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] (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]

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 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 (a) To earn marks, you must identify the correct negative ion, provide both correct ion formulae, and calculate the correct mass of sodium ions. (b) To earn marks, you must describe a flame test and state that the observation is a red flame. (c) To earn marks, you must state nitrogen and phosphorus as the two other elements.

4 The table shows some properties of four halogens in Group VII. halogen melting point / °C boiling point / °C density of liquid at boiling point in g / cm3 chlorine –101 –35 1.56 bromine –7 59 iodine 114 4.93 astatine 302 337 6.35 (a) (i) Complete the table by predicting: ● the boiling point of iodine ● the density of bromine. [2] (ii) Describe the trend in the melting points of the halogens down Group VII. … [1] (b) (i) Deduce the electronic structure of chlorine. Use the Periodic Table to help you. … [1] (ii) Explain why a bromide ion has a single negative charge. … … [1] (c) Scientists have predicted that sodium astatide reacts with chlorine. Complete the word equation for this reaction. sodium astatide + chlorine → … … + … [2] (d) Hydrogen chloride is produced when chlorine reacts with ammonia. An aqueous solution of hydrogen chloride is acidic. Describe how you could determine the pH of an acidic solution without using a pH meter. … … … [2] [Total: 9]

4(a)(i) boiling point of I: values from 120 to 330 °C (inclusive of these values) (1) density of Br: values from 1.6 to 4.9 (inclusive of these values) (1) 2 4(a)(ii) increases 1 4(b)(i) 2.8.7 1 4(b)(ii) it has one more electron than protons / it has 35 protons and 36 electrons (1) 1 4(c) sodium chloride (1) astatine (1) 2 4(d) idea of adding universal indicator to solution (1) compare colour with pH colour chart (1) 2 (a) (i) You must predict a boiling point for iodine within the range of 120 to 330 °C and a density for bromine within the range of 1.6 to 4.9 g/cm³. (ii) You must state that the melting points increase down Group VII. (b) (i) You must state the correct electronic structure for chlorine as 2.8.7. (ii) You must explain that a bromide ion has a single negative charge because it has one more electron than protons, or specifically, 35 protons and 36 electrons. (c) You must correctly identify the two products of the reaction: sodium chloride and astatine. (d) You must describe adding universal indicator to the solution and comparing the resulting color to a pH color chart.

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] (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]

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 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 (a) To earn marks, you must define thermal decomposition as the breakdown of a substance into two or more substances using heat, and for calcium ions, describe adding aqueous sodium hydroxide and observing a white precipitate, or adding aqueous ammonia and observing no precipitate/a very slight white precipitate. (b) To earn marks, you must draw a gas syringe or an upturned measuring cylinder in a container, ensuring the apparatus is workable and airtight, and state that decreasing acid concentration decreases the rate of reaction while increasing temperature increases the rate of reaction.

5 (a) Calcium carbonate is heated in a closed container. CaCO3 CaO + CO2 (i) State the name of a rock which is mainly calcium carbonate. … [1] (ii) State the meaning of the symbol . … [1] (iii) CaO is lime. Lime is used for neutralising acidic industrial waste. Give one other use of lime. … [1] (iv) Describe a test for carbon dioxide. 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 the apparatus used to investigate the volume of carbon dioxide produced during this reaction. gas syringe [2] (ii) Describe the effect of each of the following on the rate of reaction of dilute hydrochloric acid with calcium carbonate. ● The temperature is decreased. All other conditions stay the same. … ● Calcium carbonate powder is used instead of large pieces of calcium carbonate. All other conditions stay the same. … [2] (c) Carbon dioxide is also formed when the hydrocarbon C4H8 is completely combusted. (i) The hydrocarbon C4H8 is an alkene. Complete the structure of this alkene by adding the missing bonds and atom. H C H H C H C H H H C [2] (ii) The incomplete combustion of C4H8 produces carbon monoxide. State the meaning of the term incomplete combustion. … … [1] [Total: 12]

5(a)(i) limestone 1 5(a)(ii) reversible (reaction) 1 5(a)(iii) neutralising (acidic) soil / making cement / steelmaking 1 5(a)(iv) limewater (1) turns milky / goes cloudy / white precipitate (1) 2 5(b)(i) flask or other suitable container (1) connecting tubing AND apparatus gas-tight / no air gaps (1) 2 5(b)(ii) lower temperature: (rate) decreases / (rate) lower (1) / (rate) slower powdered CaCO3: (rate) increases / (rate) higher (1) / (rate) faster 2 5(c)(i) double bond between 3rd and 4th C atoms from left (1) ─ H connected to 4th carbon from the left (1) 2 5(c)(ii) (combustion with) limited oxygen / the hydrocarbon is in excess (1) 1 To earn marks, you must name limestone as a rock mainly composed of calcium carbonate in part (a)(i) and state that the symbol means a reversible reaction in part (a)(ii). For part (a)(iii), provide another correct use for lime, such as neutralising acidic soil or making cement. In part (a)(iv), describe the test for carbon dioxide using limewater and state the observation of it turning milky or cloudy. For part (b)(i), complete the diagram by drawing a suitable container (like a flask) and ensuring the apparatus is gas-tight with connecting tubing. In part (b)(ii), state that a lower temperature decreases the reaction rate and powdered CaCO3 increases the reaction rate.

2 Gases are separated from liquid air by fractional distillation. The boiling points of four gases are shown. Which gas is both monoatomic and a liquid at –200 C? gas boiling point / C A argon –186 B helium –269 C neon –246 D nitrogen –196

Answer: A To earn the mark, a student must identify the gas that is monoatomic and has a boiling point above -200 °C, indicating it would be a liquid at that temperature.

Cambridge IGCSE Chemistry · 0620

IGCSE Chemistry (0620) Experimental techniques and chemical analysis past paper questions

These questions cover separation methods, tests for ions and gases, and interpreting experimental data — skills examined heavily on the practical papers.

795 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 Chemistry 0620 exams, 2020–2025

Across 2020–2025, Experimental techniques and chemical analysis accounted for 765 questions worth 5,048 marks in Cambridge IGCSE Chemistry (0620) papers.

By year
Year	Questions	Marks
2020	142	925
2021	122	828
2022	125	808
2023	121	755
2024	136	869
2025	119	863

Most-tested subtopics

12.1 Experimental design, apparatus and measurements2544 marks
12.5 Chemical tests and qualitative analysis1505 marks
12.2 Separation and purification1067 marks

Appears in

Paper 1 · 207 qs
Paper 2 · 151 qs
Paper 3 · 79 qs
Paper 4 · 51 qs
Paper 5 · 116 qs
Paper 6 · 161 qs

All most-tested Chemistry topics

2021 May/Jun · Paper 3 · Q2 · 15 marks
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2021 Oct/Nov · Paper 3 · Q4 · 9 marks
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2021 May/Jun · Paper 3 · Q5 · 13 marks
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2021 May/Jun · Paper 3 · Q5 · 12 marks
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2021 Feb/Mar · Paper 1 · Q2 · 1 mark
$2 Gases are separated from liquid air by fractional distillation. The boiling points of four gases are shown. Which gas is…$
Marking scheme
Mark scheme — 2021 Paper 1 Q2
Answer: A
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