Wednesday, August 15, 2012

Hydrologic Cycle, Water Density, and Water Taste Test

The natural starting place for any unit on water is the Hydrologic Cycle. [When I'm teaching and need to draw diagrams, I always just tape up sheets of paper from those IKEA paper rolls on our walls or windows.]
Do you like that penguin? And the . . . eel? (it was supposed to be an otter)

This stuff wasn't new to Abey or Sebby, but we went more in-depth than they'd gone before. When we studied clouds, rain, and lightning, we had to get into static electricity, of course, and later we studied currents (did you ever put together that static electricity is so named as a contrast to moving electricity; that is, a current? I never had. It was eye-opening to realize this) when we talked about hydroelectric power. Those were some of the most interesting parts to me, since I've just never really understood electricity! Yes, after all these years (and I was a good student), I understood some of the separate concepts, but never really the deep-down causes and how they all fit together. I felt like leaping for joy when it finally all came together in my head. So that's why things turn on when we plug them in! But I'm getting ahead of myself.

Robert Krampf has a great, simple video showing how to make a model of the hydrologic cycle.

Nearly all of the books we had on water (even the ones about dams and hydropower) included chapters on the water cycle, so there were lots of chances to review this throughout the unit.

We also spent a couple different days talking about some of the interesting properties of water, like surface tension, boiling and freezing point, density, etc. Having an understanding of the basic atomic structure of water and some of its characteristics was really useful on the other days as we studied things like lightning and electricity.

We did a demonstration to compare the densities of oil, water, and corn syrup (you drop in different objects and see where they float). This also showed the intermolecular polarity of oil and water.
We did a couple different experiments with water convection currents and the densities of different temperatures of water---this one is called the "underwater volcano"

The watched pot boiling

Robert Krampf has some good videos on water:

I also thought it would be interesting to do a taste test of different types of water. We boiled some water and drank that when it cooled, along with boiled water shaken up (to re-dissolve gases from the air into it), tap water, and a few different kinds of bottled water. This led to a really fun discussion of why people buy bottled or filtered water and whether we think it's worth the price (we don't, but then, our water is the second-best in the nation!). :) Of the bottled waters, Sebby and Abe did prefer the taste of "SmartWater," though!

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