Cambridge IGCSE Chemistry (9-1) 0971 — 2021 May/June Paper 3 · Variant 1

*8992959056* CHEMISTRY 0971/31 Paper 3 Theory (Core) May/June 2021  1 hour 15 minutes You must answer on the question paper. No additional materials are needed. INSTRUCTIONS ● Answer all questions. ● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs. ● Write your name, centre number and candidate number in the boxes at the top of the page. ● Write your answer to each question in the space provided. ● Do not use an erasable pen or correction fluid. ● Do not write on any bar codes. ● You may use a calculator. ● You should show all your working and use appropriate units. INFORMATION ● The total mark for this paper is 80. ● The number of marks for each question or part question is shown in brackets [ ]. ● The Periodic Table is printed in the question paper. IB21 06_0971_31/FP © UCLES 2021 [Turn over This document has 16 pages. Any blank pages are indicated. Cambridge IGCSE™ (9–1)

2 0971/31/M/J/21 © UCLES 2021 1 (a) The electronic structures of five atoms, A, B, C, D and E, are shown. A B C D E Answer the following questions about these electronic structures. Each electronic structure may be used once, more than once or not at all. State which electronic structure, A, B, C, D or E, represents: (i) an atom in Group II of the Periodic Table … [1] (ii) an atom with a proton number of 13 … [1] (iii) an atom that forms a stable ion with a single negative charge … [1] (iv) an atom of a non-metal that forms a giant covalent structure … [1] (v) an atom of a metal used in food containers. … [1] (b) Complete the table to show the number of electrons, neutrons and protons in the vanadium atom and calcium ion shown. number of electrons number of neutrons number of protons 51V 23 23 48Ca2+ 20 28  [3]  [Total: 8]

3 0971/31/M/J/21 © UCLES 2021 [Turn over 2 The table shows the masses of some of the ions in 1000 cm3 of fruit juice. name of ion formula of ion mass of ion in 1000 cm3 of fruit juice / mg NH4 + 43 calcium Ca2+ 79 chloride Cl – 135 lithium Li+ 1 magnesium Mg2+ 80 nitrate NO3 – 35 phosphate PO4 3– 120 potassium K+ 575 sodium Na+ 120 SO4 2– 105 (a) Answer these questions using only the information in the table. (i) State which negative ion has the highest mass in 1000 cm3 of fruit juice. … [1] (ii) Give the formulae of the ions in ammonium sulfate. … and … [1] (iii) Calculate the mass of sodium ions in 200 cm3 of fruit juice.  mass = … mg [1] (b) Describe a test for lithium ions. test … observations …  [2] (c) Ions of the element potassium, K, are present in most fertilisers. State the names of two other elements that are in most fertilisers. 1 … 2 …  [2]

4 0971/31/M/J/21 © UCLES 2021 (d) Orange juice is acidic. Draw a circle around the pH of orange juice. pH 4 pH 7 pH 10 pH 13 [1] (e) Some soils are acidic. Give the names of two compounds that are used to make soils less acidic. 1 … 2 …  [2] (f) Hydrogen chloride is an acidic gas produced when concentrated hydrochloric acid evaporates. (i) Describe the arrangement and separation of the molecules in hydrogen chloride gas. arrangement … … separation … …  [2] (ii) A long glass tube is set up as shown. long glass tube cotton wool soaked in concentrated hydrochloric acid damp blue litmus paper At first, the blue litmus paper does not turn red. After a short time, the litmus paper turns red. Explain these observations using the kinetic particle model. … … … … … [3]  [Total: 15]

