In the refrigerator, we have a jar of ice cubes. Let's bring it out into the classroom and put a lid on it. Just watch the jar and see if it knows any tricks.

Wow! It knows a great trick! Look at that! There are droplets of water forming on the outside of the jar! That jar must have holes in it or something. Let's see if another jar will do the same thing. We won't take the time to put ice cubes in it--we'll just use tepid (that means almost warm) tap water, and put a lid on it. See if it knows any tricks, or if it has holes in it.

What a dumb jar! It doesn't do anything spectacular. Just sits there.

There must be a reason for the water droplets to form on the outside of the first jar.

You don't suppose that there is moisture in the air of the classroom? It doesn't feel wet. Well, there has to be moisture in the form of an invisible gas in the air. When it touches the cold surface of the jar, it condenses, and forms droplets.

Have we ever seen that before? If we have a cold drink in the house, Mom wants us to have a coaster to set the glass onto, doesn't she? The reason is that the water condensing
on the outside of the glass would run down and make a mark on the table. It could even make a puddle. Why don't you put a clean glass of ice cubes onto a clean saucer, on your kitchen counter. When the moisture condenses and makes a puddle in the saucer, you could taste it, and determine whether it tastes the same as water from the faucet.

When you come outside on cold mornings, and the plants are wet, how do you think that happened? Probably the moisture in the air settled on the cold surfaces of the plants, and
condensed into droplets of water.

Thinking backwards, look at the bathroom mirror when you step out of the shower. The mirror has a "fog" over it, doesn't it? Well, the mirror was cold, and then the air inside the bathroom was warmed by the hot water of the shower. The moisture in the air condensed on the surface of the mirror, and formed droplets. What are these droplets called? Condensation.
(Con-denn-SAY-shun)