5 (a) (i) State the percentage of oxygen and of nitrogen in a sample of clean air. oxygen …% nitrogen …% [2] (ii) A sample of air collected near a busy road contains carbon monoxide. Carbon monoxide is made by car engines. Describe how carbon monoxide is made by car engines. … … … … [3] (iii) State one harmful effect of carbon monoxide on the health of a human. … … [1] (b) The atmosphere contains small quantities of sulfur dioxide. Sulfur dioxide causes acid rain. (i) Suggest a pH for acid rain. … [1] (ii) Suggest one adverse effect of acid rain on buildings. … … [1] (iii) Sulfur dioxide is made when sulfur is burned in oxygen. This reaction is called an oxidation reaction. State the meaning of the term oxidation. … … [1] [Total: 9]

5(a)(i) oxygen 21% ; nitrogen 78% ; 2 5(a)(ii) incomplete ; combustion ; of gasoline / hydrocarbon ; 3 5(a)(iii) carboxyhaemoglobin production / unconsciousness / death / poisoning ; 1 5(b)(i) any number less than 7 ; 1 5(b)(ii) corrosion of building materials ; 1 5(b)(iii) gain of oxygen ; 1

5 (a) Petroleum is separated into useful fractions by fractional distillation. Fig. 5.1 shows a simplified diagram for the fractional distillation of petroleum. hot petroleum fraction naphtha refinery gas diesel oil 400 °C 50 °C … … Fig. 5.1 (i) On Fig. 5.1 write the names of the missing fractions in their correct place. [2] (ii) State one use for the refinery gas fraction. … [1] (iii) State why the process of fractional distillation is a physical change and not a chemical change. … … [1] (b) The diesel oil fraction is used as a fuel. (i) Diesel oil is a mixture of hydrocarbons. State what is meant by the term hydrocarbon. … … … [2] (ii) State the two products of the complete combustion of a hydrocarbon. 1 … 2 … [2] (c) (i) Name the process that produces small alkene molecules from larger alkane molecules. … [1] (ii) State how the molecular structure of an alkane molecule differs from the molecular structure of an alkene molecule. … … [1] (iii) Aqueous bromine is used to test for an alkene. State the colour change when aqueous bromine reacts with an alkene. from … to … [2] [Total: 12]

5(a)(i) gasoline ; bitumen ; 2 5(a)(ii) fuel ; 1 5(a)(iii) no new substances formed ; 1 5(b)(i) substance that contains carbon and hydrogen (atoms) ; only ; 2 5(b)(ii) carbon dioxide ; water ; 2 5(c)(i) cracking ; 1 5(c)(ii) alkane does not contain a C-C double bond / alkene does contain a C-C double bond / contains only single bonds ; 1 5(c)(iii) orange ; to colourless ; 2

8 (a) Fig. 8.1 shows three hydrocarbon molecules X, Y and Z. C C H H H H C H H H H C H H H C H H C H H C H H H X Y Z Fig. 8.1 Hydrocarbon molecule X is unsaturated. (i) Explain why molecule X is unsaturated. … … [1] (ii) State the name of molecule X. … [1] (iii) An aqueous solution of element P is used to test if hydrocarbons X and Y are saturated or unsaturated. State the name of element P. … [1] (iv) Describe what, if anything, is observed when an aqueous solution of element P is mixed with hydrocarbon molecule X and with hydrocarbon molecule Y. with hydrocarbon molecule X … … with hydrocarbon molecule Y … … [2] (b) When hydrocarbon molecule Y is completely combusted in oxygen, carbon dioxide and water are made. (i) Balance the symbol equation for this reaction. CH4 + …O2 CO2 + …H2O [2] (ii) This reaction is an exothermic reaction. State what is meant by an exothermic reaction. … … [1] (c) Ethanol has the formula C2H5OH. (i) Explain why ethanol is not a hydrocarbon. … … [1] (ii) State two methods of producing ethanol. 1 … 2 … [2] [Total: 11]

