 2Al + 3F2 → 2AlF3 2

M1 Al and F2 as reactants (1)

M2 equation correct (1)

2(f)(ii) M1 eight crosses in second shell of Al (1) 3

M2 7 dots and 1 cross in second shell of F (1)

M3 3+ charge on Al ion on correct answer line and – charge on F ion on correct answer line (1)

Question Answer Marks

3(a)(i) M1 Ag column all ✗ (1) 3

M2 ✗ in Pb AND 2 ✓ in Zn (1)

M3 Zn, Mn, Pb Ag (1)

3(a)(ii) (all) nitrates are soluble OR lead sulfate is insoluble 1

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Question Answer Marks

3(a)(iii) Zn + 2AgNO3 → Zn(NO3)2 + 2Ag 2

M1 Zn(NO3)2 on the right hand side (1)

M2 correct equation (1)

3(b)(i) M1 colourless (1) 2

M2 orange (1)

3(b)(ii) Cl2(g) + 2Br–(aq) → Br2(aq) + 2Cl–(aq) 3

M1 Br2 + Cl– as products (1)

M2 correct equation (1)

M3 state symbols (1)

3(b)(iii) tenessine / Ts 1

Question Answer Marks

4(a) test: relights 1

AND
observations: a glowing splint

4(b)(i) lower gradient (at t2) 1

4(b)(ii) M1 concentration (of H2O2 particles) decreases (1) 2

M2 frequency of collisions between particles decreases (1)

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Question Answer Marks

4(b)(iii) M1 steeper curve which does not cross original curve and levels off before the original curve (1) 2

M2 finishes at same volume (1)

4(c) M1 mol O2 = 72 / 24000 = 0.003(00) (1) 5

M2 mol H2O2 = M1  2 = 0.002  2 = 0.006(00) (1)

M3 conc H2O2 = M2  1000 / 20 = 0.006  1000 / 20 = 0.3(00) (1)

M4 Mr H2O2 = 34 (1)

M5 = M4  M3 = 34  0.3 = 10.2 (g / dm3) (1)

4(d) any transition metal oxide 1

Question Answer Marks

5(a) M1 the rate of forward reaction equals (the rate of the) reverse reaction (1) 2

M2 the concentrations of reactants and products are no longer changing (1)

5(b)(i) M1 concentration decreases (1) 2

M2 position of equilibrium shifts to left AND fewer moles of gas on left hand side (1)

5(b)(ii) M1 concentration increases (1) 2

M2 position of equilibrium shifts to the right AND forward reaction is endothermic (1)

5(b)(iii) M1 no change (1) 2

M2 catalysts do not affect position of equilibrium (1)

5(c)(i) carbon dioxide 1

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Question Answer Marks

5(c)(ii) M1 greenhouse gases absorb thermal energy (from the Earth) (1) 3

M2 and M3 one mark each for any two of:

• energy (from the sun) absorbed by Earth’s surface
• Earth emits or reflects thermal energy
• (greenhouse gases) reduces or stops thermal energy loss (into space)
• increasing in amount of greenhouse gas results in a higher atmospheric temperature

Question Answer Marks

6(a) M1 yeast (1) 2

M2 absence of air (1)

6(b)(i) M1 300 (1) 2

M2 6000 (1)

6(b)(ii) ethene 1

6(b)(iii) only one product 1

6(c)(i) proton donor 1

6(c)(ii) partial dissociation 1

6(c)(iii) M1 4  –2 or –8 (1) 2

M2 P + (4  –2) = –3 ∴ P = +5 (1)

6(d) M1 uses renewable resources (1) 2

M2 high rate of reaction (1)

6(e)(i) potassium manganate(VII) 1

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Question Answer Marks

6(e)(ii) reducing agent 1

6(f)(i) calcium ethanoate 1

6(f)(ii) (CH3COO)2Ca 1

6(f)(iii) hydrogen 1

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Cambridge IGCSE™

CHEMISTRY 0620/42
Paper 4 Theory (Extended) October/November 2023
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2023 series for most
Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level
components.

