Cloud in a Bottle

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Earth Science: Cloud Formation
Grade Range: Elementary School
Format: Hands-on

Cloud in a Bottle is a classic science demonstration that most teachers and parents will recognize immediately. Kids love to see it, and it is an easy demonstration to perform.



  • Empty 2-Liter Bottles
  • Matches
  • Water
  • A Dark Cloth/Board or Wall as Backdrop

Safety Precautions

Please read the Fire Safety section of the Demonstration Safety page before performing this demonstration.


  1. Put a tiny amount of water (no more than 1 oz) inside each bottle. Set up a backdrop with the cloth/board if there are no dark walls.
  2. When students come to see the demonstration, light a match. Let it burn for a second or two before putting it out, and once out hold an open bottle over it so it can collect some of the smoke. Put the match inside the bottle and immediately put the bottle's lid back on.
  3. Give the closed bottle to the student and ask them to squeeze it and release it a few times while holding it in front of the backdrop. After three or four squeezes, they should start seeing a cloud inside the bottle when it isn't squeezed and the cloud disappearing when they squeeze it!

Why This Works

Clouds are formed when warm, humid air rises up until they reach what is called the Homosphere, and the water in the air condenses back out. The Homosphere is the layer of the atmosphere where, because the air is really thin and cold, water vapor will condense back into liquid water and freeze into tiny ice crystals. These ice crystals are extremely small, and because they are so small and light they continue to float on the air around them, collecting into clouds. Our bottles are showing us how this happens. Some of the water we added is going to become water vapor, but we can't see it. When we add the smoke into the bottle, the smoke particles provide a spot for some of the water vapor to collect. This won't happen while we are squeezing the bottle though, because that is like having the warm, humid air at ground level. When the bottle isn't being squeezed, that is like having the warm-humid air rise up high into the atmosphere, where the air is thinner and there is less pressure. This results in some of the water vapor condensing onto the smoke particles, and therefore the creation of a cloud!

Additional Information

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