CER or Claim-Evidence-Reasoning is part of inquiry-based education. (BTW, BSCS helped develop inquiry-based, science instruction. The older textbooks have great labs!) CER usually starts with a question. I like to pair CER with discrepant events or thinkers. Here are three discrepant events: the poly density bottle, the disappearing beaker, and the shrinking volume. We use a CER Template and begin with a question. Let’s begin with the density bottle. Here is the question: Why do the beads settle in the middle? Next we shake the bottle over and over to allow kids to make observations—the evidence. As you shake the bottle, solids are evident. The kids ask more questions. What is in the bottle apart from the beads? There is alcohol, water, and salt. The other question is ‘Why do the white beads settle on top of the blue beads? Now, the kids state their claims, based on evidence, and site their reasoning. It doesn’t have to be written. I like to do a CER together. The kids will eventually talk about density and determine the fact that the white beads must be made of different material from the blue beads.
What is the point? CER helps kids make sense of experiments and results. Here is another example: the Flame Test Lab. Here is a question: What colors do different salts produce when heated in a flame? (Here is Flinn’s demo with an explanation regarding emission spectra.) If you stick to flame colors, the kids match the salt with its color as it burns. (An even better approach is to use copper chloride and copper sulfate to show that both turn a flame blue-green.) Then the reasoning is that copper compounds produce blue-green flame. Again, if you can use potassium carbonate and potassium chloride, two different potassium compounds, it is easier for the kids to understand that the potassium produces a pale, violet color.
CER doesn’t need to be cut and dry. I use the process to help kids come to a conclusion. Let me take another example, Vanishing Volume. Kids will repeat this demo because they think they did something incorrectly. Here is the question: Why is it 50 mL and 50 mL do not form 100 mL. We use five mL each. The alcohol molecules slop between the water molecules. The claims will vary. Often kids think the alcohol evaporates because some of the volume disappears. It may help to keep a small cup of alcohol out to show it won’t evaporate that quickly. It also may help to mix ping pong balls with marbles to demonstrate what is happening. Do we need to use a template and submit it as an exercise? Hardly.
How do you use this approach in lab? Start with the purpose. What data or observations were made? Draw a conclusion. For example, different metallic salts produce different colors. In the Disappearing Beaker, the conclusion is that light passes through the corn oil in the same manner as it passes though the beaker (made of Pyrex or borosilicate). They have the same index of refraction.
It is hard to find good CER examples. I’ll share what I have: Example #1
Are these liquids the same? No. Make a list of observations to create evidence and summarize or explain your reasoning. Liquids #1 and #4 are the same because they have the same properties: density, melting point, and color.
Below are a couple more CER examples I use.
Here is an example of using CER with historical experiments, which is pretty good. The Biology Corner has some CER examples, which are fine, but not great. These CER Questions (with labs or demos) are okay. Here is a good explanation and with good examples. I use a good examples to teach the process and then get kids to draw their conclusions based on the data in the lab.
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