Water

Water is an odorless, tasteless, colorless liquid. Its chemical formula is H₂O, two hydrogens and one oxygen atom.

The shape of the water molecule is a shallow V, with the oxygen in the middle and having an angle of approximately 105°. The interactions between the atoms result in the oxygen atom having a partly negative charge and the hydrogen atoms having a partly positive charge. Thus the water molecule is a strong electrical dipole, which accounts for some of its properties. Although we are accustomed to think of the word "solvent" in connection with organic solvents like gasoline or benzene, water is a powerful solvent, a fact that is sometimes overlooked because water is so familiar.

Water is essential to life as we know it, and all living organisms are comprised mostly of water.

Water, compared to other compounds, has a number of unusual properties, such as expanding rather than contracting when it freezes. As noted by Lawrence Henderson in his 1913 book, The Fitness of the Environment, its ability to support life is directly related to some of these unusual properties.