5 0971/31/M/J/21 © UCLES 2021 [Turn over 3 The table shows some properties of four Group I elements. element melting point / °C boiling point / °C atomic radius / nm sodium 98 883 0.191 potassium 63 760 rubidium 39 0.250 caesium 29 671 0.272 (a) (i) Complete the table by predicting: ● the boiling point of rubidium ● the atomic radius of potassium.  [2] (ii) Describe the trend in the melting point of the Group I elements down the group. … [1] (iii) Deduce the physical state of potassium at 60 °C. Explain your answer. … … … [2] (b) Caesium is a radioactive element with a proton number of 55. (i) Define proton number. … [1] (ii) State one industrial use of radioactive isotopes. … [1] (c) Sodium hydride, NaH, reacts with iron(III) oxide. (i) Balance the equation for this reaction. Fe2O3 + 3NaH → …Fe + …NaOH [2] (ii) Explain how this equation shows that iron(III) oxide is reduced. … [1]  [Total: 10]

6 0971/31/M/J/21 © UCLES 2021 4 The structure of malic acid is shown. C C H O O H H O C H C H O O H (a) (i) On the structure draw a circle around the alcohol functional group. [1] (ii) Deduce the formula of malic acid to show the number of carbon, hydrogen and oxygen atoms. … [1] (b) When malic acid is heated it forms compound F. The structure of compound F is shown. C C H O O H C C H O O H Explain why compound F is described as unsaturated. … [1] (c) Compound F can form polymers. (i) State the meaning of the term polymer. … … [2] (ii) State the name of the polymer formed when ethene is polymerised. … [1]

7 0971/31/M/J/21 © UCLES 2021 [Turn over (d) Ethanoic acid is a carboxylic acid. Describe the observations made when dilute ethanoic acid reacts with: magnesium … litmus solution. …  [2] (e) The graph shows how the pH changes when dilute ethanoic acid is added slowly to aqueous sodium hydroxide. 14 12 10 8 6 4 2 0 10 20 volume of dilute ethanoic acid added / cm3 30 40 pH (i) Deduce the pH of the aqueous sodium hydroxide before the addition of dilute ethanoic acid.  pH = … [1] (ii) Deduce the volume of dilute ethanoic acid added when the pH is neutral.  … cm3 [1]  [Total: 10]

8 0971/31/M/J/21 © UCLES 2021 5 (a) Calcium oxide is made by the thermal decomposition of calcium carbonate. (i) State the meaning of the term thermal decomposition. … … [2] (ii) Describe a test for calcium ions. test … observations …  [2] (b) Carbon dioxide is produced when dilute hydrochloric acid reacts with calcium carbonate. CaCO3 + 2HCl → CaCl 2 + CO2 + H2O (i) Complete the diagram to show how to measure the volume of carbon dioxide produced during this reaction. dilute hydrochloric acid calcium carbonate  [2]

9 0971/31/M/J/21 © UCLES 2021 [Turn over (ii) Describe the effect of each of the following on the rate of reaction of dilute hydrochloric acid with calcium carbonate. ● The concentration of hydrochloric acid is decreased. All other conditions stay the same. … ● The temperature is increased. All other conditions stay the same. …  [2] (c) Carbon dioxide is also formed when the hydrocarbon C3H8 is completely combusted. (i) State the meaning of the term hydrocarbon. … … [2] (ii) The hydrocarbon C3H8 is called propane. Name the homologous series that propane belongs to. … [1] (iii) Name two substances formed by the incomplete combustion of propane. … and … [2]  [Total: 13]

10 0971/31/M/J/21 © UCLES 2021 6 This question is about water. (a) The water in rivers often contains pollutants such as acids. Describe how universal indicator paper can be used to determine the pH value of the water. … … … [2] (b) The diagram shows some of the stages in water treatment. impure water aeration tank mixing tank chlorine air purified water filter (i) Air is blown through the aeration tank. Name the two gases that make up most of the air. … and … [2] (ii) After aeration, the water still contains large insoluble particles. The filter is made up of fine sand and stones. Explain how the filter helps purify the water. … … … [2] (iii) Explain why chlorine is used in water treatment. … [1] (c) Anhydrous cobalt(II) chloride is used to test for water. State the colour change in this test. from … to … [2]  [Total: 9]

