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IGCSE Chemistry 0620 Paper 3: Equations, Ions and Redox
Chemistry: balance first, then the state symbols
Paper 3 is short answers and structured questions on the Core syllabus. The marks are not in volume but in three habits: balance the equation, count ion electrons as protons plus or minus the charge, and keep oxidation and reduction straight (OIL RIG). State symbols and units are the cheapest marks on the paper.
How is IGCSE Chemistry 0620 Paper 3 assessed, and what does each part carry?
Paper 3 (Theory, Core): Short-answer and structured, 80 marks (50%); Paper 1 (Multiple Choice, Core): 40 four-option items, 40 marks (30%)
Assessment at a glance (2027)
| Component | Content | Weighting | Duration |
|---|---|---|---|
| Paper 3 (Theory, Core) | Short-answer and structured, 80 marks | 50% | 1 h 15 min |
| Paper 1 (Multiple Choice, Core) | 40 four-option items, 40 marks | 30% | 45 min |
IGCSE Chemistry Paper 3 drilling technique: balance equations; ion electrons = protons ± charge; oxidation is loss, reduction is gain (OIL RIG); ionic compounds melt high because ionic bonds are strong.
What each paper is actually testing
| Paper | Drill focus | How marks are lost |
|---|---|---|
| Paper 3 (Theory, Core) | equations + explanation | The equation is left unbalanced, and the equation mark goes even when the products are right. |
| Paper 1 (Multiple Choice, Core) | core content only | Ion electrons are miscounted (11 for Na+) or oxidation and reduction are reversed (oxidation treated as gain). |
What is each IGCSE Chemistry 0620 Paper 3 paper really testing, and what should you drill?
Paper 3 (Theory, Core): equations + explanation; Paper 1 (Multiple Choice, Core): core content only
Drill order: by topic, then by year, then the mark scheme
| Step | What you do | Why |
|---|---|---|
| 1. By topic | Work through each topic, starting with the paper that allows least help (no calculator / closed book) | Exposes what is genuinely not understood |
| 2. By year | Whole papers to time, one or two a week | Trains pace, stamina and question selection |
| 3. Mark scheme | Go through the marking scheme question by question and log the scoring steps you missed | Most lost marks are written wrong, not thought wrong |
Should drilling go by topic first or by year?
By topic first, then whole papers by year, then the mark scheme. The first third of the time goes topic by topic (8-10 years of the same topic back to back), the middle switches to timed whole papers, and the last fortnight only redoes the recurring errors from your log.
A 12-week drilling timetable
| Week | Phase | What to do |
|---|---|---|
| Weeks 1-3 | By topic: foundation | Topic by topic, starting with the easiest marks, building habits and recall |
| Weeks 4-6 | By topic: core | 8-10 years of the same topic back to back, errors classified by topic |
| Weeks 7-8 | By topic: advanced and electives | Elective and higher-order topics, now under time pressure |
| Weeks 9-10 | By year: timed papers | One full paper a week, timed, no reference materials |
| Week 11 | Mark scheme work | Question by question against the marking scheme; list the scoring steps you omitted |
| Week 12 | Plug holes and simulate | Only the recurring errors from your log, then one full exam simulation |
Subject-specific weighting for this timetable: Weeks 1-3: equations and moles. Five equations a day, counting atoms and charge on both sides immediately.
Weeks 4-6: ions and electrolysis. Protons, electrons and charge for each ion, then predict the electrode products.
Weeks 7-9: redox and acids. Label what is oxidised and what is reduced, then write the half equations.
Weeks 10-12: whole papers to time; redo only the unbalanced equations and the miscounted electrons, adding the state symbols.
Use it properly: this is not a checklist to finish. Every week must keep time for redoing errors, or from week 9 you will be repeating the same batch.
Pacing
| Paper | Time | Suggested split |
|---|---|---|
| Paper 3 (Theory, Core) | 1 h 15 min | about 9 min per question |
| Paper 1 (Multiple Choice, Core) | 45 min | about 68 s per question |
How should the time be split inside each IGCSE Chemistry 0620 Paper 3 paper?
Paper 3 (Theory, Core): about 9 min per question; Paper 1 (Multiple Choice, Core): about 68 s per question
The drilling mistakes that cost the most marks
| Mistake | What it looks like | What actually happens | Instead |
|---|---|---|---|
| Ion electron count | Na+ with 11 electrons | Na+ has 10 after losing one | 10 |
| Unbalanced equation | Miss coefficients | Check atoms on both sides | balanced |
| Redox reversed | Oxidation = gain | Oxidation = loss (OIL RIG) | loss |
The error log and the mark scheme
Three columns: the equation or value as written, the scheme key words (balanced, electron count, OIL RIG, state symbols), and which one was missing. Missing state symbols deserve their own tally – they are treated as trivial and lost again and again.
How many years should you drill?
The current Paper 3 is Core content, and older papers use different syllabus codes and wording, so do not drill them wholesale. Three to five years of current papers set the shapes, then the official specimen covers newer content.
How many years of past papers is enough?
The current Paper 3 is Core content, and older papers use different syllabus codes and wording, so do not drill them wholesale. Three to five years of current papers set the shapes, then the official specimen covers newer content.
Frequently asked questions
Is this page a mock paper or a drilling guide?
This is the IGCSE Chemistry 0620 Paper 3 drilling guide: assessment structure, drill order, a 12-week timetable, pacing, common mark losses and the error-log method. For questions with answers, use the IGCSE Chemistry 0620 Paper 3 mock papers linked under Related.
By topic or by year first?
By topic. Eight to ten years of the same topic back to back is what exposes repeating errors; going straight to whole papers just repeats the same batch under time pressure.
How should the error log be written?
Do not copy out questions. Per error record four things: question reference, which step failed (concept, wording, calculation), what the mark scheme requires, and the correct action next time.
Are state symbols always required?
When the question asks for them, which is usual for ionic and thermochemical equations, they carry their own mark. Write them in the draft so nothing is dropped on the fair copy.
Do calculations need working?
Yes. The method marks for moles, concentration and titration sit in the steps – moles, ratio, units – and a bare final answer earns only the answer mark.
Official references
| Resource | What to use it for |
|---|---|
| Cambridge IGCSE Chemistry 0620 page | Confirm the paper marks and times |
| https://www.tutorzone.com.hk/en-igcse-chemistry-0620-paper-1-mock-2027/ | IGCSE Chemistry Paper 1 drilling mock |
Related: practice area · IGCSE Chemistry Paper 2 drilling mock
Next step: find a tutor / register as a tutor
After drilling, the hard part is telling a conceptual error from a writing error. Tell us the year group, the school and your available times, and TutorZone will match you with a tutor who knows the HKEAA assessment requirements.
Demand for tutors in this subject is steady, and those who can explain the marking scheme and where marks are won are especially sought after. Register free; you pay only when a match succeeds.