Cambridge IGCSE Chemistry (0620) explains matter, atoms, bonding, reactions, quantities and the evidence scientists use to work out what substances do. This student’s guide outlines the syllabus, Core and Extended papers, practical assessment and a reliable path from basic concepts to examination problem solving.
How IGCSE Chemistry works becomes clearer when students recognise three connected questions: What particles are present? How are they arranged and changed? What evidence and calculations support the explanation? Memorising an isolated chemical equation is less useful than being able to apply these questions to a new situation.
This guide covers Cambridge IGCSE Chemistry syllabus 0620 for the 2026, 2027 and 2028 examinations. Other exam boards and Chemistry qualifications can differ. Confirm the exact syllabus code, examination year, paper tier and practical route with your school or centre before using a paper-specific revision plan.
Quick answer: Cambridge 0620 has 12 main content topics. All candidates sit three components: a multiple-choice paper worth 30%, a theory paper worth 50% and a practical-skills paper worth 20%. Core takes Papers 1 and 3, Extended takes Papers 2 and 4, and each route includes either Paper 5 Practical Test or Paper 6 Alternative to Practical. Strong performance rests on accurate particle models, balanced equations, chemical reasoning and careful experiments.
Chemistry Is About Models and Evidence
Chemistry does not ask students merely to know that a reaction happens. It asks them to explain why substances behave as they do, represent those changes with appropriate models and test claims against observations.
A particle diagram can explain the arrangement of matter. A formula can represent the composition of a substance. A balanced equation accounts for atoms in a reaction. A measurement can show whether an experimental prediction is plausible.
These forms of representation are useful for different purposes. An equation may tell us the ratio of reacting particles but not how fast a reaction proceeds. A colour change may indicate that something happened but does not, by itself, identify every product.
A careful Chemistry student learns the limits of each kind of evidence. This is a scientific skill and an examination skill at the same time.
Confirm the Cambridge Syllabus and Your Entry Route
Cambridge publishes the 0620 syllabus for 2026–2028, and students taking examinations in that period should follow the appropriate version and updates. The examination year is more important than the publication date of a textbook.
Some schools study Cambridge 0620 while others use Pearson Edexcel International GCSE Chemistry or different science combinations. Similar-sounding topic titles do not make the assessments equivalent.
Within 0620, Core focuses on Core requirements; Extended includes Core and Supplement content. Under the 2026–2028 assessment overview, Core candidates are eligible for grades C to G, while Extended candidates are eligible for **A* to G**.
Check with your school whether you will take Paper 5 or Paper 6. Your preparation needs to match the route the centre actually enters. Do not assume Paper 6 is automatically available to every private candidate or that the centre can change entry routes at any time.
The Twelve Main Chemistry Topics
The syllabus arranges content under twelve headings. A teacher may present them in a different sequence for learning, but students should know the official range.
- 1. States of matter: particle arrangement, motion, changes of state and related observations.
- 2. Atoms, elements and compounds: atomic structure, periodic identity, bonding and particle models.
- 3. Stoichiometry: formulae, equations, relative masses, amounts and quantitative reaction relationships.
- 4. Electrochemistry: the movement of charge and chemical changes in relevant electrical systems.
- 5. Chemical energetics: energy changes in chemical reactions.
- 6. Chemical reactions: rates, reversible reactions and the principles governing change.
- 7. Acids, bases and salts: reactions, pH, neutralisation and preparation of salts.
- 8. The Periodic Table: ordering elements and understanding patterns in properties.
- 9. Metals: metallic properties, reactivity, extraction and relevant uses.
- 10. Chemistry of the environment: atmospheric, water and other environmental chemistry.
- 11. Organic chemistry: carbon compounds and transformations required by the syllabus.
- 12. Experimental techniques and chemical analysis: measurement, separation, identification and safe experimental reasoning.
This list is a map rather than twelve independent islands. Atomic structure helps explain bonding. Bonding influences properties. Equations quantify reactions. Energetics and rates describe different aspects of reaction behaviour. Practical analysis checks whether our chemical models fit the evidence.
