Integrating Three Types of Chemical Representation

I spend a lot of time working with models in my classroom - developing mental models, drawing models, talking about models, testing models - you get the picture.  As I was planning my school year last summer, my colleagues and I started thinking about how our students interacted with the models.  

After seven years of using Modeling Instruction^TM, I feel I’m pretty good at predicting and addressing common misconceptions because the same types of misconceptions appear every year.  This past summer our conversations turned to, “How can we improve our instruction to try and prevent the initial misunderstanding?”  We had all read Dorothy Gabel’s article Improving Teaching and Learning Through Chemistry Education Research:  A Look to the Future¹ and were intrigued by the author’s description of the three-fold system of representing concepts in Chemistry. Figure 1 below summarizes the three types of representations.

Figure 1: Johnstone's Triangle includes 3 levels of representation

In the article, Gabel references the work of Alex Johnstone² and identifies the three levels of representations as macroscopic, (sub)microscopic or particulate, and symbolic. She goes on to suggest that one barrier to students understanding chemical concepts is that most chemical instruction occurs at the most abstract (symbolic) level where students do not always know how to interpret the symbols or translate them into the other levels of representations. Additionally, teachers tend to quickly move between levels and students often cannot merge the types of representations in their minds.  

In an effort to help students integrate these representations and to make transitions between levels more purposeful in our instruction my colleague, Jeremy Horner (@CHSchemcrazy) of Carmel High School in Carmel, Indiana came up with a planning worksheet (see figure 2):

3_levels_chart_v2.docx

3_levels_chart_v2.docx

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Figure 2: Student version with space for drawing in representations/models

Here are two samples of lessons on density (figure 3) and classification of matter (figure 4) where we have thought out ways to explicitly address each level.  This could be used as a teacher tool or shared with students.

Figure 3: Student example of lesson on density

Figure 4: Student example for lesson on classification of matter

I’m getting ready to implement these in my stoichiometry unit where I hope to see improved conceptual understanding with my students.  

References

¹ Gabel, D. J. Chem. Educ. 1999, 76 (4), 548
² Johnstone, A.H. J. Comp. Assist. Learn. 1991, 7, 701-703