Friday, April 22, 2016
Masters of Disasters: Hurricanes and Tornadoes
Last week we talked about the sun, this week we talked about water. Where do we find water? Where does it come from? Where is it going? The kids had a good theoretical grasp of the water cycle, so it was time to to get practical!
Water evaporates, but it needs energy to change phase. You can feel this if you spread a thin layer of water (or alcohol) on your forearm. You caan feel the liquid absorb heat from your arm so that it can jump to it's vapor phase!
Next up we made a cloud from water vapor: you take an empty soda bottle and add a little hot (not boiling) water. A few drops of alcohol will make this more dramatic.
Light, then blow out a match and put this in the bottle. You won't be able to see the smoke, but it's there, and it's critical - water needs something to condense on. Seal it up and squeeze the bottle a few times. Cloud!
We also made rain ( hold a pot of ice water over a pot of boiling water), and lightning (balloon rubbed against wool in a dark room - for added pizazz, catch the spark with a florescent bulb!).
We looked at cold air falling and hot air rising by using a smoking match in front of an open freezer and over a hot stove.
Then we talked about what happens when there is a lot of hot air rising and a lot of cold air falling at the same time. I had enough kids that I had them demonstrate it by having half the kids go up the stairs while the other half were going down the stairs.
Nature handles this the same way we handle traffic- everyone goes to one side. It doesn't matter if it all goes left or all goes right, all that matters is that it all goes the same way! In a natural 3 dimensional system, this means spinning- this is why hurricanes and tornadoes spin!
We looked at hurricanes by using spinning water in a big pot. We dropped in a paperclip on a thread to see where the strongest and fastest current was (near the edges) and we talked about the storm front and the eye.
We also looked at how the wind raised higher waves in shallower water by blowing through straws across a baking pan filled with varying amounts of water.
The favorite was an example of hot air rising: tea bag rockets!