A student who makes these links can approach unfamiliar tasks more confidently.
Exactly Which Examination Papers Are Taken?
Paper 1 – Multiple Choice, Core: 45 minutes, 40 marks, 30% of the grade. It has 40 four-option questions on Core content.
Paper 3 – Theory, Core: 1 hour 15 minutes, 80 marks, 50% of the grade. Questions are short-answer and structured.
Paper 2 – Multiple Choice, Extended: 45 minutes, 40 marks, 30% of the grade. It covers Core and Supplement content.
Paper 4 – Theory, Extended: 1 hour 15 minutes, 80 marks, 50% of the grade. It assesses the Extended syllabus requirements through structured answers and relevant calculations.
Paper 5 – Practical Test: 1 hour 15 minutes, 40 marks, 20% of the grade. It assesses experimental skills through a hands-on examination.
Paper 6 – Alternative to Practical: 1 hour, 40 marks, 20% of the grade. It assesses practical methods and reasoning in a written examination.
Core students take Paper 1, Paper 3 and either Paper 5 or Paper 6. Extended students take Paper 2, Paper 4 and either Paper 5 or Paper 6. Each candidate takes three papers, not all six.
The paper numbers, durations and weightings above are drawn from Cambridge’s 2026–2028 assessment overview. If a revision resource shows different details, first check whether it refers to another syllabus year or awarding body.
How to Understand States of Matter With Particles
A useful particle model explains solid, liquid and gaseous behaviour in terms of arrangement, motion and forces between particles.
In a solid, particles have positions within a structure and vibrate. In a liquid, particles remain close but move past one another. In a gas, particles move much more freely and are typically much farther apart.
Heating changes the energy and motion of particles, but it does not automatically change their chemical identity. When ice melts, it is still water; the state changes. When water is decomposed by an appropriate chemical process, the composition changes. That is a different class of event.
Students should be able to draw models, describe what changes and say what stays the same. Avoid the common mistake of explaining melting as the atoms themselves expanding or changing element.
Atoms, Elements, Ions and Bonding: Get the Language Right
An element consists of atoms with the same proton number. A compound contains atoms of two or more different elements chemically combined. A mixture combines substances without the same fixed chemical bonding relationship.
An atom can become an ion by losing or gaining electrons. Losing electrons results in a positively charged ion; gaining electrons results in a negatively charged ion. Students must not confuse the number of protons with the ion’s charge change.
Different kinds of bonding help account for structures and properties. Ionic, covalent and metallic bonding should be understood through the particles and interactions involved, not through memorised labels alone.
For every material, ask what particles exist, how they are arranged, which forces or bonds matter and how that helps explain a measurable property. Then consider an example that tests the model rather than simply recalling its definition.
Chemical Formulae and Equations: The Conservation Principle
In an ordinary chemical reaction, atoms are rearranged rather than created or destroyed. A balanced chemical equation represents this conservation.
For example, hydrogen reacts with oxygen to form water:
2H₂ + O₂ → 2H₂O
The left side has four hydrogen atoms and two oxygen atoms. The right side also has four hydrogen atoms and two oxygen atoms. The coefficients express the relationship between reacting and produced particles.
Do not balance the equation by changing the subscripts in chemical formulae. Changing H₂O to H₂O₂, for example, changes the substance being represented. Balance by adjusting coefficients while preserving correct chemical identities.
A reliable check counts each element on both sides. If a question involves ionic charge or a more advanced representation, ensure the notation also satisfies the conditions being tested.
Stoichiometry: A Worked Example
Stoichiometry uses the ratios in balanced equations to calculate quantities. It is a powerful method because it links invisible particle relationships to measurable masses and amounts.
Using 2H₂ + O₂ → 2H₂O, suppose 4 g of hydrogen reacts completely with sufficient oxygen. With simplified relative atomic masses H = 1 and O = 16, the molar mass of H₂ is 2 g/mol, so 4 g of H₂ represents 2 mol.
