# Creating Fog in a Bottle

Creating fog in a bottle, as in the photo at the left of this page, is a simple matter. A large jar or wide mouthed bottle is filled with hot water. All of the hot water is poured out except for an inch (25mm) or so at the bottom. A strainer is set over the mouth of the jar, and ice cubes are placed in the strainer. Before too long the cold air from the ice cubes will cause the water to condense from the warm, moist air in the bottle, forming fog.This lesson teaches how clouds form and how air pressure and air temperature affect their formation.

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## The Experiment:

The purpose of the experiment is to demonstrate the role temperature plays in cloud formation. A sample atmosphere is created using a plastic bottle filled with water. By squeezing the bottle, you can change the temperature of the air inside. When the air temperature is decreased, a cloud is created inside the bottle.

NOTE: This experiment should be performed under adult supervision because it involves the handling of matches.

## Materials:

a large clear plastic bottle with cap
a measuring cup
cold and hot water
matches

## Procedure

#1: Pour 1/3 cup of cold tap water into a clear plastic bottle and place cap on it. Shake the bottle for 30 seconds and then set it on your table.

#2: Squeeze the bottle and then release the pressure. Repeat this process several times.

In this step you are saturating the atmosphere inside the bottle. By squeezing the bottle, you increase the air pressure inside the bottle, which increases the air temperature. With the air heated, more water moves into the air, saturating it. When you release the pressure on the bottle, you decrease the air pressure. This lowers the air temperature and causes condensation in the bottle. These are the principles that will allow you to create a cloud in the next step.

#3: Remove the cap from the bottle and light a match. Hold the match over the mouth of the bottle. Quickly squeeze the bottle to extinguish the match; then slowly release the pressure to draw smoke into the bottle. Replace and tighten the cap. Repeat Step #2.

In this step, a cloud should have formed above the water inside the bottle. As in Step #2, squeezing the bottle forced condensation inside the bottle. Now that you have added smoke into the bottle, the water has something to condense upon. The condensed water forms the small cloud inside the bottle.

#4: Rinse the bottle thoroughly and pour 1/3 cup of hot tap water into it. Shake the bottle for 30 seconds and place it on your table.

#5: Squeeze the bottle and then release the pressure. Repeat this process several times. Then repeat Step #3, extinguishing a match over the mouth of the bottle and drawing the smoke inside. Then repeat Step #2 again, squeezing and releasing the bottle to create a cloud.

In this step, a bigger cloud should form in the bottle. This is because of the hot water has heated the atmosphere inside the bottle, so it is able to hold more water than before. So when condensation is forced inside the bottle, more water condenses and a larger cloud forms.