Primary 6 Science answers become stronger when pupils can separate what they claim from the evidence that supports it. A correct-sounding statement is not enough. The learner must know what the data show, what scientific relationship connects the data to the claim, and what alternative claim would remain possible if the evidence is weak.
This guide develops claims, evidence, reasoning and counterclaims for PSLE Science. It gives pupils a disciplined structure for explaining why a conclusion deserves to be believed.
Return to the Primary 6 Science Learning Hub.
The CER rule
CLAIM → EVIDENCE → REASONING → COUNTERCLAIM CHECK → BOUNDARY.
This is an eduKate reasoning routine, not an official SEAB marking formula.
Part I — What is a claim?
A claim is the answer or conclusion being asserted.
Examples:
- Surface Q produces a greater frictional effect than P.
- Plant A had a higher photosynthesis-related output than B.
- Cup Q reduced cooling more effectively.
- The predator may not decrease immediately.
The claim should answer the exact question.
Part II — What is evidence?
Evidence is the observation, measurement or pattern that supports the claim.
Example:
Claim: Q produces greater frictional effect.
Evidence: the same car travelled 45 cm on Q but 80 cm on P under the same release conditions.
Part III — What is reasoning?
Reasoning explains why the evidence supports the claim using scientific knowledge.
Reasoning: greater frictional effect causes the moving car to slow more quickly, so the shorter travel distance on Q supports the claim.
Without reasoning, evidence and claim remain disconnected.
Part IV — Counterclaims improve reasoning
A counterclaim is an alternative conclusion that might also fit the evidence.
Example: a plant grows less.
Possible claims:
- it received less light;
- it received less water;
- it started smaller;
- it was unhealthy.
The investigation must eliminate alternatives before one claim becomes strong.
Part V — Strong evidence fits the claim directly
If the claim is about cooling rate, use temperature measurements across time.
If the claim is about frictional effect, use motion outcomes under comparable conditions.
If the claim is about food availability, use the food-web relationships and population data.
Evidence should match the target relationship.
Part VI — Irrelevant evidence is not support
“The car is red” does not support a friction claim.
“The plant is green” does not support a lamp-distance claim.
Evidence is relevant only when it helps establish the scientific relationship in question.
Part VII — One claim can use several pieces of evidence
Example: “Cup Q insulates better.”
Evidence 1: Q has higher temperature at the same times.
Evidence 2: Q has a smaller total temperature decrease.
Evidence 3: repeated trials show the same pattern.
Several consistent pieces strengthen the claim.
Part VIII — One piece of evidence may support several claims
Observation: bubble count decreases as lamp distance increases.
This could support:
- greater distance is associated with lower measured output;
- less light may be reaching the plant;
- photosynthesis-related output may be lower.
The claim chosen should match the question and the strength of the evidence.
Part IX — Do not turn reasoning into evidence
“Friction slows objects” is scientific knowledge, not the measured evidence from the trial.
“The car travelled 45 cm” is evidence.
Keep these categories separate.
Part X — Do not turn evidence into reasoning
Weak explanation: “Q has more friction because it travelled less.”
This gives evidence but only a partial mechanism.
Stronger: “The shorter travel distance on Q shows the car slowed more quickly; greater frictional effect opposes motion more strongly, supporting the claim that Q produces greater frictional effect.”
Part XI — Counterclaims and controlled variables
Controlled variables help reject counterclaims.
If the same car, same spring compression and same starting point are used, differences in car mass, release energy and starting position are less plausible explanations.
Part XII — Counterclaims and confounding variables
If light and water both change, two causal claims remain possible.
The evidence does not isolate light alone.
A good answer can explicitly say:
“The conclusion that light caused the difference is weak because water also changed.”
Part XIII — Counterclaims and observational studies
More insects are found in shaded areas.
Claim: shade is associated with higher insect counts.
Counterclaims: moisture, plant cover or time of day may also differ.
Field evidence often leaves more counterclaims than controlled experiments.
Part XIV — Counterclaims and graphs
A graph shows that X and Y increase together.
Claim: X and Y are associated.
Counterclaim: both may be responding to another variable.
