Chemistry 0620 sits alongside Mathematics and Biology among the most-entered Cambridge subjects for Kenyan candidates, and its mark schemes are unusually consistent about where credit lives. Three habits, all fixable in the remaining weeks, separate the grades.
Balance with coefficients, never by editing a formula
Asked to balance H₂ + O₂ → H₂O, a losing script changes the water to H₂O₂. That is no longer water, and the question scores zero. Only the large numbers in front of a formula may change: 2H₂ + O₂ → 2H₂O. Candidates who understand that a subscript defines the substance stop making this error permanently.
Mole calculations: the working is the mark
| Step | Written line | Why it must appear |
|---|---|---|
| 1 | Mr of NaOH = 23 + 16 + 1 = 40 | An arithmetic slip later still earns this mark |
| 2 | moles = mass ÷ Mr = 20 ÷ 40 = 0.5 | The method mark attaches to the shown formula |
| 3 | ratio from the equation, then the answer with units | A bare number cannot collect partial credit |
The most common systematic loss is the volume conversion: concentration is per litre (per dm³), and a candidate who divides by 500 instead of 0.5 has thrown away the question. Write the conversion as its own line, every time.
Observation is what you see, conclusion is what you deduce
Practical and alternative-to-practical papers separate these ruthlessly. "Effervescence, and a colourless gas that turns limewater milky" is an observation. "Carbon dioxide is produced" is a conclusion. Write the conclusion in the observation column and the mark is gone, because the gas was never seen, it was inferred. The same discipline pays in the gas tests, which recur every series: hydrogen pops with a lighted splint, oxygen relights a glowing one, carbon dioxide turns limewater milky, ammonia turns damp red litmus blue, chlorine bleaches damp litmus.
This continues our November series set: Biology 0610, Mathematics 0580 and English 0500 are already live. Structured revision for the seven most-entered subjects is packaged in the IGCSE Countdown Bundle for November 2026, and live teaching runs through the IGCSE training programme.
Key Takeaways
- Balance equations with coefficients only; changing a subscript changes the substance.
- Mole questions are marked on the written method; convert volumes to litres on their own line.
- Observations are seen; conclusions are deduced. The columns are not interchangeable.
- The five gas tests recur every series and are close to guaranteed marks.
- Practise five papers strictly against the mark scheme rather than fifteen loosely.
Frequently Asked Questions
Core or Extended?
Grades above C require Extended. A candidate holding 60 per cent on Extended past papers belongs there.
Is the periodic table provided?
Yes, in every paper. Learning to read group and period information from it quickly is part of preparation.
How different is 0620 from CBC Integrated Science?
They are separate curricula, examined in different styles, and this site keeps their materials strictly apart. Revise each on its own terms.
What should the last two weeks look like?
Past papers under time, marked against the scheme the same day, with every dropped mark classified as content or technique and the technique list drilled directly.
IGCSE Revision Materials
Notes and topical questions for the core IGCSE subjects, timed to the Oct/Nov series.
⏳ Only 60 days to the national assessments on 26 October. Start now.
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