3 x 1 or 2 x 1.5

No, today’s post is not about math schoolwork images that went viral a couple of weeks ago. I will resist the temptation of adding to the barrage of comments already registered in the internetosphere (my poor attempt to invent a new word).

Instead this post is about my experiment this semester teaching General Chemistry on a Tue-Thu (TR) rather than on a MWF schedule. You might think the hours add up if you’re comparing two 1.5-hour classes per week with three 1-hour meetings. But there’s the problem of “passing time”, i.e., the time in between classes so students and professors can run from one class to the next. (I personally avoid teaching back-to-back classes so I never have to do this. Actually the main reason is that I’m drained of energy right after class.)

At my institution, the 3 x 1 is more precisely three 55-minute sessions, thereby giving you 165 minutes together with the students. I’m not sure why they’re not 50-minute sessions which would lead to less wacky timetables. Imagine trying to remember that your class is 7:50-8:45am or 1:15-2:10pm. Those were the old times when I first joined the college. Then they decided that 7:50am was too early and moved ALL the classes by ten minutes thereby requiring us to remember a whole new set of times. Admittedly I got used to it after a couple of years and now have the new schedule ingrained.

The 2 x 1.5 is more precisely two 80-minute sessions or 160 minutes in total thus gypping the teacher and the students of 5 minutes per week, or 75 minutes total in a 15-weeks semester. It was actually a little worse. Back in the old days when I was mostly lecturing and doing less active learning and group work in class, I would always take a 5-minute break in the middle of a TR class. (These were the non-science majors classes and there’s only so much chemistry they can take without the break. I always announced it as 3 minutes but in reality it takes 5.) Factoring in the break that’s a loss of 15 minutes per week or a whopping 225 minutes (3 hours and 45 minutes) over the semester. What a waste!

For years I have been teaching General Chemistry in the MWF format. Our department schedules these in the mornings to minimize clashes with the once a week four-hour lab sessions. But now that I’ve been trying to incorporate more active learning and group work exercises into class, I’m finding that 55 minutes is a little too short. Last semester when I overhauled my class, I found that I was always about 10 minutes short of time and this was on top of actively hounding the students to work quickly and efficiently. Not enough reflection in class. It was a smaller Honors class, so I had high expectations of what could be accomplished – and was subsequently brought back down to earth.

So what did I do? I scheduled myself (since I was department chair) to teach a TR General Chemistry class. Since these are all first-year students, we could make sure they were co-enrolled in non-conflicting lab sections. One of my colleagues had done this some years back when he was employing active learning methods (in fact, he continues to expose me to new methods and technologies). Now I have 80 minutes per class so I don’t have to rush.

There were some constraints. For one, this was not an Honors class so the students were not as strong on average. This was significantly borne out when some students outright failed the second exam. Secondly, I still have to “cover” all the material so that students aren’t ill-prepared for the second semester of General Chemistry. Many students do not have the same instructor because of scheduling issues and therefore we as instructors agree to make sure we cover a bare minimum content-wise. Except this minimum is nowhere close to being bare. It’s chock-full! Given that I could not push the students as hard as I did last semester, I opted to scale back my more fanciful ideas of what could be accomplished.

This past Thursday I tried out an exercise I had not used in a while – building actual physical models of solid-state structures so students could really get a good handle on how atoms and ions pack in a solid. It’s hard to visualize this even on the computer. These are not your typical molecular model kits used to build small covalent molecules. I had purchased the solid-state model kits about ten years ago for my upper division Inorganic Chemistry course (where I have a module on solid-state structure). The ones I use are from the Institute of Chemical Education (ICE) and here’s a snapshot of their model of ice (how appropriate).

I first tried this out maybe six years ago in second semester General Chemistry (our topic arrangements change slightly from year-to-year). It was a small Honors class. Our classroom was attached to a lab so the students could spread out and build models. But it was very hard to accomplish what I had planned in 55 minutes. We got through less than half of what I thought we could do – poor planning on my part. But since then I’d been thinking about what tweaks (or major overhauls) would be needed. Several years ago I was invited to a high school “lab” class for a two-hour hands-on session with a group of very eager students. I substantially modified my plan and brought the ICE model kits. It was a hit!

So in preparation for Thursday’s class, I scaled down my 2-hour session into a 80-minute plan. I did a 5-minute intro on how X-rays can be utilized to find the ordered arrangements of atoms in a crystalline solid. Then we went through a simple worksheet with an arrangement of four equal-sized circles touching each other in a square arrangement. In this 2D case the students were able to quickly work out the percent of empty space in between the circles, and then calculate the relative size of a circle that could be placed in that empty space (they needed a bit of help from me with this). This took less than 15 minutes. Then I spent 10 minutes lecturing on the three cubic structures (primitive, body-centered, face-centered) sketching out simple drawings on the board accompanied my nice textbook figures flashed up on the projector.

This gave the students 40 minutes of time with the model kits where they built the three cubic structures in 3D and tried to figure out which smaller spheres would fit into the holes and really get a physical feel of how the atoms were arranged. We wrapped up in 10 minutes, basically me going through slides of different unit cells of salts, and towards the end the students were able to determine the information I was looking for just by looking at the PowerPoint slide on the screen. Or so I think. The real test will be this coming Tuesday where I will put up a structure for the five-minute quiz that takes place in two thirds of my class meetings. I’m looking forward to seeing the results!

My final comment on the 3 x 1 versus 2 x 1.5 format is not related to the course material but with that subjective feeling one gets when a class “gels” together as a learning community. Usually in my General Chemistry classes, in the MWF format, this happens around weeks 4-5. The students are now much more comfortable with each other and with me. This semester I thought I was doing something wrong because I didn’t have the expected camaraderie with my students at the same point in the semester. It came later in weeks 6-7. In this case I think the number of class meetings made a difference. My hypothesis is that it takes some number of meetings for the students to get comfortable (at least in my current class format) and this process cannot be rushed. But I think reaching this point more quickly can be facilitated, and this experience has made me think about how I might structure my classes next semester to be more intentional about building a learning community