1. WATER AND THE FITNESS OF THE ENVIRONMENT
CHAPTER 3
WATER AND THE FITNESS OF THE ENVIRONMENT

2. WATER’S POLARITY AND ITS EFFECTS
WATER IS A POLAR MOLECULE
ITS POLAR BONDS AND ASSYMMETRICAL SHAPE GIVE WATER MOLECULES OPPOSITE CHARGES ON OPPOSITE SIDES

3. HYDROGEN BONDING IN WATER MOLECULES
The polar molecules of water are held together by H+ bonds
Positively charged H of one molecule is attracted to negatively charged O of another water molecule
Each water molecule can form four H bonds

4. PROPERTIES OF WATER HAS COHESIVE BEHAVIOR
RESISTS CHANGES IN TEMPERATURE
HAS A HIGH HEAT OF VAPORIZATION AND COOLS
SURFACES AS IT EVAPORATES
EXPANDS WHEN IT FREEZES
IS A VERSATILE SOLVENT

5. COHESIVE PROPERTIES OF WATER
COHESION- phenomenon of a substance being held together by hydrogen bonds
In water, enough molecules are H+ bonded together at one time to give it amazing structure not found in any other liquid
Contributes to the upward transport in plants

6. SURFACE TENSION
SURFACE TENSION- measure of how difficult it is to stretch or break the surface of a liquid
Water has a greater surface tension than most liquids due to all of the H+ bonds it forms
S.T. causes water to bead also due to H+ bonds

7. WATER MODERATES TEMPERATURES ON EARTH
KINETIC ENERGY-the energy of motion
HEAT- total kinetic energy due to molecule motion in a body of matter
TEMPERATURE-measure of heat intensity due to the average kinetic energy of molecules in a body of matter
CALORIE- amount of heat it takes to raise the temperature of one gram of water by one degree Celsius

8. CELSIUS SCALE AT SEA LEVEL
100°C (212°F) = WATER BOILS
37°C (98.6°F) = HUMAN BODY TEMP
23°C (72°F) = ROOM TEMP
0°C(32°F) = WATER FREEZES

9. WATER’S HIGH SPECIFIC HEAT
Water has a high specific heat, which means that it resists temperature changes when it absorbs or releases heat
** SPECIFIC HEAT-amount of heat that must be absorbed or lost for one gram of a substance to change its temperature by one degree Celsius.

10. BIG BODIES OF WATER
Water covers 3/4’s of the planet, keeps temp. fluctuations within a range suitable for life
Coastal areas have milder climates than inland
The marine environment has a relatively stable temperature

11. EVAPORATIVE COOLING
Vaporization(evaporation) - transformation from liquid to gas
For water molecules to evaporate, hydrogen bonds must be broken which requires heat energy
WATER’S HIGH HEAT OF VAPORIZATION:
Moderates the Earth’s climate
Stabilizes temp. in aquatic ecosystems
Helps organisms from overheating by evaporative cooling

12. WATER’S HIGH SPECIFIC HEAT
WATER HAS A HIGH SPECIFIC HEAT - THIS MEANS THAT IT TAKES A LOT OF ENERGY TO CHANGE THE TEMPERATURE OF WATER
AS THE ENVIRONMENT GETS COLDER, THE MOLECULES HAVE LESS KINETIC ENERGY AND MOVE CLOSER TOGETHER FORMING H+ BONDS THAT RELEASE ENERGY AS THEY FORM DUE TO A DECREASE IN FREE ENERGY (DG)

13. OCEANS AND LAKES DON’T FREEZE SOLID BECAUSE ICE FLOATS
Because of hydrogen bonding, water is less dense as solid than it is as a liquid, therefore ice floats
Water is densest at 4°C
Water contracts as it cools to 4°C
As water cools from 4°C to freezing (0°C) it expands and becomes less dense

14. WATER MOLECULES FORMING ICE
NOTICE THE LAYERS AND SPACING OF THE WATER MOLECULES

15. FORMATION OF ICE
AS ICE FORMS, EACH WATER MOLECULE FORMS A MAXIMUM OF 4 H+ BONDS, WHICH KEEPS WATER MOLECULES FURTHER APART THAN THEY ARE IN A LIQUID STATE

16. HOW EXPANSION OF WATER HELPS THE ENVIRONMENT
Prevents deep bodies of water from freezing solid from the bottom up
Since ice is less dense, it forms on the surface first. As water freezes it releases heat to the water below and insulates it
Makes the transitions between seasons less abrupt. As water freezes, H+ bonds form releasing heat. As ice melts, H+ bonds break absorbing heat

17. WATER IS THE SOLVENT OF LIFE
SOLUTION- a liquid that is a completely homogenous mixture of two or more substances
SOLVENT- dissolving agent of a solution
SOLUTE- substance dissolved in a solution
AQUEOUS SOLUTION - solution in which water is the solvent
***WATER IS A VERSATILE SOLVENT DUE TO THE POLARITY OF THE WATER MOLECULE

18. HYDROPHILIC AND HYDROPHOBIC
HYDROPHILIC-means water loving; ionic and polar substances
HYDROPHOBIC-means water fearing;are not water-soluble
***MOST BIOCHEMICAL RXNS INVOLVE SOLUTES DISSOLVED IN WATER; THERE ARE 2 IMPORTANT PROPERTIES OF AQUEOUS SOLUTIONS
1) SOLUTE CONCENTRATION 2) pH

19. SOLUTE CONCENTRATIONS
MOLECULAR WEIGHT-sum of the weight of all atoms in a molecule (expressed in daltons)
MOLE- amount of substance that has a mass in grams equivalent to its molecular weight in daltons
MOLARITY- number of moles of solute per liter of solution

20. THE DISSOCIATION OF WATER
WHAT HAPPENS:
A hydrogen ion (proton with +1 charge) is transferred from one water molecule to another, creating a hydronium ion (H30+)
H2O + H20 <--> H30+ + OH-
***THIS REACTIONS IS REVERSIBLE

21. DISSOCIATION OF WATER

22. ACIDS AND BASES ACID BASE
Substance that increases the [ H+] of a solution
Also removes OH- because it tends to combine with H+ to form water
BASE
Substance that reduces the relative[ H+] of a solution
May also increase [OH-]

23. THE pH SCALE pH < 7 = acid Presence of H+ ions pH of 7 = neutral
pH > 7 = base
Presence of OH- ions
** most biological fluids are within the pH range of 6 to 8
**stomach acid - 1.5

24. BUFFERS HOW BUFFERS WORK:
By minizing wide pH fluctuations, buffers help organisms maintain a healthy pH of body fluids
Buffers are combinations of H+ donor and H+ acceptor forms in a solution of weak acids or bases
They work by accepting H+ ions from solutions when they are in excess and donating them when they have been depleted

25. ACID PRECIPITATION WHAT IS IT???
Rain, snow, or fog more strongly acidic than pH 5.6
Occurs when sulfur oxides and nitrogen oxides in the atmosphere react with water in the air to form acids which fall to Earth in precipitation
Major oxide source is the combustion of fossil fuels by industry and cars
Acid rain affects the fitness of the environment to support life