11 0971/31/M/J/21 © UCLES 2021 [Turn over 7 (a) Molten lead(II) bromide is electrolysed using carbon electrodes. (i) State the products of this electrolysis at: the negative electrode … the positive electrode. …  [2] (ii) State the name of another substance which can be used as an inert electrode. … [1] (b) When aqueous magnesium chloride is electrolysed using carbon electrodes, hydrogen gas is produced at the negative electrode. Complete the dot-and-cross diagram to show the electron arrangement in one molecule of hydrogen.  [1]  [Total: 4]

12 0971/31/M/J/21 © UCLES 2021 8 This question is about elements in the Periodic Table. (a) The table shows some properties of five elements, P, Q, R, S and T. element melting point / °C density in g / cm3 electrical conductivity of the solid atomic radius / nm P 1535 7.86 very good 0.125 Q –7 3.12 does not conduct 0.114 R 1495 8.90 very good 0.126 S –157 0.0035 does not conduct 0.110 T 839 1.54 very good 0.174 Use only the elements shown in the table to answer this question. State which two of the elements, P, Q, R, S and T, are covalent molecules. Give two reasons for your answer. elements … and … reason 1 … reason 2 …  [3] (b) Element T is on the left-hand side of the Periodic Table. Suggest whether its oxide is acidic or basic. Give a reason for your answer. … … [1] (c) Krypton is an element in Group VIII of the Periodic Table. Explain, using ideas about electronic structure, why krypton is unreactive. … … [1]

13 0971/31/M/J/21 © UCLES 2021 [Turn over (d) Sodium is an element in Group I of the Periodic Table. Iron is a transition element. Iron has a higher melting point and higher boiling point than sodium. Give two other ways in which the properties of transition elements differ from the properties of Group I elements. 1 … 2 …  [2] (e) The table compares the reactivity of four metals with dilute hydrochloric acid. metal reaction with dilute hydrochloric acid calcium reacts very rapidly copper no reaction iron reacts rapidly nickel reacts slowly Put the four metals in order of their reactivity. Put the least reactive metal first. least reactive most reactive  [2] (f) Hot iron reacts with steam. The reaction is reversible. Complete the equation by writing the symbol for a reversible reaction in the box. 3Fe + 4H2O Fe3O4 + 4H2  [1] (g) Steel is an alloy of iron. State the meaning of the term alloy. … [1]  [Total: 11]

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15 0971/31/M/J/21 © UCLES 2021 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Cambridge Assessment International Education is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which itself is a department of the University of Cambridge.