This document consists of 10 printed pages.

© UCLES 2023 [Turn over

Pg 329 of 349
0620/42 Cambridge IGCSE – Mark Scheme October/November 2023
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) B 1

1(b) F 1

1(c) D 1

1(d) A AND E 1

1(e) G 1

1(f) C 1

1(g) B 1

1(h) F 1

Question Answer Marks

2(a)(i) 59 65 3
Co Cu2+

protons 27 29

neutrons 32 36

electrons 27 27

one mark for each correct row

2(a)(ii) M1 (63  70) + (65  30) = 6360 (1) 2

M2 6360 / 100 = 63.6 (1)

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Question Answer Marks

2(b) M1 (high) density (1) 2

M2 (high) melting point (1)

2(c)(i) M1 water molecules (1) 2

M2 (the water present) in hydrated crystals (1)

2(c)(ii) M1 pink (1) 2

M2 CoCl2∙6H2O (1)

2(c)(iii) M1 white (1) 2

M2 blue (1)

2(c)(iv) heating (the hydrated copper(II) sulfate) 1

Question Answer Marks

3(a) (hot) air 1

3(b)(i) hematite 1

3(b)(ii) Fe2O3 + 3CO → 3CO2 + 2Fe 1

3(b)(iii) M1 from +3 (1) 2

M2 to 0 (1)

3(b)(iv) decrease (in oxidation number) 1

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Question Answer Marks

3(c) M1 CaCO3 → CaO + CO2 (1) 4

M2 thermal decomposition (1)

M3 SiO2 + CaO → CaSiO3 (1)

M4 acid-base reaction (1)

3(d)(i) alloy 1

3(d)(ii) nickel / chromium 1

3(e) hydrated iron(III) oxide 1

3(f)(i) galvanising 1

3(f)(ii) painting / greasing / coating with plastic 1

3(f)(iii) M1 zinc more reactive (than iron) (1) 2

M2 zinc corrodes / oxidises / reacts in preference to / instead of iron (1)

Question Answer Marks

4(a)(i) M1 lead nitrate (1) 2

M2 soluble chloride e.g. sodium chloride (1)

4(a)(ii) Pb2+(aq) + 2Cl–(aq) → PbCl2(s) 3

M1 PbCl2 as only product (1)

M2 Pb2+ + 2Cl– as only reactants (1)

M3 state symbols (1)

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Question Answer Marks

4(a)(iii) M1 filter (1) 3

M2 wash (the residue) using water (1)

M3 dry the residue between filter papers / in a warm place (1)

4(b)(i) mobile ions 1

4(b)(ii) 2Cl– → Cl2 + 2e– 2

M1 any negative Cl species losing electron(s) (1)

M2 correct ionic half equation (1)

4(b)(iii) M1 (damp) litmus (paper) (1) 2

M2 is bleached / goes white (1)

4biv (shiny) grey AND solid 1

Question Answer Marks

5(a) enthalpy change (of reaction) 1

5(b)(i) M1 rate of reaction increases (1) 3

M2 more (CCl4) particles per unit volume (1)

M3 frequency of collisions between (CCl4 and H2O) particles increases (1)

5(b)(ii) M1 (position of) equilibrium moves to left hand side (1) 2

M2 more (gaseous) moles / molecules on right hand side (1)

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Question Answer Marks

5(b)(iii) M1 Labels mark 3

CCl4(g) + 2H2O(g) on reactant line
AND
CO2(g) + 4HCl(g) on product line

M2 Activation E mark
upward arrow labelled Ea from energy level of reactants to top of ‘hump’

M3 Energy change mark

one downward arrow labelled H
AND
energy change starting from E level of reactants and finishing at E level of products

5(b)(iv) M1 minimum energy (1) 2

M2 that colliding particles must have to react (1)

