Organic chemistry — IGCSE Science - Combined (0653) questions by topic
Cracking, combustion and polymerisation of hydrocarbons anchor this topic: completing word equations for methane combustion, naming the fraction that gives ethene, and describing the bromine-water test for unsaturation. State, describe and complete are the top command words, and complete specifically requires every gap filled with the correct named substance, not a partial answer.
This set contains 21 real questions from 2023 to 2025 papers, worth 1 to 11 marks, so equation completion sits alongside longer descriptive answers about fractional distillation. Practising with instant marking helps here, because it catches quickly when water is swapped for hydrogen as a combustion product, or when a colour change is described imprecisely.
What examiners look for
- A frequent slip writes hydrogen instead of water as a product of complete combustion.
- Oxygen is often omitted as the missing reactant in combustion word equations.
- Writing simply 'distillation' for separating crude oil fractions is not credited without specifying fractional distillation.
- Colour-change descriptions are marked down when 'clear' is used instead of 'colourless', since a clear solution can still be coloured.
- Strong answers state that complete combustion of methane with a plentiful oxygen supply gives carbon dioxide and water, and correctly name poly(ethene) as the addition polymer of ethene.
May–June 2025, Paper 21
Which type of reaction occurs when alkenes react with bromine? A addition B combustion C displacement D polymerisation
Answer this question and get it marked →May–June 2025, Paper 22
Which process is a physical change? A combustion of solid carbon B cracking of an alkane to give an alkene C fractional distillation of petroleum D rusting of iron
Answer this question and get it marked →May–June 2025, Paper 23
Methane, ethane and propane are all members of the same homologous series. Which statement about these compounds is correct? A They contain double carbon–carbon covalent bonds. B…
Answer this question and get it marked →Which row describes the properties of fractions obtained from petroleum, from the bottom of the fractionating column to the top? chain lengths boiling points --- --- --- A…
Answer this question and get it marked →May–June 2025, Paper 31
The formulas of some compounds of carbon are shown. C2H4 CaCO3 CH4 CO CO2 Use the formulas of these compounds to answer the following questions. Each formula may be used once,…
Answer this question and get it marked →May–June 2025, Paper 42
Alkanes and alkenes are two different homologous series. State two general characteristics of a homologous series. 1 .......... 2 ..........
Answer this question and get it marked →May–June 2025, Paper 43
Ethene is an alkene. The structure of ethene, C2H4, is shown in Fig. 6.1 (a displayed formula with two carbon atoms joined by a C=C double bond, each carbon also bonded to two…
Answer this question and get it marked →May–June 2024, Paper 31
Petroleum is a mixture of hydrocarbons. Fig. 5.1 shows the process that separates petroleum into hydrocarbons (giving refinery gas, fraction A, etc.) and another process, process…
Answer this question and get it marked →May–June 2024, Paper 32
The structures of compounds P and Q are shown in Fig. 8.1. Compound P is a saturated hydrocarbon (a chain of three carbons with single bonds) and compound Q has a carbon-carbon…
Answer this question and get it marked →May–June 2024, Paper 33
The fossil fuel petroleum is a liquid mixture of hydrocarbons. Complete the sentence about hydrocarbons. Hydrocarbons are molecules that contain and only.
Answer this question and get it marked →May–June 2024, Paper 41
Ethene, C2H4, is an alkene. Fig. 8.1 shows the structure of an ethene molecule (H2C=CH2). Naphtha is a fraction obtained from the distillation of petroleum. Naphtha undergoes a…
Answer this question and get it marked →May–June 2024, Paper 43
The structures of ethene and ethane are shown in Fig. 8.1 (ethene has a C=C double bond; ethane has only single bonds). Ethene is a member of the alkene homologous series. All…
Answer this question and get it marked →October–November 2024, Paper 31
(a) Complete the sentences about fuels. Use words from the list. Each word may be used once or not at all. bitumen fossil hydrocarbon methane petroleum Coal, ............ and…
Answer this question and get it marked →October–November 2024, Paper 43
(a) The formula for methanol is CH3OH. Complete the dot-and-cross diagram in Fig. 8.1 to show the bonding in methanol. Show outer-shell electrons only. (Fig. 8.1 shows a central…
Answer this question and get it marked →May–June 2023, Paper 31
Ethane, C2H6, is an alkane. It is one of the saturated hydrocarbons present in refinery gas obtained from petroleum (Fig. 5.1 shows a fractionating column with refinery gas at the…
Answer this question and get it marked →May–June 2023, Paper 41
Table 5.1 shows information about alkanes and alkenes (number of carbon atoms vs name and formula). The general formula of alkanes is CnH(2n+2). Deduce the general formula of…
Answer this question and get it marked →May–June 2023, Paper 42
Cracking decane, C10H22, forms three compounds (Fig. 8.1): pentane (C5H12), propene (C3H6) and ethene (C2H4). State which two compounds in Fig. 8.1 are alkanes. Give a reason for…
Answer this question and get it marked →May–June 2023, Paper 43
Cracking decane, C10H22, forms three compounds (Fig. 8.1): ethene (C2H4), butane (C4H10) and butene (C4H8). State the two compounds shown in Fig. 8.1 that turn aqueous bromine…
Answer this question and get it marked →October–November 2023, Paper 32
Natural gas and petroleum are fossil fuels. Methane is the main constituent of natural gas. Complete the word equation for the complete combustion of methane. methane + → +
Answer this question and get it marked →October–November 2023, Paper 33
Natural gas and petroleum are fossil fuels. Methane is the main constituent of natural gas. Complete the word equation for the complete combustion of methane. methane + → +
Answer this question and get it marked →October–November 2023, Paper 43
Table 8.1 shows information about some alkanes and alkenes (by number of carbon atoms): C2 alkane ethane C2H6, alkene ethene (formula missing); C3 propane C3H8, propene C3H6; C4…
Answer this question and get it marked →Other IGCSE Science - Combined topics
- Practical skills (96)
- Motion, forces and energy (53)
- Electricity and magnetism (38)
- Waves (32)
- Human nutrition (23)
- Acids, bases and salts (22)
- Organisms and their environment (21)
- Reproduction (20)
- Thermal physics (20)
- Plant nutrition (19)
- The Periodic Table (18)
- Metals (18)