Reflection: Checks for Understanding What Is A Chemical Reaction? - Section 4: Class Discussion


In order to have a better idea of what my students are thinking, I skimmed their answers to the last question on their lab activity handout: "What happens during a chemical reaction and what is evidence of that reaction?"  It is important that I know what conclusions they have made so that I can address any gross misconceptions during the next lesson when we look at examples of reactions with other types of evidence a reaction has occurred (endothermic, exothermic, and gas release).

In reading my students' answers, the majority of them listed 'color change' as evidence of a chemical reaction.  While this is sometimes true, it is not conclusive evidence.  For example, acid-base indicators change color as acids or bases are added to solution.  There is no chemical change in these cases, but there is a physical change as the indicators shift to higher dissociation or lower dissociation of their ions.  I know from their answers that I need to clearly discuss with them that color change is a tricky indicator of a chemical reaction.

  Using Student Responses to Inform Instruction
  Checks for Understanding: Using Student Responses to Inform Instruction
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What Is A Chemical Reaction?

Unit 3: Chemical Reactions and Stoichiometry
Lesson 1 of 14

Objective: SWBAT determine if a reaction has occurred when two substances are mixed and provide lab evidence for that determination.

Big Idea: When two substances are mixed, a chemical reaction may or may not occur; there are specific things that we can look for to determine if a reaction occurs or not.

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