How to Answer Alternative to Practical Questions in IGCSE Chemistry (0620)

Cambridge IGCSE Chemistry (0620) Paper 6 is called Alternative to Practical, but it is not an alternative to learning practical skills. It is a written paper that tests whether you understand how chemical experiments are carried out, measured, recorded, interpreted and improved. For the 2026–2028 syllabus, Paper 6 is one hour, worth 40 marks and tests AO3 Experimental skills and investigations. Cambridge states that Paper 5 Practical Test and Paper 6 Alternative to Practical require the same experimental skills and the same experimental contexts; the difference is that Paper 6 does not require you to perform the experiments in the examination. That means the best preparation is not memorising a collection of Paper 6 tricks. It is learning to think like the person doing the experiment.

Treat every diagram and table as a real experiment

Paper 6 often gives you apparatus diagrams, readings, tables, observations or the results of an experiment someone else has carried out. Do not treat these as abstract pictures. Ask what the student physically did. What was measured? Which apparatus was used? Which variable changed? What observation would actually be visible? That mindset makes many questions easier because you stop guessing from memory and start following the experimental situation. For example, if a diagram shows gas being collected, think about what quantity the apparatus measures and what could affect that measurement. If a question shows a thermometer and several liquid volumes, think about how the readings should be recorded and what would make the temperature change more or less reliable. Cambridge can also use unfamiliar procedures with simple apparatus, so understanding the purpose of equipment matters more than memorising one standard setup.

Read measurements at the precision the apparatus allows

Paper 6 can ask you to read values from diagrams of apparatus. The current syllabus expects candidates to take readings with appropriate precision, including reading to the nearest half-scale division where required. Look carefully at the scale before writing the number. Work out what one small division represents, then decide how precisely the reading can reasonably be recorded. Keep related readings consistent. If a table contains several readings taken from the same type of apparatus, they should normally be recorded to the same resolution. Cambridge examiner reports repeatedly flag inconsistent decimal places as a problem. Do not make a measurement look more precise simply by adding extra zeros that the apparatus could not support.

Tables need headings, units and consistent recording

When you complete or design a results table, the structure matters. Each measured quantity should have a clear heading and the unit should normally appear in the heading rather than being repeated in every cell. Record the values systematically and to an appropriate degree of precision. If the question provides some data and asks you to complete the rest, match the style already used unless the apparatus clearly requires something different. Do not mix a quantity with its unit inside the data cells unless the question specifically asks for that. A clean table makes the relationship between variables visible and reduces the chance of losing marks through inconsistent presentation.

Graphs are part of the practical, not a drawing exercise

Graph questions reward careful presentation and interpretation. Choose a linear scale that uses a substantial part of the grid. Cambridge examiner guidance recommends sensible scales based on 1, 2 or 5 and their powers of ten because awkward scales make plotting errors more likely. Plot points clearly and do not hide them under the line. Then decide what kind of best-fit line the data actually support. A line of best fit can be straight or curved. Do not force a straight line through data that clearly follow a curve, and do not join each point individually unless that is what the task requires. If the question asks you to read a value from the graph, show the construction lines where appropriate: move vertically from the required x-value to the graph, then horizontally to the y-axis. Examiner reports frequently note that candidates lose marks because their reading is unsupported or taken from the wrong position.

Separate observations from chemical conclusions

One of the most important Paper 6 habits is distinguishing what you observe from what you infer. An observation is what you can see, measure or detect directly. A conclusion identifies the substance, ion, gas or chemical change that the observation supports. If bubbles appear, the observation is effervescence, fizzing or bubbles. Saying “a gas is produced” is a conclusion rather than a visible observation. If two solutions form an opaque solid, the correct observation may be a precipitate of a particular colour. Cambridge examiner reports repeatedly warn against using the word precipitate for a solid that was already present before the reaction, and against writing an identification when the question asks only for the observation.

Use the qualitative-analysis notes instead of trying to reproduce them from memory

For Paper 6, Cambridge provides the Notes for use in qualitative analysis. From 2025 onwards these notes are included in both the Practical Test and Alternative to Practical. Use them. The purpose of the paper is to test practical interpretation, not whether you can reproduce every ion test from memory in the exam. The useful skill is matching the test, observation and conclusion. If aqueous sodium hydroxide produces a coloured precipitate, use the notes to identify which ions match that behaviour. If a gas test is positive, record the actual test result before naming the gas. Negative results matter too: if a test gives no expected change, that can rule out an ion or gas. Do not invent an extra observation because you feel every test should produce something dramatic.

