1. Should we control a chemical that:
Causes excessive sweating and vomiting.
Is a major component in acid rain.
Can cause severe burns in its gaseous state.

2. Accidental inhalation can kill you.
Contributes to erosion.
Decreases the effectiveness of car brakes.
Has been found in tumors of terminal cancer patients.

3. What is the chemical?
Dihydrogen monoxide
Otherwise known as H2O

4. Chapter 3 Water and the Fitness of the Environment

5. Question? What molecule Is the most common In living Cells?
Water - most cells are % water.

6. The Water Planet

7. Properties Of Water
Be ready and able to discuss several of the following properties.
Focus on definitions and examples.
Review water structure and H-bonds from Chapter 2.

8. Liquid Water Is Cohesive
Water sticks to water.
Why?
Because the polarity of water results in hydrogen bonding.

9. Liquid Water is Adhesive
Water sticks to other molecules.
Why?
Hydrogen bonding.

10. Water transport in trees uses Cohesion and Adhesion

11. Water Has A High Surface Tension
The surface of water is difficult to stretch or break.
Why? Hydrogen bonding.

12. Water Has A High Specific Heat
Specific Heat - the amount of heat needed to raise 1 g of the substance 1 degree C.
Why?
Hydrogen bonding.

13. Heat
Total quantity of kinetic energy due to molecular motion.

14. Temperature
Measures the average speed of the molecules.

15. Celsius Scale Will be used for most of our temperature measurements.
O oC - water freezes
100 oC - water boils
37 oC - human body

16. Water Stabilizes Temperature
Water can absorb and store a huge amount of heat from the sun.
Result - climate moderation
Result - organisms are able to survive temperature changes.

17. San Bernardino Burbank Santa Barbara 73° 100° 90° Riverside 96°
Fig. 3-5
San Bernardino
100°
Burbank
90°
Santa Barbara 73°
Riverside 96°
Los Angeles
(Airport) 75°
Santa Ana
84°
Palm Springs
106°
70s (°F)
80s
Pacific Ocean
90s
100s
Figure 3.5 The effect of a large body of water on climate
San Diego 72°
40 miles

18. Water Has A High Heat Of Vaporization
Heat of Vaporization: the quantity of heat a liquid must absorb for 1g of it to convert to a gaseous state.

19. Evaporative Cooling

20. Result: Water cools organisms from excessive heat buildup. Why?
Hydrogen bonding

21. Water Expands When It Freezes
The distance between water molecules INCREASES from the liquid to the solid form.
Why?
Hydrogen bonding

23. Solids and Liquids
Water
Benzene
Floats
Sinks

24. States of Matter
Liquid
Gas
Solid

25. Result
Aquatic life can live under ice.

26. Water Is A Versatile Solvent
Water will form a solution with many materials.
Why?
Hydrogen bonding

27. Solution
Homogeneous mixture of two or more substances.

28. Solvent
The dissolving agent.
The material in the greater quantity.

29. Solute The substance that is dissolved.
The material in the lesser quantity.

30. Hydrophilic Materials
Materials that dissolve in water.
Hydro - water
philic - to like or love
Have ionic or polar regions (polar covalent bonds) on their molecules for H+ bonds.

33. Hydrophobic Materials that repel water. Hydro - water phobic - to fear
Have non-polar covalent bonds. Ex - lipids.

34. Solution Concentration
Usually based on Molarity.
Molarity - the number of moles of solute per liter of solution.

35. Moles The molecular weight of a substance in grams.
One Avogadro’s number of molecules.
6.02 X 1023

36. One Mole of each Sugar Copper Sulfate Sulfur Mercury Oxide
Sodium Chloride
Copper

37. Comment
AP Biology students should be able to calculate solutions in Molarity.

38. Dissociation of Water Water can sometimes split into two ions.
In pure water the concentration of each ion is 10-7 M

39. Adding certain solutes disrupts the balance between the two ions.
The two ions are very reactive and can drastically affect a cell.

40. Acids
Materials that can release H+
Example: HCl
HCl H+ + Cl-

41. Acid Rain

42. Acid Rain

43. Bases Materials that can absorb H+ Often reduce H+ by producing OH-
Example: NaOH
NaOH Na+ + OH-

44. Neutrals
Materials that are neither acids nor bases.

45. pH Scale A logarithmic scale for showing H+ concentration
pH = - log [H+]

46. pH Scale

47. Example: For a neutral solution: [H+] is 10-7 or - log 10-7 or - (-7)

48. Acids: pH <7 etc.
Bases: pH >7 etc.
Each pH unit is a 10x change in H+

49. Comment
[H+] + [OH-] = 14
Therefore, if you know the concentration of one ion, you can easily calculate the other.

50. Figure 3.9 The pH scale and pH values of some aqueous solutions1
Battery acid
Gastric juice,
lemon juice 2 H+ H+ H+ H+
OH– 3
Vinegar, beer,
wine, cola
OH– H+ H+
Increasingly Acidic
[H+] > [OH–] H+ H+ 4
Acidic
solution
Tomato juice
Black coffee 5
Rainwater 6
Urine
OH–
Saliva
OH–
Neutral
[H+] = [OH–] H+ H+
OH– 7
Pure water
OH–
OH– H+
Human blood, tears H+ H+ 8
Seawater
Neutral
solution 9
Figure 3.9 The pH scale and pH values of some aqueous solutions 10
Increasingly Basic
[H+] < [OH–]
Milk of magnesia
OH–
OH– 11
OH– H+
OH–
OH–
Household ammonia
OH– H+
OH– 12
Basic
solution
Household
bleach 13
Oven cleaner 14

51. Buffers Materials that have both acid and base properties.
Resist pH shifts.
Cells and other biological solutions often contain buffers to prevent damage.

52. Summary Be able to discuss the properties of water.
Be able to measure solution concentrations in Molarity.
Be able to work pH scale questions.