Your child completes a Science investigation, records the results and draws a graph.
Then comes the final instruction:
“Write a conclusion.”
They write, “The experiment worked,” or “My prediction was correct.”
Those statements leave important questions unanswered. What did the results show? Which measurements support the conclusion? How does the Science explain the pattern?
A useful Science lab conclusion answers the investigation question, supports the answer with results and explains the scientific connection.
This guide shows how students can do that using claim, evidence and reasoning, with an original worked example and practice activity.
What Is a Science Lab Conclusion?
A conclusion explains what can reasonably be learned from an investigation.
It should connect the investigation question with the results.
For example, if a learner investigates how water temperature affects dissolving time, the conclusion should address that relationship. It should not simply repeat the equipment list or describe every step of the method.
The exact requirements depend on the task. Students should follow their teacher’s instructions, rubric or examination guidance.
What Is Claim, Evidence and Reasoning?
Claim, evidence and reasoning—often shortened to CER—is a useful structure for organising a scientific response.
PartPurposeQuestion to askClaimAnswer the investigation questionWhat do the results suggest?EvidenceSupport the answer with relevant observations or measurementsWhich results support it?ReasoningConnect the evidence to scientific understandingWhy does the evidence support the claim?
CER is a planning tool. It does not replace the requirements of a particular assignment.
1. Write a Claim That Answers the Question
A claim states the conclusion supported by the investigation.
Investigation Question
“How does water temperature affect the time taken for a fixed mass of sugar to dissolve?”
A Vague Claim
“Temperature affects sugar.”
This does not identify the relationship.
A Clearer Claim
“In this investigation, the sugar dissolved in less time as water temperature increased.”
This answers the question and keeps the statement within the investigation.
Avoid claiming that results apply to every possible condition when only a limited range was tested.
2. Select Evidence From the Results
Evidence should support the claim directly.
“The graph shows it” is less useful than identifying the relevant measurements and pattern.
Original Example Results
A learner tests the same mass of sugar in the same volume of water, keeping the stirring procedure consistent.
Water temperatureTrial 1Trial 2Trial 3Mean dissolving time20°C90 s94 s92 s92 s40°C51 s55 s53 s53 s60°C29 s31 s30 s30 s
Evidence Statement
“The mean dissolving time decreased from 92 seconds at 20°C to 30 seconds at 60°C. The mean time at 40°C was between these values, at 53 seconds.”
This supports the direction of the relationship using values and units.
Students do not need to copy the entire table into the conclusion. They should select the results that establish the relevant pattern.
3. Explain the Scientific Reasoning
Reasoning connects the measurements to the process being studied.
For the dissolving investigation, an explanation can use the particle model.
Reasoning Statement
“At higher temperatures, water molecules have greater average kinetic energy and move more rapidly. Their interactions with the sugar help it disperse through the water more quickly, so the fixed mass dissolves in less time.”
The reasoning adds a scientific explanation rather than repeating the results.
Be careful with related terms. Sugar dissolving in water is not the same process as sugar melting.
A Complete Science Lab Conclusion Example
Putting the three parts together gives:
In this investigation, increasing water temperature reduced the time taken for the fixed mass of sugar to dissolve. The mean dissolving time decreased from 92 seconds at 20°C to 53 seconds at 40°C and 30 seconds at 60°C. At higher temperatures, water molecules have greater average kinetic energy and move more rapidly, helping the sugar disperse through the water more quickly. These results support the conclusion that warmer water increased the dissolving rate under the conditions tested.
Why This Conclusion Is Useful
It:
- Answers the investigation question.
- Gives relevant measurements with units.
- Explains the pattern using scientific understanding.
- Limits the claim to the tested conditions.
The results and response are original teaching examples, not an official examination question or mark scheme.
Conclusion vs Evaluation: What Is the Difference?
These sections answer different questions.
SectionMain focusConclusionWhat do the results support?EvaluationHow well did the investigation provide evidence, and what could be improved?
Some assignments ask students to combine them. Others require separate sections.
For the dissolving investigation:
Conclusion: Warmer water was associated with a shorter mean dissolving time.
Evaluation: Deciding exactly when the sugar had fully dissolved may have introduced uncertainty. A more consistent endpoint procedure could improve comparisons.
A list of improvements alone does not answer the investigation question.
Should Students Mention Their Prediction?
If the task asks, students can explain whether the results support their prediction.
For example:
“My prediction was that sugar would dissolve in less time at higher water temperatures. The results support this prediction over the temperatures tested.”
However, stating that the prediction was correct is not enough by itself. The conclusion still needs evidence and reasoning.