16 0971/31/M/J/21 © UCLES 2021 Group The Periodic Table of Elements 1 H hydrogen 1 2 He helium 4 I II III IV V VI VII VIII 3 Li lithium 7 4 Be beryllium 9 atomic number atomic symbol Key name relative atomic mass 11 Na sodium 23 12 Mg magnesium 24 19 K potassium 39 20 Ca calcium 40 37 Rb rubidium 85 38 Sr strontium 88 55 Cs caesium 133 56 Ba barium 137 87 Fr francium – 88 Ra radium – 5 B boron 11 13 Al aluminium 27 31 Ga gallium 70 49 In indium 115 81 Tl thallium 204 6 C carbon 12 14 Si silicon 28 32 Ge germanium 73 50 Sn tin 119 82 Pb lead 207 22 Ti titanium 48 40 Zr zirconium 91 72 Hf hafnium 178 104 Rf rutherfordium – 23 V vanadium 51 41 Nb niobium 93 73 Ta tantalum 181 105 Db dubnium – 24 Cr chromium 52 42 Mo molybdenum 96 74 W tungsten 184 106 Sg seaborgium – 25 Mn manganese 55 43 Tc technetium – 75 Re rhenium 186 107 Bh bohrium – 26 Fe iron 56 44 Ru ruthenium 101 76 Os osmium 190 108 Hs hassium – 27 Co cobalt 59 45 Rh rhodium 103 77 Ir iridium 192 109 Mt meitnerium – 28 Ni nickel 59 46 Pd palladium 106 78 Pt platinum 195 110 Ds darmstadtium – 29 Cu copper 64 47 Ag silver 108 79 Au gold 197 111 Rg roentgenium – 30 Zn zinc 65 48 Cd cadmium 112 80 Hg mercury 201 112 Cn copernicium – 114 Fl flerovium – 116 Lv livermorium – 7 N nitrogen 14 15 P phosphorus 31 33 As arsenic 75 51 Sb antimony 122 83 Bi bismuth 209 8 O oxygen 16 16 S sulfur 32 34 Se selenium 79 52 Te tellurium 128 84 Po polonium – 9 F fluorine 19 17 Cl chlorine 35.5 35 Br bromine 80 53 I iodine 127 85 At astatine – 10 Ne neon 20 18 Ar argon 40 36 Kr krypton 84 54 Xe xenon 131 86 Rn radon – 21 Sc scandium 45 39 Y yttrium 89 57–71 lanthanoids 89–103 actinoids 57 La lanthanum 139 89 Ac lanthanoids actinoids The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). actinium – 58 Ce cerium 140 90 Th thorium 232 59 Pr praseodymium 141 91 Pa protactinium 231 60 Nd neodymium 144 92 U uranium 238 61 Pm promethium – 93 Np neptunium – 62 Sm samarium 150 94 Pu plutonium – 63 Eu europium 152 95 Am americium – 64 Gd gadolinium 157 96 Cm curium – 65 Tb terbium 159 97 Bk berkelium – 66 Dy dysprosium 163 98 Cf californium – 67 Ho holmium 165 99 Es einsteinium – 68 Er erbium 167 100 Fm fermium – 69 Tm thulium 169 101 Md mendelevium – 70 Yb ytterbium 173 102 No nobelium – 71 Lu lutetium 175 103 Lr lawrencium –

This document consists of 9 printed pages. © UCLES 2021 [Turn over Cambridge IGCSE™ (9–1) CHEMISTRY (9–1) 0971/31 Paper 3 Theory (Core) 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.

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 2 of 9 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.

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 3 of 9 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.

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 4 of 9 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.

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 5 of 9 Question Answer Marks 1(a)(i) C 1 1(a)(ii) D 1 1(a)(iii) E 1 1(a)(iv) B 1 1(a)(v) D 1 1(b) number of electrons in Ca ion: = 18 (1) number of neutrons in V = 28 (1) number of protons in V = 23 AND number of protons in Ca ion = 20 (1) 3 Question Answer Marks 2(a)(i) Cl – / chloride 1 2(a)(ii) NH4+ AND SO42- 1 2(a)(iii) 24 (mg) 1 2(b) flame test / description of flame test (1) (flame coloured) red (1) 2 2(c) nitrogen (1) phosphorus (1) 2 pH 4 circled 1

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 6 of 9 Question Answer Marks 2(e) 1 mark each for any 2 of: • calcium carbonate • calcium oxide • calcium hydroxide 2 2(f)(i) arrangement: random (arrangement) / no fixed arrangement / no pattern / no fixed position (1) separation: far apart / far away (from each other) / distant (from each other) (1) 2 2(f)(ii) 1 mark each for any 3 of: • (HCl) molecules escape from solution • diffusion • molecules in (constant) movement / molecules collide / molecules travel • (movement of) molecules is random / haphazard / in every direction • molecules spread out / molecules mix • (molecules spread) from high(er) concentration to low(er) concentration • molecules hit the litmus paper / molecules 3 Question Answer Marks 3(a)(i) boiling point of Rb: any values between 675 and 755 (°C) (inclusive of these values) (1) atomic radius of K: any values between 0.195 and 0.245 (nm) (inclusive of these values) (1) 2 3(a)(ii) decreases (1) 1 3(a)(iii) solid (1) 60 °C is below the melting point / the melting point is above 60 °C (1) 2 3(b)(i) number of protons in the nucleus of an atom / number of positive charges in the nucleus of an atom 1 3(b)(ii) any suitable, e.g. detecting leaks in pipes / measuring thickness of paper / energy production 1 3(c)(i) 2 (Fe) (1) 3 (NaOH) (1) 2

