<P> Water is the chemical substance with chemical formula H O; one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom . Water is a tasteless, odorless liquid at ambient temperature and pressure, and appears colorless in small quantities, although it has its own intrinsic very light blue hue . Ice also appears colorless, and water vapor is essentially invisible as a gas . </P> <P> Unlike other analogous hydrides of the oxygen family, water is primarily a liquid under standard conditions due to hydrogen bonding . The molecules of water are constantly moving in relation to each other, and the hydrogen bonds are continually breaking and reforming at timescales faster than 200 femtoseconds (2 × 10 seconds). However, these bonds are strong enough to create many of the peculiar properties of water, some of which make it integral to life . </P> <P> Within the Earth's atmosphere and surface, the liquid phase is the most common and is the form that is generally denoted by the word "water". The solid phase of water is known as ice and commonly takes the structure of hard, amalgamated crystals, such as ice cubes, or loosely accumulated granular crystals, like snow . There are other crystalline and amorphous phases of ice than the common hexagonal crystalline ice . The gaseous phase of water is known as water vapor (or steam). Visible steam and clouds are formed from minute droplets of water suspended in the air . </P> <P> Water also forms a supercritical fluid . The critical temperature is 647 K and the critical pressure is 22.064 MPa . In nature this only rarely occurs in extremely hostile conditions . A likely example of naturally occurring supercritical water is in the hottest parts of deep water hydrothermal vents, in which water is heated to the critical temperature by volcanic plumes and the critical pressure is caused by the weight of the ocean at the extreme depths where the vents are located . This pressure is reached at a depth of about 2200 meters: much less than the mean depth of the ocean (3800 meters). </P>

What state of water is most common on earth's surface