How to Answer Planning, Analysis and Evaluation Questions in A Level Chemistry (9701) Paper 5

Cambridge International AS & A Level Chemistry (9701) Paper 5 is a written practical-skills paper, not a theory paper with a few experimental questions added. Under the current 2025-2027 syllabus, Paper 5 lasts 1 hour 15 minutes, is worth 30 marks and contributes 11.5% of the full A Level. The context may even sit outside the taught syllabus because the paper is assessing whether you can plan an investigation, process experimental information, draw conclusions and evaluate the quality of the method. Cambridge allocates at least 12 marks to planning and at least 12 to analysis, conclusion and evaluation, with the remaining 6 marks distributed across those skills. That is why a reliable Paper 5 approach needs to connect the whole investigation rather than memorise separate phrases for 'planning' and 'evaluation'.

Start with the practical aim before you write any method

The June 2024 examiner report says the best starting point is a clear understanding of the practical aim and methodology. Read the information until you can state what the investigation is trying to determine. Then identify the independent variable, the dependent variable and the chemical measurement that will represent the dependent variable. If the question asks how concentration affects rate, 'measure the reaction' is too vague. Decide whether rate will be represented by time to a fixed endpoint, volume of gas collected per unit time, mass loss or another measurable quantity that fits the chemistry. A strong plan begins with a measurable relationship.

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Write a prediction that links the variables

A prediction should show the expected relationship, not simply repeat the aim. You may be asked for a written hypothesis or for a sketch graph. State how the dependent variable is expected to change as the independent variable changes. If you are asked to justify the prediction, use the relevant chemistry. Keep prediction and result separate. The prediction is what you expect before collecting the data. The conclusion is what the evidence actually supports afterwards.

Choose a sensible range and enough values

The syllabus expects planning to include a suitable range and distribution of values for the independent variable. Avoid a memorised 'five values' rule. The range should be wide enough to reveal the relationship and the intervals should be useful for the expected trend. If the response may change sharply in one region, closer intervals there may be more informative. State actual values where the question gives enough information. A plan saying 'use different concentrations' is much weaker than one specifying a series that can realistically be prepared from the stock solution.

Control variables by saying how they will be controlled

Naming temperature as a control variable does not explain how temperature will be kept constant. State the method: use a thermostatically controlled water bath, allow solutions to reach the chosen temperature before mixing, or use another suitable procedure. The same applies to volumes, masses, particle size, surface area and time. Choose controls that could genuinely influence the dependent variable. A long list of constants that do not matter makes the plan look memorised rather than designed.

Name apparatus precisely and use it for the job it is designed to do

Paper 5 often rewards apparatus choice because it determines uncertainty and whether the method is practical. A volumetric pipette is for accurately transferring a fixed volume; a burette is for delivering a variable measured volume; a volumetric flask is for making a solution up to an accurately known total volume. Use the correct piece of apparatus rather than the most familiar one. The June 2024 examiner report also highlighted transfer technique. If a solution is transferred from a beaker into a volumetric flask, the beaker should be rinsed so that the transfer is quantitative. By contrast, a pipette or burette is calibrated to transfer the stated volume, so rinsing the receiving vessel with extra portions of that solution would alter the intended amount.

Plan the results table before the experiment

A planning answer becomes much stronger when the result you intend to collect is obvious. State the quantities and units that will be recorded. If a calculated quantity such as rate, concentration or enthalpy change will be needed, make that clear. A table can help you show which variable is controlled and which is measured without adding unnecessary prose. If the investigation requires repeats, say what will be repeated and how the repeat results will be used. Repeats can help identify anomalous results and allow a mean to be calculated, but they are not a cure for every experimental problem.

Treat risk assessment as chemistry, not a generic sentence

A useful safety point identifies the hazard, the route of risk and the action that reduces it. 'Wear goggles' is too generic if the question contains a more specific chemical or physical hazard. If a corrosive solution is used, identify the contact risk and suitable protection. If a flammable substance is heated, avoid a naked flame and use an appropriate heat source. Do not invent hazards simply because you think every plan needs several safety points. One relevant, specific risk-control link is more valuable than a list of generic laboratory rules.

Use significant figures that match A Level experimental work

The June 2024 examiner report notes that most numerical answers, when no other instruction is given, should usually be expressed to three significant figures. Follow the question if it specifies a different precision, and make sure the number of significant figures is sensible for the data and apparatus used. Do not write a mass to more decimal places than the balance can measure, and do not carry an obviously over-precise final result simply because the calculator displays it.

Understand maximum uncertainty before calculating percentage error

The current syllabus defines the maximum uncertainty in a quantitative measurement as half the difference between the closest calibrations. If a thermometer is marked every 1 °C, one reading has a maximum uncertainty of ±0.5 °C. When a result is found from the difference between two readings, the uncertainties from both readings contribute. This is a common trap in temperature-change questions. If ΔT is calculated from two thermometer readings, Cambridge's syllabus example doubles the ±0.5 °C uncertainty before dividing by ΔT and multiplying by 100. The June 2024 examiner report specifically noted candidates who divided by one of the original temperature readings instead of the temperature change.

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Do not confuse uncertainty with percentage error

Absolute uncertainty is expressed in the same unit as the measurement. Percentage error expresses that uncertainty relative to the size of the measured value. A larger measured change with the same instrument uncertainty gives a smaller percentage error. That principle is often more important than memorising a single formula. When asked how a modification affects uncertainty and percentage error, consider whether the instrument resolution changes, whether the measured quantity becomes larger or smaller, and which of those changes affects the ratio.

