IGCSE Chemistry Syllabus: Topics, Assessment and Exam Structure

The Cambridge IGCSE Chemistry syllabus (codes 0620 and 0971) divides content into ten main topic areas: the particulate nature of matter, experimental techniques, atoms and elements, stoichiometry, electricity and chemistry, chemical energetics, chemical reactions, acids and bases, the periodic table, and organic chemistry. Assessment combines written examinations—structured as Core and Extended tiers—with either practical tests or alternative-to-practical papers. The syllabus specifies learning objectives at two levels: Core content for grades C to G, and Extended content that includes all Core material plus additional depth for grades A* to G.

What the IGCSE Chemistry Syllabus Covers

The syllabus organises chemistry knowledge into ten numbered sections, each building conceptual understanding from macroscopic observations to particulate models. Students begin with observable properties of matter—states, diffusion, dissolving—then progress to atomic structure, bonding theories, and quantitative relationships in reactions.

Section 1 introduces the particulate nature of matter: kinetic theory, states of matter, and changes of state. Section 2 covers experimental techniques including separation methods (filtration, crystallisation, distillation, chromatography), measurement precision, and safety procedures. These practical foundations support all subsequent work.

Sections 3 through 5 build atomic and quantitative chemistry. Section 3 defines atoms, elements, compounds, and mixtures, then introduces atomic structure (protons, neutrons, electrons), isotopes, and electronic configuration. Section 4 develops stoichiometry: relative atomic and molecular mass, the mole concept, empirical and molecular formulae, and calculations involving mass, volume, and concentration. Section 5 connects electricity to chemistry through electrolysis, including electrode reactions and industrial applications.

Sections 6 and 7 address energy and reaction types. Section 6 covers exothermic and endothermic reactions, bond energies, and the interpretation of energy profile diagrams. Section 7 classifies chemical reactions: oxidation-reduction (including electron transfer definitions), displacement reactions, and the reactivity series of metals.

Sections 8 through 10 complete the chemical landscape. Section 8 examines acids, bases, and salts: neutralisation, pH, preparation of salts, and titration calculations. Section 9 explores the periodic table systematically, covering Group I metals, Group VII halogens, Group VIII noble gases, and transition elements. Section 10 introduces organic chemistry: alkanes, alkenes, alcohols, carboxylic acids, polymers, and the distinction between addition and condensation polymerisation.

IGCSE Chemistry Exam Structure

Cambridge offers two assessment routes for IGCSE Chemistry. Both routes require two written papers plus one practical component, but they differ in practical assessment method.

For syllabus 0620, candidates take:

• Paper 1 or Paper 2 (written examination, multiple choice)
• Paper 3 or Paper 4 (written examination, structured questions)
• Paper 5 or Paper 6 (practical assessment)

Paper 1 (Core) contains 40 multiple-choice questions in 45 minutes, weighted at 30% of total marks. Paper 2 (Extended) contains 40 multiple-choice questions in 45 minutes, also 30% weighting, but assesses the full Extended content.

Paper 3 (Core) presents structured questions totalling 80 marks over 1 hour 15 minutes, contributing 50% of the final grade. Paper 4 (Extended) similarly offers 80 marks in 1 hour 15 minutes at 50% weighting, examining Extended material.

Paper 5 (Practical Test) requires candidates to perform experiments, record observations, and analyse results in 1 hour 15 minutes for 40 marks (20% weighting). Paper 6 (Alternative to Practical) assesses practical skills through written questions about experiments, also 1 hour 15 minutes, 40 marks, 20% weighting. Schools choose Paper 5 when laboratory facilities permit direct assessment; Paper 6 serves centres without suitable practical resources.

Syllabus 0971 follows the same structure but delivers all papers on-screen as part of Cambridge's digital examination programme.

Core vs Extended: How the Tiers Differ

The distinction between Core and Extended determines both content depth and grade range. Core content targets fundamental concepts accessible to all students, with grades available from C (the highest Core grade) down to G. Extended content includes all Core material plus additional topics, more complex applications, and harder calculations, enabling grades from A* down to G.

