Reflection: Developing a Conceptual Understanding Classifying Evidence of a Chemical Reaction - Section 5: Student Reflection


I struggled with the apparent lack of "getting it" during today's lesson.  During the demonstrations, it really appeared that students did understand, but reading the student answers to the Reflection prompt was really discouraging!  I knew right away that my students clearly did not learn the differences between physical and chemical changes.  

Traditionally, I would have realized the disconnect and then inserted a lesson about physical versus chemical changes the next day to catch-up my students.  This time, however, I started asking why did my students have that disconnect and how could I help them adjust their thinking--without spending an entire class period on chemical versus physical changes.

It seemed to me that my students could not differentiate between chemical and physical changes without having a firm grasp on what chemical reactions are: that bonds are broken between some atoms and new bonds are formed between others.  As we spend more time moving through this unit (which includes stoichiometry), I need to make sure that I am addressing chemical  changes versus physical ones, but I have decided to do that within the context of those lessons.  As students become more familiar with what is happening on a molecular level during a chemical reaction, they should make the connections to what we might observe on a macroscopic level to indicate bond-breaking and bond-making.  

I will also emphasize chemical versus physical changes during our thermodynamics unit when we study energy flow and compare endothermic/exothermic reactions (chemical) versus processes (physical).

  When Students Just Aren't Getting It...
  Developing a Conceptual Understanding: When Students Just Aren't Getting It...
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Classifying Evidence of a Chemical Reaction

Unit 3: Chemical Reactions and Stoichiometry
Lesson 2 of 14

Objective: SWBAT articulate specific signs that a chemical reaction has occurred based on the evaluation of their data from prior lab investigation.

Big Idea: Four observable indicators of chemical change are temperature change, color change, formation of a gas, and formation of a solid.

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