You’re about to play with one of the first methods of underwater breathing developed for scuba divers hundreds of years ago.! Back then, scientists would invert a very large clear, bell-shaped jar over a diver standing on a platform, then lower the whole thing into the water. Everyone thought this was a great idea, until the diver ran out of breathable air…
Materials: 12″ flexible tubing, two clear plastic cups, bathtub
[am4show have=’p8;p9;p11;p38;p92;p93;p30;p57;p84;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Part I: Fill the tub and climb in. Plunge one cup underwater so it fills completely with water. While the cup is underwater, point its mouth downward. Insert one end of the tubing into the cup and blow hard into the other end. The water is forced out of the cup!
Part II: While still in the tub, invert one cup (mouth downwards) and plunge it into the tub so that air gets trapped inside the cup. Place the second cup in the water so it fills with water. Invert the water-filled cup while underwater and position it above the first cup so when you tilt the first cup to release the air bubbles, they get trapped inside the second cup. Here you see that air takes space, because in both variations of this experiment the air forced the water out of the cups.
[/am4show]