Thursday, February 3, 2011

Weather Science Round 2

This was fun! After a quick review, we started talking about the water cycle.

I like to start with a globe and the question: Where does all that water come from?
Rain? Streams and rivers? Yes, but where does that water come from? The water cycle!

We experienced evaporation and evaporative cooling. This was interesting. As you may know, phase changes require energy. A super easy way to see this is to moisten one forearm with a damp paper towel and then blow on both arms. As the water evaporates from the wet arm, it uses the heat from your body to make the conversion from a liquid to a gas: presto! Evaporative cooling! This is why sweating cools you off (unless it's summer near Washington DC with 97% humidity).

We went on to look at the different kinds of clouds. Then we went into the kitchen to make our own. I used a quart mason jar for this and a saucer that I had put into the freezer. Here is what we did:

1. I filled the jar 1/3 full with very hot water (just off the boil).

2. I added a few drops of rubbing alcohol and a drop of blue food coloring.

3. I put the frozen saucer over the mouth of the jar and added some ice to the top to keep the saucer cool.

A cloud (fog) quickly formed inside the jar. One of the interesting things you can point out is that the water is blue and the cloud is not. This shows that it's just the water evaporating - the main reason the sea is salt!

Next we made some rain. I used two large pots for this. The lower pot was boiling on the stove and the upper pot contained ice water. I just held the cold pot over the warm pot and got an unexpectedly large cloud (!) but also quite a bit of water condensing off the cold pot and raining back into the lower pot. Look! It's our own water cycle! Our energy is being produced by the stove instead of the sun.

This class is giving me food for thought about teaching. One thing I find is: I really like to teach. Another: I like to teach small, short, hands on classes where I can get total engagement from the kids. Still more: I end up teaching on two levels during these classes. The younger kids are absorbing the basics, but we have a steady stream of questions and commentary from the older Zoomlians. And then: I like to have a basic plan for the class, but be ready to go in other directions as questions come up. Lastly: I owe a lot to the Emperor for teaching me so much about teaching!

No comments: