After a Board meeting, we began unit 2.
The first activity involved opening a fragrant substance (freshly popped popcorn) at a certain location at the room. In student mode, we were asked to raise our hands when we could smell it. Once it had reached the entire room, we were asked to draw a particle diagram describing how the smell got from the front of the room to our noses. Afterwards, we compared our whiteboards, and discussed the differences between them. In order to get from point A (the front of room) to point B (our noses), the “popcorn smell particles” had to move. The mechanism for this movement varied from board to board. One group included air particles, so we discussed whether they were moving as well. This applet was used to guide the discussion towards how the air particles and “popcorn smell particles” interacted.
Now that we’ve determined that particles moved, we had to come up with a way to indicate moving particles in our model. Again, it varied from board to board, but we tend to use cartoon-like “swhooshes” attached to our circle particles.
Next, we looked at food dye added to hot and cold water, and drew whiteboard comparisons. Discussion lead to incorporating into our model how heating a substance increases the speed of particle movement.
States of matter
The instructor placed two large test tubes filled with water, methanol, and separate food dyes into a heated water bath. Each test tube had a one-hole stopper and a thin tube inside. As we watched another Eureka episode, the test tubes were heated. Afterwards, there was a clear difference between how far the liquid had expanded up the tube in the two solutions due to heat.
In student mode, we discussed how a thermometer works in terms of energy, particles and movement. With the new idea of expansion (not necessarily phase change) we also discussed whether density might be a temperature-specific property.
Next (probably on a different day) the instructor asks students to draw a whiteboard diagram of how a straw works. I did this last year, and our group tried to recreate in our board a common student response:
The instructor walked us through how to remove student misconceptions here, and utilize our particle model to describe what actually happens. Afterwards, we blew up a student.
No really. Trashbag. Four straws. Light as a feather, stiff as a board flashbacks from elementary school. But after the straw discussion, students are able to describe how four tiny straws can lift a student off of a table.
Next, we went into a pressure lecture that I didn’t particularly like, and seemed to break the “modeling” flow. Overall, we define pressure as “force per area (which contradicts our avoidance of “per” in the density lab). The only goal is to make sure students have a similar idea and definition of pressure, so that going forward we can focus on the particle model of pressure.
Read Dorothy Gabel Article (Improving Teaching and Learning Through Chemistry Education Research: A Look Forward) If you can get your hands on this article, its a great read.