Gas tests need the test and the positive result

When a question asks how to test a gas, give the actual procedure and the positive result. For hydrogen, that means using a lighted splint and obtaining the characteristic pop. For oxygen, use a glowing splint and state the result. For ammonia, damp red litmus paper is required and the colour change matters. The same principle applies to the other gas tests listed in the qualitative-analysis notes. Do not write only the gas name if the question asks for the test, and do not write only the reagent without the expected observation. Practical chemistry is about evidence: the conclusion comes from the result of the test.

Calculations still need experimental logic

Paper 6 can include calculations using experimental data, such as temperature changes, volumes, rates or differences between readings. Set up the calculation from the data the question actually gives. Keep the units attached to the quantity and round sensibly rather than truncating the answer. If the question asks for an average rate, think about what changed and over what time interval. If it asks for a difference between two graph readings, take both readings from the graph and subtract them. Cambridge examiner reports show that some candidates instead read a midpoint value, add the two readings or find a mean because they focus on the numbers without first deciding what the physical quantity represents.

When improving a method, name the apparatus and say what it replaces

Questions about improvements are not asking for a vague statement such as “use more accurate equipment”. Say what should change and why. If a measuring cylinder is limiting the precision of a volume measurement, you might suggest a burette or volumetric pipette where suitable, but you should state what volume it would measure or what apparatus it would replace. Do not assume that a digital device is automatically more accurate simply because it shows more decimal places. Accuracy depends on the instrument, its calibration and how it is used. Likewise, using a gas syringe does not automatically make an experiment more accurate if the main source of uncertainty lies somewhere else. The improvement must target a specific weakness in the existing method.

Planning questions reward a workable method, not a list

Extended planning questions are often where students write too much of the wrong thing. Cambridge examiner reports explicitly state that there is no need to begin with separate lists of apparatus, aims, safety precautions, or independent and dependent variables. If the use of apparatus earns credit, the mark is for explaining how that apparatus is used, not for naming it in a disconnected list. Write the plan as a sequence someone could carry out. State what you will change, what you will measure, how the measurement will be made, which conditions must be controlled, how many values or repeats are needed, what safety issue matters and how the results will be processed. If the experiment compares rates, make clear how rate will be measured. If it compares temperature change, make clear how initial and final temperatures are obtained. The method should make the variables visible through the actions.

Original practice example: comparing the rate of reaction

Suppose you are asked to plan an experiment to investigate how the concentration of an acid affects its reaction rate with a fixed mass of a solid carbonate. A strong plan might use several acid concentrations while keeping the total acid volume, mass and particle size of the carbonate, temperature and apparatus constant. Add the carbonate, start the stopwatch immediately and measure the volume of gas collected in a gas syringe at regular time intervals, or measure the time taken to collect a fixed gas volume. Repeat each concentration and calculate a mean. Record concentration, time and/or gas volume in a table with units. If you are comparing full gas-volume curves, plot gas volume against time and compare gradients over the same part of the reaction. A useful safety point should match the reagents used, such as eye protection when handling an irritant or corrosive solution. The strength of the plan comes from the link between the variable, the measurement and the rate—not from how many pieces of apparatus you can name.

Common Paper 6 mistakes

1. Reading an apparatus scale without first checking what one division represents.
2. Recording readings from the same apparatus to inconsistent precision.
3. Choosing an awkward graph scale that makes plotting unnecessarily difficult.
4. Drawing a straight best-fit line through data that clearly follow a curve.
5. Writing a chemical conclusion when the question asks for an observation.
6. Writing “gas produced” instead of the visible observation of effervescence, fizzing or bubbles.
7. Calling any solid a precipitate even when it was not formed by mixing solutions.
8. Ignoring a negative qualitative-analysis result even though it rules out a possible ion.
9. Suggesting “more accurate equipment” without naming the apparatus and what measurement it improves.
10. Listing apparatus or variables at the start of a planning answer instead of writing a usable experimental method.

A practical Paper 6 checklist

1. Have I read every apparatus scale at the correct precision?
2. Are table headings clear, with units and consistent recording?
3. Does my graph use a sensible linear scale and the correct best-fit line or curve?
4. If I read from a graph, have I shown the construction clearly where useful?
5. Have I written the observation before the chemical conclusion?
6. For a gas test, have I given both the test and the positive result?
7. Have I used the qualitative-analysis notes rather than guessed?
8. Does each method improvement target a real limitation?
9. In a planning question, have I explained what the apparatus is used for?
10. Can another student follow my method and collect data that would answer the question?

Put it into practice

Do one Paper 6 question without the mark scheme beside you and review it by skill rather than by total score. Separate your mistakes into measurement, tables, graphs, observations, qualitative analysis, calculations, method evaluation and planning. That tells you what to practise next. If graph work is weak, isolate graph questions. If qualitative observations are costing marks, practise writing observation first and identification second. Inside NeuraGeek, you can use Chemistry (0620) past papers and topical practice to repeat the specific practical skill instead of simply doing another full paper and hoping the same mistake disappears.