Water Beats Gravity

 

Fill a glass with water. Use a rubber band to hold a handkerchief or bandanna tightly over the top. Over a sink, quickly turn the glass upside down. The water should stay in the glass.

Use a finger to press upward gently on the handkerchief. The pressure will cause water to trickle out and air to flow in, with bubbles rising through the water.

What keeps the water from running out of the glass?

Explanation

The water didn't flow out of the glass because of a property called surface tension. Water is made up of tiny molecules that act like magnets. They stick to one another, making a stretchy surface across each hole in the handkerchief. These surfaces hold up the water. When you press on the handkerchief, your finger breaks some of the surfaces. That lets water come out and air go in.

Photo by Guy Cali Associates, Inc.