The equation shows a 1:1 mole ratio between H₂ and H₂O: two moles of H₂ form two moles of H₂O when oxygen is not limiting. The molar mass of H₂O is 18 g/mol, giving 2 × 18 = 36 g of water.
The answer is not obtained by multiplying 4 g by an arbitrary coefficient. The sequence is mass → amount in moles → equation ratio → amount of product → mass of product.
When a question adds more than one reacting quantity, identify whether a limiting reactant must be considered. Do not assume the reactant mentioned first is necessarily the one that determines the amount of product.
Acids, Bases and Salts: Recognise the Reaction Pattern
A reaction equation is useful only when the student knows what classes of substances are involved and what products can reasonably form.
For example, acid–base neutralisation produces a salt and water under the relevant conditions. Many reactive metals can react with suitable acids to give a salt and hydrogen. A carbonate reacting with acid can produce a salt, water and carbon dioxide.
These are patterns, not an excuse to ignore conditions. The actual substances, their reactivity and the exam question’s details matter. Learn how to distinguish observations from chemical conclusions.
A student may see bubbling and immediately write ‘hydrogen gas’. Bubbling merely indicates gas release. Depending on reactants and the experiment, it could be a different gas. Chemical identification needs the correct context or a specified test.
A good answer names the observation, links it to the reaction and avoids assuming more than the evidence supports.
The Periodic Table: Patterns With Explanations
The Periodic Table organises elements by atomic number and can reveal patterns in chemical behaviour. It is not merely a chart to memorise.
For main-group elements in appropriate parts of the syllabus, electronic structure helps explain patterns such as common ion formation and related reactivity. Comparisons of groups should use the actual properties in the course, not broad statements without exceptions or conditions.
When a question asks why two elements behave similarly, look for the relevant structural relationship. When a question asks which is more reactive, specify the group and the applicable trend. The trend for one group should not be transferred blindly to all groups.
It is useful to practise interpreting unfamiliar periodic information as well as recalling familiar examples. The examination may supply data that require reasoning rather than a stock sentence.
Reaction Rates and Energy: Two Different Questions
Reaction rate asks how quickly a reaction proceeds. Energetics asks about the energy involved or transferred. A reaction can be fast or slow independently of whether its overall energy change is exothermic or endothermic.
For rates, students investigate factors such as concentration, temperature, surface area and catalysts where required. A valid explanation links changed conditions to particle interactions and successful collisions, within the level expected by the syllabus.
For energetics, an exothermic process transfers energy to the surroundings; an endothermic process takes in energy from the surroundings. Data, graphs or temperature changes need to be interpreted carefully.
Do not explain an exothermic reaction merely by saying ‘the temperature rises’ without identifying what is gaining energy and under what measurement conditions. The causal relationship is what matters.
Organic Chemistry: Look for Structures and Changes
Organic Chemistry can initially feel like a large vocabulary burden. The better starting point is to identify functional features, molecular formulas, the arrangement of atoms and the type of transformation being described.
A series of related carbon compounds can share general behaviour while differing in chain length. Different structural arrangements may change properties. Students should recognise the exact classes and reactions covered by their syllabus tier.
Do not make every organic question a memorisation exercise. Draw the structure carefully, account for the atoms present, check the conditions and explain what kind of change occurred.
Where industrial uses or environmental consequences are discussed, connect a stated property or process to the practical result. Avoid sweeping claims about all organic compounds.
Chemistry of the Environment: Evidence Before Opinion
Chemistry provides tools for understanding air pollutants, greenhouse gases, water treatment and the movement of substances through environmental systems.
The strongest answers explain a mechanism. They identify the chemical substance or process, the conditions involved and a supported consequence. They do not simply announce that an activity is ‘good’ or ‘bad’ for the planet.
