1. Water and the Fitness of the Environment
Chapter 3

2. I. Water Molecule What is a polar molecule?
How does the polarity of water effect this molecule?

3. II. Properties of Water
What are the four characteristics of water that emerge due to this hydrogen bonding?
Water is cohesive
Moderation of temperature
Water expands when it freezes
Water is a versatile solvent

4. A. Water is Cohesive Cohesion Adhesion due to hydrogen bonding
water molecules are attracted to other water molecules
Surface tension
Adhesion
Attraction of water molecules to a surface

5. B. Moderation of Temperature
Water has a high specific heat. What is specific heat?
Why is it high for water?
Where do we see this characteristic in our lives?
Lake Michigan
Boiling water

6. B. Moderation of Temperature
Evaporative Cooling - molecules with the greatest kinetic energy are the most likely to leave as a gas
Ex: evaporation of sweat from human skin
Heat of vaporization - quantity of heat a liquid must absorb to be converted to a gas
Helps to moderate Earth’s climate
Accounts for the severity of steam burns of the skin

7. C. Water Expands When It Freezes
Why is water less dense as a solid than as a liquid?

8. Important factors that result from water’s expansion as it freezes:
Prevents deep bodies of water from freezing from the bottom up
As water freezes it releases heat to water below and insulates it
As water freezes H bonds form releasing heat. As ice melts H bonds break absorbing heat. Both of these factors make seasonal transitions less abrupt

9. D. Water is a Versatile Solvent
Polar compounds dissolve in water.
Nonpolar compounds do not dissolve in water.

10. III. Acids Bases and pH Water molecules dissociate into H+ and OH-
At equilibrium the [H+ ] = [OH-]
The molar concentrations of these ions = 10-7, which represents a neutral solution
pH of a solution = -log [H+ ]
Therefore what is the pH of a neutral solution? 7

11. Acids Bases Increase the relative [H+ ] of a solution
[H+ ] > [OH-] in an acidic solution
Remove [OH-] from a solution which increases the relative [H+ ]
For example the acid HCl in a solution converts to [H+ ] + Cl-
pH of acidic solution<7
Bases
Reduce the relative [H+ ] of a solution
[H+ ] < [OH-] in a basic solution
Bases either reduce [H+ ] directly…….. NH3 + H+ --> NH or indirectly ……... NaOH --> Na+ + OH-
pH of basic solution > 7

12. How much greater is the [H+ ] in a solution with a pH of 2 than a solution with a pH of 6?
10,000

14. Water Transport in Plants