Discrepant Events: Poly Density Bottle

Yesterday, I taught a lesson about CER Claim Evidence Reasoning with a Poly Density bottle.  (The video is below.). Discrepancy events are a popular science ‘hook’.  I use them to teach kids how to report data from a lab.  It helps to have a question.  I asked the kids if the white and blue plastic beads were the same. 

 

So, when is the CER process useful?  My teens write four formal lab reports each year.  One Chemistry lab is Can You Make 2Grams?  The kids dry a white powder, a precipitate.  First they report the data.  The goal is to produce two grams of a white powder.  They don’t.  Instead, one kid may produce 1.0 gram and another teen might produce 4.6 grams.  The teens record the results with the errent error in the report.  Next, in the discussion section, the teen explains what went wrong.   Here is where CER or claim-evidence-reasoning helps.  If a student has 4.6 grams, the white powder is still wet.  It may feel damp or the mass decrease after a few days, evidence the powder is still wet.  Students may reason that the powder had not had sufficient time to dry to produce meaningful results.  Basically, CER is useful to help kids draw conclusions from data or observations.