Do not claim cause from pattern alone unless the method supports it.
Part XV — Claim size must match evidence size
Small claim: “In these trials, Q produced shorter travel distances than P.”
Large claim: “Q always produces more friction than every possible surface.”
The second claim is much larger than the evidence.
Part XVI — Original workshop 1 — friction
Claim: Q produces greater frictional effect.
Evidence: car travels 45 cm on Q and 80 cm on P under the same release conditions.
Reasoning: greater frictional effect causes the car to slow more quickly, producing shorter travel distance.
Counterclaim: different release strength.
Rejected because: release condition was controlled.
Original workshop 2 — photosynthesis
Claim: greater lamp distance lowers measured photosynthesis-related output.
Evidence: bubble count falls from 42 to 20 over the tested distance range.
Reasoning: greater distance reduces light reaching the plant, leaving less light energy available for photosynthesis under otherwise suitable conditions.
Boundary: bubble count is an indirect measure.
Original workshop 3 — food web
Claim: Bird A may remain stable after prey X decreases.
Evidence: Bird A also feeds on Y, which remains available.
Reasoning: the alternative food source reduces dependence on X alone.
Counterclaim: Bird A must decline immediately.
Rejected because: the food web shows an alternative feeding pathway.
Original workshop 4 — cooling
Claim: Q insulates more effectively.
Evidence: Q cools by 19°C while P cools by 28°C over the same ten minutes.
Reasoning: smaller temperature decrease indicates slower thermal-energy transfer to the surroundings under the tested conditions.
Part XVII — Strong counterclaim questions
When checking your own answer, ask:
- What else could explain this result?
- Did the method rule it out?
- Does the counterclaim fit all the data?
- Would another measurement distinguish the two claims?
Part XVIII — Claims from multiple representations
Text may establish controls.
Table may provide exact data.
Graph may show the pattern.
Diagram may show structure.
A strong claim can synthesize all four.
Part XIX — Evidence strength language
| Evidence strength | Useful wording |
|---|---|
| Direct controlled evidence | supports, shows under these conditions |
| Indirect but consistent | suggests, is consistent with |
| Competing counterclaims remain | cannot conclude confidently |
| Prediction outside range | may, would be expected if trend continues |
Part XX — The CER-C test
- C — Claim: what am I asserting?
- E — Evidence: what measured fact supports it?
- R — Reasoning: why does the evidence support the claim?
- C — Counterclaim: what alternative remains, and has the method ruled it out?
This is an eduKate teaching mnemonic.
Part XXI — Common CER errors
- Claim does not answer the question.
- Evidence is irrelevant.
- Reasoning simply repeats the claim.
- Counterclaim ignored despite confounding.
- Absolute claim from one trial.
- Mechanism invented beyond the syllabus.
- Data copied without interpretation.
Part XXII — Why counterclaims matter in MCQ
Strong distractors are often counterclaims that fit part of the evidence.
Eliminate them by finding the condition they contradict or the assumption they require.
Part XXIII — Why counterclaims matter in open-ended questions
Evaluation questions often ask whether a conclusion is justified. The best answer may identify an alternative explanation the method failed to rule out.
Where to connect
- Confidence, Uncertainty, Anomalies & Strength of Evidence
- Alternative Explanations, Contradictions & Anomaly Resolution
- Primary 4 Claims, Evidence & Reasoning
Retrieval checklist
- I can separate claim, evidence and reasoning.
- I use measured facts as evidence.
- I connect evidence to claim with scientific mechanism.
- I can generate a counterclaim.
- I use controls to reject alternatives.
- I recognise when confounding leaves counterclaims open.
- I distinguish association from cause.
- I keep claim size proportional to evidence.
- I can compare two claims against the same evidence.
- I can write a concise CER response under PSLE conditions.
The quiet return
Scientific answers become trustworthy when every claim can point backward to evidence and forward through reasoning. Counterclaims keep the explanation disciplined by asking whether another story still survives.
Make the claim. Show the evidence. Explain the link. Test the counterclaim. Keep only what the evidence earns.
Return to the Primary 6 Science Learning Hub.