5(b)(v) (decreased by adding) catalyst 1

5(c) energy needed to break bonds in reactants 4

M1 [(4  340) + (4  460) = 3200 (kJ / mol) (1)

energy released when bond in carbon dioxide form

M2 2  805 = 1610 (kJ / mol) (1)

calculate H–Cl bond energy

M3 3200 – (1610 + E(4H–Cl)) = – 130
E(4H–Cl) = 3330 – 1610 = 1720 (kJ / mol) (1)

M4 1720 / 4 = 430 (kJ / mol) (1)

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Question Answer Marks

6(a) M1 (same) general formula (1) 2

M2 (contain the same) functional group (1)

6(b) -CH2- unit 1

M1 alkenes (1) 3
6(c)(i)
M2 alkanes (1)

M3 carboxylic acids (1)

6(c)(ii) M1 propanoic acid (1) 2

M2 displayed formula of propanoic acid (1)

6(d)(i) M1 working to give the mass of atoms shown in Fig 6.1 2

103 – 14 – (2  12) – (2  16) – (4  1)
(= 29)

M2 ‘R’ = C2H5

6(d)(ii) proteins 1

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Cambridge IGCSE™

CHEMISTRY 0620/43
Paper 4 Theory (Extended) October/November 2023
MARK SCHEME
Maximum Mark: 80

Published

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 International will not enter into discussions about these mark schemes.

Cambridge International is publishing the mark schemes for the October/November 2023 series for most
Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level
components.

This document consists of 11 printed pages.

© UCLES 2023 [Turn over

Pg 339 of 349
0620/43 Cambridge IGCSE – Mark Scheme October/November 2023
PUBLISHED
Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.

GENERIC MARKING PRINCIPLE 1:

Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.

GENERIC MARKING PRINCIPLE 2:

Marks awarded are always whole marks (not half marks, or other fractions).

GENERIC MARKING PRINCIPLE 3:

Marks must be awarded positively:

• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond
the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.

GENERIC MARKING PRINCIPLE 4:

Rules must be applied consistently, e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.

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PUBLISHED
GENERIC MARKING PRINCIPLE 5:

Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).

GENERIC MARKING PRINCIPLE 6:

Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.

Science-Specific Marking Principles

1 Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks
should not be awarded if the keywords are used incorrectly.

2 The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for
any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.

3 Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other
syllabus terms with which they may be confused (e.g. ethane / ethene, glucagon / glycogen, refraction / reflection).

4 The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically
correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme
where necessary and any exceptions to this general principle will be noted.

5 ‘List rule’ guidance

For questions that require n responses (e.g. State two reasons …):

• The response should be read as continuous prose, even when numbered answer spaces are provided.
• Any response marked ignore in the mark scheme should not count towards n.
• Incorrect responses should not be awarded credit but will still count towards n.
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be
awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this
should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science.

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PUBLISHED
6 Calculation specific guidance

Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show
your working’.

For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded
by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values.

For answers given in standard form (e.g. a  10n) in which the convention of restricting the value of the coefficient (a) to a value between 1
and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme.

Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded.
Exceptions to this general principle will be noted in the mark scheme.

7 Guidance for chemical equations

Multiples / fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme.

State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

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Question Answer Marks

1(a) potassium iodide 1

1(b) sodium bromide 1

1(c) sulfur dioxide 1

1(d) propene 1

1(e) carbon monoxide 1

1(f) anhydrous copper(II) sulfate 1

Question Answer Marks

2(a)(i) A, B, F 1

2(a)(ii) D 1

2(a)(iii) C 1

2(b) 5 1

2(c) 33 1

2(d) 2,8,8 1

2(e) 5 1

2(f) 2 1

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Question Answer Marks

3(a)(i) 78 1

3(a)(ii) natural gas 1

3(a)(iii) M1 three single bonding pairs containing one dot and one cross (1) 2

M2 two dots or two crosses on N (and no additional electrons on Hs) to complete the outer shell on N and all 3 Hs (1)

