Today we explored the amazing properties of a chemical we are exposed to every day: Water! The lab was complex, with six different stations at which various properties were investigated that related to how water behaves and how it influences the living world. Why is it so strange that ice floats? Why does fresh water float on salt water? Why is it so much warmer near the ocean? How do trees and plants transport water from their roots to their tops? The students investigated the answers to these questions and more!
We all know that water expands when it freezes. This seems very normal because we are so used to it, but this property is actually the opposite of what you would expect most materials to do. Most substances become more dense, not less, when they transition from liquid to solid state. We tested this in our petrolatum plunk activity when students hypothesized if the Vaseline would sink or float in melted liquid Vaseline. It sank, as expected! Next time it freezes outside, think about how important it is that ice floats so animals living underwater can live year round.
We also examined water’s ability to absorb a lot of heat without changing temperature, the nature of water to stick to itself and to glass as it climbed up a capillary tube, and the change in height of the meniscus as an ice cube melts in a flask of water. Students also simulated the Gulf Stream and observed how trade winds cause a boundary current that brings warm water from the tropics to Massachusetts.