A CER (Claim-Evidence-Reasoning) writing format can be used for:
Lab write ups where evidence includes data collected,
Assessment at the end of a unit of study or as a quiz, or
Explanation of phenomena.
A CER is usually 3/4 of a page to a 1 1/2 pages long. The claim is first and stated in a sentence. I often have students write their claim on a write board first and share with others for feedback. Evidence is provided to support the claim and reasoning connects the evidence to the claim. Scientific vocabulary that has been presented is used correctly.
Sample questions for a CER are included to get you started. Always model an entire CER for your students to help them be successful. This is a challenging task for students. Set them on the path to success with a clear rubric.