An inflated balloon full of air goes down slowly (becomes smaller and smallers lowly) even though the knot at the mouth of the balloon is air tight. And after a week all the air has escaped from the balloon. Explain how the air particles got out of the balloon.

Air molecules can slowly diffuse through the surface, or leak through the knot. The fast moving molecules of air trapped in the inflated balloon exert continuous pressure on the thin, stretched rubber sheet of balloon and keep on diffusing out gradually through it.


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