One glass mason jar filled with water and capped off with a simple index card put the fear of getting wet into 9News Weathercaster Becky Ditchfield. She was worried she’d get wet. The threat of moisture invading her hair style and outfit was low, but she didn’t know that.
Fill the jar to the top with water, then cover the opening with a card. Turn the jar upside down and remove the card. Place said jar over a lucky volunteer’s head and the water doesn’t spill out. How does this work?
The science lies in the screen that secretly covers the top of the jar.
As long as the jar wasn’t tipped, Becky had nothing to worry about. The water is suspended in the jar because of air pressure and surface tension. When the jar is turned over, air pressure pushes up on the card and keeps it in place while it is on top. The water stays in the jar when the card is removed thanks to surface tension. The molecules are joined together through cohesion to form a thin membrane in the screen.
For more information and activities read the Mysterious Water Suspension experiment.