Unique physical properties of water – see Table 1 p.20

Question 1

Water Clings: Cohesion

Answer 1

Property: Water molecules form hydrogen bonds with each other.
Effect: High surface tension.
Example: A water strider walks on the surface of a pond.

Question 2

Water Clings: Adhesion

Answer 2

Property: Water molecules form hydrogen bonds with other polar molecules.
Effect: Capillary action and solubility of polar compounds.
Example: Capillary action causes water to move up the xylem tubes in plants. Polar substances, such as sugars, are highly soluble in water.

Question 3

Water Absorbs Thermal Energy: High Specific Heat Capacity

Answer 3

Property: Hydrogen bonding causes water to absorb large amounts of thermal energy as its temperature increases, or lose large amounts of thermal energy as its temperature decreases.
Effect: Temperature moderation.
Example: High heat capacity helps organisms maintain a constant body temperature.

Question 4

Water Absorbs Thermal Energy: High Specific Heat of Vaporization

Answer 4

Property: Hydrogen bonding causes liquid water to absorb large amounts of thermal energy and become a vapour (gas).
Effect: Evaporation and cooling.
Example: Many organisms, including humans, dissipate body heat by the evaporation of water from the surface of the body, often by sweating.

Question 5

Solid Water is Less Dense than Liquid Water

Answer 5

Property: Water has its highest density at 4°C. As water molecules cool below 0°C, they form an ice lattice. The hydrogen bonds keep the water molecules spread apart, reducing the density so that it is below the density of liquid water.
Effect: Ice floats on water.
Example: Fish and other aquatic organisms survive in winter because water freezes from the top down. Snow is an excellent insulator, protecting from extreme cold for many organisms.