OCR A-Level Chemistry revision: H432 modules, papers and the plan
OCR A-Level Chemistry A (H432) is taught as six modules and examined in three papers: Paper 1 'Periodic table, elements and physical chemistry' (2h15, 100 marks) covers modules 1, 2, 3 and 5, Paper 2 'Synthesis and analytical techniques' (2h15, 100 marks) covers modules 1, 2, 4 and 6, and Paper 3 'Unified chemistry' (1h30, 70 marks) is synoptic across everything. Revision should be organised by module, then train the connections for the synoptic paper.
OCR chemistry's module system is the tidiest of the three boards — six modules, two big content papers, one short synoptic paper. The trap is assuming the papers respect the module boundaries. They do not, and Paper 3 ignores them on purpose.
The specification, in plain English
| Module | Content | Where it's examined |
|---|---|---|
| 1. Practical skills | Planning, implementing, analysis, evaluation | All papers |
| 2. Foundations | Atoms, bonding, moles, acids, redox | Papers 1 & 2 |
| 3. Periodic table & energy | Periodicity, groups, enthalpy, kinetics, equilibria | Paper 1 |
| 4. Core organic | Basic organic, alcohols, haloalkanes, synthesis, analysis | Paper 2 |
| 5. Physical & transition metals | Rates, equilibria, pH, energetics, transition metals | Paper 1 |
| 6. Organic & analysis | Aromatics, carbonyls, amines, synthesis, spectroscopy | Paper 2 |
| Paper | Modules | Time | Marks | Weight |
|---|---|---|---|---|
| Paper 1 — Periodic table, elements & physical | 1, 2, 3, 5 | 2h 15m | 100 | 37% |
| Paper 2 — Synthesis & analytical techniques | 1, 2, 4, 6 | 2h 15m | 100 | 37% |
| Paper 3 — Unified chemistry | All, synoptic | 1h 30m | 70 | 26% |
The Unified paper
Paper 3 is 70 marks in 90 minutes covering everything — synoptic by design, so a question can open in organic chemistry and close in kinetics. The preparation is different from the content papers: not module revision but connection revision, practising questions that deliberately cross the boundaries you revised within.
Worked questions in the OCR style
A reaction is first order in A and second order in B. Write the rate equation and state the overall order.
- Rate equation: rate = k[A]¹[B]².
- Overall order is the sum of the powers: 1 + 2 = 3.
- Units of k come from rearranging: k = rate/([A][B]²) → mol⁻² dm⁶ s⁻¹.
- The units question follows every rate equation — derive it rather than memorising it.
rate = k[A][B]², third order overall, k in mol⁻² dm⁶ s⁻¹.
Explain how the structure of a transition metal complex relates to its colour, using an example.
- The d-orbitals split in the ligand field — the gap corresponds to a visible-light frequency.
- The complex absorbs the complementary colour and reflects/transmits what we see.
- Example: [Cu(H₂O)₆]²⁺ is blue — it absorbs orange light.
- Changing the ligand changes the split and the colour — that is why ligand exchange changes colour.
- The synoptic reach: electronic structure, d-orbitals, ligands and spectroscopy in one answer.
d-orbital splitting → selective absorption → complementary colour. Paper 3 wants the full chain.
Common OCR mistakes
- Treating Modules 1 and 2 as done — they are on both content papers and carry the heaviest weight.
- Revising modules in isolation — Paper 3 specifically rewards connections.
- Rate equation units memorised instead of derived — they change with the orders.
- Mechanisms with arrows from charges instead of lone pairs.
- Practical questions answered from memory, not from the method asked about.
Your OCR checklist
- I have revised each module and know which paper covers it.
- Modules 1 and 2 are secured first — they are on both content papers.
- I have done at least two Unified papers and can answer cross-module questions.
- I can derive rate-equation units from the orders, not memorise them.
- I can draw every mechanism with correct curly arrows.
- I have done timed sections for all three papers including the 1h30 Paper 3.
OCR's Unified paper tests the connections the module structure hides — and those have to exist before the exam asks. If your modules still feel like separate subjects, ask Lumi to question you across them: 'how does what you know about equilibrium connect to what you know about acids?' That is the paper's real demand.
What to take from this
- Paper 1 = modules 1, 2, 3, 5 (inorganic + physical); Paper 2 = modules 1, 2, 4, 6 (organic + analytical).
- Module 1 practical skills and Module 2 foundations are on both content papers — highest value.
- Paper 3 is short (70 marks, 1h30) and synoptic — it rewards connections over depth.
- *-marked questions assess quality of extended response.
- OCR mark schemes reward precise mechanisms and named concepts.
Questions people also ask
Paper 3 — a 70-mark, 90-minute synoptic paper covering the whole course. Questions deliberately cross module boundaries and reward connecting ideas over deep recall of one topic.
Modules 1 (practical skills) and 2 (foundations) — they are examined on both content papers, so they carry more weight than any single content module.
No — but there is a practical endorsement, a separate pass/fail on lab skills. Module 1's practical content is examined on the written papers as method and analysis questions.
Same content, different structure. OCR has longer content papers and a short synoptic paper; AQA has a dedicated MCQ section. Students who prefer clearly-organised content often prefer OCR's module system.