Showing That Water is a Polar Molecule
Posted August 28, 2008on:
Let’s start off with the theory. Water has more of a positive charge on one side and a negative charge on the other. This is because of the way the molecules bond. The picture on the right shows the Mickey Mouse structure of water molecules. Oxygen has six electrons on the outer shell and wants to have eight. So it uses the electrons from the Hydrogen atoms to complete its shell. I’m not a chemist, I don’t know why the molecules make a Mickey Mouse and don’t spread out onto opposite sides, but they don’t. The result is a net positive charge near the ears and a negative charge on the other side.
There is a really cool and simple demonstration to show the polar nature of water. Turn on the faucet so that you have a laminar stream of water coming out. Alternatively, you could set up a simple apparatus that controls the flow of water from a flask. You want the stream to be a small as possible but still laminar (flowing in a parallel stream with no turbulence). Now charge up a plastic rod or a comb or anything that will hold a static charge (even a balloon rubbed on your hair will work. Put the charged object near the water and the stream will deflect. This freaks the kids out. I love freaking the kids out.