Grades K–2 · Materials & Matter
How does air make a balloon bigger?
An empty-looking balloon is not the same as a full one. Air takes up space, even though we cannot see it. More air inside can make the balloon's soft rubber stretch outward.
In the diagramAir takes up room inside a balloonDots stand for air that our eyes cannot see.Inside air pushes while the skin stretches.
Air pushes on the inside of the balloon. The stretched rubber pulls inward. The balloon's shape depends on these pushes and pulls, so its skin must be able to move as the air inside changes.
When air escapes, there is less air inside to keep the rubber stretched. The rubber pulls back and the balloon becomes smaller. The air has moved out into the room; it has not vanished.
A filled balloon lets us see something air can do. The air itself is hard to see, but the stretched skin makes its effect visible.
About this explanation
The dots stand for air, not a count of real particles. The picture does not calculate pressure.
Starting knowledge: Recognize a balloon and compare a less stretched shape with a larger one.
Sources
- American Chemical Society — Simulations & Videos: Air, It's Really There