Playing catch-up

It's been a while since the last update, but over the past month there have been a lot of days where school has been canceled, half-days where my classes don't meet, or when the students have been taking tests, so there's been less to report on than I would like. However, I did give another presentation a couple weeks ago that seemed to have gone over much better than my first attempt, given the slightly different way I approached the material. This time, in addition to including as many illustrative photos as possible, I also kept myself from delving into long-winded explanations of unnecessary detail and used the presentation, covering different types of mixtures (View it here), to lead into an activity during the second half of the class (See the instructions here). I found it easier to engage the students this time around and found them more willing to offer up ideas for examples of different types of mixtures. I think this was partially because the material was more familiar and accessible, compared to the idea of standards, and also because the students have become more comfortable with me since my last presentation and find participating in my talks to be a nice change of pace.

That said, there are still some students who seem to make it their job to be as disengaged as possible. There is one girl who sits near the front of the room, right in the middle, and the completely flaccid expression on her face and the use of her arm to prop her head up--lest it fall to her desk in boredom--pains me every time. I don't think I could be that unenthusiastic about anything if I tried. That is the breed of student to whom I was trying to tailor my talk, but it seems I have a ways to go still.

One of the persistent problems I've noticed in Ms. Hardy's class is that the students frequently don't bother reading the instructions for things before asking for help. Although I don't mind explaining things if they don't make sense, there are too many students to go around explaining the entire activity or lab to everyone individually. Because of this, you'll notice in the last slide of my presentation the emphasis on reading the instructions before giving up and asking for clarification. However, at the last minute, I found out that there was not enough glassware in the classroom to have each of the substances for the activity measured out for the students in advance. I asked Ms. Hardy during her planning period just before the Physical Science class if there was enough time to change the instructions to indicate that they were to measure out certain substances from a communal container at the center bench and print out new copies, but she said that wouldn't be necessary, that I could just write the modifications on the board and tell the students to refer to them as they worked. It seemed reasonable enough, but as I had predicted, this led to confusion and a lot of people asking, "What beaker of vinegar? There ain't no vinegar. Ms. Hardy, what do we do?" Even many of the students who were participating in the talk seemed to have turned on their selective hearing when I started talking about the modified instructions. I think I was on the right track with trying to streamline the instructions and encourage the students to try everything independently before asking for help, but I have to avoid making any changes after I say something or hand out written instructions.

Anyway, once everyone finally got on the same page with what they were supposed to do, I think the activity was a success. I had the students create a homogeneous mixture, a heterogeneous mixture, and a heterogeneous suspension by mixing sugar and water, oil and vinegar, and water and cornstarch, respectively. I was particularly excited to be able to do this activity, since the water and cornstarch mixture produces a non-Newtonian fluid that many people are probably familiar with, either from playing around with it at home, or from watching people walk on pools of it on programs like Myth Busters. Although there wasn't too much excitement at the water and sugar mixture, the students were endlessly fascinated with this liquid? solid? cornstarch mixture. I think it was a nice demonstration of how something that seems familiar can act in a non-intuitive way. I want to try to incorporate as many of these examples into future activities as possible, since I think a fascination with and a desire to understand those non-intuitive properties is a good way to lead into a pursuit of studies in a scientific field.

Speaking of counterintuitive physical principles, I've recently discovered the fascinating concept of thermoacoustic refrigeration. A friend of mine sent me this article that profiles a new three-in-one refrigerator/oven/electric generator that is powered by a wood fire. Of course, the fire doesn't directly power the other components. They're powered by harnessing the vibrations of the pipe through which the water being heated by the fire passes. The electricity is produced in a pretty straightforward manner, via a linear actuator that acts as a generator, but the refrigeration is the really neat part. A thermoacoustic heat engine is used to induce cooling--essentially, sound is used to keep your food cold. I was blown away by this, since this was a concept with which I had no familiarity. I promptly searched the web for ideas of how to demonstrate this to my students. As luck would have it, a professor at my undergrad university had published a paper on how to build a tabletop demonstration thermoacoustic refrigerator (check it out). It looks pretty simple, so I plan on constructing one of these and presenting it next semester when the physical science class gets to their unit covering waves.