Methodology

This list is based on analysis of Pearson Edexcel IGCSE Chemistry 4CH1 past papers (2019–2025), examiner reports, mark schemes and specification. Topics are ranked by frequency and mark allocation.

Top 10 most frequently tested topics

1. Organic chemistry

Evidence: Alkanes, alkenes, alcohols, carboxylic acids. Examiner reports note compound naming and bonding errors.

Covers: homologous series; alkanes, alkenes, alcohols; reactions; polymerisation; cracking.

2. Stoichiometry and mole calculations

Evidence: Mole calculations appear in almost every paper. Examiner reports note limiting reagent errors.

Covers: mole concept; reacting masses; empirical formula; limiting reagent.

3. Chemical bonding

Evidence: Ionic, covalent, metallic. Examiner reports note “bonds between atoms” vs “molecules” errors.

Covers: ionic and covalent bonding; structure; properties.

4. Acids, bases and salts

Evidence: Titration, neutralisation, salt preparation. Core practical work.

Covers: acids and bases; titration; salt preparation; pH.

5. Electrolysis

Evidence: Products at electrodes; aqueous vs molten. Examiner reports highlight electrolysis errors.

Covers: electrolysis rules; products; aqueous solutions.

6. Rates of reaction

Evidence: Factors affecting rate; collision theory. Examiner reports note diffusion vs rate confusion.

Covers: factors affecting rate; collision theory; catalysts; graphs.

7. Atomic structure and periodic table

Evidence: Atomic structure, periodic table, Group properties. Foundation for many questions.

Covers: atomic structure; isotopes; periodic table; Group 1, 7, 0.

8. Energetics

Evidence: Exothermic, endothermic; bond energies. Examiner reports note calculation errors.

Covers: energy changes; bond enthalpy; calculations.

9. Chemical tests

Evidence: Cations, anions, gases. Practical and theory papers.

Covers: flame tests; cation and anion tests; gas tests.

10. States of matter and separation

Evidence: Separation techniques; particle model. Examiner reports note chromatography and burette errors.

Covers: separation techniques; particle model; purity.

Revision priority

Organic chemistry, mole calculations and bonding appear most often. Check common mistakes for examiner-reported errors.

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Sources: Edexcel past papers 2019–2025, examiner reports, specification.

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