Why do balloon activities frequently instruct us to "blow up a balloon?" Are we supposed to get some dynamite and blow the balloon to smithereens? (Have you ever heard somebody suggest that they have a photograph blown up? - Some of them probably should get the dynamite treatment!)

Partially inflate a balloon, tie it with a rubber band, and squeeze it into a transparent plastic jug.

Prepare a stopper with a glass tube about 10 inches long and place it in the mouth of the jug. Attach a piece of rubber tubing to the glass tube and tighten the stopper in the jug.

Suck some air from the jug, crimping the tube or using a clothespin to squeeze the tube together whenever you stop to exhale.

Try to explain what is causing the balloon inside the jug to enlarge.

Since this writer is not a brilliant scientist, and since the solution to this problem is not in the notes from which the activities are being written, you students will have to get the answer for yourselves! No fair asking the teacher to explain it.