Cloud in a Bottle: A Simple Weather Experiment for Curious Seniors

At Science4Seniors we believe that learning new things keeps our minds active and engaged at any age. This quick experiment lets you create a cloud inside a bottle using everyday items from around the house. It’s safe, fun and a great way to explore how weather works.

What you’ll need

• A clear plastic bottle with a screw‑on lid (a 2‑liter soda bottle works well)

• A wine cork

• A bike pump with needle attachment

• A skewer, drill bit or thick needle to make a hole in the cork

• About one teaspoon of rubbing alcohol

How to make a cloud

1. Make sure the cork fits tightly in the bottle’s opening. If it’s too long, trim it to about the same length as the pump needle. Use your skewer or drill bit to carefully make a hole through the cork so the pump needle can fit.

2. Pour about one teaspoon of rubbing alcohol into the empty bottle and screw on the lid. Swirl and roll the bottle so that the alcohol coats the entire inside surface.

3. Remove the lid and insert the cork into the bottle. Then push the pump needle through the hole in the cork so it reaches inside the bottle.

4. Pump five times. If the cork pops out by itself, watch as a small cloud forms behind it! If it stays put, remove the needle after pumping and look for the cloud forming inside.

5. Observe the cloud, then open the bottle completely to let it dissipate. Be sure to hold the bottle away from your face.

The science behind it

Rubbing alcohol evaporates easily, so swirling it inside the bottle fills the bottle with vapor. Pumping air into the bottle increases the air pressure. When you stop pumping and release the pressure, the temperature and pressure drop quickly; the alcohol vapor condenses into tiny droplets suspended in the air. That sudden condensation is just like the cloud formation we see in the sky when warm moist air rises and cools.

Discuss and explore

Try the experiment again using warm water in place of rubbing alcohol and compare the results. Have you noticed the way clouds build on summer afternoons or disappear after a storm? Share your observations in the comments! If you have ideas for other simple experiments or topics you’d like to explore, let us know – we’d love to feature them in future posts.

Keep exploring and stay curious!