Chemistry is one of the most rewarding subjects to revise, because a small set of skills comes up again and again. These ten tips come from years of teaching Cambridge IGCSE Chemistry (0620) and O Level Chemistry (5070).
1. Make the mole your daily habit
Stoichiometry appears across almost every paper. Do three mole calculations every day, always writing the formula (moles = mass ÷ Mr, moles = concentration × volume, moles of gas = volume ÷ 24 dm³ at room temperature and pressure) before substituting numbers. Method marks are awarded even when the final answer is wrong.
2. Balance equations with state symbols
Examiners often reserve a mark for state symbols. Write (s), (l), (g) and (aq) every time in practice, so you never forget them in the exam.
3. Learn ion tests as a table
Tests for cations, anions and gases are free marks if you know them exactly. Make one table with the reagent, the observation and the result, and test yourself until you can reproduce it from memory.
4. Draw the reactivity series and use it
Displacement reactions, extraction of metals and electrolysis products all depend on it. When you meet a new question, first ask: which element is more reactive?
5. Treat electrolysis as a set of rules
- Positive ions go to the cathode; negative ions go to the anode.
- At the cathode, the less reactive of the metal and hydrogen is discharged.
- At the anode, halide ions are discharged if concentrated; otherwise oxygen is produced from aqueous solutions.
- Write half-equations for every electrolysis question you practise.
6. Build an organic chemistry map
Put alkanes, alkenes, alcohols, carboxylic acids and esters on one page, with arrows showing each reaction, its conditions and its reagent. Most organic questions are simply a route across this map.
7. Use mark scheme wording for definitions
Definitions like isotope, relative atomic mass, oxidation and catalyst are marked on key phrases. Learn them from the mark scheme, not from memory of a textbook paragraph.
8. Don't skip the practical paper
Alternative to Practical (and the practical test) rewards the same skills every year: reading apparatus correctly, drawing results tables with units, plotting best-fit graphs, and suggesting sources of error and improvements. Two or three papers of practice make a big difference.
9. Show working on every calculation
Write every step, include units, and give answers to the number of significant figures in the question. It protects your marks when something goes wrong midway.
10. Do topical past papers, then timed papers
Follow the two-stage approach in our past papers guide: topic-wise practice first, then full timed papers in the last three months.
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Frequently asked questions
01What is the hardest topic in IGCSE Chemistry?
Most students find stoichiometry (mole calculations) the hardest, followed by electrolysis and organic chemistry. All three improve quickly with daily worked practice.
02How do I get an A* in O Level Chemistry?
Master the definitions and tests word for word, practise calculations daily, do topical past papers for every topic, and sit full timed papers in the final three months, fixing every lost mark.
03Is Alternative to Practical hard?
It is very predictable once you have practised it. The same skills come up every year: reading apparatus, recording results in tables, plotting graphs, identifying errors and suggesting improvements.
