The Most-Tested Topics in IGCSE Chemistry (CIE 0620)
Every 0620 past-paper question, tagged to its syllabus topic — ranked by how often each is tested (2020–2025).
Core tier (Papers 1 / 3)
80 papers analysed · top 15 of 49 topics
| # | Topic | % of tier's questions | Questions | Avg marks |
|---|---|---|---|---|
| 1 | Identification of ions and gases | 8.6% | 164 | 9.7 |
| 2 | The characteristic properties of acids and bases | 7.6% | 145 | 10.9 |
| 3 | Air quality and climate | 7.1% | 135 | 9.7 |
| 4 | Formulae | 6.9% | 132 | 10.9 |
| 5 | Fuels | 5.7% | 108 | 10.2 |
| 6 | Solids, liquids and gases | 5.4% | 103 | 10.5 |
| 7 | Rate of reaction | 4.8% | 92 | 9.5 |
| 8 | Ions and ionic bonds | 4.7% | 90 | 9.5 |
| 9 | Electrolysis | 4.7% | 89 | 10.6 |
| 10 | Formulae, functional groups and terminology | 4.6% | 88 | 11.1 |
| 11 | Reactivity series | 4.3% | 83 | 10.8 |
| 12 | Redox | 4.2% | 81 | 10.8 |
| 13 | Exothermic and endothermic reactions | 4.1% | 78 | 10 |
| 14 | Atomic structure and the Periodic Table | 4% | 76 | 9.5 |
| 15 | Alkenes | 3.8% | 72 | 11.1 |
Extended tier (Papers 2 / 4)
80 papers analysed · top 15 of 49 topics
| # | Topic | % of tier's questions | Questions | Avg marks |
|---|---|---|---|---|
| 1 | Formulae | 6.7% | 122 | 14.1 |
| 2 | The mole and the Avogadro constant | 6% | 109 | 15.2 |
| 3 | Redox | 5.8% | 106 | 15 |
| 4 | Electrolysis | 5.4% | 99 | 14.7 |
| 5 | Reversible reactions and equilibrium | 5.3% | 96 | 14 |
| 6 | Polymers | 4.9% | 90 | 13.4 |
| 7 | Air quality and climate | 4.8% | 87 | 10.3 |
| 8 | The characteristic properties of acids and bases | 4.7% | 86 | 14.6 |
| 9 | Exothermic and endothermic reactions | 4.4% | 80 | 13.8 |
| 10 | Ions and ionic bonds | 4.4% | 80 | 13.2 |
| 11 | Oxides | 4.3% | 79 | 12.7 |
| 12 | Formulae, functional groups and terminology | 4.3% | 79 | 14.3 |
| 13 | Rate of reaction | 4.3% | 79 | 14.6 |
| 14 | Extraction of metals | 4.2% | 76 | 12.3 |
| 15 | Identification of ions and gases | 4% | 74 | 13.5 |
How this was measured
Based on OwlsPrep's database of official CIE 0620 past papers (2020–2025), 4012 questions each tagged to its syllabus topic. Topics are grouped by paper tier; “% of tier's questions” = the share of that tier's tagged questions testing the topic. Because one question can test several topics, shares do not sum to 100%. Figures are aggregate statistics from question metadata — no exam questions or mark schemes are reproduced.
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