For example, a question may describe a contaminant and ask how a treatment step addresses it. The student needs to connect the treatment to the substance and outcome. General enthusiasm about recycling is not a substitute for the requested explanation.
Students should also distinguish scientific findings from broader policy decisions. Chemistry can explain reactions and evidence, while decisions about cost, infrastructure and priorities involve additional considerations.
Experimental Techniques: Why Method Matters
In Chemistry, practical work can involve measuring masses, temperatures or volumes, separating mixtures, observing colour changes and identifying substances using suitable tests.
A good investigation begins with a clear purpose. Identify the independent variable, measured result and relevant controls. Choose apparatus that fits the precision needed. Record data with units and note observations rather than turning every observation immediately into a conclusion.
For example, in an investigation of reaction rate using gas production, the measured gas volume can change over time. A graph of gas volume against time shows how gas accumulation proceeds. The slope can indicate the rate over the selected interval.
A steeper initial slope indicates faster gas production, all else equal. But the final volume alone does not always tell you which reaction was faster; two experiments may finish at the same final volume while taking different amounts of time.
Students should rehearse these distinctions using real or specimen data, not just memorise the expected curve shape.
A Worked Practical Reasoning Example
Suppose a class compares the rate of a reaction at two temperatures. The measured outcome is the time taken to reach a clearly defined observable endpoint.
The student should keep relevant conditions consistent, such as reactant quantities and the stated concentration where applicable. Temperature is the changed variable. Recording temperature accurately is important because the claim depends on that variable.
After collecting times, the student can compare how long the endpoint took and decide what the data support. If the investigation uses 1/time as a relative-rate measure, the definition should be stated and used consistently.
A common error is to write that a higher temperature ‘produces more product’ when the actual observation only showed that the endpoint was reached sooner. The experiment may support a rate conclusion, not automatically a greater final yield.
An improvement should address a genuine weakness: for example, maintaining a consistent reaction temperature or making the endpoint judgement less subjective. Generic calls to ‘be more careful’ are not enough.
Paper 5 and Paper 6: Both Test Practical Science
Paper 5 is a hands-on practical examination. Students may need to use apparatus and reagents safely, make observations, obtain measurements, process data and draw appropriate conclusions.
Paper 6, the Alternative to Practical, is written but still asks how experiments are conducted and interpreted. Students may analyse apparatus diagrams, observations, chemical tests, graphs and sources of error.
Preparation for either route should include understanding of laboratory safety and the techniques prescribed by the current syllabus. Do not carry out hazardous experiments at home. Use supervised school laboratories or safe teacher-guided resources for practical learning.
Paper 6 is not a loophole in which remembering a few generic evaluation sentences replaces actual experimental understanding.
How to Study Chemical Tests Without Mixing Them Up
Chemical analysis requires reliable distinctions. Students may be asked to interpret observations from appropriate tests for gases, ions or other substances covered by the official syllabus.
Do not learn only an observation such as ‘white precipitate’. A similar appearance can occur in different tests. Record the test reagent, the conditions, the original sample, the observation and the conclusion together.
For gas testing, know what counts as the distinguishing observation and how the apparatus should be used safely under teacher supervision. For ionic tests, identify whether additional reagents or excess reagent conditions matter.
An effective revision method is to start from an unknown observation and work towards a possible conclusion, then reverse the question: given a substance, predict the appropriate test and observation. That two-way retrieval builds stronger recognition.
Multiple Choice: Treat Every Option as a Hypothesis
The 40-question multiple-choice paper is not merely a speed test. It often distinguishes small but important conceptual differences.
Read the question and determine the required relationship before looking at the options. If the problem is numerical, estimate the expected answer and check units. If it is conceptual, identify what must be true for the statement to hold.
Then test the options. A distractor may represent a real chemical statement that fails the specific conditions, an unbalanced equation or a common unit error.
After marking practice, explain why the chosen wrong option was attractive. That reveals the misconception more clearly than memorising the correct letter.
