The Chemistry of Water

The chemical formula of water is H2O. Two hydrogen atoms  (H2) attached to one atom of oxygen.  Hydrogen and oxygen atoms are held together by covalent bonds by sharing electrons.

The Water Molecule H2O

When two different atoms make bonding, bonding electrons spend more time near the atom that is more electronegative than the other. In water, the bonding electrons spend much more time near oxygen than the hydrogen atoms. This property gives water molecule “polar” character; the opposite ends have opposite charges. Polarity allows water molecules to form hydrogen bonds with each other. Positive pole around hydrogen atoms bonds to negative pole around the oxygen atoms of a different water molecule.


One of the properties that results from hydrogen bonds is high cohesion of water, which results in high surface tension. Water has the highest cohesion of any non-metallic liquid.

Polarity also promotes interactions between water and other polar molecules or dissolved ions. Solutes and substances can be dissolved within water much more than any other liquid. Therefore, water is an excellent solvent.

The Physical States of Water

At room temperature water is liquid. In liquid water, the H2O molecules are disordered, they move around a lot. Hydrogen bonds between neighboring molecules break and reform quickly. As it gets colder, the water turns into ice. The molecules slow down. Ice is basically ordered H2O by hydrogen bonds. In a solid the molecules are arranged on a lattice and just vibrate. In gaseous state, there is no hydrogen bonding between molecules.

The states of water molecule