Same Science › Explaining results › CER in science
How does CER work in science?
In science, CER turns results into an explanation. The claim answers the question in one sentence. The evidence is the data, with numbers: “plants with 12 hours of light grew 15 cm; plants with none grew 2 cm.” The reasoning is the science idea that connects the evidence to the claim: plants use light to make food. Most kids write the claim and evidence fine and skip the reasoning.
- Claim: a one-sentence answer to the question.
- Evidence: specific data, with numbers and units.
- Reasoning: the science rule that explains why the data supports the claim.
Why schools teach it
It's how scientists argue from data
NGSS asks students to construct explanations and argue from evidence (science practices 6 and 7) in every grade from 3 to 8. CER is the scaffold most schools use for it, the same one taught in writing class.
The reasoning step is where science learning shows. Saying “because the data shows it” isn't reasoning; naming the science idea, like heat moving from warm to cold, is.
At the kitchen table
What to say, and what to skip
Say this
What's your answer to the question, in one sentence?
That's the claim.Which numbers from the data prove it?
Include units.What science idea explains why that happened?
That's the reasoning.Does your reasoning connect back to your claim?
Skip this
- Accepting “the data shows it” as reasoning.Ask what science idea explains the data.
- Evidence without numbers.“It grew more” becomes “it grew 15 cm.”
- Giving the science idea before they try.Ask what they learned in class that might explain it.
See it in action
Which cup kept water warmest?
Data after 20 minutes, starting at 80°C: no wrap 52°C, foil 58°C, wool 68°C.
Claim
Wool kept the water warmest.Evidence
The wool cup was 68°C, 10° warmer than foil and 16° warmer than no wrap.Reasoning
Wool traps air, which slows heat moving out of the cup, so it's a better insulator.
The reasoning names the science idea: insulators slow heat transfer.
Free practice sheet
Make a science CER sheet
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Parents: tell your child's teacher about this guide
Parents also ask
Is this the same CER as in writing class?
Yes, same three parts. In science the evidence is usually data from an experiment.
What counts as reasoning?
A science rule or idea from class: photosynthesis, friction, heat transfer, density. It explains why the evidence proves the claim.
How much evidence is enough?
Usually two pieces of data, often comparing the highest and lowest results.
What if the data doesn't support what my child expected?
That's fine. The claim follows the data, and explaining a surprise is great science.