If results disagree with the prediction, report that honestly and examine possible explanations. An unexpected result does not automatically mean the investigation failed.
What If the Results Do Not Show a Clear Pattern?
Do not force a relationship into the data.
A suitable statement might be:
“The results do not show a consistent increase or decrease, so they do not support a clear conclusion about the relationship under these conditions.”
Then, where evaluation is required, discuss what limits the interpretation.
Possible questions include:
- Were there enough measurements?
- Was the range suitable?
- Were important variables controlled?
- Were measurements precise enough to identify a difference?
- Was the procedure applied consistently?
Explain the specific issue rather than writing only “human error.”
How Should Students Handle Anomalous Results?
An anomalous result differs noticeably from the overall pattern.
Students should identify it and consider possible reasons. They should not remove a result simply because it does not fit their prediction.
For example:
“One repeat at 40°C took much longer than the others. This should be checked because it differs substantially from the other measurements at that temperature.”
Follow the teacher’s instructions about identifying anomalies, repeating measurements and calculating means.
Keep a record of any decision to exclude a measurement and the reason for doing so.
Common Science Conclusion Mistakes
Mistake 1: Writing “The Experiment Worked”
This does not explain what was learned.
Improve it: State the relationship supported by the results.
Mistake 2: Giving a Claim Without Evidence
“More light increased bubble production” needs supporting observations if results are available.
Improve it: Include relevant values and units.
Mistake 3: Repeating the Results Without Explaining Them
A description of the pattern does not supply a scientific explanation.
Improve it: Connect the pattern to the relevant process.
Mistake 4: Claiming the Investigation Proves Everything
A small classroom investigation has limits.
Improve it: Use wording such as “supports” and state the tested range or conditions where relevant.
Mistake 5: Including Unrelated Facts
A conclusion about dissolving does not need every fact the learner knows about solids and liquids.
Improve it: Choose information that helps answer the investigation question.
A Simple Science Conclusion Template
Students can adapt these prompts:
Claim:
“The results suggest that…”
Evidence:
“When ___ changed from ___ to ___, the measured ___ changed from ___ to ___.”
Reasoning:
“This can be explained by…”
Scope or uncertainty, where relevant:
“This conclusion applies to…”
or
“The results are insufficient to conclude…”
Avoid filling the template mechanically. The response must fit the investigation and the available evidence.
Practice Activity: Light and Bubble Production
A learner measures bubbles released by an aquatic plant at three light levels.
Light levelMean bubbles per minuteLow5Medium11High17
For this activity, assume other relevant conditions were kept consistent.
Questions
- Write a claim describing the relationship.
- Select numerical evidence.
- Explain how light could affect photosynthesis.
- Identify one limitation of counting bubbles.
Suggested Response
Claim:
“Bubble production increased as the light level increased under the conditions tested.”
Evidence:
“The mean number increased from 5 bubbles per minute at low light to 17 at high light.”
Reasoning:
“Light supplies energy for photosynthesis. If light is a limiting factor, increasing it can increase photosynthesis and oxygen production.”
Limitation:
“Bubbles can have different volumes, so counting them does not directly measure the volume of gas produced.”
This keeps the measured observation—bubble count—distinct from the biological process it is being used to investigate.
How Parents Can Help
Ask your child:
- What question did you investigate?
- What do your results show?
- Which values support your answer?
- What Science explains the pattern?
- What can you reasonably conclude?
- What remains uncertain?
Let them explain aloud before writing. If the scientific reasoning is unclear, revisit the concept before polishing the paragraph.
Science Tutoring With Glareminds
Glareminds provides one-to-one online Science tutoring, including Biology, Chemistry and Physics support.
Lessons can help learners interpret results, explain scientific processes and develop clear written responses.
Share your child’s class, curriculum and recent teacher feedback when making an enquiry.
A free 30–40-minute consultation and diagnostic session provides an opportunity to discuss learning priorities and a suitable support plan.
Frequently Asked Questions
How long should a Science lab conclusion be?
Long enough to answer the question with relevant evidence and reasoning. Follow the assignment instructions rather than aiming for a fixed word count.
Does every conclusion need numbers?
Use numerical evidence when suitable measurements are available. Some investigations rely on qualitative observations, which should be described precisely.
Can a conclusion disagree with a prediction?
Yes. Report what the evidence supports, even when the outcome was unexpected.
Is CER required in every Science course?
No. It is a useful organising approach. The teacher’s instructions and assessment criteria determine the required response.
Connect the Answer, Evidence and Science
A useful conclusion explains what the results mean and why.
Help your child answer the investigation question, select relevant evidence and connect it to scientific understanding.
To discuss personalised Science support, book a free consultation with Glareminds.
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