What's matter?

I start off my physical science class with the usual introductions, procedures and such, but before the first day is over, I tell them that by the end of the year they won't even know what "stuff" is anymore.

"Stuff" is as good a definition of matter as you are going to get at 9th grade, and it's probably as good as you're going to get for most of us without degrees in physics.

The kids look at me quizzically, I gawk back, and away we go!

***

"Stuff" ends up being circular. We can get fancy and call it matter, and the text will tell you that matter is anything with mass that takes up space.

Seems that just about any type of mass a 9th grader is going to run into takes up space, and just about anything that takes up space will have mass.

(OK, OK, bear with me--think about the definitions as presented to our students. Newtonian physics starts with a deceptively simple definition of matter. Teachers fall into the same trap as the students, but if we cannot get the kids curious about what we mean by "stuff", the rest of physics is just a dog and pony show.)

Eventually (months later) we will get to inertia, an operational definition of mass (and again a bit circular), but on the first day of class, the kids are pretty smug about what they know.

OK, Mister Dr. D, matter is "stuff"--we got that, everyone knows what "stuff" is.
So that's it? that's all we gotta know today?

Before I go any further, I tell them that if I do my job, by the end of the year they won't even know what "stuff" is anymore. And more important, they'll know they don't know.

Ah, grasshopper!

***

"So what's mass?"

I'm not looking for a post-doctoral account here, but I don't want to cheat the kids, either.

So I push the issue, even on the first day of class.

If you want someone to learn science, you must first shake them off the ledge of certainty, or rather, convince them they want to jump.

***

OK, so what is it, Mister Dr. D?

I shrug, palms up....Kids don't like it when teachers feign ignorance. They hate it when they realize the teacher isn't faking. A few get mad.

Why we gotta learn this stuff if you don't even know what you're talking about?

I was surprised the first time I saw the anger--I welcome it now.

***

Before the end of the period, I'll review what they know about atoms, or rather, review their misconceptions.

This year I'll show them this model, then take then out to the hall with a grain of sand representing the nucleus of an atom. How far would the electrons roam?

I'll let them walk around. Then tell them to walk farther still. I must have been in a summer daydream--yes, we'll do the walk-through, but not on day one.

I then tell them that if the nucleus was the size of a grain of sand, then the atom would be the size of a football stadium.

(OK, I haven't done the calculations myself yet, not to mention that I have no clue what the standard football stadium size is. A high school stadium? Giants Stadium? OK, so I need to go back to the chalkboard.)

***

OK, we got two minutes left now, and I need closure. Shoot, I forgot to hand out the texts. Closure...closure...closure.

This is when I need to keep my mouth shut. A good lesson in general.

Now the children are really squirming. The teacher is an idiot, and now he's standing up there speechless. They can't take the pressure.

Uh, that means stuff is mostly space, right?

I smile. And it's nowhere near winter break yet.