Bill Nye & Buoyancy
However, now that I moved, my public library Bill Nye supply has been cut off. And the videos are quite expensive to purchase. Luckily, someone has been posting episodes on YouTube. I know, I know, I should feel bad about viewing copyrighted material for free. But, as you know, many teachers depend on the CASE* method. {UPDATE FEB 2010: Apparently, the videos have been removed due to copyright violation, and the user's account suspended.}

In the "Buoyancy 1" clip, 0:58 to 4:34 is possibly the clearest displacement demonstration I have ever seen. I showed this 4 minute clip to my group of 2nd graders. They were more clearly able to understand the concept of the displaced water weighing the same as the submerged part of the boat, and they literally squealed in delight when they found out the water filled up the exact print of the boat. (Well, at least until they have the magic broken when they find out that only works for liquids with a density of 1 g/ml.)
I am now inspired to set up a similar contraption next year so that the kids can mass the displaced water, rather than indirectly figuring it out by measuring the mass of the object and the volume of the displaced liquid. I'll add that to the list of things Bill Nye (or at least his writers) has taught me.
* Copy And Steal Everything
Labels: science topics, teaching