How to Perform in PSLE | Learner’s Guide Vol 0033 | Science: Match the Command Word Before You Write the Science

A strong PSLE Science answer can still lose marks when it performs the wrong job. A learner may explain when the question only asks for a description, describe when a mechanism is required, predict without using the stated pattern, or justify with a general fact that does not support the decision. The Science knowledge may be correct; the response job is not.

This volume develops one advanced examination habit: match the command word before you write the Science. The command word tells the learner what type of reasoning must appear in the answer. Before writing a concept, identify whether the task is to state, identify, describe, compare, explain, predict, suggest, conclude, justify or evaluate.

This builds on Vol 0004 for evidence before explanation, Vol 0017 for measurement identity, Vol 0025 for comparing change and Vol 0029 for evidence discrimination. The command word decides which part of that reasoning system the answer must expose.

State and identify need directness

State or identify questions usually require the relevant fact, object, variable, process or feature without a long mechanism unless the task adds another demand.

Over-answering can introduce unnecessary claims. Give the exact requested item first.

Describe tells what the evidence shows

Describe questions focus on observable pattern, direction, sequence, feature or change.

Do not add a cause unless the question asks why. A description should remain anchored to data, graph, diagram or observation.

Compare needs both sides on the same basis

A comparison must name the same property for both objects or set-ups and state the relationship clearly.

Avoid describing one side’s temperature and the other side’s time, or one side’s cause and the other’s result.

Explain needs a mechanism

An explanation connects the condition in the question to the observed outcome using the relevant scientific relationship.

A good chain is condition → process or relationship → outcome. A keyword alone is not a mechanism.

Predict needs a direction and a reason

Prediction begins with what is expected to happen under a new condition, then uses the established pattern or concept to support that direction.

Do not merely repeat the old result. Apply the relationship to the changed condition.

Suggest allows a plausible evidence-based possibility

Suggest questions often allow more than one defensible answer, but the response should still be scientifically reasonable and linked to the context.

Do not treat suggest as permission to guess without evidence.

Conclude should stay inside the evidence

A conclusion states what the results support about the tested relationship.

Avoid converting one investigation into an always-or-never rule or extending beyond the measured conditions.

Justify needs a decision plus support

A justification answers why a choice, conclusion or method is appropriate.

State the decision and the specific evidence or scientific reason that makes it defensible.

Evaluate asks about quality, limitation or strength

Evaluation may require commenting on fairness, reliability, measurement quality, repeated trials, control of variables or strength of evidence.

Do not answer with a generic ‘fair test’ label when the task expects the specific reason.

Explain and describe are not interchangeable

A graph may show temperature rising. ‘Temperature rose from X to Y’ describes. ‘It rose because…’ begins explanation.

Learners should know when to stop at pattern and when to continue into mechanism.

Predict and conclude look in different directions

Prediction looks forward to an unobserved case. Conclusion looks backward across observed evidence.

The evidence source and verb tense may differ even when the same scientific relationship is involved.

Suggest and predict have different certainty

Predict uses an established pattern or known relationship to state an expected outcome. Suggest can offer a plausible explanation or improvement where more than one answer may be acceptable.

Both still require evidence or scientific reasoning.

Justify and explain can overlap

An explanation accounts for why an outcome occurs. A justification supports why a choice or statement is reasonable.

If the question asks why a set-up is better, the answer may need both methodological reasoning and evidence.

Command words can appear in multi-part questions

One part may ask to describe a graph, the next to explain the trend, and the next to predict a new point.

Keep each response job separate. Do not combine them into one paragraph that leaves one command unanswered.

The command word is a first-move trigger

Before writing, circle or mentally name the command. Translate it into a response template: describe = pattern, explain = mechanism, compare = both sides, justify = decision plus support.

This is an exam-control habit, not a memorised sentence frame.

A seven-step command-word routine

1. Find the command word.
2. Name the evidence object: graph, table, diagram, set-up, observation or concept.
3. Translate the command into the required reasoning job.
4. Write the minimum complete response for that job.
5. Add only relevant scientific detail.
6. Check that the answer does not drift into a different command type.
7. Stop when the requested job is complete.

