Air may be cooled below its dew-point temperature by coming into contact with a cool surface. This is what happens when moisture forms on a pitcher of ice water. This is also what happens when dew, frost, and fog form during the night and early morning.
Air is also cooled when it is lifted above the earth in convection currents. Most of the water vapor in the atmosphere is found in the troposphere, which is the zone of the atmosphere nearest the earth's surface. In the troposphere, it normally gets colder as altitude above sea level increases.
In this activity the students will create a Cloud In A Jar. It will help them learn how clouds form in the atmosphere. It can be done in groups of four or as a teacher demonstration.
Click Here to see a drawing of our Homemade Cloud Chamber. As you read the directions you may want to go back and forth between the two pages.
Materials:
- One glass canning jar. (8 oz )
- 2 cm of tap water. (You may have to experiment with the amount)
- One match (This is needed for the smoke particles. The students are only given one match and not an entire box.)
- One large round rubber balloon with the mouth end cut off. (This will be placed over the canning jar.)
- One rubber band that will fit the mouth of the jar.
- One flashlight. (At least a 2 cm diameter top.)
Safety Note: Matches will be used in this experiment. Make sure your have your teachers and your parents permission to light the match. Only light it if you are not afraid. If you do not feel comfortable lighting the match let the teacher or another person light the match. The smoke from the match is used to provide a place for condensation to form on. You only need to light it one time. And you will only need one match.
Procedure:
Step 1 (This part my be prepared ahead of time by the teacher.)
- Make sure your jar is clean and dry to start with.
- Cut the mouth end off of a large round rubber balloon.
- Place the balloon over the mouth of the canning jar to see if it fits.
- Attach it with a rubber band by stretching the rubber band around the top of the jar. Make sure it is snug.
Step 2
- Now that you know the balloon sheath fits over the jar take it off and set it aside along with the rubber band.
- Put 2 cm of water into the jar.
- Light a match over the jar and blow it out. If you are afraid you may let it fall into the jar. The water will put it out. The reason for the match is to catch the smoke particles.
- Quickly place the balloon sheath back over the jar mouth and secure it with the rubber band.
- Let the jar stand undisturbed for 2 minutes. This should be enough time for the smoke to disappear.
Step 3
- Turn off the light in your classroom.
- The students turn on their flashlight. And place it near the glass jar.(If this is a teacher demonstration use the overhead projector for a light source.)
- One student pushes down on the balloon sheath for a few seconds and the quickly pulls it up. When they pull it up they should see a white cloud form. It will look like fog.
- Do the previous procedure several times. The students should notice water droplets forming on the sides of the jar.
How did the cloud form in the jar?
Send questions and suggestions to: pdukerich@aldine.k12.tx.us