2 (a) Fig. 2.1 shows a process used to separate substances in a fossil fuel. fossil fuel Fig. 2.1 (i) Name this process. … [1] (ii) Name the fossil fuel that is separated by this process. … [1] (b) Methane is the main constituent of another fossil fuel. (i) Name this fossil fuel. … [1] (ii) Complete Fig. 2.2 to show the dot-and-cross diagram of one molecule of methane, CH4. H H H H C Fig. 2.2 [2] (iii) Identify a greenhouse gas that is formed by the complete combustion of methane. … [1] (c) Carbon has atomic number 6 and mass number 12. Hydrogen has atomic number 1 and mass number 1. Complete Table 2.1 to show the number of protons and the number of neutrons in one atom of carbon and in one atom of hydrogen. Table 2.1 atom number of protons number of neutrons carbon hydrogen [2] [Total: 8]

2(a)(i) fractional distillation ; 1 2(a)(ii) petroleum ; 1 2(b)(i) natural gas ; 1 2(b)(ii) ;; four bonding pairs of electrons = 2 marks one bonding pair correct = 1 mark 2 2(b)(iii) carbon dioxide / CO2 ; 1 2(c) number of protons number of neturons carbon 6 6 hydrogen 1 0 carbon row correct ; hydrogen row correct ; 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

5 The Periodic Table lists all of the known elements. (a) State the name of the element used to kill bacteria in water supplies. … [1] (b) Iron is mixed with other elements to change its properties. State the name of the type of mixture that contains a metal and other elements. … [1] (c) Table 5.1 shows the chemical and physical properties of four elements in the Periodic Table. Complete Table 5.1 by choosing four elements from the list. argon carbon hydrogen iron magnesium nitrogen oxygen Table 5.1 element properties … • boils at –252.9 °C • present in molecules of methane … • boils at –185.8 °C • is unreactive (and so is used in lamps) … • boils at –182.95 °C • required for the rusting of iron … • melts at 650 °C • reacts slowly with cold water • reacts rapidly with steam forming a white solid [4] (d) Methane is a compound. Describe the difference between an element and a compound. Use ideas about types of atom in your answer. element … … compound … … [2] [Total: 8]

5(a) chlorine ; 1 5(b) alloy(s) ; 1 5(c) hydrogen ; argon ; oxygen ; magnesium ; 4 5(d) element: contains only one type of atom ; compound: contains two (or more) types of atom ; 2

5 The Periodic Table lists all of the known elements. (a) State the name of the element used to kill bacteria in water supplies. … [1] (b) Iron is mixed with other elements to change its properties. State the name of the type of mixture that contains a metal and other elements. … [1] (c) Table 5.1 shows the chemical and physical properties of four elements in the Periodic Table. Complete Table 5.1 by choosing four elements from the list. argon carbon hydrogen iron magnesium nitrogen oxygen Table 5.1 element properties … • boils at –252.9 °C • present in molecules of methane … • boils at –185.8 °C • is unreactive (and so is used in lamps) … • boils at –182.95 °C • required for the rusting of iron … • melts at 650 °C • reacts slowly with cold water • reacts rapidly with steam forming a white solid [4] (d) Methane is a compound. Describe the difference between an element and a compound. Use ideas about types of atom in your answer. element … … compound … … [2] [Total: 8]

5(a) chlorine ; 1 5(b) alloy(s) ; 1 5(c) hydrogen ; argon ; oxygen ; magnesium ; 4 5(d) element: contains only one type of atom ; compound: contains two (or more) types of atom ; 2

Cambridge IGCSE Combined Science · 0653

IGCSE Combined Science (0653) Chemistry of the environment past paper questions

Revise IGCSE Combined Science (0653) — Chemistry of the environment 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.

124 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 Combined Science 0653 exams, 2020–2025

Across 2020–2025, Chemistry of the environment accounted for 118 questions worth 490 marks in Cambridge IGCSE Combined Science (0653) papers.

By year
Year	Questions	Marks
2020	15	88
2021	18	88
2022	21	73
2023	23	82
2024	24	78
2025	17	81

Most-tested subtopics

C10.2 Air quality and climate328 marks
C10.1 Water125 marks

Appears in

Paper 1 · 32 qs
Paper 2 · 37 qs
Paper 3 · 27 qs
Paper 4 · 22 qs

All most-tested Combined Science topics

2021 May/Jun · Paper 3 · Q2 · 8 marks
Marking scheme
$Mark scheme: 2(a)(i) fractional distillation ; 1 2(a)(ii) petroleum ; 1 2(b)(i) natural gas ; 1 2(b)(ii) ;; four bonding pairs of…$ $Mark scheme: 2(a)(i) fractional distillation ; 1 2(a)(ii) petroleum ; 1 2(b)(i) natural gas ; 1 2(b)(ii) ;; four bonding pairs of… (continued)$ Get Steven’s plain-English explanation
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 Oct/Nov · Paper 3 · Q5 · 8 marks
Marking scheme
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2021 Oct/Nov · Paper 3 · Q5 · 8 marks
Marking scheme
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2021 Feb/Mar · Paper 1 · Q24 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q24
Answer: C
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