The common name of the chemical compound H₂O is water.
Each water molecule contains two hydrogen atoms chemically bonded to one oxygen atom, giving it the formula H₂O. Its molecules have a bent shape and unequal distribution of electrical charge, which makes water a polar substance. That polarity helps water dissolve many ionic and polar materials, earning it the familiar description “the universal solvent,” although it does not dissolve everything.
Under standard atmospheric pressure, pure water freezes at 0°C and boils at 100°C. It is unusual because solid ice is less dense than liquid water, so ice floats. This happens because hydrogen bonds hold water molecules in a more open arrangement when they freeze.
H₂O is not the same as every liquid called water in daily life. Tap water and seawater contain dissolved minerals, gases, or salts, while distilled water has had most impurities removed. Water is also essential to known life and covers roughly 71% of Earth’s surface.