8(a)(i) has a carbon-carbon double bond; 1 8(a)(ii) ethene; 1 8(a)(iii) bromine; 1 8(a)(iv) decolourises/becomes colourless; stays orange/does not decolourise; 2 8(b)(i) CH4 + 2O2 → CO2 + 2H2O ;; 2 8(b)(ii) thermal energy released; 1 8(c)(i) contains oxygen / does not contain only carbon and hydrogen; 1 8(c)(ii) fermentation; reaction of ethene and steam; 2 (a)(i) To earn the mark, you must explain that molecule X is unsaturated because it has a carbon-carbon double bond. (a)(ii) To earn the mark, you must state 'ethene' as the name of molecule X. (a)(iii) To earn the mark, you must state 'bromine' as the element P. (a)(iv) To earn the marks, you must describe that the aqueous solution of element P 'decolourises/becomes colourless' with hydrocarbon X and 'stays orange/does not decolourise' with hydrocarbon Y. (b)(i) To earn the marks, you must provide the complete and correctly balanced chemical equation: CH4 + 2O2 → CO2 + 2H2O. (b)(ii) To earn the mark, you must state that 'thermal energy is released' during the complete combustion of methane. (c)(i) To earn the mark, you must explain that ethanol is not a hydrocarbon because it 'contains oxygen' or 'does not contain only carbon and hydrogen'. (c)(ii) To earn the marks, you must name 'fermentation' and 'reaction of ethene and steam' as two methods for producing ethanol.

8 (a) Fig. 8.1 shows three molecules A, B and C. H H H H H C C O H H H H H C C H H H C H A B C Fig. 8.1 State the formula of the substance that reacts with molecule C to make molecule A. … [1] (b) Molecule B, CH4, is methane which is a compound. Methane contains the elements carbon and hydrogen. Use this information to explain the difference between an element and a compound. … … … [2] (c) State the two products made when methane undergoes complete combustion in oxygen. 1 … 2 … [2] (d) The combustion of methane is an exothermic reaction. State what is meant by exothermic. … … [1] (e) An atom of carbon has a nucleon number (mass number) of 12 and a proton number (atomic number) of 6. An atom of hydrogen has a nucleon number (mass number) of 1 and a proton number (atomic number) of 1. (i) State the number of electrons in an atom of carbon and in an atom of hydrogen. carbon … hydrogen … [1] (ii) State the number of neutrons in this atom of hydrogen. … [1] (f) Complete the dot‑and‑cross diagram in Fig. 8.2 to show the bonding in a methane, CH4, molecule. H H C H H Fig. 8.2 [2] [Total: 10]

8(a) H2O ; 1 8(b) an element (e.g. carbon) contains only one type of atom ; a compound (e.g. methane) contains two or more elements / different atoms chemically combined ; 2 8(c) carbon dioxide ; water ; 2 8(d) releases thermal energy ; 1 8(e)(i) carbon 6 and hydrogen 1 ; 1 8(e)(ii) zero ; 1 8(f) one shared pair seen ; all correct ;; 2 (a) To earn the mark, state 'H2O' as the formula. (b) To earn marks, define an element as containing only one type of atom and a compound as containing two or more different atoms chemically combined. (c) To earn marks, state 'carbon dioxide' and 'water' as the two products. (d) To earn the mark, state that exothermic means the reaction releases thermal energy.

Cambridge IGCSE Co-ordinated Sciences · 0654

IGCSE Co-ordinated Sciences (0654) Organic chemistry past paper questions

Revise IGCSE Co-ordinated Sciences (0654) — Organic chemistry 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.

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

Organic chemistry in IGCSE Co-ordinated Sciences 0654 exams, 2020–2025

Across 2020–2025, Organic chemistry accounted for 268 questions worth 1,099 marks in Cambridge IGCSE Co-ordinated Sciences (0654) papers.

By year
Year	Questions	Marks
2020	51	199
2021	47	197
2022	39	185
2023	43	158
2024	43	188
2025	45	172

Most-tested subtopics

C11.4 Alkanes605 marks
C11.5 Alkenes584 marks
C11.3 Fuels404 marks

Appears in

Paper 1 · 84 qs
Paper 2 · 90 qs
Paper 3 · 50 qs
Paper 4 · 42 qs
Paper 6 · 2 qs

All most-tested Co-ordinated Sciences topics

2021 Oct/Nov · Paper 3 · Q5 · 9 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Oct/Nov · Paper 3 · Q5 · 12 marks
$5 (a) Petroleum is separated into useful fractions by fractional distillation. Fig. 5.1 shows a simplified diagram for the…$ $5 (a) Petroleum is separated into useful fractions by fractional distillation. Fig. 5.1 shows a simplified diagram for the… (continued)$
Marking scheme
Get Steven’s plain-English explanation
2021 Feb/Mar · Paper 3 · Q8 · 11 marks
Marking scheme
Get Steven’s plain-English explanation
2021 May/Jun · Paper 3 · Q8 · 10 marks
Marking scheme
Get Steven’s plain-English explanation
2021 May/Jun · Paper 1 · Q23 · 1 mark
Marking scheme
Mark scheme — 2021 Paper 1 Q23
Answer: A
Get Steven’s plain-English explanation