Thursday, October 30, 2014


We've learned that clouds are tiny bits of liquid water or ice floating in the part of our sky called the troposphere.
And we know that when there is water in the air that is not like tiny ice or water drops, that is called water vapor.

One way that water vapor is made is by something called evaporation.

Remember that water and air are all just tiny bunches of little things called molecules.

If you have a glass of water, there are water molecules in the glass, glass molecules around the water, and air molecules above the water.

You can think of water molecules sometimes as crazy little balls of energy that don't want to sit still.
The only way you can make them stay still is to trap them with other molecules like the ones that make a glass.

When you have dry air that is next to water, the water really wants to go jump to where the air is.
So the water molecules right at the top of the glass get really excited and then shoot off into the air.
When they shoot off into the air, they make the air a little more humid, and they create water vapor.
This happens over and over and over until the air is really humid and wet, then the water doesn't want to jump out anymore.

This isn't something you can see happening with your eyes, but we can tell it happens by watching the water disappear from a glass very slowly over time and then measuring the air for humidity.

The excited water shooting out of the glass into the air is called evaporation.

When the sun is heating up the oceans and lakes, lots and lots of water gets excited, and evaporates into the water vapor that creates clouds.

(from: wikipedia - evaporation)

Kid Facts - Blast from the past: Lava Domes