Draw the graph the data require

When plotting data, choose axes that make the relationship easy to interpret, include units and use a sensible scale. If the task requires a line of best fit, do not join points one by one unless instructed to do so. Use the overall trend. For gradients, Cambridge's June 2024 Paper 52 report gives a particularly useful warning: select points from the line of best fit, not simply from plotted data points. Experimental points do not necessarily lie exactly on the best-fit line. Choose points far enough apart to make the gradient less sensitive to small reading errors.

Use transformed graphs when the relationship is not linear

Paper 5 may ask you to manipulate variables so a predicted relationship becomes a straight line. The important skill is to connect the mathematical transformation to the chemical model. Decide which variable belongs on each axis and what the gradient or intercept would represent. Do not perform transformations mechanically. Check the units of the transformed quantity and make sure the calculated values are consistent before plotting.

Draw a conclusion from the evidence, then explain the chemistry

A conclusion should state the main feature of the data and whether the evidence supports the prediction or hypothesis. Quote relevant values or graph features where they are needed to justify the statement. Then use chemical reasoning to explain the result. Keep the direction of reasoning clear. The data establish what happened; chemistry explains why it is plausible. Do not ignore an anomalous result simply because the theory predicts a smooth trend.

Distinguish systematic and random errors

The syllabus explicitly requires this distinction. A systematic error biases measurements in a consistent direction, such as a balance with a zero error. A random error varies unpredictably between readings, such as small changes in room temperature during a rate experiment. Do not write 'human error' as a catch-all explanation. Cambridge states that 'human errors' is not an acceptable generic category. If observation introduces random variation, describe the actual difficulty, such as judging the disappearance of a cross or deciding exactly when a colour endpoint is reached.

Evaluate the largest limitation, not every imaginable one

A strong evaluation identifies the errors that materially affect the reliability or accuracy of the conclusion. For a calorimetry experiment, heat exchange with the surroundings may dominate. For a timing experiment, an imprecise endpoint may matter more. For a gas experiment, leakage or incomplete reaction may be the main limitation. Rank the problems mentally. A real but tiny source of uncertainty should not receive more attention than the major limitation of the method.

Suggest an improvement that targets the identified error

An improvement earns value when the link is specific: problem, consequence, modification. If heat is lost to the surroundings, use better insulation, a lid or a method that reduces the heat-transfer problem. If an endpoint is subjective, use an instrumental measurement where suitable. If a small mass creates a large percentage uncertainty, use a more precise balance or a larger appropriate sample. Repeating the experiment can reduce the influence of random variation and help identify anomalous results, but it does not remove a systematic error. Likewise, saying 'use more accurate equipment' is incomplete unless you name the equipment and explain which measurement improves.

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Original example: concentration and rate

Imagine an original investigation into how hydrochloric acid concentration affects the rate of reaction with a fixed length of magnesium ribbon. A workable plan could prepare several acid concentrations using volumetric apparatus, keep total solution volume and temperature constant, use equal lengths of magnesium cleaned in the same way, and measure the time required to collect a fixed volume of hydrogen. Rate can then be represented by fixed gas volume divided by time or, if the gas volume is constant, by a quantity proportional to 1/time. Repeating each concentration allows a mean time to be calculated. A graph can test the relationship between concentration and rate. Evaluation might identify difficulty starting the timer at exactly the same moment as mixing, gas lost before the bung is secured, or temperature drift. Each improvement should target whichever of those errors is most significant in the chosen setup.

Common Paper 5 mistakes

1. Writing a memorised method before identifying the actual practical aim.
2. Naming an independent or dependent variable without saying how it will be changed or measured.
3. Listing control variables without explaining how they will be kept constant.
4. Choosing apparatus by habit rather than by the precision and transfer required.
5. Giving a generic safety statement with no specific hazard.
6. Using too many significant figures simply because the calculator displays them.
7. Calculating percentage error using the wrong denominator, such as one temperature reading instead of ΔT.
8. Taking gradient points from raw plotted points instead of from the line of best fit.
9. Ignoring an anomalous result because it does not match the expected chemistry.
10. Writing 'human error' instead of identifying the actual random or systematic error.
11. Suggesting repeats as the solution to a systematic error.
12. Giving more than one contradictory answer when the question asks for a single conclusion or improvement.

A reliable Paper 5 routine

1. State the practical aim in your own words before planning.
2. Identify the independent and dependent variables and how each will be changed or measured.
3. Choose a useful range, intervals and apparatus that match the precision required.
4. Explain how each important control variable will be standardised.
5. Plan the table, repeats and data processing before writing the method in full.
6. Use significant figures and units that match the apparatus and the instruction.
7. For uncertainty questions, count how many readings contribute to the measured quantity before calculating percentage error.
8. For graphs, use the best-fit line or curve and take gradient points from that fitted line.
9. Base the conclusion on the data first, then add the chemical explanation.
10. Evaluate by identifying the most important limitation and proposing a specific modification that addresses it.

Put it into practice

Take one recent Chemistry (9701) Paper 5 and split your review into three columns: planning, analysis/conclusion and evaluation. For every lost mark, record the practical skill rather than the chemical topic. If you lost a mark for uncertainty, repeat uncertainty questions. If the problem was a weak control variable or vague apparatus choice, practise planning tasks. If your evaluation was generic, rewrite it as limitation -> consequence -> improvement. Inside NeuraGeek, you can use Chemistry (9701) past-paper practice alongside the existing Paper 3 practical guide, treating Paper 3 as hands-on execution and Paper 5 as the written design, analysis and evaluation of practical chemistry.