3(a)(iv) M1 N2 + 3H2 → 2NH3 (1) 5

M2 ⇌ (1)

M3 450 °C (1)

M4 200 atmospheres / 20 000 kPa (1)

M5 iron (1)

3(b)(i) platinum 1

3(b)(ii) M1 –3 (1) 2

M2 +2 (1)

3(b)(iii) oxidation AND oxidation number increases 1

3(b)(iv) 4
M1 increase (1) M4 decrease (1)

M2 increase (1)

M3 no change (1)

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Question Answer Marks

3(b)(v) M1 kinetic energy of particles is lower (1) 3

M2 frequency of collisions between particles is lower (1)

M3 fewer / lower percentage / lower proportion / lower fraction of particles have energy greater than / equal to activation
energy
OR
fewer / lower percentage / lower fraction of collisions have energy greater than / equal to activation energy (1)

3(c) 4NO + 3O2 + 2H2O → 4HNO3 1

Question Answer Marks

4(a)(i) dilute sulfuric acid 1

4(a)(ii) M1 solid remains / solid undissolved (1) 2

M2 bubbling / effervescence / fizzing stops (1)

4(a)(iii) aqueous zinc sulfate 1

4(a)(iv) any two 2

• zinc oxide
• zinc carbonate
• zinc hydroxide

4(b)(i) M1 (a solution containing the) maximum amount of solute dissolved / no more solute can dissolve (1) 2

M2 at a given temperature (1)

4(b)(ii) solubility decreases as temperature decreases 1

4(c)(i) hydrated 1

4(c)(ii) to ensure all the water of crystallisation is removed 1

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Question Answer Marks

4(c)(iii) M1 2  10-3 / 0.002 (1) 4

M2 0.144 (g) (1)

M3 (0.144  18 = ) 8  10-3 / 0.008 (1)

M4 (0.008  0.002 = ) 4 (1)

Question Answer Marks

5(a)(i) M1 positive ions / cations (1) 3

M2 sea of electrons / mobile electrons / delocalised electrons (1)

M3 attraction between positive ions and electrons (1)

5(a)(ii) electrons move / electrons mobile / electrons flow 1

5(b)(i) any two 2

• (coke) releases heat
• (coke) reduces iron(III) oxide
• (coke) reacts with carbon dioxide to form carbon monoxide

5(b)(ii) M1 limestone decomposes to calcium oxide (1) 2

M2 calcium oxide reacts with / neutralises silicon(IV) oxide to produce slag / calcium silicate (1)

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Question Answer Marks

5(b)(iii) Fe2O3 + 3C → 2Fe + 3CO 2

OR

Fe2O3 + 3CO → 2Fe + 3CO2

OR

2Fe2O3 + 3C → 4Fe + 3CO2

M1 all formulae (1)

M2 equation correct (1)

5(b)(iv) temperature in the furnace is above the melting point of iron 1

5(c) M1 atoms have different sizes (1) 2

M2 layers cannot slide over or past each other (1)

5(d)(i) oxygen AND water 1

5(d)(ii) galvanising 1

5(d)(iii) acts as a barrier which prevents oxygen and water reaching the iron 1

5(d)(iv) M1 zinc is more reactive than iron (1) 2

M2 zinc is oxidised / zinc loses electrons / zinc forms positive ions / forms zinc ions (1)

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Question Answer Marks

6(a) any two 2

• general formula
• functional group
• chemical properties

6(b) ethyl propanoate 1

6(c)(i) M1 propan-1-ol (1) 2

M2 methanoic acid (1)

6(c)(ii) C4H8O2 1

6(d) C2H4O 1

6(e)(i) condensation 1

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Question Answer Marks

6(e)(ii) 2

M1
2 –COOH groups fully displayed (1)

M2

2 –NH2 groups fully displayed (1)

6(f)(i) proteins 1

6(f)(ii) amino acids 1

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