Overview
Science revision feels infinite until you count what examiners actually repeat. Across Cambridge Biology, Chemistry, and Physics past papers from 2019–2025, certain topics dominate marks every series. This guide ranks them for A-Level (9700/9701/9702) and O-Level (5090/5070/5054) — then shows how to turn the list into marked practice.
Key takeaway: High-frequency topics are not predictions — they are where past-paper hours pay off fastest. Skip them at your own risk.
How this list was built
For Cambridge Cambridge past paper revision, we weighted:
- Frequency across June and November sessions
- Mark allocation on structured papers (not just MCQ)
- Examiner report “candidates found difficult” flags
- Syllabus weighting where published
Always confirm your exact syllabus code and year with your centre — see per-subject guides linked below.
A-Level Biology (9700)
For Cambridge Cambridge past paper revision, practise: One structured question per topic per week → mark with scheme → rewrite lost mark points in scheme wording.
| Priority | Topic | Why it repeats |
|---|---|---|
| 1 | Cell membranes & transport | Almost every Paper 2/4 — osmosis, active transport, water potential |
| 2 | Enzymes & kinetics | Graph interpretation, inhibitors, temperature/pH |
| 3 | DNA, replication & protein synthesis | Extended responses; precise terminology marked |
| 4 | Gas exchange & transport in plants/animals | Comparison questions; diagram labels |
| 5 | Immunity & disease | Vaccination, antibodies, HIV context questions |
| 6 | Photosynthesis & respiration | Multi-step pathways; limiting factors |
| 7 | Selection & evolution | Data interpretation from populations |
| 8 | Homeostasis | Blood glucose, thermoregulation, negative feedback loops |
Full guide: 9700 past papers.
A-Level Chemistry (9701)
For Cambridge Cambridge past paper revision, practise: Mole questions daily (10 min) + one organic mechanism drawn from memory each session.
| Priority | Topic | Why it repeats |
|---|---|---|
| 1 | Stoichiometry & mole calculations | Every paper; error cascades without ECF discipline |
| 2 | Organic mechanisms & synthesis | Curly arrows, reagents, isomerism |
| 3 | Equilibria & Kc/Kp | ICE tables, partial pressure reasoning |
| 4 | Electrochemistry & cells | E° calculations, electrode equations |
| 5 | Acids, bases & pH | Weak acid calculations, buffers |
| 6 | Periodicity & Group trends | Comparison of elements; data tables |
| 7 | Lattice enthalpy & Born-Haber | Cycle completion; sign errors common |
| 8 | Rates & catalysis | Maxwell-Boltzmann, mechanism steps |
Full guide: 9701 past papers.
A-Level Physics (9702)
For Cambridge Cambridge past paper revision, practise: Draw diagrams before equations — examiners reward clear setup (M marks).
| Priority | Topic | Why it repeats |
|---|---|---|
| 1 | Forces & Newton’s laws | Free-body diagrams; resultant force |
| 2 | Electricity & circuits | Kirchhoff, internal resistance, power |
| 3 | Waves & superposition | Phase, interference, standing waves |
| 4 | Fields (gravitational & electric) | Potential, field lines, comparative questions |
| 5 | Circular motion & SHM | Direction of acceleration; graph reading |
| 6 | Momentum & energy | Conservation laws; inelastic collisions |
| 7 | Ideal gases & thermodynamics | pV = nRT manipulations |
| 8 | Quantum & photoelectric effect | Threshold frequency, photon energy |
Full guide: 9702 past papers.
O-Level Biology (5090)
Guide: [5090 past papers](/blog/cambridge-5090-o-level-biology-past-papers-guide) · [5090 boundaries 2026](/blog/cambridge-5090-biology-grade-boundaries-2026).
| Priority | Topic | Notes |
|---|---|---|
| 1 | Enzymes | Graphs + denaturation explanations |
| 2 | Plant nutrition & transport | Xylem/phloem, transpiration |
| 3 | Human digestion & circulation | Multi-part structured Qs |
| 4 | Ecology & food webs | Energy transfer, pyramids |
| 5 | Reproduction & inheritance | Punnett-style reasoning |
| 6 | Disease & immunity | Vaccination, pathogens |
| 7 | Coordination & hormones | Reflex arc, homeostasis lite |
| 8 | Practical skills (Paper 6) | Variables, fair test, graph plotting |
O-Level Chemistry (5070)
Guide: [5070 past papers](/blog/cambridge-5070-o-level-chemistry-past-papers-guide) · [5070 boundaries 2026](/blog/cambridge-5070-chemistry-grade-boundaries-2026).
| Priority | Topic | Notes |
|---|---|---|
| 1 | Mole calculations & equations | Balancing, limiting reagent |
| 2 | Acids, bases & salts | Preparation, titration logic |
| 3 | Electrolysis | Products at electrodes — examiner favourite |
| 4 | Rates of reaction | Collision theory, graphs |
| 5 | Periodic table & bonding | Ionic vs covalent properties |
| 6 | Organic basics | Alkanes/alkenes, combustion |
| 7 | Metals & reactivity | Displacement series |
| 8 | Tests for ions & gases | Practical recognition |
O-Level Physics (5054)
Guide: [5054 past papers](/blog/cambridge-5054-o-level-physics-past-papers-guide) · [5054 boundaries 2026](/blog/cambridge-5054-physics-grade-boundaries-2026).
| Priority | Topic | Notes |
|---|---|---|
| 1 | Forces & motion | Speed-time graphs, Newton |
| 2 | Electricity | Ohm’s law, series/parallel |
| 3 | Waves | Reflection, refraction, sound |
| 4 | Energy & work | Efficiency, power |
| 5 | Thermal physics | Expansion, change of state |
| 6 | Magnetism & electromagnetism | Motors, generators basics |
| 7 | Radioactivity | Half-life calculations |
| 8 | Pressure & moments | Lever, liquid pressure |
The 4-week high-yield rotation (any science)
Cross-subject habits: [ECF in mark schemes](/blog/understanding-error-carried-forward-ecf), [practical papers](/blog/cambridge-practical-papers-revision-guide).
| Week | Mon–Wed | Thu–Fri | Weekend |
|---|---|---|---|
| 1 | Topic 1–2 drills | Half structured paper | Mark + error log |
| 2 | Topic 3–4 drills | Half structured paper | Rewrite worst Q |
| 3 | Topic 5–6 + practical | Full timed paper | Examiner report |
| 4 | Mixed synoptic | Full timed paper | Upload to MarkScheme |
What “most repeated” does not mean
This section covers What “most repeated” does not mean — ranked by what Cambridge examiners return to most often in past papers.
- Examiners can still surprise you on low-frequency topics
- Command words change how the same topic is marked — see command words guide
- Reading lists without marking builds false confidence
FAQ
No — cover the full syllabus once, then weight past papers toward these topics in the final month.
Should I only revise this table?
AS vs A2 — same topics?
AS papers emphasise foundations (cells, mechanics, stoichiometry). A2 adds synoptic depth — use AS vs A2 strategy.
IGCSE sciences instead?
See IGCSE most-tested topics for 0610/0620/0625 — with 0610, 0620, and 0625 boundary guides.