What you will need:
- Air pump
- Rubber stopper (with hole in center)
- Empty 2 liter pop bottle
- Isopropyl alcohol
- Adult supervision
1. Pour about a teaspoon of isopropyl alcohol into your 2 liter pop bottle.
2. “Swish” it around for a minute and pour the remaining liquid back out.
3. Place the rubber stopper on the end of your air pump so that the air goes through the hole in the center of the stopper. Make sure that the larger end of the stopper is facing towards the pump.
4. Push the smaller end of the stopper into the opening of your pop bottle.
5. Pump air into the bottle while making sure to hold the stopper in place. Start off by trying about 5-10 pumps of air. Be careful not to pump too much air into the bottle as this could cause it to explode. You want the bottle to feel very firm when you try to squeeze it.
6. Quickly pull the stopper out of the top of your pop bottle to create a cloud inside of the bottle.
** Note: if no cloud appeared, try pumping a little more air into it the next time. Again, be careful not to over inflate the bottle as it could explode.
What is going on?
Water vapors are in the air all around us. Natural clouds form when the air near the Earth's surface rises and experiences a reduction in pressure. This lower air pressure allows the air molecules to expand and cool, in turn allowing the water vapor to condense forming what we see as clouds. Clouds are nothing more that tiny water droplets grouped together. The Isopropyl alcohol has weaker bonds and evaporates quicker than water which creates a really cool cloud inside your pop bottle.
Pumping air back into the bottle increases the air pressure “squeezing” the air molecules tightly together making the cloud disappear.
Since releasing the pressure quickly cools the air and helps the cloud form, try creating a cloud then placing the lid back on the bottle and running the bottle under very warm water. What happens to the cloud? What would happen if you now run it under cold water?