How to Get an A* in IGCSE Chemistry

An A* in IGCSE Chemistry 0620 is not won by knowing more facts. It is won by losing fewer marks, on three papers, on the same day-week. Most students who miss the A* by 5-10 marks knew the chemistry. They bled marks on technique.

What the A* actually requires

First, the route. The A* only exists on the Extended route: Paper 2 (MCQ), Paper 4 (theory) and Paper 5 or 6 (practical assessment). Core candidates sit Papers 1, 3 and 5/6 and are capped at a C. If you are unsure which route you are on, ask your school this week. The full breakdown is in our guide to Core vs Extended.

Second, the weighting. Paper 2 carries 30% of the grade, Paper 4 carries 50%, and Paper 5 or 6 carries 20%. That means consistency matters more than brilliance. A student who scores 90% on Paper 4 but 55% on Paper 6 lands an A. A student who scores 80%, 80% and 80% lands the A*. The exam rewards the candidate with no weak paper.

Third, the boundary. A* boundaries shift each series, but recent Extended sittings have sat around 70-80% of the weighted total. Your working target in mock conditions should be 85%. That buffer absorbs a hard paper, an examiner’s strict marking, or one bad question.

The high-yield skill list

Five skills decide the A*. Every one of them is teachable, and every one of them appears in essentially every Paper 4.

1. Mole calculations. The single biggest mark-loser in 0620. Reacting masses, gas volumes at r.t.p. (24 dm³ per mole), solution concentration, limiting reagents, percentage yield. Paper 4 typically carries 8-12 marks of mole work. Top candidates use one fixed method every time. We break it down step by step in mole calculations technique, and the underlying content lives in the Stoichiometry topic.

2. Electrolysis. Predicting products at each electrode, writing half-equations, explaining why concentrated and dilute solutions give different products. The Supplement detail in Electrochemistry, preferential discharge and the fuel cell, is classic A*-separator material.

3. Organic naming and reactions. Naming up to C4 compounds, drawing displayed formulae, knowing the reaction map: alkane → alkene (cracking), alkene → alcohol (hydration), alcohol → carboxylic acid (oxidation), acid + alcohol → ester. Organic Chemistry is the largest topic in the syllabus and Paper 4 reflects that.

4. Qualitative analysis. The cation, anion and gas tests must be word-perfect: “white precipitate, soluble in excess” earns the mark; “it goes cloudy” does not. These tests dominate Paper 6.

5. Six-mark extended responses. Paper 4 ends questions with 4-6 mark explain/describe tasks. A* candidates plan one mark-worthy point per sentence before writing. The named method is in our 6-mark technique guide.

How to past-paper properly

Doing past papers is not the same as doing them properly. The A* routine looks like this:

1. Timed, full paper, no notes. 45 minutes for Paper 2, 75 minutes for Paper 4. Phone in another room.
2. Mark it against the real mark scheme, harshly. If your wording does not match the scheme’s accepted answers, no mark. This is how the examiner treats you.
3. Log every dropped mark by cause. Three columns: didn’t know it, knew it but phrased it wrong, careless slip. After three papers the pattern is obvious, and for most students, fewer than half the lost marks are knowledge gaps.
4. Fix the cause before the next paper. A phrasing problem needs mark-scheme vocabulary drills, not re-reading the textbook.

Work through papers from 2021 onwards first: they match the current syllabus. Our full strategy, including which series to save for final mocks, is in how to use past papers.

Timeline by term

For a May/June candidate at a Malaysian international school, the A* calendar looks like this:

Year 10 (both terms). Master content as it is taught. Do not let mole calculations stay fuzzy past Term 1: everything quantitative builds on them. Start a single notebook of mark-scheme phrasings.

Year 11, Term 1 (Aug-Dec). Finish the syllabus content by December, including all Supplement material. Begin topic-level past-paper questions, not full papers yet. One Paper 6 per month from October. It is the paper schools prepare least.

Year 11, Term 2 (Jan-Mar). Full timed papers begin. One Paper 4 and one Paper 2 per week, marked and logged. Trial exams usually land in February or March; treat them as a full dress rehearsal.

Final 8 weeks (Apr-May). Pure exam mode: two full papers a week, error-log review, qualitative analysis tables drilled to recall. Follow the structure in our 8-week revision plan.

Worked exam question

A typical A*-separator from Paper 4:

Dilute aqueous copper(II) sulfate is electrolysed using carbon electrodes. Predict the product at each electrode and write the half-equation for the reaction at the anode. Explain why copper is not formed if the electrolysis is repeated with very dilute copper(II) sulfate replaced by dilute sulfuric acid. [5]

Model answer with mark breakdown:

• Cathode: copper is deposited [1]
• Anode: oxygen is given off [1]
• Anode half-equation: 4OH⁻ → O2 + 2H2O + 4e⁻ [1 for species, 1 for balancing including electrons]
• With dilute sulfuric acid there are no copper ions present, so hydrogen ions are discharged and hydrogen forms at the cathode [1]

Notice the precision: the half-equation mark splits into species and balancing. Writing “OH⁻ loses electrons” earns nothing.

The mistakes that cost marks

• Treating Paper 6 as an afterthought. It is 20% of the grade and has its own question style. See the Paper 6 guide.
• Vague colour and observation language. “Blue precipitate” for copper(II) hydroxide should be “light blue precipitate”. The scheme is literal.
• Skipping units and significant figures. A correct number with no unit drops the mark on most calculation lines.
• Revising by re-reading. Recognition feels like knowledge. Only closed-book recall and timed papers measure it.
• Ignoring command words. “Explain” answered with a description scores zero, even if every fact is correct.

How to phrase it for full marks

Student language: “The reaction is faster because the particles are hotter.” Mark-scheme language: “At a higher temperature, particles have more kinetic energy, so a greater proportion of collisions have energy above the activation energy, so there are more successful collisions per second.”

The difference is not intelligence. It is trained vocabulary. Every explain-question answer should name the particle-level cause, the mechanism, and the measurable effect, in that order.

Worried that fixing all this alone is unrealistic? That is the honest case for a specialist. Every tutor on our team teaches 0620 only, and the free 1-hour trial lesson is a real taught lesson: your child works a past-paper question with a specialist before you pay anything. No forms. WhatsApp us and we reply the same day.

The Malaysia note

Most Malaysian international schools enter capable students for Extended by default, and most sit the May/June series, with Oct/Nov used for retakes or accelerated candidates. The pattern we see locally: students are strong on recall (school drilling works) but lose the A* on Paper 6 and on explain-question phrasing, because school marking is more forgiving than Cambridge marking. Fixing those two areas is usually worth a full grade.