Surface Tension Experiment
How we did it:
- jar / glass jar / mason jar (or cup)
- mesh bag
- rubber bands
- index card paper
It's always so fun when science has such a "wow!" factor that it seems like magic. This demonstration sure had us saying "Wow!"
Even though we're familiar with air pressure and water, it's always fun to start something like this by filling up a glass, putting a piece of index card over the top, flipping it upside down and letting go of the paper. Tada! Always a big hit!
But now we were moving on to the fancier stuff. First we had to play with the mesh. "Everything is green!"
We put it over the jar, and fastened it on tight by wrapping a rubber band around it. Time to fill it up! Water flows in just fine! The mesh doesn't stop it at all. Hmmm...
Next we put a piece of index card on the top of the 3/4 full jar.... and flipped it over! (Three quarters full worked best for us, but you might find that a fuller glass or jar works better for your shape.)
Now it's time to sloooowly slide that index card off the bottom of the jar (unless you get lucky like we did a few times, and the index card just falls off!).... And would you look at that!?!
Water molecules are attracted to the other water molecules --a force called cohesion--and so they form a membrane between the mesh fibers. That's some strong surface tension! But it sure seems like magic!