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Do you live in a foggy area? Is there no fog at all in area? Either way, you might find it fun to create some of your own fog and take it around with you in a jar. Follow these directions for a foggy experiment.

• One gallon (3.5 liter) clear glass or plastic jar with a wide mouth.
• A rubber glove
• Matches
• Tap water

Always ask for an adult’s help when dealing with matches!

1. Pour a small amount of water into the jar, so that it just covers the bottom.
2. Hang the glove inside the jar with the fingers pointing downward. Now, stretch the opening of the glove over the mouth of the jar to create a seal.
3. Next, put your hand inside the glove and pull it quickly out without breaking the seal-what happens? Nothing, right?
4. Now, remove the glove from the jar. Drop a lit match into the jar and fasten the glove over the mouth of the jar like you did before.
5. Put your hand in the glove and pull it outward like you did before, maintaining the seal. What happens this time? Do you notice a different substance in the jar when the glove is pulled outwards, as opposed to when it is taking up space inside of the jar?
6. Fog should appear when you pull the glove outward, and it should disappear when you replace the glove.

What Happened:

When you drop a match into the wet jar, you provide nuclei for the water molecules to grasp onto. Now, the water molecules are in the jar as soon as you pour the water in there (duh), but by pulling the glove outwards, you allow the air in the jar to expand. When air expands, it loses some of its thermal energy and the molecules in the jar-including the water vapor molecules-slow down slightly. Consequently, the air cools down.

Slowing the thermal energy allows the molecules to stick together more easily, and they bunch together in miniscule droplets. The temperature at which water molecules form droplets on a surface is known as dew point. The smoke particles help bind the water molecules bind more readily. Now, when you push the glove back into the jar, the air warms slightly, and the fog you’ve created disappears. Cool, huh?

Try projecting light though the fog you’ve made in the jar. Notice the difference in light wavelength and color as it dissipates. Does it remind you of anything?