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Create a Cloud in a Bottle

Students learn how clouds form by making a model cloud form in a bottle. Materials:
  • Clean, clear 2-liter plastic beverage bottle with cap (1 bottle per student or group of students)
  • 1 Fizz Keeper per bottle (available in most large supermarkets in the pop or soda aisle
  • 1 temperature strip attached to each Fizz Keeper with tape (can be purchased at aquarium supply stores)
  • Matches or air freshener (Glade Powder Fresh works well)

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UCAR Office of Education and Outreach, parts adapted from the Little Shop of Physics.
Grade level:
Adaptable for grades 3-8
15-30 minutes
Student Learning Outcomes:
  • Students learn the four conditions needed for clouds to form
  • Students observe cloud formation in a bottle
Lesson format:
Class discussion and hands-on activity

National Standards Addressed:


  1. Have students turn their bottle so the temperature strips are facing them and are easy to read. Tell them not to handle the bottle any more than necessary, so that the inside temperature of the bottle will not be affected by the warmth of their hands.
  2. Instruct students to record the initial temperature of the bottle.
  3. Have students pump the Fizz Keeper 20 times and then record the temperature. Have them repeat this step 3 more times (pump 20 times and record the temperature) until the Fizz Keeper has been pumped 80 times total, and the temperature has been recorded 4 times.
  4. Unscrew the Fizz Keeper and record the temperature of the bottle. Discuss with the student what happened with the temperature as the pressure increased and decreased in the bottle.
  5. Have students add a small amount of water to the bottles. Either light a match and drop it into the bottle, or spray one squirt of the air freshener into the bottle.
  6. Quickly screw the Fizz Keeper on the bottle. Repeat steps 1-4 above.
  7. Go over the following questions with your students.
  • Pumping the Fizz Keeper compressed the air inside the bottle. What happened to the air temperature inside the bottle when you pumped the Fizz Keeper?
  • When you unscrewed the Fizz Keeper so the air inside the bottle was no longer being compressed, what happened to the air temperature inside the bottle?
  • When you added water and a match or air freshener to the bottle and repeated the activity, did a cloud appear? If so, why do you think this happened? Was there any difference between using a match or air freshener?


The cloud inside our bottle, as well as clouds in the atmosphere, form when four conditions are present: water vapor, cooled air, supersaturation, and condensation. Water is the only substance in the atmosphere that naturally occurs as a gas, solid, or liquid. The water that makes up clouds is all around us in the gaseous form of water, called water vapor.

Water vapor can condense to form liquid water if the air is cooled, because cooler air can hold less water vapor than warmer air. Air cools as it rises due to adiabatic cooling. (Adiabatic means that there is no transfer of heat between an air parcel and its surroundings.) When a parcel of air rises, it expands; the expansion requires energy, which comes from the thermal energy of the air, so the air cools. Cold air holds less water, so when the air rises, as it cools, the water vapor will condense out of the air and form droplets. The air can become supersaturated, with a relative humidity greater than 100%, but the liquid droplets don't form yet.

Liquid water has surface tension. This means that making a droplet requires energy to create this surface tension. The water molecules can get around the energy barrier by condensing on a surface. In the summer, when a cold glass of ice water meets warm, moist air, water droplets form on the outside of the glass.

In the atmosphere, condensation nuclei provide the surfaces on which water vapor can condense. Condensation nuclei in the atmosphere include dust, volcanic ash, and pollution. With these nuclei, the water vapor in the air can condense to form a cloud made of billions of tiny droplets of water.



Last modified April 15, 2009 by Becca Hatheway.

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