Cambridge IGCSE Combined Science Tutors Online

Cambridge IGCSE Combined Science is syllabus 0653. This page works from the syllabus for exams in 2025, 2026 and 2027. Exams are available in the June and November series, and also in the March series in India.

This is the qualification for students who study biology, chemistry and physics together rather than taking them as separate subjects. The subject content is divided into three sections, Biology from B1 to B16, Chemistry from C1 to C12, and Physics from P1 to P5, and candidates must study all three sections. There is no choosing a favourite science.

All candidates take three papers, and the first decision is which route to follow. Candidates who have studied the Core syllabus content, or who are expected to achieve a grade D or below, are entered for Paper 1, Paper 3 and either Paper 5 or Paper 6, and are eligible for grades C to G. Candidates who have studied the Extended syllabus content, which is the Core plus the Supplement, and who are expected to achieve a grade C or above, are entered for Paper 2, Paper 4 and either Paper 5 or Paper 6, and are eligible for grades A* to G.

That decision governs the whole course. A candidate who is only taught the Core subject content can achieve a maximum of grade C, so anyone aiming for grades A* to C must be taught the Extended subject content throughout, not as a late top-up.

Paper 1 is Multiple Choice (Core) and Paper 2 is Multiple Choice (Extended). Each lasts 45 minutes, carries 40 marks and is worth 30% of the qualification, and each consists of 40 four-option multiple-choice questions. Paper 1 is based on the Core content only and Paper 2 on the Core and Supplement.

Paper 3 is Theory (Core) and Paper 4 is Theory (Extended). Each lasts 1 hour 15 minutes, carries 80 marks and is worth 50% of the qualification, and each consists of short-answer and structured questions.

The third paper is a choice between the Practical Test and the Alternative to Practical, and both are worth 20% and carry 40 marks. Paper 5 is the Practical Test, lasting 1 hour 15 minutes, where candidates do experiments. Paper 6 is the Alternative to Practical, lasting 1 hour, where they do not. Both are based on the experimental skills set out in section 4 of the syllabus, so the thinking tested is the same and the difference is whether the work is done at a bench.

Those experimental skills are worth understanding in detail, because 20% of the marks depend on them and they are often taught thinly. Candidates are expected to be able to use, or explain the use of, common techniques, apparatus and materials, select the most appropriate apparatus or method and justify the choice, describe tests including food tests, gas tests and qualitative tests, describe and explain hazards and identify safety precautions, and describe and explain techniques used to ensure accuracy.

They are also expected to plan experiments and investigations: identify the independent and dependent variables, describe how and explain why variables should be controlled, suggest an appropriate number and range of values for the independent variable, suggest and justify apparatus or technique, describe procedures including a suitable control experiment, identify risks and safety precautions, describe how to record and process results, and make reasoned predictions.

On the bench or in the written alternative, candidates must be able to take readings from analogue and digital apparatus or from diagrams of apparatus, read to the nearest half-scale division where required, correct for zero errors, take sufficient measurements including repeats, record qualitative observations from chemical and food tests, and record systematically in a suitable table to an appropriate degree of precision using appropriate units.

Then comes interpretation: processing data for further calculation or graph plotting, presenting data graphically including best-fit lines, analysing and interpreting including data presented graphically, using interpolation and extrapolation to determine a gradient or intercept, forming conclusions justified by reference to the data, and evaluating the quality of data by identifying anomalous results. The syllabus also states that comment on whether results are equal should be made within the limits of experimental accuracy, assumed to be plus or minus 10% at this level of study.

Finally, candidates must be able to evaluate methods and suggest improvements: evaluating experimental arrangements, methods and techniques including the control of variables, identifying sources of error including measurement error, random error and systematic error, identifying possible causes of uncertainty, and suggesting improvements to apparatus, arrangements, methods or techniques. The syllabus also sets out the language of measurement, defining true value, measurement error, accuracy and precision.

The Biology section runs from B1 to B16: Characteristics of living organisms, Cells, Movement into and out of cells, Biological molecules, Enzymes, Plant nutrition, Human nutrition, Transport in plants, Transport in animals, Diseases and immunity, Gas exchange in humans, Respiration, Drugs, Reproduction, Organisms and their environment, and Human influences on ecosystems.

The Chemistry section runs from C1 to C12: States of matter, Atoms, elements and compounds, Stoichiometry, Electrochemistry, Chemical energetics, Chemical reactions, Acids, bases and salts, The Periodic Table, Metals, Chemistry of the environment, Organic chemistry, and Experimental techniques and chemical analysis.

The Physics section runs from P1 to P5: Motion, forces and energy, Thermal physics, Waves, Electricity, and Space physics.

So this is a genuine three science course rather than a light version of one. A student has to hold biological processes, chemical reactions and physical laws at the same time, and the papers mix them rather than separating them by paper. That breadth is the defining challenge of the qualification, and it is why a student who is strong in one science but weak in another loses marks across every paper.

The assessment objectives are three. AO1 is knowledge with understanding. AO2 is handling information and problem-solving. AO3 is experimental skills and investigations.

The overall weightings are AO1 at 50 per cent, AO2 at 30 per cent and AO3 at 20 per cent of the qualification. Within the examined papers the split is 63 per cent AO1 and 37 per cent AO2 for both the multiple-choice pair and the theory pair, with nothing on AO3 in either. The practical papers are 100 per cent AO3.

The qualification is graded A*, A, B, C, D, E, F or G, with A* the highest and G the lowest. A candidate whose performance does not meet the standard required for grade G is ungraded, which is reported on the statement of results but not on the certificate.