Diffusion

One of the areas that I noticed my students struggling with when I taught science in the past was diffusion and osmosis.  There were a few ways I could tell this was a topic rife with misconceptions:

  1. They were concepts that most students struggled to define/explain adequately on tests.
  2. Even high performing students had trouble differentiating the two.
  3. Their hypotheses and reflections on labs showed a lack of understanding

I think one of the reasons is that they have difficulty with the scale that is involved and the concept of concentration gradients.  From a scale point of view, I think students have misconceptions about liquids because of their sensory observations.  They see liquids as homogenous substances, and struggle to understand that there are tiny atoms/molecules moving around and colliding.  With concentration gradients, I think they have a difficult time understanding why particles move from areas of high concentration to areas of low concentration.  Two prominent misconceptions I have noticed arise from some of the most popular ways of describing diffusion.  The first is the personification of particles – teachers often imbue consciousness on particles by describing diffusion in terms of particles ‘seeing’ the high concentration and ‘knowing’ that they must move to another place.  Another way of describing concentration gradients is the idea of a ‘downhill’ force that takes particles from high concentration to low concentration.  My students would often take this explanation and turn it into a misconception that diffusion was driven by gravity.

For the purposes of my T-GEM, I have ‘created’ a new tech tool –  an interactive demo/game in which particles move around the screen in a way consistent with kinetic molecular theory (please forgive my improvised attempt at showing this visually in my video!), and students can control the variables.  I think interacting with a demo/game like this would help dispel misconceptions and help students make meaning of the process.

 

3 comments

  1. Wow! An exceptional way of revealing your T-GEM to us!

    Your first-hand experience and knowledge of common misconceptions has projected your T-GEM idea. I appreciate that Samia asked for us to consider concepts that students often carry misconceptions about. Reflecting on common misconceptions as educators helps us to address them more intentionally with our students, proactively rather than reactively. You did this well with requesting students to evaluate “what is wrong” with the two models and then moving into the distinctly modified version of the model game.

  2. I am not a science teacher, but I can definitely appreciate how understanding the movement of molecules would be difficult for students to visualize. I think that one of the significant implications of what you have shared is that when teachers create analogies to help explain complex or unobservable properties or conditions, some students take these analogies in a more literal sense, or make inappropriate connections within their understandings. Sometimes even the subtleties of word choices can provide students with a skewed understanding, such as “downhill force”. This reinforces the need to provide students will multiple opportunities to “experience” concepts and to show their understanding so that they have the most information possible available to them in formulating their understandings and so that we have the most information available regarding how to best support their accurate learning of the concepts.

  3. Thank you Tyler for the video. I imagine our class community being interested in how you made it!
    One hopes that, borrowing the language in the video, “misconceptions are crushed”; however, as you articulate well in your post, even after instruction,students later on “struggled to define/explain adequately on tests”, and “even high performing students had trouble differentiating the two”. Students’ [alternative] conceptions are highly robust to change (as we saw in the video of the Harvard graduating class. I like how you are hypothesizing where do these conceptions come from and targeting instruction to address these misconceptions? As you noted, sometimes these misconceptions are generated by personification of scientific phenomenon or analogies where the transfer and the linkages are not apparent to students.
    Class, are there analogies that you use to teach that are often effective but may inadvertently promote a misconception?
    Samia

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