Twenty-eight worked command-word cases

State the variable

A question asks the learner to state the variable that was changed.

The likely failure is explaining instead of naming. Name the changed variable directly.

A long mechanism does not improve a state response unless another part asks for explanation. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Identify the apparatus

The diagram shows several pieces of equipment and the question asks which measures temperature.

The likely failure is describing function without naming. Identify the thermometer first.

If needed, add the function only when the wording requires it. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Describe a graph trend

A graph rises steadily as time increases.

The likely failure is jumping to cause. State that the measured quantity increases as time increases.

Do not invent the mechanism when the task asks only for description. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Describe a no-change region

A graph becomes flat over part of the interval.

The likely failure is calling it increasing. State that the measured value remains approximately constant over that interval.

Use the axis quantities and relevant range. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Compare two temperatures

Two set-ups end at different temperatures.

The likely failure is one-sided answer. State which set-up has the higher or lower temperature and, where useful, include both values.

Comparison needs both sides on the same basis. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Compare changes

Two set-ups start at different temperatures.

The likely failure is endpoint comparison. Compare the change from start to end, not only final values.

This links directly to Vol 0025. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Explain insulation

An insulated container cools less.

The likely failure is keyword answer. Connect insulation to reduced transfer and then to smaller temperature decrease.

Mechanism should explain the measured outcome. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Explain faster dissolving

One condition produces shorter dissolving time.

The likely failure is amount-rate confusion. Explain why the condition changes the rate under the tested set-up.

Do not claim greater solubility when only time was measured. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Predict after increasing a condition

A graph shows an increasing relationship within a tested range.

The likely failure is repeating old point. State the expected direction for the new condition and support it with the observed pattern.

Keep the prediction within reasonable evidence bounds. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Predict after decreasing a factor

A known relationship suggests the response should fall.

The likely failure is missing direction. State decrease first, then connect it to the scientific relationship.

Prediction should be explicit before explanation. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Suggest a reason

An unexpected result appears in one trial.

The likely failure is random guess. Offer a plausible scientific or methodological reason connected to the set-up.

The suggestion should fit the evidence and not contradict known conditions. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Suggest an improvement

An experiment has inconsistent readings.

The likely failure is generic ‘repeat’ only. Name a specific improvement such as repeated trials, better control or more precise measurement.

Explain how the improvement addresses the observed weakness if required. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Conclude from fair comparison

Two set-ups differ only in one intended condition and show consistent result difference.

The likely failure is universal overclaim. State that under the tested conditions the changed factor is associated with the measured difference.

Keep the conclusion proportional to the design. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Conclude from confounded comparison

Two relevant conditions changed together.

The likely failure is strong causal claim. State the observed difference but avoid attributing it uniquely to one factor.

The evidence cannot isolate the intended cause. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Justify a choice of instrument

Two tools measure the same quantity at different precision.

The likely failure is naming without support. Choose the more appropriate tool and cite precision, range or suitability.

Justification needs decision plus reason. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Justify a fairer set-up

One proposed design keeps more relevant conditions constant.

The likely failure is generic fair-test phrase. Choose the design and name the controlled conditions that make comparison stronger.

Specific evidence beats labels. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Evaluate repeated trials

Three similar readings are obtained.

The likely failure is saying ‘accurate’ automatically. Comment that repeated similar results improve confidence in reliability.

Reliability does not by itself prove validity of the method. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Evaluate anomalous data

One result differs sharply from repeated pattern.

The likely failure is ignoring the anomaly. Acknowledge the anomalous result and suggest checking or repeating the trial.

Evaluation includes conflicting evidence. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Describe then explain

A question has two parts: first describe the trend, then explain it.

The likely failure is merging jobs. Part one states the pattern; part two adds mechanism.

Keeping the parts separate protects marks. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Compare then justify

Two designs are shown, then learner must choose one.

The likely failure is comparison without decision. First compare relevant differences, then select and justify the stronger design.

The final answer should answer both sub-jobs. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Predict from data table

Values show a clear direction across tested conditions.

