How to get an A or A* in Cambridge IGCSE Chemistry (0620)

Connect visible changes to particle explanations

For each reaction you revise, make a three-column note: observation, chemical explanation and equation. A colour change is an observation. Naming the substance formed is an interpretation. Keep those roles separate so you answer the exact question asked.

Use particle diagrams to explain bonding and structure rather than treating diagrams as decoration. When discussing properties, identify the particles, the forces between them and what must happen for melting or conduction. Avoid calling every substance a collection of molecules.

Make equation writing a daily habit

Write formulas correctly before balancing an equation. Balance by changing coefficients, not by changing the chemical identity of a substance. Check atoms on both sides and, for ionic equations, check the total charge as well.

Practise moving from a word description to a symbolic equation. Include state symbols when the task requires them. A short routine of several equations can expose weak knowledge more quickly than rereading an entire chapter on reactions.

Use a consistent route through mole questions

Begin with the balanced equation, then identify what you know and what you need. Convert the given amount into moles, apply the stoichiometric ratio and convert to the requested quantity. Write each stage so you can see where a mistake entered.

Keep units visible, particularly when using concentration and volume. A number of cubic centimetres cannot be substituted as if it were the same number of cubic decimetres. Finally, ask whether the mass or volume you calculated is reasonable for the amount of reactant available.

Learn practical reasoning through decisions

For a separation or preparation question, ask which property makes the method work. Filtration separates an insoluble solid from a liquid; crystallisation can recover a dissolved solid. Choosing the apparatus is easier when you understand the property being used.

In rate investigations, identify the changed factor, the measured outcome and the controls. Describe a measurable endpoint. For qualitative tests, practise the reagent, the expected observation and the conclusion together, using the official syllabus to decide which tests you need.

Turn marking into a targeted revision task

When an answer loses marks, classify the problem: inaccurate chemistry, incomplete explanation, arithmetic or misunderstood command word. Repair one category at a time. For example, if explanations stop too early, practise completing the chain from a structural feature to the observed property.

Use Extended questions if you are aiming for A or A*. Mix multiple-choice, structured and practical-style work rather than relying on one favourite paper. Choose current specimen materials when a syllabus update makes older questions less representative.

Common mistakes—and how to fix them

Your four-week revision plan

Use this as a focused revision cycle alongside your lessons. If you are still learning the course, give unfamiliar topics more time before attempting full papers.

1. Week 1

   Map understanding

   • Audit particles, bonding and reaction knowledge.
   • Build observation–explanation–equation notes for weak topics.
2. Week 2

   Secure calculations

   • Practise formulas, balanced equations and mole ratios.
   • Check concentration-volume conversions and annotate every unit.
3. Week 3

   Work like an investigator

   • Choose separation methods by the properties involved.
   • Practise qualitative tests and fair rate investigations.
4. Week 4

   Rehearse complete answers

   • Attempt a timed Extended paper and practical-style questions.
   • Redo errors and explain the corrected chemistry without notes.

Your questions, answered