Integrating Three Types of Chemical Representation

Three levels of 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 InstructionTM, 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):

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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

 

NGSS

Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds.

Summary:

Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. Use a model to predict the relationships between systems or between components of a system.

Assessment Boundary:
Clarification:
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Comments 4

Sean Fisk's picture
Sean Fisk | Thu, 02/11/2016 - 20:34

I'm getting ready to start stoichiometry too, and I've done a bunch with my students with the three frames of reference.  I'd love to see how these help that process especially for my ELL students.  I'll be trying them myself.

 

Thanks!

Bob Worley's picture
Bob Worley | Sat, 02/13/2016 - 09:20

Erica and Sean

The triangle is well known amongst reseachers in chemical education but not so much by teachers. Peter Mahaffy of Toronto made it a tetrahedron but these are diffiult to draw with words attached. The fourth part was the human aspect. Here in this blog I call it relevance, http://microchemuk.weebly.com/2-blog-is-this-supposed-to-happen .

Now you might like to watch this sketch from an English comedy actress Catherine Tate as Sharon in https://www.youtube.com/watch?v=KM9d_eZhFnk. Her catch phrase was "Am I bovvered?". Oh my goodness you might need subtitles for this. That is the East London accent , "bothered".

So why should I be bothered about density? Why should I be bothered about stoichiometry?

Alex Johnstone's biog is here http://www.rsc.org/images/ahj%20biography%20revised_tcm18-52105.pdf. His writing (along with Norman Reid) is easy to follow as they remove the jargon. Look him up on google

Take care over there.

Bob Worley

 

Erica Posthuma's picture
Erica Posthuma | Mon, 02/22/2016 - 20:41

Thanks for the resources!  I'll check them out!