Let's Make Rain

Supplies:

Potting soil | zip-lock bag | tap water | masking tape

Put the soil in the bottom of the zip-lock bag.

Add just enough water to moisten the soil so that it's damp, but not wet.

Lock the zip-lock.

Tape the bag to a sunny window.

Now watch what happens.

Do you see water droplets form at the top of the bag? And then do they drop back to the soil, like rain?

This is because of the water cycle that we have here on Earth. A "cycle" is like a circle or something that repeats. There are many cycles in nature. One of them is the cycle of the seasons: spring, summer, fall, winter, spring, summer, fall, winter . . . you get the picture.

Well, with water, the cycle sends water from the Earth up into the clouds and then back down to Earth again. How does it get from the ground up to the clouds? Through the heat of the sun.

When water gets warm, it evaporates (ee VAP or rates). It kind of disappears, but not really. The heat has just made it split into smaller little blobs of water called "water vapor." It's kind of like steam that you see coming out of a teapot.

Outside, when the sun shines after a rain, the water vapor forms, and it is so lightweight that it can float up in the air. You've heard that warm air rises? Well, it's true, even if the warm air is carrying tiny water vapor droplets with it.

Once it gets up there high in the sky and meets up with other water vapor, it can condense (con DENSE), or come together, into a cloud. After a while, the water vapor in a cloud gets heavier and cooler as more and more water droplets join together, and eventually, the water drops down to Earth again. That's what we call rain!

So what happened in your bag is that the water we put in there first evaporated up at the top of the bag, where it couldn't get out, but then condensed, got heavy, and fell back down to the soil, just like rain.