Cloud in a Bottle

Materials Needed:

  • 1-liter clear plastic bottle
  • Foot pump/bike pump with rubber stopper attached
  • Matches
  • Rubbing alcohol
  • Safety glasses
  • Adult supervision

Procedure:

  1. Put on your safety glasses and start by pouring just enough rubbing alcohol in the bottle to cover the bottom.
  2. Swirl the rubbing alcohol around
  3. Attach the pump to the rubber stopper
  4. Light a match, blow it out and drop it into the bottle.
  5. Quickly put the rubber stopper on the bottle (this should be attached to the pump)
  6. Pump the pump ten times. You’ll notice that the more you pump, the harder it is to keep the stopper in the bottle. Just remember to hold it in there tightly.
  7. When you are done pumping, pull out the stopper. You should see a visible cloud.You want to put about 9 kg (20 lbs) of pressure in the bottle.

How Does it Work?

Although we can see clouds up in the sky, we can’t always see the tiny water molecules (also called water vapor) that they are made up of. In order to see them in the form of a cloud, they have to be packed tightly together. When you pump pressure into the bottle, these water molecules are being compressed together which is an important step in cloud formation because it increases the temperature. In order to see the cloud, the pressure must be released from the bottle so that the air temperature can suddenly cool down. This allows the water molecules to condense and form tiny water droplets which is what clouds are made out of.