1. Water and the Fitness of the Environment
CHAPTER 3
Water and the Fitness of the Environment

2. OUTLINE Water’s Polarity and the Effects
A. Polarity results in H bonding
B. Organism’s depend on the cohesion of water
C. Water moderates earth’s temps.
D. Ocean’s and lakes don’t freeze solid
E. Water is the solvent of life

3. Outline, Part II Dissociation of water A. Organism’s sensitive to pH
III. Acid precipitation threatens the fitness of the environment

4. WATER Life evolved in it Cells are 70-95% water
71% of earth are oceans
Exists in all 3 states: NY,NJ,CT
(Uh, solid, liquid, gas…excuse me)

5. POLARITY Water is Polar, it has an ASSYMETRICAL molecular shape
It’s 4 valence orbitals point to the corners of a tetrahedron
e-’s spend WAY more time around the Oxygen
H bonding orders water into a higher level of structural organization
Each water molecule can form 4 H bonds w/neighboring waters. This causes: Cohesive behavior, Resistance to Temp. changes, High Vaporization point, expansion when it freezes, Versatility as a solvent.

6. Organisms Depend on Cohesion
Transpirational pull (cohesion), and adhesion allow plants to survive
SURFACE TENSION: The measure of how difficult it is to stretch or break the surface of a liquid
Water has a greater surface tension than most liquids: At the air-water interface, the surface molecules are H bonded to each other and the water below. Why does water “bead” on smooth surfaces?

7. Water Moderates Temperatures
Define:
Kinetic Energy:
Energy of Motion
Heat:
The total kinetic energy due to molecular motion in a body of matter
Temperature:
The measure of heat intensity due to the avg. kinetic energy of molecules in the a body of matter

8. More Temperature Moderation Vocabulary
Define:
Calorie:
The heat required to raise 1gram of water 1 degree Celsius
Kilocalorie:
1000 cal, or heat amt. Necessary to raise 1Kg of water 1 degree C.

9. Water and It’s High Specific Heat
It resists Temp. changes when it absorbs/releases heat
Specific Heat: Amt. Of heat necessary to raise 1g of a material 1deg. Celsius. Water: 1Cal/g/deg C
H bonds absorb heat to break, release heat when they form
Much of absorbed heat disrupts H bonds before the temp rises
Because so much of the Earth is water, it’s temp is stabilized

10. Evaporative Cooling
Molecules with enough kinetic energy jump from liquidgas, thus lowering the average kinetic energy of the remaining liquid (temperature!)
Heat of Vaporization: How much heat is required for 1 gram to convert to a gas
For water: 540 Cal/g, or 2260Joules/g. A Joule is .239 Cal.
This cools animals, plants, and the planet

11. Hey! Ice Floats! So lakes, oceans don’t freeze solid
The H bonding between H2O molecules forms rings, so ice is less dense
Water is densest at 4 deg C
As water freezes, it releases heat into the water below it, thus insulating it further

12. Water…The solvent of life! Why? It’s POLAR!
Define:
Solution:
Liquid that is a completely homogeneous mixture of 2 substances
Solvent:
Dissolving agent in a solution
Solute:
The substance dissolved in a solution.
An aqueous soln: water is solvent.

13. Hydrophilic Substances
Hydrophilic: Water loving
Ionic Compounds: charged regions of polar water have an electrical attraction to ions. Water surrounds individual ions, separating and shielding them from one another
Polar compounds: Charged regions of water molecules have an affinity for the oppositely charged regions of other polar molecules

14. Hydrophobic Substances
Water “fearing/hating”
Nonpolar compounds (symmetrically charged) are NOT water soluble

15. A water soluble protein

16. Solute Concentrations in Aqueous Solutions
Solute concentration and pH are important quantitative properties
Molecular Weight: Sum of weight of all atoms in a molecule in Daltons
Mole: Amt. of a substance so that it’s mass in grams=its molecular weight in daltons.

17. Example: Sucrose C12H22O11 : C= 12X12= 144 dal H=1X22= 22 dal
O=16X11= 176 dal
________
342 dal
So 342g=1 Mole
Molarity : Moles of solute/1 liter of solution: In this case add 342g to 1L water

18. Water, A salted

19. Dissociation of water H2O + H2O-- H3O + OH-
The H ion transfers from the H bond w/ O to unshared orbitals of O. This equation simplified is:
H2O<--- ->H+ + OH-
At equilibrium, most of the water is NOT ionized

20. Organisms are Sensitive to pH Changes
ACIDS and BASES: At equilibrium, in pure water at 25* C, H ions=OH ions
An ACID increases H+, removes OH- ( OH- combines with H+ to make water). H+>OH-. Weak acids dissociate partially and reversibly.
A Base decreases H+, Increases OH- and H+<OH-

21. pH Scale Measures the degree of acidity [H+][OH-]=1.0X10-14
Most biological fluids are within the range from 6-8
Each pH unit represents a logarithmic (tenfold) difference in H+

22. The pH of some Aqueous Solutions

23. Buffers (the vampire slayer?)
Substances that minimize large, sudden changes in pH
They’re usually a combo of H+ donor and H+ acceptors in a solution of weak acids or bases
They donate H+ when depleted, accept H+ when in excess

24. Acid Precipitation and Environmental Fitness
Considered acidic precip.if pH<5.6
In W. Virginia, recorded 1.5!!!!!
SO2 and NO in air react w/ water to form sulferic and nitric acids.
Fossil fuels (COAL) and autos are the biggest source
Lowers soil pH, leaches heavy metals
Aquatic ecosystems are threatened first
Cure? Pollution control (scrubbers, reduction of burning)

25. Hydrogen Bonds in Water

26. ICE, ICE BABY
you tube ICE ICE Baby