Most of us understand that clouds are made of cooled water vapor, but we forget that the vapor needs something to cling to--in this case, microscopic dust particles. This experiment demonstrates how to cook up a cloud with water, soot, and a little fast cooling. You'll need water, a glass gallon jug, a candle, and matches.

PROJECT:
Demonstrate various weather phenomena

GOAL:
To learn the principles of cloud formation and air pressure

AGES:
6 to 12

COOKING UP A CLOUD

STEP 1
Swish a little water around the bottom of your jug and pour out the excess. Light your candle and, inverting the jug, hold the burning candle just inside the mouth of the jug for a few seconds to fill it with soot.

STEP 2
Give the glass a moment to cool, then put your mouth over the jar. Blow hard into the jug, then quickly take your mouth away (you are introducing warm, moist air, then quickly releasing the pressure). Watch what happens, then try it again and again.

AIR PRESSURE

This experiment is a huge hit with kids and you only need a drinking glass, water and a four-inch-square of poster board or lightweight cardboard. To avoid a mishap, perform this experiment outside or over the kitchen sink.

STEP 1
Fill the glass about three-quarters full with water. Wet the rim.

STEP 2
Place the cardboard on top of the glass. Hold the cardboard firmly in place and invert the glass, then let go of the cardboard. Because the pressure on the cardboard from the air outside the glass is greater than the pressure of the water inside it, the water stays inside the glass. This shows how the water inside a homemade barometer is no match for air pressure.