Materials you'll need
- Empty plastic water bottle with cap
- Rubbing alcohol (isopropyl alcohol)
Step-by-step tutorial
Step 1: Pour a small splash of rubbing alcohol into an empty bottle, just enough to lightly coat the inside. You don't need much!
Step 2: Cap the bottle tightly and shake it, rotating it so the alcohol coats all the inner walls of the bottle.
Step 3: Grip the bottle with both hands right in the middle and twist as tightly as you can in opposite directions. The tighter you twist, the better your cloud will be!
Step 4: Let go of your twist and watch a cloud instantly appear inside the bottle!
Learn more
When you twist the bottle, you squeeze all the air molecules inside closer together, raising the pressure. The moment you release, that pressure drops suddenly and the air rapidly expands — and this quick expansion causes the air to cool down fast. Scientists call this
adiabatic cooling. Something very similar happens in the sky: warm, moist air rises, expands into lower pressure, and cools. Once it's cool enough, water vapor (which is the invisible, gaseous form of water in the air) condenses into tiny droplets that cling to floating particles like dust or pollen, forming a real cloud. In our bottle, the alcohol vapor does the same thing: it cools and condenses into tiny floating droplets right before your eyes. Alcohol works especially well because it evaporates faster than water, putting more vapor in the bottle to work with!
