Hephaestus Bellows

Today I ventured yet again into the world of SCALE-UP classrooms. This time with a bit of success! The professor that teaches the class I help out with talked for a while about crystal structures – simple cubic, body centered cubic, and face centered cubic.

The structure of how the material was presented itself went a little bit like the following:

• Introduce the concept that atoms pack together
• Speak on the three main cubic crystal types: SC, BCC, FCC
• Figure out coordination numbers and “n;” how many full atoms belong to a unit cell
• From the above, do theoretical density calculations
• Build ball-and-stick models to look back at the prior items discussed.

In hindsight (isn’t it beautiful?!) the order should have been a little bit different, and I think will wholly influence what we do going forward with models and hands-on activities.  Distribute materials early on so students can manipulate them and practice ALONG WITH the lecture rather than practice AFTER the lecture.  Specifically these 3D style models a few students struggled to see it right away. I think they would have benefited to look at the models with the lecture as opposed to after.

I’m intrigued to see, going forward, what happens when we give out materials early on during a lecture. I can see (as I know I would have been this type of person!) how it would be tempting to play with “toys” and not pay attention. The balance between the two is going to be the most difficult part to manage.  Do you give students hands on examples early and let them tinker at the expense of their full attention? Or does that tinkering immediately instead keep their attention for longer periods of time?

[SCIENCE CONTENT, STEER CLEAR]

I learned a few things that some people struggle with and yet I take for granted.  First off, seeing how a unit cell clips spheres into eighths comes naturally. To some people, it doesn’t. I made this little doodad in Mathematica to illustrate it for a few students and it seemed to help them out quite a bit.

A bit of fun on-the-fly learning happened, too.  As I was teaching them that no matter what atom you are in a crystal structure you see the SAME crystal structure all around you. If we start out with just the center atom of a BCC crystal other center-BCCs would make their own cube with a previous corner as their center-of-cell.

Another Mathematica doodad:

BCC structure with blue at the body center

BCC structure with yellow at the body center

Still a BCC structure. Notice the lower left corner of the yellow unit cell functions as the body center atom of the blue while the upper right corner of the blue unit cell functions as the body center atom of the yellow.

Anyway, that was pretty mindless rambling, but what we discussed in class today. FCC was very difficult to construct and didn’t really teach much – it looks more like a mess than anything.  I’d stick to BCC in the future.

or how not to use a SCALE-UP classroom

With the primary instructor out of town, I was left to teach my first full class period in our SCALE-UP classroom. I was confident in the material and had no qualms about presenting it but I wasn’t sure quite how to involve the students. I, despite my best efforts, lectured to them.

First off, the material was DRY. Seriously. We first talked about electron configurations in atoms [1s² 2s² 2p³, anybody?], then how these electrons interacted and created bonds between particles and finally wound up with how one might discern a physical property from these bonding types. There was a LITTLE bit of success when I asked them to talk among themselves about σ (electrical conductivity) as well as strength, but I wouldn’t consider it an incredibly useful discussion.  It took… two minutes. Not sure that counts as a problem-based learning exercise.

But then I tried for one. I had thought about it ahead of time, made this fancy little graphic [actual science content – warning!]. I asked the students to come up with some geometrical terms that might be used to describe the picture below. I prompted them with a few – how deep was the well? how symmetrical were the halves? how quickly did it change direction? – only after I saw they had no idea what I was asking about the first time.

Not surprisingly, the three answers I gave them were indeed THE answers. But what physical properties might the correspond to? Dead silence. Nobody had any idea.  The exercise had flopped.  So I guess I learned a few things.

1. One instructor is NOT sufficient to facilitate conversation with 120 students.  Not that there was much conversation… but if there had been I certainly would not have been able to structure any degree of it.
2. PBL (Problem Based Learning) in the future is going to require very specific prompts. I think what I asked them to do was more of a suggestion. Handouts (or even physical words on the chalkboard or overhead) would have provided better direction.
3. The dryer the material the more effective an example like this is.  But dang, it’s got to be a better example than this one!

Live and learn, right? That’s what the education process is about.  Speaking of education… who wants a quiz? Of the above, which has the highest T_m? highest stiffness? highest strength? Lowest CTE? Answers: ˙ssǝuɟɟıʇs ʇsǝɥbıɥ :q ˙ǝʇɔ ʇsǝʍoן :ɔ ˙ʇuıod buıʇןǝɯ puɐ ɥʇbuǝɹʇs ʇsǝɥbıɥ :p