Educating Risa

Last Friday night the boys and I did a simple experiment with water and different shaped containers to understand better the nature of science. The idea for the experiment was inspired by an experiment in the Oxford First Book of Science. Specifically, I wanted them to understand the idea of a reasoned hypothesis: in most cases, scientists make educated guesses as to what will happen, based on previous data and knowledge. They do not often make blind, crazy, random guesses. So we lined up 5 different vessels and poured 1 cup of water in a measuring cup:

I began by asking the boys what they thought would happen when I poured 1 cup of water into the wine glass. Would the wine glass hold the water, and if so, to what level would the water come? Both thought the wine glass was too small and that it would overflow. As it turned out, their hypothesis—this one a fairly wild guess, as my 5- and 7-year old do not have much experience with wine glasses (tee hee!)—turned out to be incorrect. The wine glass held the water easily. We moved on to the other containers, with the boys showing me with their finger how high up they thought the water would go.

Here, the boys estimates were getting closer; the truth was that the water level ended up in the middle of their hypotheses for the short, wide glass.

Here, the boys estimates are closer again, with Gareth (age 5) getting it almost bang on: the water rose very close to the top of the bird glass. Daegan (age 7) found this VERY frustrating, thinking that there was something wrong with him as he wasn’t getting his hypotheses correct.

“Aha!” I said. “That was the point. You’ve been doing little more than blind guesses so far, whereas when scientists make a reasoned hypothesis, they use known facts and data and results from other experiments to guide their thinking. So let’s try that now.” I got a new vessel out of the cupboard, a coffee press that was tall like the bird glass, but wider—yet not as wide as the short, wide glass. I placed the coffee press in between these two vessels and asked the boys for their hypothesis. This time they both made a reasoned hypothesis: the water should come to a level between that of the bird glass and the short, wide glass.  It did.

I also brought out a low pyrex bowl. The boys decided it was most similar to the low, wide glass, and as it was wider, the water level would not go as high. Again, they were right.

Lastly, I talked about one other characteristic of science: it’s experimental data must be replicable, or repeatable. If I poured another cup of water into an identical low, wide glass, the level should come to the same height. If it didn’t—if it was sometimes high, sometimes low, sometimes overflowed—we would have a very hard time generating laws or knowledge of our world. This is a pretty complex idea, but the boys grasped it with this simple demonstration: