2 (a) Fig. 2.1 shows part of Group I of the Periodic Table. lithium 7 3 Li sodium 23 11 Na potassium 39 19 K Fig. 2.1 (i) State the trend in the reactivity of the elements going down Group I. … [1] (ii) Explain why lithium does not react with helium, a Group VIII element. … … [1] (iii) Lithium is a solid and helium is a gas. Describe two differences between the structures of a solid and a gas. 1 … … 2 … … [2] (b) A piece of sodium is added to water, as shown in Fig. 2.2. sodium water Fig. 2.2 The sodium reacts with water. The reaction is exothermic. (i) State one other observation that is seen when sodium reacts with water. … [1] (ii) Complete the word equation for the reaction of sodium with water. sodium + water + [2] (c) X is a compound that reacts with dilute hydrochloric acid to form sodium chloride and water. Suggest the identity of X. … [1] (d) Concentrated aqueous sodium chloride is broken down by electrolysis. (i) State the type of chemical bond in sodium chloride. … [1] (ii) Identify the product that forms at the anode (positive electrode). … [1] [Total: 10]

2(a)(i) increasing / more reactive / faster reaction ; 1 2(a)(ii) helium / He is, unreactive / inert ; 1 2(a)(iii) any two from: (solid/lithium) particles close(r) (together) ORA ; (solid/lithium) particles regular arrangement ORA ; (solid/lithium) particles vibrate / not free-moving ORA ; 2 2(b)(i) fizzes / bubbles OR gets smaller / disappears OR moves around ; 1 2(b)(ii) sodium + water → sodium hydroxide + hydrogen in either order sodium hydroxide ; hydrogen ; 2 2(c) sodium hydroxide / NaOH OR sodium carbonate / Na2CO3 ; 1 2(d)(i) ionic ; 1 2(d)(ii) chlorine / Cl2 ; 1 (a)(i) You must state that the reactivity of Group I elements increases as you go down the group. (a)(ii) You need to explain that helium is unreactive or inert. (a)(iii) You must describe two differences between the structure of a solid and a gas, such as particle spacing (closer in solid), arrangement (regular in solid), or movement (vibrating in solid, free-moving in gas). (b)(i) You need to describe an observable change when sodium reacts with water, such as fizzing, bubbling, getting smaller, disappearing, or moving around. (b)(ii) You must correctly identify both products of the reaction: sodium hydroxide and hydrogen. (c) You need to name a suitable substance that turns universal indicator purple, such as sodium hydroxide or sodium carbonate. (d)(i) You must state that the bonding in sodium chloride is 'ionic'. (d)(ii) You need to identify 'chlorine' as the other product formed when sodium reacts with a Group VII element.

5 (a) The boxes on the left of Fig. 5.1 show some separation and collection methods. The boxes on the right of Fig. 5.1 show some substances and the mixtures they come from. Complete Fig. 5.1 to show the method used to separate and collect each substance from its mixture. Draw one line from each box on the left to one box on the right. Distillation of water from salty water has been done as an example for you. method substance and its mixture chromatography dyes ink crystallisation insoluble copper oxide aqueous copper sulfate distillation naphtha petroleum filtration salt salty water fractional distillation water salty water Fig. 5.1 [2] (b) Evaporation is also used to separate some mixtures. During evaporation, a liquid becomes a gas. (i) Explain why evaporation is a physical change and not a chemical change. … … [1] (ii) Describe how the structure of a gas is different to the structure of a liquid in terms of particle arrangement and particle motion. particle arrangement … … particle motion … … [2] (c) Copper sulfate and water are made when copper oxide reacts with an acid. State the name of this acid. … [1] (d) State one use for naphtha. … [1] [Total: 7]

5(a) two correct ; all correct ; 2 5(b)(i) only a state change / no new substance made ; 1 5(b)(ii) particles in a gas are: ORA far apart / (more) spread out ; move more freely ; 2 5(c) sulfuric (acid) ; 1 5(d) (as a) feedstock / for making chemicals ; 1

