1. Water

2. Properties of Water Polar molecule Cohesion and adhesion
High specific heat and evaporative cooling
Density – greatest at 4oC
Universal solvent of life

3. Organisms Depend on Cohesion and Adhesion
Cohesion – water sticking to itself
Adhesion – water sticking to other molecules
Cohesion among water molecules plays a key role in the transport of water against gravity in plants
Adhesion, clinging of one substance to another, contributes too, as water adheres to the wall of the vessels.

4. Surface tension, a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion.
Water has a greater surface tension than most other liquids of cohesion.
Water behaves as if covered by an invisible film.
Some animals can stand, walk, or run on water without breaking the surface.
Fig. 3.3

5. Water stabilizes air temperatures by absorbing heat from warmer air and releasing heat to cooler air.
Three-fourths of the earth is covered by water. The water serves as a large heat sink responsible for:
Prevention of temperature fluctuations that are outside the range suitable for life.
Coastal areas having a mild climate
A stable marine environment

6. Evaporative Cooling
The cooling of a surface occurs when the liquid evaporates
This is responsible for:
Moderating earth’s climate
Stabilizes temperature in aquatic ecosystems
Preventing organisms from overheating

7. Density of Water Most dense at 4oC Contracts until 4oC
Expands from 4oC to 0oC
The density of water:
Prevents water from freezing from the bottom up.
Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation.
Makes transition between season less abrupt.

8. Solvent for Life
Solution – when all of the solvent is evenly distributed in the solvent. (evenly mixed)
Solute –the item being dissolved or mixed in. Usually in lower concentration
Solvent – the substance that the solute is dissolved in.
Suspension – the materials mixed on the solute are not dissolved completely and are instead suspended in the solution.

9. Water Cycle

11. The Water Cycle All living things need water to survive.
Water is recycled.
Evaporation: liquid gas
Transpiration: evaporation from plant leaves
Condensation: gas  liquid (forms clouds)
Precipitation: rain (droplets fall from the sky)
Runoff: rain runs along the surface of the ground until entering a stream or river
Seepage: seeps into the soil and becomes ground water