IGCSE Chemistry 0620 — A Kenyan Student's Method To Score An A*

IGCSE Chemistry 0620 has a reputation among Kenyan students: it punishes anyone who studied only theory and never picked up a beaker. The practical-heavy structure (Paper 6, the alternative-to-practical) and the lab-reasoning sprinkled through Paper 4 mean candidates who memorised reactions without thinking about why they happen get caught out. Here is the method that produces repeated A* candidates in Kenyan IGCSE classrooms.

The three papers — and which one wins or loses A*

Extended tier is the only route to A*. Three papers:

• Paper 2 (multiple choice, 45 min, 40 marks) — pure pattern recognition. The fastest to score on if you have drilled enough past papers.
• Paper 4 (theory, 1h 15min, 80 marks) — structured questions. This is where A* is won. Half the marks are calculation, half are explanation. Most candidates underperform on the explanation marks because they treat them as factual recall instead of cause-and-effect reasoning.
• Paper 6 (alternative to practical, 1 hour, 40 marks) — paper-based but tests practical understanding. THIS is where most Kenyan candidates lose A*. If your school's lab is under-equipped, you have to compensate by doing every past Paper 6 you can find.

A* needs roughly 85% overall (boundary shifts slightly session to session). At Extended, that means you can drop at most about 25 marks across all three papers.

The Cambridge command words for Chemistry

Read these once. Then read them again. Then practise spotting them in past papers:

• State — one short fact. No working. One mark, one line.
• Describe — observed features only. What you would see, hear, feel. NOT why.
• Explain — describe AND give the reason. The reason mark is half the marks; if you skip "because…" you lose half.
• Suggest — Cambridge accepts any plausible chemistry that fits. Wider acceptance than "state" but must be chemistry.
• Compare — both similarities AND differences. Most candidates only give differences and lose 50% of the marks.
• Calculate — show working. Method mark (M1) + answer mark (A1) + unit. Skip the unit, lose a mark every time.
• Determine — calculate from given data (usually a graph or table). Show how you used the data.

The four strands of Chemistry 0620 (and where marks live)

The Cambridge syllabus organises Chemistry 0620 into broad areas. Roughly where marks live in the typical paper:

• States of matter, atomic structure, bonding — about 20% of marks. High-yield because it underpins everything else.
• Stoichiometry and quantitative chemistry (moles, calculations) — about 20%. The calculation backbone. Every IGCSE Chemistry calculation goes back to moles.
• Chemistry of the elements (acids/bases/salts, metals/reactivity, group I/VII trends) — about 30%. Easy marks if you memorised the reactivity series and ion colours; brutal if you didn't.
• Organic chemistry (alkanes, alkenes, alcohols, polymers) — about 15%. Specific and rule-based; high-leverage if you nail it.
• Air, water, electrochemistry, environmental chemistry — about 15%. Often tested as application or environmental questions in Paper 4.

The five mistakes that kill A* candidates

1. Ion colours and reactions memorised wrong

Examiners love testing test-tube reactions. You should know cold: Cu²⁺ is blue, Fe²⁺ is green, Fe³⁺ is yellow/brown, Cl⁻ + Ag⁺ gives white precipitate, SO₄²⁻ + Ba²⁺ gives white precipitate. Write these on a flashcard. Drill them daily.

2. Mole calculations without writing the balanced equation first

Every Chemistry calculation question starts with the balanced equation. If you don't write it down, you have no mole ratio, and your calculation is guessing. Always: balanced equation first, then moles of known, then mole ratio, then moles of unknown, then mass/volume/concentration of unknown.

3. Skipping units on calculation answers

Cambridge reserves a separate B1 mark for the unit. "5.2" earns the calculation mark but loses the unit mark. "5.2 g" or "5.2 mol/dm³" earns both. A* candidates simply never lose unit marks.

4. Confusing oxidation and reduction

OIL RIG (Oxidation Is Loss, Reduction Is Gain) of electrons. Every electrochemistry question rewards candidates who confidently identify what is being oxidised and what is being reduced. Get this wrong and you blow half the electrolysis questions.

5. Practical paper (Paper 6) treated as an afterthought

If you only start Paper 6 prep two weeks before the exam, you will fail it relative to your potential. Begin Paper 6 practice 12 weeks out. Doing one Paper 6 per week teaches you HOW Cambridge phrases practical questions — that pattern bleeds into Paper 4 as well.

The 12-week A* schedule

Weeks 1–3: Strand audit. Print the official 0620 syllabus from cambridgeinternational.org. Go through each sub-strand and self-rate "strong / shaky / blank". Spend three weeks pulling "blank" up to "shaky".

Weeks 4–6: Paper 6 weekly. One Paper 6 per week, marked with the official mark scheme. This builds your practical reasoning early.

Weeks 7–9: Paper 4 weekly. One full Paper 4 per week, timed, marked. For every lost mark, write a single line in a notebook on WHY (forgot units / misread question / missing balanced equation / confused oxidation).

Weeks 10–11: Paper 2 MCQ intensity. Three Paper 2s per week. Pattern recognition kicks in.

Week 12: Sleep, light review. No new learning. Re-read your "why I lost marks" notebook. Sleep eight hours every night.

How CBCEduKenya supports IGCSE Chemistry 0620

We publish a full Chemistry 0620 revision pack — 13 pages, 8 syllabus-aligned strands, 40 multiple-choice questions (Paper 2 style), 24 short-answer questions (Paper 4 style), complete mark scheme with M1/A1/B1 notation. KSH 200 standalone, or part of the KSH 700 Complete Cambridge Revision Bundle (all 7 core IGCSE subjects, 95 pages).

Start your A* method today.
→ IGCSE Chemistry 0620 Revision Pack — KSH 200
→ Complete Cambridge Revision Bundle (all 7 subjects, 95 pages) — KSH 700
→ Free Smart Flashcards — Cambridge-aligned, tap to flip.
→ Ask Somo on WhatsApp — step-by-step working in English.

Sources: Cambridge International IGCSE Chemistry 0620 syllabus 2025-2027; published examiner reports and mark schemes (multiple sessions); teaching observation in Nairobi IGCSE classrooms. Last updated: June 2026.