2 (a) A mixture contains water, dissolved sodium chloride and an insoluble solid compound. (i) State what is meant by insoluble and compound. insoluble … … compound … … [2] (ii) Describe how crystals of sodium chloride are obtained from this mixture. … … … … … [3] (b) Water is a covalent molecule. Complete Fig. 2.1 to show the dot-and-cross diagram of a molecule of water. Show all the outer shell electrons. H O H Fig. 2.1 [2] (c) An atom of oxygen contains 8 electrons and it has the nucleon number (mass number) 16. State what is meant by nucleon number. … … [1] (d) Complete Table 2.1 to show the charges and approximate relative masses of neutrons and protons. Table 2.1 particle charge relative mass neutron proton [2] [Total: 10]

2(a)(i) insoluble: cannot / does not, dissolve (in water) ; compound: two (or more) elements (chemically) combined ; 2 2(a)(ii) any three from: filter (at the start) / filter (off the insoluble solid) ; evaporate / heat (the NaCl solution) ; leave to (cool and) crystallise ; filter off the crystals / dry between folds of filter paper ; 3 2(b) two bond pairs ; two lone pairs on O ; 2 2(c) (the total number of) protons and neutrons (in the nucleus of an atom) ; 1 2(d) particle charge relative mass neutron 0 1 proton +1 1 ;; neutron row correct ; proton row correct ; 2 (a)(i) To earn these marks, you must define 'insoluble' as something that cannot or does not dissolve, and 'compound' as two or more elements chemically combined. (a)(ii) You need to describe three steps from filtering the insoluble solid, evaporating/heating the solution, allowing it to cool and crystallise, and then filtering/drying the crystals. (b) To earn these marks, you must state that water has two bond pairs and two lone pairs on the oxygen atom. (c) The mark is earned by defining mass number as the total number of protons and neutrons in the nucleus of an atom. (d) You must correctly fill in the charge and relative mass for both neutron and proton to earn the marks, with one mark for each correct row.

2 (a) A student separates some insoluble solid material from concentrated aqueous sodium chloride. (i) State the name of the separation method that the student uses. … [1] (ii) Identify the solute and the solvent in concentrated aqueous sodium chloride. solute … solvent … [1] (iii) State what is meant by concentrated. Use ideas about particles in your answer. … … [1] (b) The student passes an electric current through concentrated aqueous sodium chloride, as shown in Fig. 2.1. concentrated aqueous sodium chloride inert carbon electrodes low voltage d.c. supply – + Fig. 2.1 (i) State the name of this process. … [1] (ii) State the name of the positive electrode. … [1] (iii) Identify the product that forms at the negative electrode. … [1] (c) Sodium is a metal, and chlorine is a diatomic non-metal. When sodium and chlorine are heated together, sodium chloride is formed. (i) State what is meant by diatomic. … … [1] (ii) State the type of chemical bonding present in sodium chloride. … [1] (iii) Describe a chemical test for the presence of chloride ions in aqueous sodium chloride. State the observation for a positive result. test … … observation … … [2] [Total: 10]

2(a)(i) filtration / filter(ing) ; 1 2(a)(ii) solute: sodium chloride / NaCl AND solvent: water / H2O ; 1 2(a)(iii) there are many / more solute particles in (a solution) ; 1 2(b)(i) electrolysis ; 1 2(b)(ii) anode ; 1 2(b)(iii) hydrogen ; 1 2(c)(i) (contains) only two atoms joined (in a molecule) ; 1 2(c)(ii) ionic ; 1 2(c)(iii) test: (aqueous) silver nitrate AND (dilute) nitric acid ; result: white precipitate ; 2

2 (a) A student separates some insoluble solid material from concentrated aqueous sodium chloride. (i) State the name of the separation method that the student uses. … [1] (ii) Identify the solute and the solvent in concentrated aqueous sodium chloride. solute … solvent … [1] (iii) State what is meant by concentrated. Use ideas about particles in your answer. … … [1] (b) The student passes an electric current through concentrated aqueous sodium chloride, as shown in Fig. 2.1. concentrated aqueous sodium chloride inert carbon electrodes low voltage d.c. supply – + Fig. 2.1 (i) State the name of this process. … [1] (ii) State the name of the positive electrode. … [1] (iii) Identify the product that forms at the negative electrode. … [1] (c) Sodium is a metal, and chlorine is a diatomic non-metal. When sodium and chlorine are heated together, sodium chloride is formed. (i) State what is meant by diatomic. … … [1] (ii) State the type of chemical bonding present in sodium chloride. … [1] (iii) Describe a chemical test for the presence of chloride ions in aqueous sodium chloride. State the observation for a positive result. test … … observation … … [2] [Total: 10]

