Water is composed of two elements, hydrogen and oxygen. H2O is the chemical formula for water. This means that every water molecule has two hydrogen atoms that are bonded to one oxygen atom.
Water exists in three different states: liquid, solid and gas. The liquid state is the one that is commonly referred to as "water." In its solid state, it is referred to as ice, while in it's gaseous state, water is usually referred to as steam or vapor. Water is tasteless and odorless. As a gas, it is colorless, but the liquid and solid states of water have a pale blue appearance. Water is vital to sustaining life on Earth because human bodies need it to avoid dehydration.