Energy in Clouds

In this demo, you will need 3 identical thermometers per group. One thermometer is kept dry, one's bulb is wrapped in room temperature water, and the other in rubbing alcohol. Let them set for a few minutes. The kids should take temperature readings every 30 seconds or so. I have them make temp v. time graphs from there nd explain the meanings. As molecules evaporate from the two wet bulbs, heat - a form of energy - is carried away by the evaporating liquid. Since alcohol evaporates faster than water, that thermometer gets cooler quicker than the other two. This is how human "sweating" causes a cooling effect.

Understanding the role that energy plays in phase changes is a crucial concept in weather. Have you ever heard a Hurrican Schwartz on channel 10 say that "this storm has lots of energy"? This energy is carried by water molecules as they evaporate from the ocean, similar to the way they took energy away from the thermometer bulbs. The more vapor, the more energy available. Then, as the vapor molecules condense to form clouds, this energy, latent heat, is released. This heat can make the air less dense, causing it to rise, in turn causing the pressure associated with that region to decrease, giving rise (no pun intended...) to a LOW PRESSURE SYSTEM, and causing winds to flow from any local HIGH PRESSURE system into it.


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