Sticky Water

This experiment recreates one of my other experiments (The Tricky Bottle) in order to explore the way that water molecules stick to each other.

For this experiment, you will need:

  • a plastic, 2 liter soft drink bottle, or some other large, plastic bottle with a top that seals well
  • a sharp nail
  • water

Use the nail to CAREFULLY make a hole in the side of the bottle, about two inches above the bottom. Then make another hole about 1/4 of an inch to the right of the first, and another 1/4 of an inch to the left. This will give you three holes that are very close together. Place the bottle in the sink and fill it with water. As soon as it is full, put the top on tightly. Notice that the water is not coming out of the holes. As we learned before, air pressure holds the water in. To get the water to come out of the holes, loosen the top of the bottle. Do this over the sink, in the bathtub or outside, so that you don't make a mess and get me in trouble for telling you to do it. And of course you would not think of handing the bottle to someone and asking them to open the top, as that would get them wet.

Holding the bottle over the sink, loosen the top so that the water comes out of the holes in three streams. Now, take your fingers and gently squeeze the streams of water together into one. Just pretend that they are solid instead of liquid and squeeze them between your finger and thumb. When you take your fingers away, the three streams stick together into one stream. Tighten the cap and the water stops. When you loosen it, you have three streams again.

Why does this happen? Water molecules are polar. This means that the ends of the molecule have a charge and in some ways act like tiny magnets. To understand this imagine the water molecule. It is made up of two atoms of hydrogen and one atom of oxygen. That is why it has the formula, H2O. The hydrogens stick to one end of the oxygen. To visualize this, picture Micky Mouse's head. (I live in Florida. Micky is everywhere down here.) The head is the oxygen and the ears are the hydrogens.

The hydrogens cause the molecule to be lopsided. One end gets a positive charge and the other end gets a negative charge. If you have ever played with magnets, you know that two ends that are different will stick together. The same thing happens with water molecules. Water molecules tend to stick together. This "sticky" property causes the three streams of water to stick together into one.