Consider stoichiometry as an example. Core students calculate moles from mass using \( n = \frac{m}{M} \), determine empirical formulae, and perform straightforward mass-to-mass calculations in reactions. Extended students additionally work with limiting reagents, calculate percentage yields, determine molecular formulae from empirical formulae and relative molecular mass, and handle more complex multi-step problems.

In organic chemistry, Core students identify the homologous series (alkanes, alkenes, alcohols, carboxylic acids) and describe their general properties. Extended students write structural formulae, explain isomerism, predict products of specific reactions (combustion, addition of hydrogen or halogens, oxidation of alcohols), and distinguish between saturated and unsaturated compounds using chemical tests.

For electrolysis, Core students describe what happens at electrodes during electrolysis of molten ionic compounds and aqueous solutions. Extended students predict products at each electrode, write half-equations for electrode reactions, and explain the competition between ions when multiple species could be discharged.

The syllabus document marks Extended-only content with a shaded background, making the distinction clear. Teachers and students should identify which tier they're targeting early, as this shapes the entire revision strategy.

Syllabus Topics by Section

Each syllabus section specifies learning objectives that describe what students should know and be able to do. Here we examine several sections in detail to show the reasoning expected.

Atomic Structure and the Periodic Table

Students must understand that atomic number defines an element: it's the number of protons in the nucleus, which determines chemical identity. The mass number counts total nucleons (protons plus neutrons). For an atom of chlorine-35, written \( ^{35}_{17}\text{Cl} \), the subscript 17 tells us there are 17 protons, so atomic number = 17. The superscript 35 is the mass number, so neutrons = 35 − 17 = 18.

Isotopes are atoms of the same element (same proton count) with different neutron counts. Chlorine has two stable isotopes: chlorine-35 and chlorine-37. Both have 17 protons—that's what makes them chlorine—but chlorine-35 has 18 neutrons while chlorine-37 has 20. The relative atomic mass of chlorine (approximately 35.5) reflects the weighted average of these isotopes in nature.

Electronic configuration follows the shell model: the first shell holds up to 2 electrons, the second up to 8, the third up to 8 (for the first 20 elements). Sodium (atomic number 11) has 11 electrons arranged as 2,8,1. This outermost single electron explains sodium's vigorous reactivity: it readily loses that electron to achieve a stable 2,8 configuration like neon.

The periodic table groups elements by electronic structure. Group I elements (lithium, sodium, potassium) all have one electron in their outer shell, giving them similar chemical properties. Group VII elements (fluorine, chlorine, bromine, iodine) all have seven outer electrons, one short of a stable octet, explaining why they readily gain electrons in reactions.

Stoichiometry and the Mole

The mole is the central counting unit in chemistry. One mole contains \( 6.02 \times 10^{23} \) particles (Avogadro's number), and the molar mass in grams equals the relative atomic or molecular mass. For carbon (relative atomic mass 12), one mole of carbon atoms has mass 12 g. For water, \( \text{H}_2\text{O} \), the relative molecular mass is \( 2(1) + 16 = 18 \), so one mole of water molecules has mass 18 g.

Calculating moles from mass uses \( n = \frac{m}{M} \) where \( n \) is moles, \( m \) is mass in grams, and \( M \) is molar mass. If we have 5.4 g of aluminium (molar mass 27 g/mol), we have \( n = \frac{5.4}{27} = 0.2 \) moles.

Balanced equations give mole ratios. For the reaction:

\[ 2\text{Mg} + \text{O}_2 \to 2\text{MgO} \]

Two moles of magnesium react with one mole of oxygen to produce two moles of magnesium oxide. If we start with 0.5 moles of magnesium, we need 0.25 moles of oxygen and will produce 0.5 moles of magnesium oxide.

