Ready-to-use classroom activity
Students make a claim, provide evidence to support it, and explain their reasoning connecting evidence to the claim.
Grade range
Works across
Activity style
Classroom walkthrough
One concrete example you can borrow, adapt, or teach as written.
Example lesson context
Gather these before class.
What to have ready before students begin.
Prepare moon phase observation data spanning a month. Create a CER graphic organizer with sections for each component. Develop a reference sheet explaining the difference between evidence and reasoning. Gather examples of strong scientific explanations.
A classroom-ready sequence from launch to follow-up.
Introduce the CER framework as a method scientists use to explain phenomena:
Claim: A statement that answers the question or explains the phenomenon
Evidence: Scientific data that supports the claim
Reasoning: Explanation connecting the evidence to the claim using scientific principles
Model the process using a simple example unrelated to the moon:
Question: 'Why do ice cubes melt faster in warm water than in cold water?'
Claim: 'The temperature of water affects how quickly ice melts.'
Evidence: 'In our experiment, ice in 80°F water melted in 3 minutes, while ice in 40°F water took 12 minutes to melt.'
Reasoning: 'When water molecules have more thermal energy (higher temperature), they collide with the ice more energetically, transferring heat faster and breaking the solid bonds in the ice more quickly.'
Present the moon phase investigation question: 'What causes the moon to appear to change shape throughout the month?'
Evidence collection (10-15 minutes):
Students analyze moon phase observation data
Use moon phase models or simulations to investigate the Earth-Moon-Sun system
Record relevant data and observations
Individual CER development (15 minutes):
Students write a claim about what causes moon phases
List specific evidence from observations and simulations
Develop reasoning that connects evidence to their claim using scientific principles about light, shadows, and the Earth-Moon-Sun relationship
Peer review process (10 minutes):
Partners exchange CER responses
Use checklist to evaluate strength of each component
Provide specific feedback for improvement
Revision and finalization (10 minutes):
Students revise their CER based on feedback
Ensure reasoning clearly connects evidence to claim
Add diagrams if helpful for explanation
Class discussion: Compare different approaches to reasoning and discuss how the same evidence can be used to support claims.
Adjust the activity without losing its core purpose.
For struggling students, provide sentence frames for each CER component. For English learners, allow drawing and labeling to supplement written responses. For advanced students, challenge them to address counter-arguments or alternative explanations.
Use these signals to assess understanding.
Evaluate completed CER responses using a rubric that assesses accuracy of claim, relevance and specificity of evidence, and depth of reasoning. Note common misconceptions about moon phases to address in future lessons.