1. CHAPTER 5 Water and Seawater

2. The Water Planet Water covers about 71% of the Earth’s surface.
biosphere –
Considering the depth and volume, the world’s oceans provide 99% of the biosphere
Total Water on Earth
97% = _______________
2% = ______________
1% = _____________
Of that ________ = surface water
________= ground water
________= atmosphere
The Water Cycle -
The Water Planet
Chapter 6 Pages 6-2 to 6-4

3. The Polar Molecule Water is a simple molecule; =
The hydrogen atoms bond to the oxygen atoms with a covalent bond.=
Water is Polar =
Water’s Unique Properties
Chapter 6 Pages 6-5 & 6-6

4. Water molecules in different states of matter Solid= Liquid= Gas=
Fig. 5.5

5. Changes of state due to adding or subtracting heat
Temperature=
Calorie=

6. Unusual thermal properties of H2O
H2O has high boiling point =
H2O has high freezing point =
latent heats of
Vaporization/condensation=
Melting/freezing=

7. Fig. 5.6

8. 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
Rocks low heat capacity
Rocks quickly change temperature as they gain/lose heat

9. 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

10. Density of water Water is the only substance that
Density of water increases as temperature decreases
Density of ice is less than density of water
From 4oC to 0oC density of water decreases as temperature decreases

12. Density of water
Fig. 5.10

13. Salinity
Total amount of solid material dissolved in water- Traditional definition
Typical salinity is 3.5% or 35o/oo or parts per thousand (ppt) = grams of salt per kilogram of waterg/Kg
Six elements make up 99% of dissolved solids in seawater
Fig. 5.12

14. The Colligative Properties of Seawater
Properties of Pure Water=
4. 5.
Colligative properties =
Ability to conduct an electrical current. A solution that can do this is called an electrolyte.
Decreased heat capacity. Takes less heat to raise the temperature of seawater.
Raised boiling point. Seawater boils at a higher temperature than pure fresh water.
Decreased freezing temperature. Seawater freezes at a lower temperature than fresh water due to increased salinity.
Slowed evaporation. Seawater evaporates more slowly than fresh due to the attraction between ions and water molecules.
The Inorganic Chemistry of Water
Chapter 6 Pages 6-12 & 6-13

15. Salinity variations Open ocean salinity 33 to 38 o/oo
Coastal areas salinity varies more widely
brackish conditions=
hypersaline conditions=
Salinity may vary with seasons (dry/rain)

16. Why the Seas Are Salty
Source of sea salts = minerals and chemicals on land eroding and dissolving into fresh water flowing into the ocean.
Waves and surf appear to contribute by eroding coastal rock.
Hydrothermal vents change seawater by adding some materials while removing others.
Scientists believe these processes all counterbalance so the average salinity of seawater remains constant.
The ocean is said to be in chemical equilibrium.
The Inorganic Chemistry of Water
Chapter 6 Page 6-17

17. 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

18. Hydrologic cycle describes recycling of water near Earth’s surface
Fig. 5.15

19. Processes that add/subtract dissolved substances
Salinity increases through:
Salinity decreases through:
Salt spray
Chemical reactions at seawater-sea floor interface
Biologic interactions
Evaporite formation
Adsorption
River flow
Volcanic eruptions
Atmosphere
Biologic interactions

20. Residence time and steady state
Fig. 5.16

21. Acidity and Alkalinity
pH measures acidity or alkalinity.
Pure water =
Acids add =
Bases add =
Acidic solutions have a lot of hydrogen ions, pH value of 0 to less than 7.
Solutions that have a lot of hydroxyl ions are considered alkaline. They are also called basic solutions. The pH is
The Inorganic Chemistry of Water
Chapter 6 Pages 6-19 to 6-20

22. Carbon Cycle The Organic Chemistry of Water
Chapter 6 Pages 6-24 & 6-25

23. Carbonate buffering Keeps ocean pH about same (8.1)
pH too high, carbonic acid releases H+
pH too low, bicarbonate combines with H+
Precipitation/dissolution of calcium carbonate CaCO3 buffers ocean pH
Oceans can absorb CO2 from atmosphere without much change in pH

24. Carbonate buffering
Fig. 5.18

25. Surface ocean variation of salinity
Polar regions: salinity lower, lots of rain/snow and runoff
Mid-latitudes: salinity higher, high rate of evaporation
Equator: salinity lower, lots of rain
Thus, salinity at surface varies primarily with latitude

26. Surface ocean variation of salinity
Fig. 5.21

27. Density versus depth Density differences cause a layered ocean
Halocline=
Thermocline=
Pycnocline=

28. Fig. 5.23

29. Desalination processes
Remove salt from seawater
Distillation--most common process
Electrolysis
Reverse osmosis
Freeze separation

30. Fig. 5.24