|MadSci Network: Physics|
If the balloon is placed in hot water, the air particles' speed increases so the balloon should get larger (unless the water is very very hot in which case your balloon could pop - meaning the particles moved so fast they overcame the force holding the balloon together). If the balloon is placed in cold water, then the air particles' speed will decrease. This will be evident in a reduction in the size of the balloon, the amount of which is based on how cold the water is. I teach college physics so you can use me as a reference. Of course the easiest thing to do is to do the experiment and, if the temperature difference is great enough, you will see the expected results. If you could cool the balloon down to -269 degrees Celsius, then the particles would be almost motionless (its hard to get down to -273 degrees Celsius - which is absolute zero). If the balloon hadn't broken from being cooled so much, then it would be almost flat, as the particles would be very close to each other and not moving.
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