1. CHAPTER 5 Water and Seawater

2. S Types of Bonding Water Molecule Formation & Configuration
Unusual Properties
Hydrogen Bonding
Heat Capacity
Phases of Water
Adding Salts to Water
Constituents of Seawater
Sampling Devices
Effects of Density and Salinity
Hydrologic Cycle
Composition of River Water
Residence Times
Dissolved Gases
pH of Seawater

3. P
Covalent Bonding

4. P
Ionic Bonding

5. P

6. WATER’S UNUSUAL PROPERTIES

7. Hydrogen bonding Polarity means small negative charge at O end
Small positive charge at H end
Attraction between + and – ends of water molecules to each other or other ions
Fig. 5.3

8. P
Hydrogen bonding
Hydrogen bonds are weaker than covalent bonds but still strong enough to result in:
High surface tension
High solubility of chemical compounds in water
Solid, liquid, gas at Earth’s surface
Unusual thermal properties
Unusual density

9. Surface tension S

10. CALORIE P the amount of energy required to raise
the temperature of 1 gm of liquid water 1 degree Centigrade

11. HEAT CAPACITY (SPECIFIC HEAT)
The amount of energy required to raise the temperature of 1 gm of a substance 1 degree Centigrade

12. P Soil (average) 0.70 Granite 0.19** Quartz 0.19** ** ** (liquid) 0.5
(ice)
0.5

13. What does this mean? If we had 3 cookie sheets each 1 cm deep
One filled with water, one with soil and one with sand
The amount of incoming energy that would heat the water 1oC, would heat the soil 1.4oC and the sand 5oC

14. Unusual thermal properties of H2O
Water - high heat capacity
Amount of heat required to raise the temperature of 1 gram of any substance 1o C
Water can take in/lose lots of heat without changing temperature very much
Rocks - low heat capacity
Rocks quickly change temperature as they gain/lose heat

15. Day/Night Temperature Differences Large on land, small in the ocean

16. Global thermostatic effects
Moderate temperature on Earth’s surface
Equatorial oceans (hot) don’t boil
Polar oceans (cold) don’t freeze solid
Marine effect
Oceans moderate temperature changes day/night; different seasons
Continental effect
Land areas have greater range of temperatures day/night and during different seasons

17. Unusual thermal properties of H2O
H2O has high boiling point
H2O has high freezing point
Most H2O is in the form of water (liquid) on Earth’s surface (good for life)
High latent (hidden) heats of
Vaporization/condensation
Melting/freezing
Evaporation

18. P Specific Heat = 1.0 calories/ gm Specific Heat = 0.5 calories/gm
Fig. 5.6

19. Water molecules in different states of matterP
Water molecules in different states of matter
Fig. 5.5

20. Show water phase animation

21. Changes of state due to adding or subtracting heatP
Changes of state due to adding or subtracting heat
Heat is energy of moving molecules
Temperature is measurement of average kinetic energy

22. Elements within columns share similar properties

23. P

24. Ionic bonding, loosely held together

25. P Dipolar water molecules break ionic bonds by
surrounding sodium and chloride ions

26. CONSTITUENTS OF SEAWATER

28. Salinity P Total amount of solid material dissolved in water
Typical salinity is 3.5% or 35o/oo
Six elements make up 99% of dissolved solids in seawater
Fig. 5.12

29. % = PERCENT OR PARTS PER HUNDRED (PPH)
SALINITY UNITS
% = PERCENT OR PARTS PER HUNDRED (PPH)
Since open ocean salinity varies from %, we move the decimal one place to the right and express it as 0/00 OT PARTS PER THOUSAND (PPT)
% BECOMES o/oo

30. Measuring salinity Evaporation Chemical analysis
Principle of constant proportions
Major dissolved constituents in same proportion regardless of total salinity
Measure amount of chlorine (chlorinity)
Electrical conductivity
Salinometer
CTD

31. Salinity variations Open ocean salinity 33 to 37 o/oo
Coastal areas salinity varies more widely
Influx of freshwater lowers salinity or creates brackish conditions
Greater rate of evaporation raises salinity or creates hypersaline conditions
Salinity may vary with seasons (dry/rain)

32. 9/23 P
> 100 ppm
>1, <100 ppm
< 1 ppm

33. Forchammer’s Principle (Rule of Constant Proportions)
Although the salinity of seawater may change
from place to place, the ratio of ions
to each other remains constant
Importance: You only need to measure one ion
to calculate the concentration of others -
this can be the cheapest or easiest one to measure

34. How to change salinity Add water Remove water Add dissolved substancesP
How to change salinity
Add water
Remove water
Add dissolved substances
Remove dissolved substances

35. Processes that add/subtract water from oceans
Salinity increases through:
Salinity decreases through:
Precipitation (rain or snow)
Runoff (river flow)
Melting icebergs
Melting sea ice
Evaporation
Formation of sea ice

36. S
Nansen
bottle

37. S

39. Reversing Thermometer - takes only a single measurement
Expendable Bathythermograph (XBT) -
Takes a continuous profile as it falls through the water column

40. S
Water-sampling
bottles

41. S
Salinity is most commonly
measured by electrical
conductivity

42. P
Density of water
Density of water increases as temperature decreases down to 4oC
From 4oC to 0oC density of water decreases as temperature decreases
Density of ice is less than density of water

43. Density of water P
Fig. 5.10

44. S

45. S

46. S

47. S

48. S

49. S

50. S

51. S

52. Freshwater lake
10oC
8oC
6oC
5oC
4oC

53. Freshwater lake
8oC
6oC
5oC
4oC

54. Freshwater lake
6oC
5oC
4oC

55. Freshwater lake
5oC
4oC

56. Freshwater lake
ice
0oC
1oC
2oC
3oC
4oC

57. P

58. P