Structured Theory: Show the Reasoning, Not Just the Result
Theory papers can include short calculations, explanations, equations, diagrams and interpretation of unfamiliar experimental evidence.
For calculations, state the relationship, substitute data and retain sensible units. For explanations, use the relevant particle-level mechanism. For reaction predictions, identify the class of reactants and the conditions.
A student might correctly write an equation but lose marks when asked to explain a trend. Conversely, an accurate explanation cannot repair an unbalanced equation if the task specifically requires an equation.
Follow the command word. ‘State’ usually requires a concise fact. ‘Explain’ requires the reason. ‘Calculate’ requires numerical work. ‘Suggest’ invites a plausible inference supported by the conditions provided. ‘Evaluate’ means assessing evidence or method quality.
The Most Common Chemistry Errors and Their Repairs
- Particle-model error: treating physical change as chemical change. Repair by asking whether chemical identity changed.
- Formula error: changing subscripts while balancing. Repair by conserving each element with coefficients.
- Mole-ratio error: using coefficients as mass multipliers. Repair using amount in moles before returning to mass.
- Charge error: confusing ions with neutral atoms. Repair by tracing electron gain or loss and the resulting charge.
- Energy-rate confusion: treating temperature, reaction speed and overall energy transfer as the same idea. Repair by identifying the exact question being asked.
- Evidence error: naming a gas from bubbles alone. Repair by distinguishing observation, hypothesis and identifying test.
- Practical-design error: changing multiple conditions together. Repair with a table of variables and controls.
- Calculation-presentation error: omitting units, rounding too early or failing to check plausibility. Repair with explicit final-answer checks.
A good revision notebook lists the actual mistake and a correction task, not simply ‘Chemistry is hard’. The smaller and more precise the repair, the more likely it is to work.
Repair, Stabilise and Extend: Three Student Pathways
Repair: the student has unreliable foundations in atomic structure, bonding, formulae, simple equations or arithmetic. Rebuild those before asking for lengthy stoichiometry sets. A misconception about formulae will reproduce itself in nearly every reaction calculation.
Stabilisation: the student can follow examples but loses marks when topics are mixed. Use short retrieval sessions, unfamiliar contexts and timed practice. Focus on recognising which chemical model applies before doing any algebra.
Extension: the student already has dependable fundamentals. Explore alternative solution methods, compare competing explanations, evaluate experimental limitations and practise multi-step questions that combine equations, observations and calculations.
A learner may need different pathways in different chapters. Accurate diagnosis is more useful than calling every struggle ‘carelessness’.
A Weekly Revision Routine That Produces Transfer
Session 1: concept and model. Rebuild one chemical idea with a particle drawing, a formal explanation and one independent example. Finish by identifying what the model can and cannot explain.
Session 2: equations and quantities. Practise formulae, balancing and calculations with clear units. Explain the ratio before touching the calculator.
Session 3: mixed application. Answer questions from several topics without their headings. Decide which concept the question is testing and justify the decision briefly.
Session 4: practical reasoning and correction. Interpret observations, plan a fair test, use data or review wrong answers from the week. Return to the same errors after a delay.
Adjust duration to the student’s actual timetable. Frequent and accurate correction is more effective than long sessions that end in fatigue and unreviewed mistakes.
A Twelve-Week Exam Preparation Plan
Weeks 1–2: verify Cambridge 0620, the exam year, Core or Extended entry and practical-paper route. Diagnose strengths in particle models, formulae, quantitative work and data interpretation.
Weeks 3–5: repair high-impact foundations. Prioritise formulas, bonding, equations, conservation, mole relationships and the language of chemical reactions.
Weeks 6–8: connect reaction rates, energetics, acids, periodic patterns, organic chemistry and environmental applications to these foundations. Practise experiments and graphs throughout.
Weeks 9–10: use current-format question sets and selected full papers. Match the correct components, time limits and grade route. Review mistakes by cause.
