Kids Crafts -
Large glass jar with a wide mouth, such as an industrial size pickle jar;
A sheet of rubber (a balloon that has been slit open);
A rubber band large enough to fit over the mouth of the jar;
Some chalk dust (or talcum powder);
Some cold water.
How To Make It
Wash out the jar and put about an inch (25mm) of water in the bottom.
- Cover the mouth of the jar with the piece of rubber and cover with a book to hold it in place.
- After 10-15 minutes, remove the book and rubber from the jar.
- Drop in a spoonful of chalk dust or talcum and quickly replace the rubber over the mouth.
- Wrap the rubber band tightly around the rim to keep the rubber sheet firmly in place over the mouth.
- Push down on the rubber with your fist until it is depressed a little way into the jar. The air is compressed and warmed, so it is able to hold more water vapor.
- After 15 seconds or so, quickly remove your fist. The air will cool, and will not be able to hold as much water vapor. This excess vapor condenses around the chalk dust, forming a cloud inside the jar.
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