Water has two important properties: adhesion and cohesion.
Adhesion is water’s ability to cling to other things. (Think “adhesive,” like the glue or tape we use to stick things together.)
Cohesion is how water molecules like to cling to each other. You may have seen this bond while watching raindrops sliding down a glass window. When one drop touches another, they turn into a larger drop. (The water clinging to the glass is adhesion.)
Both adhesion and cohesion are responsible for many fascinating and important abilities of water. This magic trick works because using the cardboard to stop the water from spilling out (gravity) allows time for adhesive and cohesive bonds to form, with water clinging to the screen and water clinging to itself. These forces are stronger than the force of gravity, so the water remains in the jar.
____________
Follow Willy's Wilderness on Facebook for more kid-friendly nature stories and activities.