A Cloud in a Bottle

Clouds are really what weather is all about !


1. 2 or 3 liter clear soda bottle with cap.
2. A few drops of water.
3. A Match
4. A thermometer or temperature strip.

1. Place the thermometer, or better yet a temperature strip, in the empty soda bottle. Place the cap on tightly.
2. Record the temperature inside the bottle.
3. Squeeze the bottle with two hands and observe the temperature. It will go up.
4. Release the bottle and the temperature will return to normal.
5. Remove the cap and add a few drops of water, swirl around to wet the inside of the bottle.
6. Light a match and let it burn a few seconds and then drop it into the wet bottle, quickly place the cap on tightly.
7. Squeeze the bottle tightly, and then release quickly. You will see a
cloud inside the bottle. Squeeze and it disappears, release and it appears !

Squeezing the bottle increases pressure and temperature, also decreasing the volume, all of which you might have learned in High School Chemistry or Physics when you studied the Gas Laws. See there really was a reason to learn that little formula ! So when you release the bottle the gas expands, the pressure drops and the temperature drops. The smoke supplies a surface for the water which was vaporized when the temperature went up, to condense upon, thus forming a cloud.

Scientific Concepts:
The Combined Gas Law states: P1V1 / T1 = P2V2 / T2 where P1,V1, and T1 are the beginning pressure, volume and temperature. When you squeeze the bottle; P goes up, V goes down and T goes up. When you release the bottle; P goes down, V goes up and T goes down.
The net effect being a drop in temperature. Clouds need three things to form; water, a nucleus ( dust, smoke, etc.) and a low temperature. Water comes from evaporation, the nucleus is dust that is normally in the air and the low temperature comes from many sources. It could be from the expansion of air as it rises, a cold front, altitude, etc.