2 Natural gas and petroleum are two types of fossil fuel. (a) Name one other fossil fuel. … [1] (b) State the main constituent of natural gas. … [1] (c) Petroleum is separated by the process shown in Fig. 2.1. petroleum gasoline gas oil naphtha bitumen refinery gas Fig. 2.1 (i) Name this process. … [1] (ii) State one use for bitumen. … [1] (d) Ethane and ethene are both hydrocarbons. Ethane is an alkane. Ethene is an alkene. (i) Two compounds are made during the complete combustion of ethane and of ethene. Water is one of these compounds. Identify the other compound. … [1] (ii) Describe one difference between molecules of ethane and molecules of ethene. … … [1] (e) The structure of a molecule of another hydrocarbon is shown in Fig. 2.2. H H H C H H C H H C H Fig. 2.2 Deduce the formula of this hydrocarbon. … [1] [Total: 7]

2(a) coal ; 1 2(b) methane / CH4 ; 1 2(c)(i) fractional distillation ; 1 2(c)(ii) (for making) roads ; 1 2(d)(i) carbon dioxide / CO2 ; 1 2(d)(ii) ethene, is unsaturated / contains double bonds ; 1 2(e) C3H8 ; 1

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 (a) The boxes on the left of Fig. 5.1 show some separation and collection methods. The boxes on the right of Fig. 5.1 show some substances and the mixtures they come from. Complete Fig. 5.1 to show the method used to separate and collect each substance from its mixture. Draw one line from each box on the left to one box on the right. Distillation of water from salty water has been done as an example for you. method substance and its mixture chromatography dyes ink crystallisation insoluble copper oxide aqueous copper sulfate distillation naphtha petroleum filtration salt salty water fractional distillation water salty water Fig. 5.1 [2] (b) Evaporation is also used to separate some mixtures. During evaporation, a liquid becomes a gas. (i) Explain why evaporation is a physical change and not a chemical change. … … [1] (ii) Describe how the structure of a gas is different to the structure of a liquid in terms of particle arrangement and particle motion. particle arrangement … … particle motion … … [2] (c) Copper sulfate and water are made when copper oxide reacts with an acid. State the name of this acid. … [1] (d) State one use for naphtha. … [1] [Total: 7]

5(a) two correct ; all correct ; 2 5(b)(i) only a state change / no new substance made ; 1 5(b)(ii) particles in a gas are: ORA far apart / (more) spread out ; move more freely ; 2 5(c) sulfuric (acid) ; 1 5(d) (as a) feedstock / for making chemicals ; 1

Cambridge IGCSE Combined Science · 0653

IGCSE Combined Science (0653) Organic chemistry past paper questions

Revise IGCSE Combined Science (0653) — 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.

188 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 Combined Science 0653 exams, 2020–2025

Across 2020–2025, Organic chemistry accounted for 192 questions worth 680 marks in Cambridge IGCSE Combined Science (0653) papers.

By year
Year	Questions	Marks
2020	25	105
2021	29	91
2022	46	142
2023	34	112
2024	37	135
2025	21	95

Most-tested subtopics

C11.4 Alkenes400 marks
C11.3 Alkanes399 marks
C11.1 Terminology351 marks

Appears in

Paper 1 · 59 qs
Paper 2 · 68 qs
Paper 3 · 35 qs
Paper 4 · 30 qs

All most-tested Combined Science topics

2021 Feb/Mar · Paper 3 · Q2 · 7 marks
Marking scheme
$Mark scheme: 2(a) coal ; 1 2(b) methane / CH4 ; 1 2(c)(i) fractional distillation ; 1 2(c)(ii) (for making) roads ; 1 2(d)(i) carbon…$ Get Steven’s plain-English explanation
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 · 7 marks
Marking scheme
Get Steven’s plain-English explanation
2021 Feb/Mar · Paper 1 · Q26 · 1 mark
$26 Which petroleum fraction is used to make road surfaces? A bitumen B diesel oil C gasoline D naphtha$
Marking scheme
Mark scheme — 2021 Paper 1 Q26
Answer: A
Get Steven’s plain-English explanation