Snow, ice and liquid waterWater is a molecule. It is made up of two chemical elements: hydrogen (chemical symbol H) and oxygen (O). Each atom of oxygen is bonded to two hydrogen atoms. This is why water has the chemical formula H2O. Water occurs in nature in all three states of matter: solid (ice), liquid and gas (water vapour). All known forms of life need water to survive. Every living thing is made up mostly of water. Our own bodies are more than two-thirds water.
Freezing and boiling points
Liquid water freezes into solid ice when the temperature falls to 0°C (32°F) or below. As liquid water, it is found in rivers, lakes, seas and raindrops. The process of turning from liquid into gas is called evaporation. When water evaporates, it becomes an invisible part of the air. When water vapour cools and turns back to water, it is called condensation.
Evaporation speeds up the warmer the water becomes. At temperatures of 100°C (212°F), the boiling point of water, all water evaporates.
Water is one of the commonest compounds on Earth. It is the only one found naturally in solid, liquid and gaseous forms.
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