Let’s play with air!
Take an empty mineral water bottle or any other bottle made of
thin plastic. Drill a hole in the cap, insert a straw into it and seal it
with clay. Or seal the mouth of the bottle with clay and poke a
straw through. Now suck in the air through the straw. The bottle
crumples. Why? The air outside is pushing against it, and there
isn’t enough air inside the bottle to push it back with equal force.