Tuesday, July 29, 2008

Musing on mufflers: introducing aerobic respiration

Kids know a thing or two about cars. Or pretend to. It’s not like the olden days when you’d fidget with a carburetor (“Oh, so that’s what a gasoline fireball looks like” with singed eyebrows, looking more surprised than your already very surprised look.)

So I no longer ask sophisticated questions about cars. But I still ask questions.
What makes a car go?

After a variety of answers, you work your way to gasoline as fuel, planning to eventually work your way to hydrocarbon bonds and photosynthesis and all that. But not yet.

Some students are already in over their heads. Not every family has a car and kids have better things to ponder than gas stations. So make it even simpler:
What comes out of the tail pipe?

Again, you plow through a variety of answers, go through a side discussion on smoke, break up the fight when someone comments on someone else’s family hoopdie, then finally get back to a refined version of the question:
What do you observe coming out of the tailpipe of a well-tuned 2008 Honda Civic on a 70 degree day?

Well, now the answers are fewer. “Um, nothing…?” Before you get any farther, explain to your Wackadoodles that you are not looking for them to go play with a tailpipe. They’re hot, and even a finely tuned car may spew out more than carbon dioxide. Maybe when I have tenure I’ll go there, but not yet.

So now I stand there, waiting. The Pause©.

The students know something’s up. It’s an easy question. What do you see coming out of the tailpipe? “Nothing” is not cutting it. Finally, someone will offer that well, once they saw some water come out of it, maybe leftover rain, but water nonetheless. (I do not ask them how they know it’s water—no sense encouraging the Wackadoodles).

Give them the dead stare. Nod.
Yes, that’s right. It’s water. But it’s not rain.

Again, The Pause©

“Er, Doc D....OK, so it's water...what's that got to do with biology?”

You know they don't believe you, but students pacifying teachers in awkward moments has a long tradition in classrooms. You think it's a teachable moment. Time to throw aerobic respiration at them.

Before you get too enamored of your fine contextual scaffolding, admiring your anticipatory set setting the stage for authentic learning by cognitive apprentices, remember it's actually just a room of children trying to deflect their delusional teacher back into their reality. They'll say anything at this point to steer your delusional butt back to the classroom.

The Sirens are calling—you want to be the Erudite Educator, instilling the Krebs cycle into the masses. The kids win, anything to get their teacher away from this silly nonsense about water in tailpipes.

Don't do it. Take two deep breaths. Forget about NCLB, NJASK, HSPA, EOC Biology Exam. Forget about tidying things up. Silently say over and over:
No confusion, no science, know confusion, know science....

I grab my handy-dandy propane torch, fire it up. Now the kids think I've completely lost it—some are texting wildly under their desks, thumbs moving for dear life.
What's coming out of the torch?

“Well, Doc, um, fire?”
What do you observe?

“Doc, I just said fire...like, um, you're holding it.”
I rephrase the question--
What besides fire is coming out of this propane nozzle?

“Ah, gotcha Doc, I know where you're going—carbon dioxide!”

I shrug. I can't see it, smell it, taste it, so I'll admit that's what the books say, but give a look like I'm not convinced.
What else?

Silence. The Pause©

I point the flame at a cool mirror and write my name in condensation.

“That's soot, Doc.” My name fades away.
Nope. Water.

And I let them spend the last few minutes of class trying to disprove it—and, of course, they cannot, and we have a grand time trying to figure out if the condensation from the flame is the same stuff as the condensation on the bathroom mirror, and away we go.

They still may not believe that the tailpipe has water in it. But they're closer than they were an hour ago. And maybe, just maybe, mitochondria will be a tad more interesting this time around.

1 comment:

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