Sunday, November 1, 2009

"I am a molecule, I cannot stop moving...."

Early in the year, I introduced a very simplified version of the kinetic theory, itself a simple (but powerful) idea. Something happened about 14 billion years ago, give or take a billion, and things have been moving ever since.

This past week we've been working on diffusion.

I get my kids up into a corner, then tell them to pick a direction, walk in that direction until they hit something, then ricochet as though you were a billiard ball.

After a few moments, I ask them to stop and note their positions. I tie their motion to the "Whoever Smelt It, Dealt It" hypothesis of fart diffusion--silly but effective--then ask them to keep moving again. The students are interspersed throughout the room, but two critical ideas emerge:
1) They are not evenly dispersed, and
2) Their positions keep changing even when they are at equilibrium. (Equilibrium is a dynamic state--true equilibrium, in the sense that every part of a system has the same concentration of particles, does not hold in tiny volumes.)

I have a box of balls--yellow on one side, black on the other, with a free agent blue ball (yes, sophomores giggle at "blue ball") randomly tossed in the mix. I shake them up until the blacks and yellow balls are reasonably interspersed.
"Will this arrangement of balls ever happen again if I keep shaking the box?"
Most say no.
"Is this arrangement possible?"
Well, yeah, Dr. D, duh--it just happened.
"Will this arrangement of balls ever happen again."
It could, maybe...
"Will it?"

Most think not, and I agree with them. I think. Playing with an infinite number of possible arrangements over an infinite number of trials scrambles the mind.

A child muttered in class this week that she keeps knowing less than she thought she knew.


I stole this exercise from Ms. Rinaldi here at BHS--I steal from a lot of folks.
Leslie makes a good point--Michael Franti rocks!


Leslie said...

"Seems like everywhere I go,
the more I see the less I know."
--Michael Franti

Kathryn J said...

As someone who hopes someday to have a classroom in which to teach the kinetic theory, this post is a treasure trove of ideas. When I subbed in 6th grade a few weeks ago, I spritzed some perfume in one corner of the class and had the students raise their hand when they could smell it. We also all crowded in the corner and spread out until we were comfortable spinning with our arms outstretched. The fart analogy would forever entrench diffusion in their minds. I plan to use all of these ideas.

I have subbed often for biology in the past few weeks. I taught osmosis to 6th graders, then later taught it to honors 9th graders, then another day to 7th graders in a different district. Love the idea of throwing the blue ball into the box of marbles and yes the giggles also cement things in someones brain permanently.

momomom said...

Great video!

John Spencer said...

It was cool to get a glimpse of your classroom and how it works.

This Brazen Teacher said...

Saw Franti live in Salt Lake City back in 2006 when Spearhead was still "cool and underground-ish." Indeed- they DO ROCK :-)