Video: Watch this demo | Demo #2: Bell Jar with Balloon; Boiling Water
Description: This demonstration shows what happens to the volume of a balloon when pressure is reduced.
Equipment:
- Vacuum pump
- Bell jar
- Balloon
Setup Procedure:
- Inflate the balloon only a little as shown in the first picture. Place in the bell jar.
- Connect the bell jar to the vacuum pump.
- The valve that connects to the pump should be open (Pointing towards the pump tube), and the other valve should be closed (Pointing perpendicular to connector).
Demonstration Procedure:
- Note to the students the size of the balloon.
- Turn on the vacuum pump.
- Note that the balloon inflates due to the decreased pressure inside the bell jar.
- Turning off the pump will stop the balloon from inflating any further, and will keep it at the current size.
- (Note: This is also a good time to demonstrate the fact that the bell jar cannot be opened)
- Opening the second valve will re-deflate the balloon, and the bell jar can once again be opened.
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