Weeks 11–12: consolidate recurring weaknesses, complete a manageable number of accurate simulations and revisit practical techniques. Use revision as evidence gathering rather than panic-driven repetition.
The schedule is an example, not an official required teaching order. Students with a longer runway should build in more spaced practice and independent experimentation under appropriate supervision.
Past Papers, Mark Schemes and Syllabus Accuracy
The starting point is Cambridge IGCSE Chemistry 0620. Use the exam-year syllabus for the content and paper rules.
The 2026–2028 syllabus PDF identifies the twelve topics, paper combinations, time limits and practical expectations. Cambridge may issue updates, so check the syllabus page when preparing examinations.
Older past papers are useful for some stable skills but not necessarily an exact model of every later examination. Use up-to-date specimen materials where available and avoid treating one past paper as a prediction of what must appear next.
After marking, diagnose the first incorrect reasoning step, correct it and reattempt the question later. A mark scheme should help a student learn what is required, not become a collection of sentences to copy in advance.
What Parents Should Look For
A useful sign of improvement is that the student can explain why an equation is balanced, what a graph shows and why an experiment’s conclusion is limited. These are more revealing than the number of highlighted pages in a revision guide.
Ask the student which Chemistry topic needs repair and what exactly will be done this week. ‘I’ll read Chapter 3 again’ is weaker than ‘I’ll practise converting masses to moles and checking equation ratios without notes’.
Tutors should teach transparent methods, correct misconceptions and support independent practice. No responsible Chemistry support can promise a particular grade after a fixed number of lessons.
For Singapore families, Cambridge IGCSE Chemistry 0620 is not identical to Singapore SEC or O-Level Chemistry specifications. Some concepts overlap, but examination codes, topic boundaries and assessment routes differ.
Frequently Asked Questions
Is IGCSE Chemistry mainly memorisation?
It requires definitions, formulae and knowledge of reactions, but examination questions also test calculations, mechanisms, data interpretation and experimental reasoning. Memory alone is insufficient for unfamiliar applications.
What papers does a Core student take?
Under the 2026–2028 0620 syllabus, Core candidates take Papers 1 and 3, plus either Paper 5 or Paper 6. Extended candidates take Papers 2 and 4, plus either Paper 5 or Paper 6.
Is Alternative to Practical easier?
It is a different assessment mode, not a reason to neglect practical skills. It requires understanding of experimental design, observation, analysis and evaluation. The correct entry route depends on the centre.
Can Core students get A*?
Not through the Core entry route in the published 2026–2028 assessment scheme. Its grade range is C–G. The Extended route covers higher grade eligibility.
How can I improve mole calculations?
Begin with the balanced equation, convert known data to moles, use the coefficient ratio, then convert to the requested quantity. Check units and whether a limiting reactant matters.
Why do I know the equation but lose marks?
The question may require an explanation, observation, calculation or interpretation rather than simply an equation. Identify the exact command word and what evidence or reasoning it asks for.
Should I memorise experimental improvements?
Learn common sources of error, but explain how a proposed improvement fixes the specific weakness in the given setup. Generic memorised suggestions can be irrelevant.
Final Student Checklist
- I know the correct Cambridge syllabus code and examination year.
- I know my Core or Extended entry and the correct three components.
- I understand particles, bonding and chemical change rather than only labels.
- I can write and balance formula equations without changing chemical identities.
- I can use mole ratios, units and numerical checks accurately.
- I can distinguish reaction rate from energy change.
- I can interpret observations without inventing unsupported conclusions.
- I can plan fair investigations and explain useful improvements.
- I practise retrieval, mixed questions and specific error correction.
- I check the official Cambridge documents for updates before examinations.
IGCSE Chemistry works when particle models, equations, quantitative relationships and experimental evidence reinforce one another. A well-prepared student does more than recognise a textbook example. The student can make a reasoned, defensible explanation when a new chemical problem appears.
Official source: Cambridge IGCSE Chemistry (0620). This eduKateSG guide is independent educational commentary and is not an official Cambridge publication.
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