Have you ever heard someone who was really thirsty say they needed some H₂O? When someone refers to H₂O, that’s actually just a nickname for water!

Water is made up of little units called “molecules.” Molecules are extremely tiny – way too tiny for you to see with just your eyes. In fact, they’re so tiny that a single droplet of water contains millions and millions of water molecules! But believe it or not, the water molecules can get even smaller! Every water molecule is made up of two units of the element hydrogen and one unit of the element oxygen! (That’s where we get the name H₂O – the H₂ stands for “two hydrogen” and the O stands for “one oxygen”!)

The H₂O makeup of water is part of what makes water so special. The two units of hydrogen and the one unit of oxygen in each molecule of water carry a charge, with the two hydrogen each having a positive charge and the oxygen having a negative charge. It’s because of these special charges that water molecules stick to each other in the special way that lets them move and swish about, sometimes sticking together and sometimes breaking apart!