When I visit my grandchildren I like to bring activities that I think will amuse them. One of the things I brought last summer was clear old-fashioned film canisters and some AlkaSeltzer tablets. We take a glass of water outside and sit on the steps. Add water to the canister, drop in a half tablet of the AlkaSeltzer, hastily put on the lid, and wait. The lid will fly up into the air in a few seconds. (So don’t stare straight down at it…!) We discovered that if the lid was picked up and stuck back on quickly enough, we could get another flying lid, or maybe two more.

This is really a summer activity so we hadn’t tried again this year until recently. The kids are six, four, and two and demonstrated quite a lot about how brains work, as we played this game. Last year the kids had trouble finding the lids quickly enough so this year I thought I would just do one canister, and put the second lid on myself to maximize the fun. This actually worked quite well and we got really good pops. But the six-year old was advanced enough to realize that he could find the first flying lid and bring it back quickly, while the second lid popped. This upped our number of pops per single dose of water and tablet. We got five or six and even seven once.

The four-year old watched the six-year old and his technique for finding the lid, and got a lot better at finding it himself. (Remember, last year, the five-year old couldn’t manage that step quickly.) They didn’t use words but I’m pretty sure that part of the improvement this year was listening, to see if they could hear the lid hit the ground. That improved their search patterns. The four-year old was not able to adjust to the idea of both lids going on the same bottle, so when he had the second lid in his hand, he would only find the first lid and give it to me. I didn’t fuss; it was too much fun to watch the brains working all around me.

I think we could do some interesting experiments on the situation. I did notice that the amount of water I was putting in the canister was just a bit higher than last summer. It is a tiny container so it’s not a big difference but it might have contributed to our extra pops. We might try to see how much water it really takes to dissolve a half tablet. The six year old is dying to try using a whole tablet. I hadn’t been willing to let him do it last year because we were having a lot of mishaps and spills and it would have cut down on the number of times we could fill the canister, but now it might be interesting.

There’s a couple of tests to look at. Question number one is, would a bigger tablet give a bigger pop? Would the lid go higher? Would it just dissolve at the same rate but we’d get more pops because there’s more tablet? Would we run out of water? Currently the limiter is the half tablet. When it is all dissolved the round is over. Would that amount of water even dissolve a whole tablet? Good questions!

The two year old likes to sit on my lap and chuckle when this goes on. But eventually a decision point was reached in that mind. “There’s a part I can do,” the little mind said. Next thing I know water is cascading down my side. The two year old had decided to fill the canister for the next round. I was impressed that the water was going into the canister, and chilly, as it splashed right back out, because the concept of, that’s enough better stop pouring was somewhat underdeveloped. We can work on that too.