The likely failure is unsupported extrapolation. Use the observed relationship to make a bounded prediction.

Do not claim indefinite continuation beyond reasonable context. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Suggest another variable

The task asks what else could affect the result.

The likely failure is restating tested variable. Name a scientifically relevant alternative factor not already controlled.

The suggestion should be connected to the measured response. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Explain control variable

The question asks why time is kept the same in two set-ups.

The likely failure is describing equality only. Explain that equal time prevents duration from becoming another cause of the result difference.

The answer should connect control to fair comparison. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

State versus explain in MCQ review

A learner knows the correct option but writes a long reason in revision.

The likely failure is response mismatch. For the actual MCQ, select the option; use explanation during review to strengthen reasoning.

Exam output and learning output are different jobs. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Conclusion with no difference

Two fair set-ups produce similar measured results.

The likely failure is invented effect. Conclude that no clear difference was observed under those tested conditions.

Do not force the expected mechanism onto unchanged evidence. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Justify a conclusion

A learner must say why a conclusion is supported.

The likely failure is general topic fact. Cite the specific pattern, fair comparison and relevant scientific relationship.

Justification should show why this evidence supports this conclusion. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Evaluate measurement method

A ruler with coarse markings is used for a small change.

The likely failure is topic-only response. Comment on whether the instrument can detect the change with suitable resolution.

Evaluation should target the actual measurement limitation. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

Predict and justify

The task asks what happens next and why.

The likely failure is answering only direction. State the predicted outcome and then give the supporting concept or pattern.

Both parts are needed for a complete response. The learner should be able to say which command word controls the answer and what information that command requires.

Now rewrite the same Science content under a different command. Notice how the evidence may stay the same while the response structure changes. This is useful practice because it separates subject knowledge from examination job.

For checking, compare the first verb of the answer with the question’s command. If the response begins doing a different job, repair the structure before adding more science.

For delayed transfer, use a different topic with the same command. The learner should recognise the reasoning job even when the chapter changes.

A seven-day command-word cycle

1. Day 1: state and identify.
2. Day 2: describe and compare.
3. Day 3: explain with condition–mechanism–outcome.
4. Day 4: predict and suggest.
5. Day 5: conclude and justify.
6. Day 6: evaluate investigations and measurements.
7. Day 7: mixed timed questions with command words unhighlighted.

Parents and tutors: ask what job the question is buying

When a learner gives a scientifically correct but poorly targeted answer, ask: “What is the command word buying from you here?” The learner should answer with a response job such as pattern, mechanism, prediction or justification.

This feedback is more transferable than simply supplying the model answer.

Frequently asked questions

Do command words always have exactly one answer format?

No. Context matters, but the command strongly indicates the reasoning job the examiner expects.

Can ‘explain’ include evidence?

Yes. Good explanations often refer to the observed result and connect it to a mechanism.

Does ‘suggest’ mean any answer is accepted?

No. The suggestion must still be scientifically reasonable and relevant to the evidence or method.

Should a conclusion include a mechanism?

Only if the question requires it. A conclusion primarily states what the evidence supports.

What if a question has two command words?

Treat them as two required jobs and make sure both appear in the response.

How do command words help timing?

They prevent over-answering and help the learner write the minimum complete response for the task.

Official 2026 PSLE Science frame

The 2026 PSLE Science syllabus assesses knowledge with understanding and application of knowledge and scientific inquiry, including interpreting information, making predictions, evaluating observations and methods, and communicating explanations and reasoning. Command-word control helps learners match that reasoning to the exact task. See the 2026 PSLE Science syllabus.

Next route

Use Vol 0004 for evidence before explanation, Vol 0017 for measurement identity, Vol 0025 for change comparison and Vol 0029 for evidence discrimination. Continue to Vol 0034: Reset After One Difficult Question Before You Start the Next. The wider Science route is the PSLE Science Learning Guide and PSLE Learning Guide.

The performance rule

Before writing the science, match the command word to the response job. The right knowledge in the wrong answer form is still the wrong exam response.

Series: How to Perform in PSLE | Learner’s Guide · Vol 0033 · Science command-word control