Every Friday (okay, every other Friday when I’m busy) I teach a science lesson at a local elementary school. Mostly, I try to keep my lessons fairly fun– a little science followed by some explosions, a laser, bubbles, and now and then some green goo. Today, I taught the kids a little about phase changes and sublimation. I brought in some dry ice for all of us to play with. We first dropped dry ice in water and made dramatic horror-flick fog. Nest, we inflated balloons and plastic trash bags by putting a little dry ice inside. Finally, we watched bubbles (as if dry ice wasn’t fun enough… bubbles!) float mysteriously on the carbon dioxide vapor then sink as the carbon dioxide permeated through the bubble membrane, making the bubble heavier. Some of the bubbles even froze when they reached the dry ice cubes. All very cool stuff, and I think the kids had fun.
On my way back to my MIT office, however, I became caught in a warm, spring thundershower. I was still carrying a couple of pounds of dry ice when I was caught in the downpour.
Since I’m at MIT now, let me put this in equation form:
Warm rain + dry ice cubes in a cardboard box = crazy lady carrying a foaming cauldron.
Let’s just say people looked at me awfully strangely on the street… and it’s certainly good I didn’t need to take the T anywhere.