1. Chapter 3: Water and the Fitness of the Environment

2. I. Importance of Polarity
Polarity in water results in hydrogen bonding
One water molecule can create 4 hydrogen bonds

5. II. Unique Characteristics of Water
Cohesion
Moderates Temperature
Density
Use as a solvent

6. A. Cohesion Water molecules stick together, why?
-cohesion, hydrogen bonds hold water together
Adhesion - substances sticking together
High Surface Tension

9. B. Moderating Temperature
Water absorbs and releases heat with little temperature change
- heat: measure of the total quantity of kinetic energy
- temperature: measure the intensity of heat due to average kinetic energy
- specific heat: measure of how well a substance resists changing its temperature when it absorbs or releases heat

10. B. Moderating Temperature (cont.)
Water has a very high specific heat, 10X iron
Water resists temperature change because hydrogen bonds have to be broken to raise the temperature which takes a lot of heat / energy
Maintains temperature of oceans, organisms, and Earth
Water has a high heat of vaporization which allows for evaporative cooling

11. C. Density Water is less dense in solid form then liquid form
Water freezes when it can no longer break H-bonds.
H-bonds become rigid when they can not break and form a matrix
Ecological implications?

14. D. Solvent Solvent, Solute, and Solution
Great solvent for ionic solutions and polar molecules
Aqueous Solution - one with water as the solvent
Hydrophobic vs. Hydrophilic

16. III. Mole
Mole (mol) - equal in number to the molecular weight of a substance but upscaled from daltons to units of grams.
One mole of table salt would weigh…
58 grams
Avagadro’s number - number of molecules in a mol x 1023
Molarity - number of moles of solute per liter of solution

17. IV. pH Hydrogen Ion - single proton with a charge of +1 (H+)
Hydroxide Ion - (OH-) charge of -1
Dissociation - transfer of H+ ions

18. H20 goes back and forth H+ and OH-

19. A. Acid Substance that increases the H+ concentration of a solution
Acids donate H+ ions to a solution
Examples: HCL and H2SO4

20. B. Base Substance that increases the OH- concentration of a solution.
It can do this by giving off OH- ions or taking on H+ ions
Examples: NaOH and NH3 (why?)

21. V. pH Scale
Scale ranging from 0-14 and expresses the concentration of H+ ions in a solution.
Product of OH- and H+ concentrations is always
Defined as -log(H+) base 10
pH declines as H+ concentrations increase
Each pH unit represents a 10 fold difference in H+ and OH- concentrations

23. VI. Buffer Substance that minimizes the change of pH in a substance
Accepts and donates ions in solution when needed
Usually an acid-base pair like H2CO3 in blood