A visit from Eugenia Etkina
Last week we had the great honor of having PER legend Eugenia Etkina visit our department for the day to coach our faculty and talk about physics teaching. It was an incredible day.
Immediately upon arriving, Eugenia started observing classes, and by the time she’d seen one of my classes she had two great points.
In my intro physics class, we had gotten off on a tangent about whether air would have a higher or lower specific heat than water. I was trying to elicit arguments from the students, ask them to back them up with evidence and then try to compare them. One of the arguments revolved around comparing the mass of a water molecule and a nitrogen molecule (the main constituent of air). Without thinking too much about the final answer, I was sort of hoping that this student would help us to see that there are many more air molecules in a given mass than there are in an equal mass of water. But in our calculation, we saw that the atomic mass of water was 18, while the mass of a nitrogen molecule is 28. Puzzled, i realized I’d lead us into a bit of a dead end, and so I admitted my confusion and set the students to work on a lab to measure the specific heat of zinc and copper. Not my finest moment. However, afterward, Eugenia reminded me that it is true that water molecules have less mass than nitrogen molecules, and this is exactly why we have clouds, and why water vapor remains suspended int he air. It was a flash of insight that helped me to see just how much I was missing when I was trying to drive the class toward a “correct” justification that air has a lower specific heat than water.
When Mark and I first debriefed with Eugenia, she jumped right into some direct and honest feedback, “You guys like Socratic dialogue way too much,” she explained to us that we were walking students down the arguments and lab setups we had devised in our own heads, when what we need to be doing is having students construct those arguments for themselves. She then told us that the lab experiment to measure specific heat that we were having a group design discussion about (“what will you measure? how will you measure it, etc”) was a waste of time and we should just have students design the lab.
At this point, I was skeptical. My students were struggling with designing experiments—they didn’t see the reason for the decisions we were making and often seemed to crave step by step instructions (which we did not provide). How would they be ready to design experiments for themselves? “Your students are ready,” Eugenia said, and so in the second section of my intro physics class, I simply wrote the question on the board “Devise an experiment to measure the specific heat of Zinc or Copper.” I asked students to write up their proposed experiments on whiteboards, and here is what I got.
- Heat a copper rod by burning peanuts under it. You could then measure the temperature difference, and since you know each peanut has approximately 5 kcal, you can find the specific heat.
- Heat copper rod by putting it in boiling water and then dropping it into room temperature water.
- Put room temperature copper into warm water.
- Put 10 grams of each substance into a bunsen burner, and measure the time that it takes to raise the temperature of each substance by 10°. Then the ratios of the times are the same as the ratios of the specific heats.
These experiments were incredible—students were connecting to some of our past understanding of the energy content of peanuts, as well much of the work we’d done with heat transfer to talk about why you would want to work with metal in very small bits rather than one large cylinder. Afterward, we had a discussion of the strengths and flaws of each experiment, and students were able to carefully refine their design until they came away with an experiment that was very similar to the experiment I was intending to have them do, but was so much better because they had figured out the rationale for each design decision and had a far better grasp of how each decision they would make would affect the overall quality of their measurement.
And of course, their engagement in this task was higher than almost any previous experiment we’ve done. It was a complete turnaround.
Here’s the puzzling thing to me. This idea that students are ready to design their own experiments is something I’ve known for years. We build it into our curriculum many times, and even started the intro class with designing their own experiments to measure the energy content of peanuts and batteries. So why do we later turn to offering more scaffolding and as Eugenia described it “giving them a cookbook lab via discussion?” I’m not completely sure—I think it has something to do with feeling that when we are doing an experiment that is more than just exploration, they need to follow some sort of proper procedure that I’ve designed and given to them. I now see the error of my ways.
Wrap up time
One thing I’ve always done with my classes is tried to maximize the amount of time students are working and thinking about physics. This means that I often just have students working right up until the end of class, when I’ll then shout a quick reminder of the work I’d like them to do that evening.
Eugenia re-emphasized to me the importance of having students go back and reflect on what they learned that day, and offered a number of questions one could ask to help prompt this reflection:
- What did you learn today?
- How did you learn it?
- Why is it important?
Eugenia reminded me of research into human learning that having students try to summarize what they learned is a powerful tool for understanding and helps to form much stronger connections in their brains. So I’ve been setting my phone to remind me when there are 3 minutes left in class, and I take that opportunity to ask the class to try to summarize our learning.
Overall, it was fabulous day that reminded me of the need to constantly seek out new and honest feedback on our teaching. Eugenia is a gifted teacher who had a major impact on my teaching with just a few questions.
This also reminds me of the virtual coaching project from a few years back. Maybe it’s time to get this idea going…