Extended students tackle problems involving limiting reagents. Suppose we have 4.8 g of magnesium (molar mass 24) and 3.2 g of oxygen (molar mass 32). Moles of magnesium: \( \frac{4.8}{24} = 0.2 \) mol. Moles of oxygen: \( \frac{3.2}{32} = 0.1 \) mol. The equation shows 2 moles of Mg need 1 mole of O₂, so 0.2 moles of Mg need 0.1 moles of O₂. We have exactly the right amount—neither is in excess. The product will be \( 0.2 \) moles of MgO, which has mass \( 0.2 \times 40 = 8.0 \) g.

Acids, Bases and Salts

Acids release hydrogen ions (\( \text{H}^+ \)) in aqueous solution. Hydrochloric acid dissociates: \( \text{HCl} \to \text{H}^+ + \text{Cl}^- \). Bases are oxides or hydroxides of metals that neutralise acids. Alkalis are soluble bases, like sodium hydroxide, which releases hydroxide ions: \( \text{NaOH} \to \text{Na}^+ + \text{OH}^- \).

Neutralisation combines hydrogen ions and hydroxide ions to form water:

\[ \text{H}^+ + \text{OH}^- \to \text{H}_2\text{O} \]

The full equation for hydrochloric acid neutralising sodium hydroxide is:

\[ \text{HCl} + \text{NaOH} \to \text{NaCl} + \text{H}_2\text{O} \]

The salt formed (sodium chloride) comes from the metal in the base and the non-metal in the acid.

Titration determines unknown concentrations. If 25.0 cm³ of sodium hydroxide solution neutralises 20.0 cm³ of 0.100 mol/dm³ hydrochloric acid, we calculate the concentration of the alkali. Moles of HCl = \( 0.100 \times \frac{20.0}{1000} = 0.00200 \) mol. The 1:1 equation ratio means 0.00200 mol of NaOH reacted. Concentration of NaOH = \( \frac{0.00200}{25.0/1000} = 0.0800 \) mol/dm³.

Practical Skills and Assessment

Practical work develops observational precision, measurement technique, and the ability to draw conclusions from data. The syllabus specifies practical skills through Paper 5 or Paper 6.

In Paper 5 (Practical Test), candidates perform experiments at a laboratory bench. A typical task might ask students to investigate the rate of reaction between hydrochloric acid and magnesium ribbon by measuring gas volume at timed intervals. Students must set up apparatus correctly (inverted burette or gas syringe), ensure the system is sealed, record measurements accurately, and present results in a table. They then plot a graph, draw a smooth curve, and calculate the rate by finding the gradient.

Observational skills matter. When adding sodium hydroxide solution to copper(II) sulfate solution, the correct observation is "a blue precipitate forms", not "a reaction happens" or "it goes cloudy". The syllabus expects specific colour descriptions and identification of precipitates, gases, and other products.

Paper 6 (Alternative to Practical) tests the same skills through written questions about experiments. Candidates might see a diagram of apparatus, then answer questions about why that setup was chosen, what measurements to take, how to improve accuracy, or what sources of error exist. Another question type presents experimental data in a table and asks students to plot a graph, identify patterns, or calculate a result.

Both papers assess planning, observation, recording, analysis, and evaluation. Students must suggest improvements to experimental methods, identify anomalous results, and explain why certain procedures (like repeating measurements) improve reliability.

What Changed in the Latest Syllabus Cycle

Cambridge periodically reviews and updates syllabuses. Changes typically involve clarifying learning objectives, adjusting content emphasis, or modifying assessment weightings rather than wholesale restructuring.

Recent updates have emphasised mathematical skills within chemistry contexts. The syllabus now explicitly states that students should be able to perform calculations involving ratios, percentages, reciprocals, and standard form, and should manipulate equations (for example, rearranging \( n = \frac{m}{M} \) to find mass or molar mass). These skills were always implicit, but making them explicit helps teachers ensure adequate preparation.