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 7 of 9 Question Answer Marks 3(c)(ii) iron(III) oxide loses oxygen / it loses oxygen 1 Question Answer Marks 4(a)(i) OH alcohol group circled 1 4(a)(ii) C4H6O5 1 4(b) it has a C=C double bond 1 4(c)(i) large molecules / long chain molecules / macromolecules (1) built up from (many) small units / made from monomers (1) 2 4(c)(ii) poly(ethene) 1 4(d) with Mg: fizzes / bubbles / effervescence (1) litmus: turns red / turns pink (1) 2 4(e)(i) pH 13 1 4(e)(ii) 18 (cm3) 1 Question Answer Marks 5(a)(i) breakdown of substance / idea of one substance forming two or more substances (1) using heat / on heating (1) 2 5(a)(ii) add (aqueous) sodium hydroxide (1) white precipitate / white solid (1) OR add (aqueous) ammonia (1) no precipitate / very slight white precipitate (1) 2 5(b)(i) gas syringe / upturned measuring cylinder dipping into container (1) apparatus is workable and airtight (1) 2

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 8 of 9 Question Answer Marks 5(b)(ii) lower concentration of acid: decreases (in rate) / reaction slower / lower rate / slows down (1) higher temperature: increases (in rate) / reaction faster / higher rate / speeds up (1) 2 5(c)(i) compound containing hydrogen and carbon only / compound containing hydrogen and carbon and no other substance (2) if two marks not scored, 1 mark for: compound containing hydrogen and carbon / it contains hydrogen and carbon only 2 5(c)(ii) alkane(s) 1 5(c)(iii) 1 mark each for any 2 of: • carbon monoxide • carbon • water 2 Question Answer Marks 6(a) dip indicator paper in to water (and record the colour) (1) compare the colour with (universal indicator) colour chart match colour with colour chart (1) 2 6(b)(i) nitrogen (1) oxygen (1) 2 6(b)(ii) large(r) particles cannot get through (the small gaps in) the filter / large(r) particles get trapped in the filter / large(r) particles too big to get through (filter) (1) water passes through (1) 2 6(b)(iii) to kill bacteria / to kill micro-organisms 1 6(c) (from) blue (1) (to) pink (1) 2

0971/31 Cambridge IGCSE (9–1) – Mark Scheme PUBLISHED May/June 2021 © UCLES 2021 Page 9 of 9 Question Answer Marks 7(a)(i) negative electrode: lead (1) positive electrode: bromine (1) 2 7(a)(ii) platinum (1) 1 7(b) 1 shared pair of electrons AND no other electrons on either H atom (1) 1 8(a) Q AND S (1) low melting points (1) poor conductor (of electricity) / does not conduct (electricity) (1) 3 8(b) basic (oxide) AND T is a metal / metal oxides are basic 1 8(c) has a complete outer (electron) shell / has a full outer (electron) shell 1 8(d) 1 mark each for any 2 of: • transition elements have a high(er) density / Group I has a low(er) density • transition elements form coloured compounds / Group I compounds are not coloured • transition elements form ions with different charges / Group I forms only one type of ion • transition elements are good catalysts / Group I elements not catalysts 2 8(e) copper < nickel < iron < calcium (2) if 2 marks not scored, 1 mark for: 1 consecutive pair reversed / calcium < iron < nickel < copper 2 8(f) ⇌ 1 8(g) mixture of metal with another element 1