8 A student investigates the rate of the reaction between lumps of calcium carbonate and dilute hydrochloric acid. The student uses the pieces of apparatus shown in Fig. 8.1. apparatus X calcium carbonate dilute hydrochloric acid Fig. 8.1 (a) State the name of apparatus X. … [1] (b) Suggest one piece of apparatus that is not shown in Fig. 8.1 which the student needs to investigate the rate of this reaction. … [1] (c) Complete the word equation for this reaction. calcium carbonate + hydrochloric acid + + [2] (d) The student repeats the experiment using the same mass of calcium carbonate and the same volume of dilute hydrochloric acid. (i) Suggest one change that the student makes to the calcium carbonate to increase the rate of the reaction. … [1] (ii) Suggest one change that the student makes to the hydrochloric acid to increase the rate of the reaction. … [1] (e) A type of calcium atom has the symbol shown. 36 20Ca (i) Deduce the number of neutrons in this atom. … [1] (ii) Deduce the number of electrons in one Ca2+ ion. … [1] [Total: 8]

8(a) (gas) syringe ; 1 8(b) stop-watch ; 1 8(c) calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide calcium chloride / water AND carbon dioxide ; all correct ; 2 8(d)(i) (use) powder / crush (lumps) ; 1 8(d)(ii) (use) more concentrated / increase temperature ; 1 8(e)(i) 16 ; 1 8(e)(ii) 18 ; 1

8 A student investigates the rate of the reaction between lumps of calcium carbonate and dilute hydrochloric acid. The student uses the pieces of apparatus shown in Fig. 8.1. apparatus X calcium carbonate dilute hydrochloric acid Fig. 8.1 (a) State the name of apparatus X. … [1] (b) Suggest one piece of apparatus that is not shown in Fig. 8.1 which the student needs to investigate the rate of this reaction. … [1] (c) Complete the word equation for this reaction. calcium carbonate + hydrochloric acid + + [2] (d) The student repeats the experiment using the same mass of calcium carbonate and the same volume of dilute hydrochloric acid. (i) Suggest one change that the student makes to the calcium carbonate to increase the rate of the reaction. … [1] (ii) Suggest one change that the student makes to the hydrochloric acid to increase the rate of the reaction. … [1] (e) A type of calcium atom has the symbol shown. 36 20Ca (i) Deduce the number of neutrons in this atom. … [1] (ii) Deduce the number of electrons in one Ca2+ ion. … [1] [Total: 8]

8(a) (gas) syringe ; 1 8(b) stop-watch ; 1 8(c) calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide calcium chloride / water AND carbon dioxide ; all correct ; 2 8(d)(i) (use) powder / crush (lumps) ; 1 8(d)(ii) (use) more concentrated / increase temperature ; 1 8(e)(i) 16 ; 1 8(e)(ii) 18 ; 1

19 Barium hydroxide is an alkali. Which statement about barium hydroxide is correct? A It has a pH greater than 7 in aqueous solution. B It reacts with aqueous sodium hydroxide. C It reacts with metal carbonates. D It turns Universal Indicator red.

Answer: A To earn the mark, a student must correctly state that an alkali like barium hydroxide has a pH greater than 7 in aqueous solution.

Cambridge IGCSE Combined Science · 0653

IGCSE Combined Science (0653) Acids, bases and salts past paper questions

Revise IGCSE Combined Science (0653) — Acids, bases and salts with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

172 free questions from 2016–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.

Acids, bases and salts in IGCSE Combined Science 0653 exams, 2020–2025

Across 2020–2025, Acids, bases and salts accounted for 208 questions worth 1,018 marks in Cambridge IGCSE Combined Science (0653) papers.

By year
Year	Questions	Marks
2020	33	169
2021	43	231
2022	40	181
2023	37	175
2024	29	131
2025	26	131

Most-tested subtopics

C7.1 The characteristic properties of acids and bases784 marks
C7.3 Preparation of salts359 marks

Appears in

Paper 1 · 51 qs
Paper 2 · 58 qs
Paper 3 · 27 qs
Paper 4 · 26 qs
Paper 5 · 17 qs
Paper 6 · 29 qs

All most-tested Combined Science topics

2021 May/Jun · Paper 3 · Q2 · 10 marks
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2021 Oct/Nov · Paper 3 · Q5 · 7 marks
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2021 Oct/Nov · Paper 3 · Q8 · 8 marks
Marking scheme
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2021 Oct/Nov · Paper 3 · Q8 · 8 marks
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2021 May/Jun · Paper 1 · Q19 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q19
Answer: A
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