Hydrogen Bonding in Water
The weak but powerful attractions between water molecules that give water its high boiling point, surface tension, and many life-supporting properties.
A water molecule (H₂O) is polar: the oxygen atom pulls electrons more strongly than the hydrogen atoms, creating a partial negative charge near oxygen and partial positive charges near the hydrogens. This polarity allows water molecules to form hydrogen bonds with one another.
What is a Hydrogen Bond?
A hydrogen bond is a relatively weak attraction between the partially positive hydrogen of one molecule and the partially negative oxygen of another. Each water molecule can form up to four hydrogen bonds. Although individual bonds are weak, the large number of them produces strong collective effects.
Consequences of Hydrogen Bonding
- High boiling and melting points — water remains liquid over a wide temperature range
- High surface tension — water forms droplets and supports small insects on its surface
- High specific heat capacity — water moderates temperature changes in climate and in living organisms
- Cohesion and adhesion — essential for water transport in plants
- Lower density of ice — the open crystal structure of ice
Hydrogen Bonding and Life
Hydrogen bonds also stabilise the structures of proteins and DNA. Without them, the complex molecules of life would not hold their shapes. In this sense, the same interaction that makes water special is also fundamental to biology itself.
Hydrogen bonds are invisible, yet they are among the most important forces shaping Earth’s environment and the chemistry of life.