Water is one of the most important needs of living things. It is second only to the air we breathe. In fact, some scientists believe that all life began in water. Today, our space explorations have found signs that water exists not only on Earth but throughout the universe. If this is so, it may be that living things exist or have existed on these other planets.
Water is a molecule that consists of two hydrogen atoms and one oxygen atom. When these atoms are heated to a high temperature, they join to form water. The scientific way to write this molecule is "H2O." Since most of the water on earth was created when the earth was forming, the water you are drinking today may have been a drink for a dinosaur or maybe a part of Cleopatra's bath water!
Water occurs naturally in three forms that people see every day.
- It can be vapor - as the steam from your breath or cooking, or unseen as humidity in the air.
- It can be liquid - as a beverage or a lake, stream, river or ocean.
- It can be solid - as ice.