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Designing Science Inquiry: Claim + Evidence + Reasoning = Explanation

Eric Brunsell

Asst Professor of Science Education @ UW-Oshkosh
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In an interview with students, MIT's Kerry Emmanuel stated, "At the end of the day, it's just raw curiosity. I think almost everybody that gets seriously into science is driven by curiosity." Curiosity -- the desire to explain how the world works -- drives the questions we ask and the investigations we conduct.

Let's say that we are planning a unit on matter. By having students observe solids and liquids, we have helped them define matter as something that has mass (or weight -- don’t worry about the difference with elementary kids!) and takes up space. The next step is to start thinking about air: "I'm curious, is it matter? Or something else?" The students are now driven by a need to explain if air is or is not matter. The question becomes clear, and we can ask:

Is air matter?

Next, we can ask our students what data they need to answer the question, and how they can collect that data -- how they can investigate. Students will need to determine if air has mass and/or takes up space. Perhaps they'll suggest that they weigh a basketball multiple times as they use a pump to add more air. Once students conduct the investigation and have data, they can create an explanation. But what does a good explanation look like?


According to the CER model, an explanation consists of:

  • A claim that answers the question
  • Evidence from students' data
  • Reasoning that involves a "rule" or scientific principle that describes why the evidence supports the claim

Your students might suggest the following explanation:

Air is matter (claim). We found that the weight of the ball increases each time we pumped more air into it (evidence). This shows that air has weight, one of the characteristics of matter (reasoning).

The explanation could be made more complete by including evidence and reasoning related to air taking up space.

Introducing CER to your Students

The CER format to writing explanations is not a trivial thing for your students. You will need to explicitly introduce and model it for them. They will need support throughout the year as they get better at writing explanations.

The idea that explanations drive science can be illustrated for students by using NASA's aptly named Curiosity Mars Rover. After watching the video about the mission's science goals, ask your students:

  1. What are these scientists curious about -- what do they want to know?
  2. What data will the rover collect?
  3. How will this data help scientists answer -- make claims about -- their questions?

Jeff Rohr, a fifth grade teacher in Beaver Dam, Wisconsin, suggests using the following Audi commercial to introduce students to the components of an explanation by asking them to identify the claim, the evidence, and the reasoning – or rule – that connects the evidence to the little girl's claim that her dad is a space alien.

Let the Inquiry Begin

As you work with your students on CER throughout the year, do the following:

  • Introduce CER as the "goal" of science
  • Use concrete (non-science) situations, like mysteries, images, artwork, etc. (Download an example PDF worksheet)
  • Create an anchor chart
  • Use a rubric with students to critique examples
  • Provide examples from science or scientists
  • Create CER worksheets with data provided by the teacher (Download an example PDF worksheet)
  • Connect to other content areas (e.g. argumentation in social studies)
  • Feedback!
  • Peer Critique
Was this useful? (4)

Eric Brunsell

Asst Professor of Science Education @ UW-Oshkosh

Comments (4) Sign in or register to comment Follow Subscribe to comments via RSS

Geri Sundermier's picture

Very thought provoking article on C-E-R with great hooks to get your students involved. I couldn't access any of the documents though.

Kristen Franklin's picture
Kristen Franklin
Managing Editor at Edutopia

Thanks Geri - the file issue should be remedied, if you'd like to try again. Thanks for the heads up!

Joe Morin's picture

The claims-evidence-reasoning is a pretty good basis for making an argument, but I don't think it's a logical process for figuring out an answer to a question.

It seems to me that scientific inquiry and problem solving begin with posing a question, evidence is gathered, scientific reasoning using models of the phenomena being studied are applied to the question, and an explanation and answer to the question is obtained. Question-Evidence-Reasoning-Explanation is a better way for inquiry and problem solving.

The Question-Evidence-Reasoning-Explanation approach is an expository approach that proceeds in a logical progression to reach (or explain) a conclusion. The difference (between this and CER) is that it doesn't start with the conclusion, which is a backwards argument in my opinion. The argument should start from evidence and proceed with a coherent, well reasoned exposition culminating in the conclusion.

Byron Philhour's picture

Hi - checking in on Thursday, April 28, 2016. I link to this page for my students to learn about Claim/Evidence/Reasoning but discovered today that the YouTube video as been set to private. The URL of the video is: ... is this a permanent change? Should I find another online resource for this? Thank you!

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