As we explored the concept of density through investigations with floating friction, one pair of preservice teachers wondered if the size of the container holding the water would affect the buoyancy of the apple they we observing. They carefully outlined with marker the water line representing the amount of the apple above water. From there they worked through their idea that a bigger container would hold more water, consequently the total water would have more mass and would push the apple further out of the water.
Yes, these are precious moments as a teacher. If it happens with adults, it certainly happens with our kids.
I had several responses I could have made. One would have been to simply tell them the size of the container would not make a difference. It would have been efficient, we could have moved on – but it would have left lingering doubts, an unsatisfied experience, and a lost opportunity. I responded with asking questions back. How big would the container have to be? The size of a bathtub? A swimming pool? They were pretty convinced a swimming pool would make a difference. Not having a pool readily available, we thought together of other ways to investigate this idea. Through this discussion, they had the idea that, similarly, if they put more apples in the container, the mass of the apples would increase and they would sink lower in the water. That we could do. We gathered more apples and filled the container. To their surprise, the apple floated no differently. We were on our way to understanding, but not quite there. I asked if making the container smaller would make a difference. Given a smaller container, they tried it once again. And again, the apple floated the same. By now, they were ready to set aside their old, naive, conceptions regarding the buoyancy of fruit and replace it with a more appropriate understanding of the nature of the relative density of the apple in water.
It took time, but in the end, they were convinced, their schema successfully accommodated, amidst the joy and satisfaction of discovery. If our target is for our students to understand, it takes time – time to listen, time to question, and the time necessary to investigate further. When we feel hurried, feel pressured “teach” the lesson and “cover” the material we may walk away feeling as if we did our job, but our students have not learned what they might have. Be prepared to take the time to listen to your students and give them the opportunities to construct their understandings.