2(a)(i) filtration / filter(ing) ; 1 2(a)(ii) solute: sodium chloride / NaCl AND solvent: water / H2O ; 1 2(a)(iii) there are many / more solute particles in (a solution) ; 1 2(b)(i) electrolysis ; 1 2(b)(ii) anode ; 1 2(b)(iii) hydrogen ; 1 2(c)(i) (contains) only two atoms joined (in a molecule) ; 1 2(c)(ii) ionic ; 1 2(c)(iii) test: (aqueous) silver nitrate AND (dilute) nitric acid ; result: white precipitate ; 2

5 (a) Petroleum is a mixture of hydrocarbons. Useful products are obtained by process X and process Y, as shown in Fig. 5.1. petroleum strong heat alkenes gasoline process X process Y naphtha naphtha Fig. 5.1 (i) Process X separates gasoline and naphtha from petroleum. Name process X. … [1] (ii) Process Y produces alkenes. Name process Y. … [1] (iii) State whether process Y is a chemical change or a physical change. Explain your answer. change … explanation … … [1] (iv) Describe a chemical test for alkenes, and state the observation for a positive result. test … result … [2] (b) The structure of a molecule of propene, an alkene, is shown in Fig. 5.2. C H C C H H H H H Fig. 5.2 Water is formed during the complete combustion of propene. (i) Identify the other substance that is formed during this combustion. … [1] (ii) Name the gas in air that reacts with propene during combustion, and state the percentage of this gas in clean air. gas … percentage … [1] (iii) Use Fig. 5.2 to deduce the formula of propene. … [1] [Total: 8]

5(a)(i) fractional distillation ; 1 5(a)(ii) cracking ; 1 5(a)(iii) change: chemical AND explanation: new substances are made / bonds are broken / new bonds are formed ; 1 5(a)(iv) test: (add aqueous) bromine ; result: (orange to) colourless / decolourises ; 2 5(b)(i) carbon dioxide / CO2 ; 1 5(b)(ii) gas: oxygen AND percentage: 21(%) ; 1 5(b)(iii) C3H6 ; 1

8 What can be used to test for the presence of carbon dioxide? A Benedict’s solution B ethanol C iodine solution D limewater

Answer: D To earn the mark, a student must correctly identify limewater as the substance used to test for the presence of carbon dioxide.

Cambridge IGCSE Combined Science · 0653

IGCSE Combined Science (0653) Experimental techniques and chemical analysis past paper questions

Revise IGCSE Combined Science (0653) — Experimental techniques and chemical analysis 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.

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

Experimental techniques and chemical analysis in IGCSE Combined Science 0653 exams, 2020–2025

Across 2020–2025, Experimental techniques and chemical analysis accounted for 240 questions worth 1,120 marks in Cambridge IGCSE Combined Science (0653) papers.

By year
Year	Questions	Marks
2020	31	163
2021	54	247
2022	45	226
2023	48	250
2024	33	143
2025	29	91

Most-tested subtopics

C12.4 Identification of ions and gases633 marks
C12.3 Separation and purification319 marks
C12.1 Experimental design275 marks

Appears in

Paper 1 · 72 qs
Paper 2 · 65 qs
Paper 3 · 31 qs
Paper 4 · 16 qs
Paper 5 · 20 qs
Paper 6 · 36 qs

All most-tested Combined Science topics

2021 May/Jun · Paper 3 · Q2 · 10 marks
Marking scheme
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2021 Oct/Nov · Paper 3 · Q2 · 10 marks
Marking scheme
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2021 Oct/Nov · Paper 3 · Q2 · 10 marks
Marking scheme
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2021 May/Jun · Paper 3 · Q5 · 8 marks
Marking scheme
$Mark scheme: 5(a)(i) fractional distillation ; 1 5(a)(ii) cracking ; 1 5(a)(iii) change: chemical AND explanation: new substances are…$ Get Steven’s plain-English explanation
2021 May/Jun · Paper 1 · Q8 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q8
Answer: D
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