1.1 - Structure of Water and Hydrogen Bonding

Key Properties Resulting from Hydrogen Bonds

• Cohesion: Water molecules strongly attract each other due to hydrogen bonding. This cohesion creates a high surface tension, allowing insects like water striders to walk on water.

• Adhesion: Water molecules also attract other polar substances. This is essential for capillary action, the movement of water up narrow tubes against gravity (e.g., in the xylem of plants).

• High Specific Heat: Water can absorb or release a large amount of heat with only a small change in temperature. This helps moderate temperatures in organisms and ecosystems.

• High Heat of Vaporization: A large amount of energy is needed to convert liquid water into vapor (gas). This property allows evaporative cooling (like sweating) to effectively cool organisms.

• Universal Solvent: Water is an excellent solvent for polar and ionic substances due to its polarity. This is crucial for biological processes like cell metabolism and transport.

Surface Tension

Surface tension is a measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension due to the strong cohesive forces between its molecules. At the surface, water molecules form hydrogen bonds with their neighbors below and beside them, but not with the air above. This creates a net inward force, making the surface act like a stretched elastic membrane.