Bottle Clouds

This is a classic science demo, but one, I think, that has been lost thru the ages and forgotten in favor of the evil computer simulation. You will need :

• A large glass jar with a wide mouth - a pickle or relish jar from Sam's Club or BJ's or some such bulk house works well.
• A sheet of rubber to fit over the opening - a large cut balloon will do.
• A tuff rubber band big enuf for the lid.
• Some chalk dust, talcum powder, or lycopodium powder.
• COLD water.

Make sure the jar is clean and add about an inch (OOPS! Make that 2.5cm) of COLD water. Cover the mouth with the balloon but do not attach with the rubber band. Hold the balloon in place with a heavy book or something. Wait a few minutes - 10 maybe. Remove the book and balloon from the jar. Drop in a spoonful of dust and quickly replace the balloon and NOW fasten securely with the rubber band. Now comes the fun part. Jam your fist down onto the balloon so it pushes into the jar. This compresses the air and warms it, so it can hold more water vapor. After about 15-20 seconds, quickly remove your hand. The air is now allowed to expand, causing quik cooling and will not be able to hold as much water vapor as it did just a second ago. What happens? The extra water vapor condenses onto the dust and forms a very visible cloud in the jar. Cool Beans!

Here's another, and embarrassingly, EASIER Demo!

Sent by B Snellin from Virginia!

• 1 two-liter PETE pop bottle (PETE is the usual plastic that the pop bottles are made of; use clear bottles) with a cap water (luke warm works well)
• aerosol such as spray air freshener or smoke from a lit/extinguished match

• Put 10 or so ounces of water in the bottle and replace the lid.
• Shake the bottle for a few seconds to saturate the air with water vapor.
• Open the lid and inject the aerosols (or squeeze the bottle and "suck" the smoke particles into the bottle). Replace the lid.
• I like to turn the bottle upside down. Squeeze hard and release suddenly.