I had a really good day and I want to share what my students did today. I was at #educon this past weekend and was fascinated by the focus on Problem Based Learning throughout the school. The problem that I have been having is getting over the traditional methods of how I was taught and break out into the PBL world. If it was Bio or Physics, I think the transition would be easier, but Chemistry is a different animal. There are certain parts of the curriculum that needs to be taught by direct instruction, and yet SLA is doing it by PBL. So, while there I picked the brain of a couple of the teachers and they really inspired me. So, today it happened. Let me describe the activity.
We just started the Gas Laws unit. The best part of gases is it has a lot of real-world connections and tons of ways to demo the different properties. So, I rearranged my room (on the right) to mimic a rigid container. Then, as the students came into the room they picked a colored index card that had either H2, CO2, Scribe or ? on it. What I wanted was someone to keep notes for me (Scribe), a gas with low mass (H2), a gas with a high mass (CO2), and then some added molecules that can be throw in when I needed to increase moles.
There are four properties that we needed to focus on: Pressure, Volume, Temperature and moles. I had the Hydrogen students jump up into the center and explained that gases act like billiard balls on a pool table. Every time they collided with a desk they were to pat the desk to simulate pressure. The students at the desks were to record every time a gas molecule collided with their desk.
My biggest concern is to keep the students moving at the same pace. A brilliant friend of mine recommended that I find an online metronome and to have the students moving one step per click. The metronome then doubled as my temperature because it was easy to increase or decrease the clicks which changed the pace of the students.
So, on to the activity. The students wanted to compare pressure and temperature first so I started the metronome and they started bouncing around. Slowly I increased the speed and watched a little bit of mayhem occur as the students continuously crashed into each other. About a minute later I stopped and had the students sum up what they observed. Immediately they saw the connection between the speed of the molecules and the rising temperature. The students at the desks saw immediately the connection with pressure and several threw out that they were directly proportional. I then started the molecules moving again but began slowing down the metronome to simulate the temp dropping. It didn’t even take the full minute before my pressure students said that they saw a decrease in hits. One student even commented that not a single molecule struck his desk in the minute. Of course, my scribe is writing the notes on the board based on her classmates comments.
Next they wanted to talk about moles so in come the ? students. There were 9 in the middle and now there were 12. Again, the pressure connection came out immediately. Besides colliding with the desks more often, they commented that they felt that there was more chaos in the vessel as they collided with each other more often as well. This demo was a little self-evident, but was important to reinforce visually.
So now came the tough part: inverse relationship between Pressure and Volume. When I was first planning this, I couldn’t figure out how to make the volume change. And then it dawned on me: moved the desks! My desk students slid in the short ends and the gas students kind of panicked. One asked where they were supposed to move, “we’re collide with everything so much.” Did I just hear understanding? So as volume decreased, sure enough the pressure increased. My direct relationship student from earlier jumped right in to offer up the inverse relationship between pressure and volume.
We are more than halfway through the period and the Carbon Dioxide students are tired of sitting and watching their classmates having all of the fun. So Hydrogens sit and the heavier gas molecules step up. But, there was a catch. I needed to demonstrate to them how the heavier gas will exhibit slightly different properties because of the added mass. Well, I can’t make the students weigh 2200 pounds (CO2 is 22 times heavier than H2) so I load up every student with every backpack, book, purse, you name they had to carry it. With Pressure still as our focus I changed the temperature and watched the heavy gases struggle to move around the “container.” Now the questioning here needed to change a little. We needed to see the effect on pressure from the perspective of the gases versus the container. The container noted that they saw no real difference in the collisions they were experiencing. The gases, on the other hand, mentioned that they felt they were colliding a lot harder with both the container and other molecules with greater force as the temperature increased. Combining the speed and the added mass definitely had an impact on the overall results.
This ran us pretty much to the final bell so I didn’t have a chance to talk about how the students felt about the activity. I tweeted with some students later and they commented that they really enjoyed class today. I have to say that I had a blast. It was so much fun watching the students physically demonstrate the concepts for the unit they were studying. Those students who like the more formal notes still have all of the podcasts posted on my YouTube channel so no information is lost.
Overall, I definitely want to do this again. Could I do this every day like this? No way. But, it definitely makes me question more of my semi-traditional methods for instruction. Labs will need to be restructured so they start the unit and more information can be drawn from them instead of the labs reinforcing what I have already taught.
Sorry that this was so long, but I wanted to describe as much as I could so you could get a better feel for the lesson. I would love to hear your thoughts on the lesson and your experience in PBL.