Materials

1. One liter clear plastic bottle with cap

2. Warm water

3. Matches

Procedure

1. Fill up one-third of the one liter bottle and shake.

2. Light a match for two seconds and then blow it out.

3. Immediately put the match in the bottle and screw shut the lid.

4. Squeeze the bottle six or seven times.

5. Squeeze the bottle again, hold the squeeze then let go.

Explanation: Squeezing the sides of the bottle forces the molecules to squish together or compress. Releasing the pressure allows the air to expand, and in doing so, the temperature of the air becomes cooler and that allows the molecules to stick together more easily forming clouds.