The chemical formula for water is H2O. A molecule of water consists of two hydrogen atom that bond with one atom of oxygen. The hydrogen and oxygen atoms share electrons because they are covalently bonded.
Water has the molecular weight of 18.1 grams per moles. It also has a high surface tension. This compound is a solvent in which many solutes can dissolve in, including solids, other liquids and gases. For example, methane and ethanol are very soluble in water. It can also exists in three phases. As a solid, it is ice, while its gaseous form is steam. On Earth, water is very abundant, and it makes up about 70 percent of its surface.