Clues about Clouds

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1. Fill the bottle about 1/4 to 1/3 full of warm water. As the warm water evaporates, it adds water vapor to the air in the bottle. This is the first ingredient needed to make a cloud! Have an adult strike a match and let it burn a little

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2. Drop the match into the bottle and quickly put on the cap, trapping the smoke inside. Dust, smoke or other particles in the air are the second ingredient needed to make a cloud. The smoke particles give the water vapor a center to condense around.

3. Squeeze the bottle hard. As you let go, the cloud should form. The third ingredient in a cloud is a drop in air pressure. You have just created this pressure drop by first raising the pressure (squeezing the bottle) and then letting go.

4. If the cloud did not form, light another match and try again. If it still did not form, try warmer water. If it STILL did not form, perhaps you didn’t squeeze hard enough, or there could be a hole in the bottle.

Now, explore! Record your observations during the procedures and notice how hard you squeeze the bottle and hot the water was... what do you think is happening? Form your hypotheses.

In the bottle, the water vapor comes from the warm water evaporating. In the atmosphere, the water vapor comes from the evaporation of natural bodies of water such as lakes, rivers and oceans. There must be particles in the air for the water vapor to condense around. In our experiment, the smoke provides the particles.

In the real world, pollution and naturally occurring dust from volcanoes and dust storms provides the particles. Cloud formation only occurs when there is a drop in pressure. In the atmosphere, this occurs when warm air rises and expands. When the air expands, the air molecules are farther apart and there is less pressure, so cloud formation can occur if there is water vapor in the air and particles for the cloud to condense around.