As I mentioned in a previous post, I’ve been inspired by @Central Science to explore things at the particle-level within my class. I’ve started following (when I have time!) the #modchem conversations on Twitter along with #chemchat to get ideas and find ways to improve my practice. The modeling pedagogy is heavy on students working in groups, whiteboarding their work together showing lots of diagrams of what is happening at the particle level within the different topics of chemistry that are taught in a traditional chemistry class. And #modchem folks, feel free to correct any misconceptions I may have about the pedagogy, as I’m really a neophyte here. Speaking of misconceptions, that’s one of the strengths of this method of teaching in my mind. In looking at student diagrams and hearing their explanations of what is happening at the particle level, I can really assess their understanding and identify misconceptions that need to be discussed.
And yet more speaking of misconceptions: My lesson actually started with a look at the misconception discussed in my blog post here, and shown in the diagram below. My students really struggled with the idea that since ice floats, it has to be less dense…therefore the particles must be farther apart in ice compared to liquid water. This discussion started by asking my students to develop a working definition of density and draw the particles of two substances, A and B, where substance A is more dense then substance B. And their drawings of this were spot-on. (Although as I type this, I realize that this makes the assumption that the molar masses of the substances drawn are relatively equal. Hmmm.) Then I challenged them to compare that to water floating. Lots of puzzled looks and brains turning as they struggled with the comparison of MOST solids being more dense when compared to the liquid form of the same substance. This isn’t the case with water. Luckily, we had just performed a lab with lauric acid. One student pointed out that we got to observe lauric acid as a solid in liquid lauric acid and it SANK! So this was a fantastic discussion.
Now on to the actual modeling lesson. Let me start by saying that I have not yet attended a modeling chemistry workshop, so I’m certainly no expert here. In fact, I’m hoping for some feedback from people that DO modeling and have been to workshops so I can improve. First, some background on the lesson. It’s within a unit on states of matter and phase changes. The first day of the unit involved creating melting and freezing curves for lauric acid, a good compound for this as its freezing point is about 43 degrees celcius. Within the lab, students got to see the temperature stay relatively stable for quite a while during the melting and freezing cycles. This challenges them a bit, as they wonder if the temperature probe is ‘stuck’ or something. Nothing but great teachable moments throughout the lab. So for day 2 I had planned a relatively traditional lecture on states of matter and phase changes. (On a quick side note: traditional lectures in my class aren’t just me talking and students listening. They are quite interactive. But they are limited, and I’m moving away from them more and more.) Rather than do the same lesson as last year, I wanted to delve into modeling as an experiment. I planned a series of demonstrations and had the kids do some predictions and discussions within groups about each demo. Then, once the demo was finished the students had to assess their predictions and explain what was happening at the particle level. Whiteboarding at its finest! Except for one small detail. I don’t have whiteboards for the groups yet. So they worked on paper and we did some in-class discussion.
One demonstration involved dropping (without stirring) food coloring into hot and cold water and observing the changes. For this, I had the groups draw what the beaker would look like at time=0, time = 2 minutes, and time = 20 minutes. See the image below. And while this diagram specifically isn’t at the particle level, the discussion within the groups involved motion of the particles and the interactions between the water and the dye.
Other demos included the following: creating two balloons and putting one in the freezer for about 45 minutes, putting melted lauric acid into a beaker of water and tracking the temperature change as it heated, and a replay (with discussion) of a demo the students had actually seen through a video. This demonstration shows saturdated sodium acetate solution doing some really weird things – linked here and a few screenshots below. The purpose of the video was to get their curiosity going a bit about phase changes.
Now for some reflection: First, what worked? Certainly the structure of getting students into groups and asking them to DISCUSS their ideas was really beneficial in my mind. I really would have liked having some whiteboards (they are on order!) to make sharing easier. The demos were all helpful. The students had probably seen the food coloring demo before, and the baloons also. I challenged them to go beyond a basic understanding and really get at the details of the changes at the particle level. That’s the recurring theme here, and I think it worked to some degree. The students were talking in ways I hadn’t gotten them to discuss before. It was fantastic!
So what didn’t work? As I mentioned, I’d really like the whiteboards to center the discussion. But that’s a minor detail – and a bit too obvious. I think I could have done a better job of pacing, going forward when their discussions lagged and drawing back and waiting while they finished other discussions. I also felt I could have pushed for more class discussion after the group discussion and done fewer demos – or spread it out over another class – so that we could have gone deeper into the content. I also need to find a good demo to prompt their thinking about energy transitions during phase changes.
And how did the students like it? Their closure activity was an exit pass. Question 1: On a scale of 1-4 (4 being the highest), how much ‘learning’ did you have today? Explain. Question 2: Explain – using particle theory – how a straw works to drink. From 19 responses (out of 20 students…not sure who I missed) the average rating was 3.4. Obviously this is a bit open-ended. The more valuable piece of feedback here was their explanations. The students provided some good feedback about wanting more class discussion after the group discussion and pacing ideas. The second question will need to be addressed at some point, because many answers described the ‘sucking’ as the driving force, rather than the pushing up the straw by atmospheric pressure.
The bottom line for me is that I’ve really started to transform my teaching in order to really get at what students understand. And I’ve worked at addressing their misconceptions based on this data. I can’t wait for more!
My request: If you are a #modchem or #modphysics person, what ideas do you have based on my reflection above? Where can I improve? Any feedback would be appreciated.
Until next time…keep it minty fresh!