Every living organism contains water. Water circulates throughout the body to support the organs. Without it, plants and animals could not survive. The human body is about two thirds water, essentially we are a walking bag of water on dry land.
But what is water, really? Like every other substance on Earth, water is made up of tiny particles called atoms. A water molecule consists of two hydrogen atoms and one oxygen atom. Water is very special because, under normal Earth conditions it can exist as a liquid, as ice, and as a gas. Think of the polar seas with icebergs floating in them. Water vapor is present in the air. Most water, however, is in the oceans which is salty. When the sun heats the water, it evaporates without the salt and forms clouds. These clouds bring rain or snow. When this precipitation falls on land, it flows back to the sea through rivers or the ground, where it can eventually evaporate again. This process is called the water cycle. Water can also remain in the ground for a very long time, sometimes for thousands of years.
