1.1 Structure Of Water And Hydrogen Bonding

Water contains polar covalent bonds because oxygen is more electronegative than hydrogen, creating partial charges within each molecule. The partially positive hydrogen of one water molecule is attracted to the partially negative oxygen of a neighboring water molecule, forming a hydrogen bond.

The polarity of water enables hydrogen bonding not only between water molecules but also between and within biological molecules. For example, polar regions of proteins and nucleic acids can form hydrogen bonds with water or with other polar regions within the same molecule, which influences molecular structure and function.

Water’s high specific heat capacity means that a large amount of heat energy must be absorbed or released to change its temperature. Because organisms contain a high proportion of water, their internal temperatures remain relatively stable despite fluctuations in the external environment, supporting homeostasis.

If water’s heat of vaporization were significantly lower, each gram of sweat that evaporated would carry away less heat energy from the body. The organism would need to produce much more sweat to achieve the same cooling effect, making thermoregulation less efficient and potentially leading to overheating in warm environments.

Water molecules in the liquid phase are connected by an extensive network of hydrogen bonds. To vaporize, individual molecules must break free from these bonds, which requires substantial energy input. Therefore, the strength and number of hydrogen bonds directly account for water’s high heat of vaporization.

Adhesion pulls water molecules along the polar walls of xylem vessels, while cohesion holds the water molecules together as a continuous column. Together, these properties allow water to move upward from roots to leaves against the force of gravity during transpiration.

At the surface of a body of water, molecules lack hydrogen-bonding partners above them and therefore form stronger hydrogen bonds with neighboring molecules beside and below them. This creates a net inward pull that makes the surface behave like an elastic film, resisting disruption.

A substance that disrupts hydrogen bonding would reduce surface tension. Surface tension depends on the net inward hydrogen bonding among surface water molecules; weakening these bonds would decrease the cohesive force at the surface, making it easier for objects to break through the water’s surface layer.