IGCSE Chemistry Revision Guide: Topics and Exam Tips

IGCSE Chemistry punishes vague language more than almost any other subject. Two students can understand ionic bonding equally well and score three marks apart, because one wrote "because it's stronger" and the other wrote "because of the strong electrostatic attraction between oppositely charged ions in a giant lattice."

That's the whole game. This guide covers the highest-yield topics, the precise language each demands, how to handle practical questions, and the mistakes that quietly cost grades.

High-frequency IGCSE Chemistry topics

These appear in almost every paper. If your revision time is limited, it belongs here:

Atomic structure and bonding — ionic, covalent and metallic; dot-and-cross diagrams; linking structure to properties
Stoichiometry — moles, reacting masses, concentration, limiting reagents
Electrolysis — products at each electrode, half equations, the effect of electrolyte concentration
Acids, bases and salts — neutralisation, titration, the salt-preparation routes
Organic chemistry — alkanes, alkenes, alcohols, carboxylic acids, addition vs condensation polymers
Energetics — exothermic and endothermic, energy profile diagrams, bond energy calculations
Rates of reaction — collision theory, catalysts, interpreting rate graphs
The Periodic Table — group trends and the reasoning behind them

Group 1 and Group 7 trends are worth singling out. Examiners want the explanation — more shells means the outer electron sits further from the nucleus and is more shielded, so it's lost more easily — not just the observation that reactivity increases down the group.

The language that earns the marks

Chemistry mark schemes are strict about vocabulary. These are the swaps that most often decide a grade:

Common phrasing	What earns the mark
"It's stronger"	"Strong electrostatic attraction between oppositely charged ions"
"The particles move faster"	"The particles have greater kinetic energy"
"More collisions"	"A greater proportion of collisions exceeds the activation energy"
"It dissolves"	"It is soluble in water, forming aqueous ions"
"Weak bonds between molecules"	"Weak intermolecular forces — the covalent bonds themselves are strong"

That last one is the most common conceptual error in the subject. When simple molecular substances melt, you overcome intermolecular forces, not covalent bonds. Examiners look for it specifically.

Command words that decide your grade

State / Name — short and factual. No explanation needed, and adding one wastes time.
Describe — say what happens, step by step. No causes.
Explain — give the reason, linking structure to property. If you can't fit "because" into your answer, you haven't explained.
Suggest — apply what you know to an unfamiliar context. There's no memorised answer, and blank is the only wrong response.
Calculate — show working, include units, round sensibly. Method marks live here.

Practise writing one paragraph per command word from memory, then check the structure against a mark scheme. Our IGCSE command words guide covers what each demands across every subject.

Calculations: where marks leak

Stoichiometry is the most reliably examinable part of the course, and the most reliably fumbled.

Always show the mole step. Even when you can see the answer, writing out moles = mass ÷ Mr banks a method mark if the arithmetic later goes wrong.
Watch significant figures. Match the precision of the data you were given, unless told otherwise.
Units are marks. g, dm³, mol/dm³ — an unlabelled number is an incomplete answer.
Balance the equation first. A ratio error early destroys everything downstream, and no method mark survives it.

Practical and alternative-to-practical skills

Even if you don't sit a practical exam, practical understanding is examined. Cambridge Paper 6 questions typically test:

Reading and labelling apparatus diagrams
Spotting errors or hazards in a described method
Interpreting data tables and drawing best-fit lines
Suggesting improvements — usually repeating readings, controlling a variable, or improving measurement precision
Naming the right equipment for a required precision (measuring cylinder vs pipette vs burette)

Work through Paper 6 questions even if you aren't entered for the practical component. They're some of the best-value revision in the subject, because the reasoning transfers directly to the theory papers.

An eight-week past paper plan

Week	Focus
1–2	Topical questions: bonding, structure, the Periodic Table
3–4	Stoichiometry and calculations — accuracy over speed
5	Electrolysis, acids and salts
6	Organic chemistry and energetics
7	Practical-style questions (Paper 6 format)
8	Full timed papers plus mark scheme review

Mark harshly. If your wording doesn't match the mark scheme's, it's wrong — that's the entire point of the exercise. See our past papers guide for the full method, including the error log that turns marking into a revision plan.

Common mistakes

Vague explanations that never link structure to property
Missing state symbols in equations — (s), (l), (g), (aq)
Forgetting units, or losing them halfway through a calculation
Not drawing a diagram when the question clearly wants one
Confusing intermolecular forces with covalent bonds
Writing "reacts" where the mark scheme wants the product named
Describing when the question said explain

Core vs Extended

Check which tier you're entered for before you revise. Extended covers additional content and accesses the higher grades, while Core is capped — revising Extended-only material for a Core paper is wasted time, and the reverse leaves gaps. Confirm with your teacher, and if you're unsure which board you sit, Edexcel vs Cambridge IGCSE covers the differences.

Frequently asked questions

Which IGCSE Chemistry topics come up most? Bonding and structure, stoichiometry, electrolysis and rates appear in some form on almost every paper. If you're short on time, secure those four before touching anything else — they also underpin the harder questions elsewhere.

Do I need to memorise the Periodic Table? No — you're given one. What you do need is fluency in reading it: proton number, relative atomic mass, group and period, and what those imply about electronic configuration and reactivity.

How do I stop losing marks on explain questions? Force the word "because" into your answer. If it doesn't fit, you've described rather than explained. Then check the mark allocation and make sure you've given that many distinct reasons rather than one reason phrased three ways.

Is Paper 6 worth revising if I'm sitting the practical paper instead? Yes. The reasoning tested — controlling variables, spotting method errors, choosing apparatus for a required precision — appears in theory papers too, and it's some of the most transferable practice available.

How many past papers should I do? Every topic should appear in at least one timed question before the exam, plus three to five full papers per subject in the final six weeks. Quality of review beats quantity of papers — an unmarked paper teaches nothing.

What's the fastest way to improve a grade in Chemistry? Rewrite answers you already lost marks on. The content is usually there; the phrasing isn't. That's a much shorter job than relearning topics.

Revise smarter with AI

Upload your Chemistry notes to build study sets — MCQs and flashcards from your own material — then use the AI tutor for topics you're stuck on, in mark-scheme language calibrated to Cambridge and Edexcel. Stuck on a specific past-paper question? Solve shows full working laid out the way it's marked.

Pair it with active recall, the week-by-week IGCSE revision plan, and the Biology and Maths guides if you're revising the sciences together.

Chemistry rewards precision over volume. Start a free trial and rewrite three answers that lost marks for being imprecise.