The liquid state of water at room temperature is as a result of

Answer Details

Water has an unusually high boiling point (100 °C) for a molecule of its small size (relative molecular mass = 18). To understand why, compare water (H₂O) with hydrogen sulphide (H₂S), which has a larger relative molecular mass of 34 but is a gas at room temperature (boiling point -60 °C). The difference lies in the type of intermolecular forces present.

Each water molecule can form up to four hydrogen bonds with neighbouring molecules. Oxygen is highly electronegative, creating a large partial positive charge on the hydrogen atoms. These hydrogen atoms are attracted to the lone pairs on the oxygen of adjacent water molecules, forming strong intermolecular hydrogen bonds. This extensive hydrogen-bonding network requires a large amount of energy to break, which raises the boiling point far above what the molecular mass alone would predict.

The covalent bonds within each water molecule (O-H bonds) hold the atoms together inside one molecule, but they do not determine the physical state. Van der Waals forces are present in all molecules but are too weak on their own to keep such a light molecule in the liquid state at room temperature. Electrovalent (ionic) bonds do not exist in water, which is a covalent molecular substance.

It is therefore the strong hydrogen bonding between water molecules that keeps water liquid at room temperature.