Improving from B to A* in IGCSE Chemistry

A B grade means you know most of the chemistry. You score well on factual recall, you can do basic calculations, and you handle the predictable question types competently. Yet the A* threshold sits 20-30 marks above you, and those marks feel invisible. Where are they?

They are in three places: the errors you still make on questions you should get right, the questions you partially answer instead of fully answering, and the hardest questions you skip or guess on. Moving from B to A* is not about learning new content. It is about refining how you deploy what you already know.

The three differences between B and A*

1. Precision under pressure

B-grade students lose 10-15 marks per paper on questions they actually know. The errors are not knowledge gaps — they are precision errors:

• Writing “atom” when the answer is “ion”
• Forgetting state symbols in equations that require them
• Giving one mark point on a two-mark question
• Missing the word “excess” in a salt preparation answer
• Writing an unbalanced equation when the balanced version was within reach

Each individual error seems minor. Collectively, they account for the entire gap between B and A*.

The fix: Ruthless error logging. After every past paper, categorise every lost mark as either “did not know” or “knew but lost due to precision.” A B-grade student will find that “knew but lost” accounts for 40-60% of their lost marks. Target these specifically.

Create a personal “precision checklist” of your most common errors. Before submitting any past paper answer, scan it against the checklist. After a few weeks, the checklist becomes automatic and the errors stop.

2. Complete answers on high-mark questions

B-grade students tend to score 3-4 marks on 6-mark questions. They know enough to start the answer but do not deliver all six mark points. The missing points are usually:

• The second half of an explanation (they state the fact but do not explain why)
• Specific examples or equations that the mark scheme requires
• The conclusion or evaluation at the end of a six-mark extended response

The fix: Before writing any answer worth 4 or more marks, plan it. Write a brief list of the points you will make, one per mark. Count them: “This is a 6-mark question and I have listed 6 points.” Then write the answer, making sure each point is clearly stated.

Study the mark scheme for high-mark questions across multiple sessions. Notice the structure: what the first mark rewards, what the second rewards, and so on. High-mark questions follow patterns, and once you see the pattern, you can produce a full answer reliably.

3. Scoring on the hardest questions

Every Paper 4 contains two or three questions that the majority of students get wrong. These are the questions that separate A from A*:

• Unfamiliar contexts where you must apply known principles to new situations (e.g., predicting the properties of a substance you have never studied based on its bonding type)
• Multi-step calculations with unusual data (e.g., back-calculating the percentage purity from a titration result)
• Suggest questions where there is no single “correct” answer but the reasoning must be sound
• Questions that require linking two or three topics together (e.g., explaining an industrial process using equilibrium, energetics, and economics)

B-grade students skip these or give superficial answers. A* students attempt them systematically.

The fix: Practise unfamiliar-context questions specifically. Collect “suggest” and “deduce” questions from past papers. Work through them slowly, without time pressure, and read the mark scheme afterwards to understand the examiner’s expected reasoning. The reasoning is always based on principles you know — the challenge is recognising which principles apply.

See our guide on linking chemistry topics together for building the cross-topic thinking these questions demand.

The A* revision routine

Daily (30 minutes)

• 10 minutes: Flashcard review. At B level, most factual content is secure. Focus flashcard time on the facts you still get wrong: obscure observations, exact definitions, and equations you confuse.
• 20 minutes: Three to five targeted questions. These should be from your weak areas, not your strong ones. Include at least one 4-6 mark structured question per session. Mark against the scheme and log every lost mark.

Weekly (90 minutes)

• One full timed Paper 4 under exam conditions. Mark meticulously. Your target is 65+ out of 80 (roughly 80%+). Track the trajectory across weeks.
• Analyse the marked paper: separate “knew but lost” marks from “did not know” marks. This analysis takes 15 minutes and is the most valuable part of the exercise.

Fortnightly

• Re-sit every question you scored below full marks on, two weeks after the original paper. This tests whether you have actually fixed the error or just noted it.
• Do a Paper 2 under timed conditions. At A* level, aim for 36-38+ out of 40. MCQ errors at this level are usually caused by misreading the question, not by lack of knowledge. See the Paper 2 time management guide.

Topic areas that carry A* marks

Stoichiometry (extended calculations)

Percentage yield, percentage purity, empirical and molecular formulae, gas volume calculations. These are heavily tested and often poorly answered. Master the five-step method until it is automatic.

Organic chemistry (extended content)

Ester formation, polymer types, isomers, and the reaction map connecting homologous series. See the organic chemistry study guide.

Electrochemistry (aqueous electrolysis predictions)

Predicting products at each electrode using the reactivity series and the halide rule. The electrochemistry study guide covers the decision rules.

Equilibrium and industrial processes

The Haber process, the Contact process, and the reasoning behind compromise conditions. The chemical reactions study guide covers the required explanations.

Paper 6 technique

A* students do not treat Paper 6 as an afterthought. Strong Paper 6 performance lifts the overall grade. Focus on graph-drawing precision (correct scales, accurately plotted points, smooth best-fit curves) and errors and improvements.

The mindset difference

B-grade students revise until they can answer most questions. A* students revise until they rarely get anything wrong. The difference is not ability — it is the willingness to drill the last 15% of precision.

A* also requires accepting that some past paper scores will be disappointing. A paper with harder questions might drop you to 60/80 when you expected 70/80. This is normal. The A* student analyses the errors and fixes them. The B-grade student gets discouraged and stops practising.

Track your scores over time, not paper by paper. A rising trend from 55 to 60 to 65 to 68 across four papers is more meaningful than any single score. If the trend is upward, you are on the right path. Keep going.