The command words used in questions have been standardised across Cambridge syllabuses. "State" means give a specific name, value or brief answer without explanation. "Describe" means state the key features or changes. "Explain" requires reasoning or justification. "Suggest" indicates that the exact answer isn't in the syllabus, so students must apply their knowledge to an unfamiliar situation. Understanding these command words prevents students from writing too much (wasting time on "state" questions) or too little (losing marks on "explain" questions).

Practical assessment criteria have been refined to more clearly distinguish between different skill levels. For example, when evaluating experimental methods, a basic response identifies one source of error, while a developed response explains how that error affects results and suggests a specific improvement.

How to Revise for IGCSE Chemistry

Effective revision for IGCSE Chemistry requires active engagement with concepts, not passive reading. Begin by identifying which tier (Core or Extended) you're taking, then work through the syllabus systematically.

For each topic, test your understanding by attempting to explain concepts without notes. Can you explain why ionic compounds conduct electricity when molten but not when solid? If you can articulate the reasoning—that ions are fixed in position in the solid lattice but free to move in the liquid, and moving charged particles constitute an electric current—then you understand. If you can't, return to your notes and work through examples.

Practice calculations daily. Stoichiometry problems, concentration calculations, and titration questions require fluency with the mole concept and unit conversions. Work through problems step-by-step:

1. Write the balanced equation
2. Calculate moles of the substance you know about
3. Use the equation ratio to find moles of the substance you're asked about
4. Convert moles to the required unit (mass, volume, concentration)

For example, what mass of carbon dioxide forms when 10.0 g of calcium carbonate reacts completely with excess hydrochloric acid?

\[ \text{CaCO}_3 + 2\text{HCl} \to \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2 \]

Molar mass of \( \text{CaCO}_3 = 40 + 12 + 3(16) = 100 \) g/mol. Moles of \( \text{CaCO}_3 = \frac{10.0}{100} = 0.100 \) mol. The equation shows 1 mole of \( \text{CaCO}_3 \) produces 1 mole of \( \text{CO}_2 \), so 0.100 mol of \( \text{CO}_2 \) forms. Molar mass of \( \text{CO}_2 = 12 + 2(16) = 44 \) g/mol. Mass of \( \text{CO}_2 = 0.100 \times 44 = 4.4 \) g.

Create summary sheets for reaction types. For acids reacting with metals, carbonates, and bases, write the general equation, then specific examples with observations. Acid + metal → salt + hydrogen (test: lighted splint gives a 'pop'). Acid + carbonate → salt + water + carbon dioxide (test: bubbles; limewater turns milky). Acid + base → salt + water (no visible change if both are in solution).

Past papers are essential. Time yourself strictly—45 minutes for multiple choice papers, 1 hour 15 minutes for structured papers. After completing a paper, mark it carefully, noting not just wrong answers but questions where you guessed or felt uncertain. These indicate gaps in understanding.

For practical papers, practice describing observations precisely. Set up common experiments if possible: displacement reactions, thermal decomposition, electrolysis, rate of reaction investigations. If you can't access a laboratory, study diagrams of apparatus carefully and think through what you would observe at each stage.

Organic chemistry requires memorisation of functional groups and reaction patterns, but understanding the logic helps. Alkanes (single bonds) are unreactive; alkenes (double bonds) are reactive because the double bond can break to add other atoms. Alcohols can be oxidised to carboxylic acids by removing hydrogen. Polymers form when many small molecules (monomers) join together, either by addition (alkenes opening their double bonds) or condensation (small molecules like water eliminated as bonds form).

The periodic table rewards pattern recognition. Group I reactivity increases down the group because the outer electron is further from the nucleus and more easily lost. Group VII reactivity decreases down the group because the atom is larger, so an incoming electron is less strongly attracted. Transition elements are similar to each other because they all have electrons in inner shells being filled, not outer shells.

Regular, focused practice across all topic areas, combined with careful analysis of mistakes, builds both knowledge and examination technique. The syllabus provides the complete map; your revision should cover every part of it.