IGCSE Chemistry: Complete Revision Guide with Key Topics

IGCSE Chemistry sits at the intersection of understanding and application. You need to know the facts — formulae, reactions, properties — but you also need to explain why things happen and apply your knowledge to unfamiliar situations. Here’s a topic-by-topic guide to revising effectively.

Paper Structure

Cambridge IGCSE (0620)

Core: Paper 1 (multiple choice) + Paper 3 (structured theory)
Extended: Paper 2 (multiple choice) + Paper 4 (structured theory)
Practical: Paper 5 (practical) or Paper 6 (alternative to practical)

Extended papers are required for grades A*–C.

Edexcel International GCSE (4CH1)

Paper 1: 2 hours, roughly two-thirds of the specification
Paper 2: 1 hour 15 minutes, remaining content plus synoptic questions

Both papers include multiple choice, short answer, and extended writing.

Key Topics

States of Matter and Atomic Structure

Start here — it underpins everything else. Know the three states of matter in terms of particle arrangement, movement, and energy. Be able to explain changes of state using the kinetic particle model.

For atomic structure, know:

Protons, neutrons, and electrons — charges, masses, and locations
Atomic number and mass number
Electron configuration (2,8,8 pattern for the first 20 elements)
Isotopes and how to calculate relative atomic mass from isotope data

Extended content: Electronic configuration determines chemical behaviour. Understanding why elements in the same group have similar properties connects atomic structure to the periodic table.

Bonding and Structure

Three types of bonding: ionic, covalent, and metallic. For each, know:

How the bond forms
How to draw dot-and-cross diagrams
The properties of substances with each bond type (melting point, electrical conductivity, solubility)

Giant structures (ionic lattices, metallic lattices, covalent giant structures like diamond and graphite) have high melting points. Simple molecular substances (water, CO₂) have low melting points because the intermolecular forces are weak, even though the covalent bonds within molecules are strong.

Common mistake: Confusing “weak bonds between molecules” with “weak bonds within molecules.” The covalent bonds are strong; it’s the forces between molecules that are weak.

Chemical Reactions

This is the largest section of the specification. Key areas:

Acids and bases: Know the reactions of acids with metals, metal oxides, metal hydroxides, and metal carbonates. Be able to write balanced equations including ionic equations. Understand pH, indicators, and neutralisation.

Rates of reaction: Explain how temperature, concentration, surface area, and catalysts affect reaction rate using collision theory. Interpret rate graphs and describe experiments to measure reaction rate.

Energetics: Exothermic and endothermic reactions, energy level diagrams, and bond energy calculations. For extended content, understand how to calculate enthalpy changes from bond energies.

Redox: Oxidation is loss of electrons; reduction is gain (OIL RIG). Be able to identify what is oxidised and what is reduced in a reaction, including ionic half-equations for extended candidates.

The Periodic Table

Understand the organisation: periods, groups, metals and non-metals. Focus on:

Group 1 (alkali metals): Increasing reactivity down the group, reactions with water
Group 7 (halogens): Decreasing reactivity down the group, displacement reactions
Group 0 (noble gases): Why they’re unreactive
Transition metals: General properties (coloured compounds, catalytic activity, variable oxidation states)

Organic Chemistry

For many students, this is the most challenging section. At IGCSE level:

Know the first four homologous series: alkanes, alkenes, alcohols, and carboxylic acids
Be able to name and draw structures for the first few members of each series
Understand addition and substitution reactions
Know the tests to distinguish alkanes from alkenes (bromine water)
Polymers: addition polymerisation (extended candidates also need condensation polymerisation)
Crude oil: fractional distillation and why different fractions have different properties

Revision tip: Draw out the structures repeatedly. Organic chemistry is structural — you need to visualise molecules to understand reactions.

Metals and Extraction

Know the reactivity series and its applications: displacement reactions, extraction methods (electrolysis for reactive metals, reduction with carbon for less reactive metals), and corrosion.

Understand electrolysis in detail: what happens at each electrode, why certain ions are discharged preferentially, and industrial applications (extraction of aluminium, purification of copper).

Exam Technique

Balanced Equations

Practise balancing equations until it’s automatic. Many marks across all papers depend on correct equations. For extended candidates, practise ionic equations and half-equations too.

Calculations

Mole calculations appear on every paper. Know:

Moles = mass / relative molecular mass
Concentration = moles / volume
How to use mole ratios from balanced equations to calculate reacting masses

Work through calculations methodically, showing each step. Units matter — always include them.

Extended Writing

For 5-6 mark questions, plan before writing. Use a logical sequence:

State the relevant principle or definition
Apply it to the specific scenario in the question
Explain the outcome or observation

Use correct chemical terminology throughout.

Past Paper Practice

Chemistry papers across both boards follow predictable patterns. Regular past paper practice under timed conditions is the most effective way to improve.

After each paper:

Mark using the official mark scheme
Note which topics you lost marks on
Distinguish between knowledge gaps and technique issues
Revisit weak topics before doing the next paper

UpGrades provides IGCSE Chemistry practice aligned to Cambridge and Edexcel specifications, helping you identify and target your weakest areas systematically.

Quick Wins

Learn your ions. Knowing common ion formulae (sulfate, nitrate, carbonate, hydroxide) speeds up equation writing.
Memorise the reactivity series. It appears across multiple topics.
Practise dot-and-cross diagrams. These earn marks efficiently and are frequently examined.
Know your colour changes. Indicators, flame tests, and precipitation reactions all involve colours that examiners love to test.

Chemistry rewards methodical, consistent revision. Build your knowledge topic by topic, practise calculations regularly, and use past papers to refine your exam technique.