Freezing Water Bottle – Background

This episode is from Responsive Teaching in Science, an NSF-funded project which focused on cultivating instructional practices of attending and responding to student thinking.


Kim Filner’s 5th grade class, at a west-coast public communications magnet school, was studying the water cycle. Their work began three months earlier with the question:

“One night it rains. When you arrive at school, you notice that there are puddles in the parking lot. When you go home, the puddles are gone. What happened to the rainwater?”

Ms. Filner’s science classes were always rich in discussion, and leading up to this episode, students had been discussing how water changes into vapor. They were working with a textbook model in which molecules in higher temperatures would spread farther apart. They noticed an inconsistency: water expands when frozen.