1 The diagram shows part of the Periodic Table. I II III IV V VI VII VIII Mg Al Ar Cl Br I C N O F Ca Cr Fe Cu Zn Pt K Answer the following questions using only the symbols of the elements in the diagram. Each symbol may be used once, more than once or not at all. Give the symbol of the element that: (a) is extracted from bauxite … [1] (b) forms 21% of clean, dry air … [1] (c) forms an oxide which contributes to acid rain … [1] (d) forms an aqueous ion that gives a red-brown precipitate on addition of aqueous sodium hydroxide … [1] (e) has an atom with a complete outer electron shell. … [1] [Total: 5]

1(a) Al 1 1(b) O 1 1(c) N 1 1(d) Fe 1 1(e) Ar 1 To earn the mark, you must correctly identify the specific element symbol for each description.

1 (a) A list of formulae is shown. Al Cl 3 CaCO3 CO CO2 CoCl 2 CuSO4 MgCl 2 N2 NaCl NH3 O2 SO2 Answer the following questions using these formulae. Each formula may be used once, more than once or not at all. State which formula represents: (i) a compound that changes colour from white to blue when water is added … [1] (ii) a compound that is used to make cement … [1] (iii) an element that forms 78% of clean, dry air … [1] (iv) a compound that contains an ion with a single positive charge … [1] (v) a compound that dissolves in water to form an alkaline solution. … [1] (b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of ammonia. N H H H [2] (c) State whether magnesium oxide is a basic oxide or an acidic oxide. Give a reason for your answer. … … [1] [Total: 8]

1(a)(i) CuSO4 1 1(a)(ii) CaCO3 1 1(a)(iii) N2 1 1(a)(iv) NaCl 1 1(a)(v) NH3 1 1(b) bonding pair of electrons between the N atom and each of the H atoms with no other electrons on the H atom (1) 2 non-bonding electrons on N atom (1) 2 1(c) basic oxide AND magnesium is a metal / metal oxides are basic (1) 1 (a)(i) To earn this mark, you must correctly identify CuSO4 as the compound that changes color from white to blue when water is added. (a)(ii) To earn this mark, you must correctly identify CaCO3 as the compound used to make cement. (a)(iii) To earn this mark, you must correctly identify N2 as the element that forms 78% of clean, dry air. (a)(iv) To earn this mark, you must correctly identify NaCl as the compound that contains an ion with a single positive charge. (a)(v) To earn this mark, you must correctly identify NH3 as the compound that dissolves in water to form an alkaline solution. (b) To earn the first mark, you must show a bonding pair of electrons between the N atom and each H atom, with no other electrons on the H atoms. To earn the second mark, you must show two non-bonding electrons on the N atom. (c) To earn this mark, you must state that magnesium oxide is a basic oxide AND provide the reason that magnesium is a metal or that metal oxides are basic.

1 (a) A list of formulae is shown. Br2 CO CO2 CH4 C2H6 HCl KBr LiCl MgCl 2 O2 SO2 Answer the following questions using these formulae. Each formula may be used once, more than once or not at all. State which formula represents: (i) a compound that gives a red colour in a flame test … [1] (ii) a compound containing an ion with a 2+ charge … [1] (iii) a compound that is a product of respiration … [1] (iv) a compound used as a food preservative … [1] (v) an element that is used in the production of steel. … [1] (b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of hydrogen chloride. Show outer shell electrons only. Cl H [2] (c) State whether carbon dioxide is a basic oxide or an acidic oxide. Give a reason for your answer. … … [1] [Total: 8]

1(a)(i) LiCl 1 1(a)(ii) MgCl2 1 1(a)(iii) CO2 1 1(a)(iv) SO2 1 1(a)(v) O2 1 1(b) bonding pair of electrons between the Cl atom and H atom and no other electrons on hydrogen atom (1) 6 non-bonding electrons on Cl atom (1) 2 1(c) acidic (oxide) AND carbon is a non-metal / non-metal oxides are acidic (1) 1 (a) To earn marks, you must correctly identify the specific chemical formula from the provided list for each description. (b) For the first mark, draw a single bonding pair of electrons between H and Cl, ensuring no other electrons are on the hydrogen atom. For the second mark, show six non-bonding electrons (three lone pairs) on the chlorine atom. (c) You must state that carbon dioxide is an acidic oxide AND provide the reason that carbon is a non-metal or that non-metal oxides are acidic.

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.

Cambridge IGCSE Chemistry · 0620

IGCSE Chemistry (0620) Chemistry of the environment past paper questions

Questions on the chemistry of water and air quality and the use of fertilisers.

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

Chemistry of the environment in IGCSE Chemistry 0620 exams, 2020–2025

Across 2020–2025, Chemistry of the environment accounted for 368 questions worth 1,496 marks in Cambridge IGCSE Chemistry (0620) papers.

By year
Year	Questions	Marks
2020	52	204
2021	62	231
2022	60	220
2023	70	348
2024	61	248
2025	63	245

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Paper 1 · 139 qs
Paper 2 · 102 qs
Paper 3 · 88 qs
Paper 4 · 36 qs
Paper 6 · 3 qs

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2021 Feb/Mar · Paper 3 · Q1 · 5 marks
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2021 Oct/Nov · Paper 3 · Q1 · 8 marks
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2021 Oct/Nov · Paper 3 · Q1 · 8 marks
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2021 May/Jun · Paper 3 · Q2 · 15 marks
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2021 May/Jun · Paper 1 · Q27 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q27
Answer: C
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