Water: Key Properties

Water: Key Properties

• Water is polar; shape is bent (approx. V); the highly electronegative oxygen pulls electron density toward itself, giving $\delta^-$ on O and $\delta^+$ on each H.
• Water covers $\tfrac{3}{4}$ of Earth's surface.

Hydrogen Bonding

• Hydrogen bonds form between a hydrogen atom on one water molecule (partly positive) and the oxygen on a neighboring molecule (partly negative).

Cohesion and Adhesion

• Cohesion: water molecules stick to each other via hydrogen bonds.
• Adhesion: water sticks to surfaces (e.g., xylem walls in plants).

Surface Tension

• Cohesion contributes to surface tension; enables phenomena like water striders.

Plant Water Transport (Xylem)

• Water transport occurs in xylem vessels; adhesion to walls + cohesion between molecules help resist gravity.
• Evaporation from leaves (transpiration) pulls up the rest of the water chain.

Biological Significance

• Water's unique properties support biology and life.