Cloud in a Bottle
What you need:
- One liter clear plastic bottle + cap
- Foot pump with rubber stopper attached
- Rubbing alcohol
- Safety glasses
By pumping the bottle with pressure, you are forcing the water molecules to compress. When the pressure is released, the molecules expand and cool the air. The cooler air allows the molecules to condense and form tiny water droplets.
You can watch Steve Spangler do the experiment and explain it on this video and you can read about the experiment here.