This is a English version of the El aire ocupa lugar
To blow a balloon up inside a bottle and to be able to serve a cup of air, as we can see in the picture, is a really difficult proof that is not within the reach of everyone. We could state that it is almost something magical. However, we could be able to get it like in a picture, just thinking about the way the gas behaves.
Air Takes a Place
To blow a balloon up inside a bottle is impossible, because the bottle is
filled with air and air takes a place in space. Even though, we insisted on blowing the balloon, it would not be blown up. Whoever tried it, would feel finally exhausted or dizzy without reaching it.
To blow it up, air should be removed at first.
How can we do it?
The experience misleads. It would be just necessary to make a little whole at the bottom of the bottle through which it let the air out. For instance, to do this you can help yourself to a hot pin.
Now, when we blow up, the air from the inside of the bottle can go through the hole meanwhile the filled balloon keeps on taking its place.
If we stop blowing the balloon up, it let the air out of it due to the tension of the rubber and the air fills the bottle up again through the hole.
But, how can we leave the balloon blown up to pretend we are serving the cup of air? It would be so simple as to fill in the hole of the bottle with a finger, once the balloon is filled.
Despite the tension of the rubber, this one cannot be deflated. To get to that point, it would be necessary that the air from outside took the free place outside, but as the hole is filled in, it cannot enter the bottle.