1. Chapter 8 The Nature of Water
Oceanography 2014

2. Earth: The Water Planet
71% of the Earth’s surface is covered in water
Water on Earth
3% freshwater
97% saltwater

3. Review of the Water Cycle

4. Review of Atomic Structure
Atoms are made of
Protons (+)
Neutrons
Electrons (-)
Number of these particles change depending on the element

5. Water’s Unique Properties
Water is a polar molecule
A molecule with positively and negatively charged ends
Hydrogen (H) atoms bond to oxygen (O) atom with a covalent bond
Covalent bond: A bond that is formed by 2 atoms sharing 1 electron
O atom shares the electrons of H atoms
Water is a very stable molecule because of these bonds

6. Water’s Unique Properties
The 5 Key Effects of Hydrogen Bonds
Liquid Water
Cohesion/Adhesion
Viscosity
Surface Tension
Ice Floats

7. The Effects of H-Bonds: Liquid Water
H-Bonds require more heat to form steam
takes more energy for water to change physical states
H-Bonds are why water is liquid at room temperature

8. The Effects of H-Bonds: Cohesion/Adhesion
Cohesion: water molecules attract to each another
gives water a more organized structure
Adhesion: water molecules “stick” to other materials
Example: water droplets cling to a leaf

9. The Effects of H-Bonds: Viscosity
Viscosity is water’s tendency to resist flow
Occurs because H-Bonds make water polar
Viscosity is inversely related to temperature
Temperature increases = Viscosity decreases
Temperature decreases = Viscosity increase

10. The Effects of H-Bonds: Surface Tension
Surface tension is water’s resistance to objects breaking its surface
Insects that can “walk on water”
Polar nature of water allows for the formation of a “skin-like” surface

11. The Effects of H-Bonds: Ice Floats
It’s unusual for the solid state to float in the liquid state
most substances get more dense as they cool from liquid to solid
Water is different: Ice takes up more space than liquid water
Ice: H-Bonds form crystals
takes up more room (volume)
Ice: same mass as liquid but greater volume
Makes ice less dense than liquid water
D=M/V

12. Solutions and Mixtures
Solution: A solution occurs when molecules of one substance are evenly spread among the molecules of another substance
Solvent: The more abundant substance in the solution
Solute: The substance being dissolved
Example: Sugar dissolved into water
Water is the solvent
Sugar is the solute

13. Solutions and Mixtures, cont.
Mixture: A mixture is a combination of 2+ substances that are not chemically bonded
Heterogeneous Mixture: Visibly different substances
Suspension: Heterogeneous but solute eventually settles
Homogeneous Mixture: Looks the same throughout

14. Salinity
Salinity is the concentration of all dissolved inorganic solids, including salt ions
Measured with conductivity testing
Tool measures electrical current transmitted through a sample to that of a standard
Salinity is measured in ratios: there are no units.
Expressed in Practical Salinity Scale (PSS)
1/6/13: Period 2 stopping point

15. Colligative Properties of Seawater
Colligative Properties: properties of a liquid that can be changed by the presence of a solute.
Increased Boiling Point
Decreased Freezing Temperature
Presence of Osmotic Pressure
-Pressure differential created when a substance exists in differing concentrations on 2 sides of a semipermeable membrane
Increased Electrical Conductivity
Decreased Heat Capacity (than Freshwater)
-How much heat energy it takes to raise 1 gram of a substance 1o C
Slowed Evaporation
-Attraction of ions & water molecules keeps water from evaporating easily

16. Dissolved Solids in Seawater
Principle of Constant Proportions The principle that the proportions of dissolved elements in seawater are constant. Proportions of Dissolved Solids in 1 kg of seawater, 35 PSS
Cl Chloride
18.98g
Na Sodium
10.56g
SO Sulfate
2.65g
Mg Magnesium
1.28g
HCO3 Bicarbonate
0.14g
Ca Calcium
0.40g
K Potassium
0.38g
Other
0.61g

17. Why the Seas are Salty Oceanic Salinity is stable.
Where do the salts come from?
Minerals & chemicals flushed in from rivers
Eroding coastal rock
+ and - of materials via hydrothermal vents
Biological Factors

18. Salinity Salinity is affected by rainfall & evaporation
The Red Sea (40) and the Mediterranean (38) have higher salinities because
Low freshwater input/rainfall
High evaporation rate
The Black Sea (18) and the Baltic Sea (8) have lower salinities because
High freshwater input from rivers
Low evaporation rates
Ocean has an average salinity of 35

19. Conditions vary with Ocean Depth
Changes Dependent on Depth
Ocean water separates into layers because of density differences
As you go deeper:
Density Increases
Temperature & Salinity Decrease

20. Key Terms
Halocline: Abrupt change in salinity that marks two different water layers
Thermocline: Temperature transition between a colder/deeper water layer and a warmer/upper layer of water
Pycnocline: A thermocline & halocline together creating a boundary between layers of differing water density
Period 7 stop point 1/10

21. pH
pH: Scale that represents the balance between the positive hydrogen ions (H+) and the negative hydroxide ions (OH-) of a liquid

22. pH cont. Acid: higher concentration of H+ ions
pH of less than 7
Alkaline (Basic): higher concentration of OH- ions
pH of greater than 7
Neutral pH: 7
pure water
Seawater
range of 7.8 to 8.3

23. Ions and Charges
Ion: the total number of electrons is not equal to the total number of protons, giving the atom a positive or negative electrical charge
Sodium (Table Salt): NaCl
Cation: ion with a positive charge (Na+)
Anion: ion with an negative charge Cl-)

24. Brackish Water
Brackish Water: Area of mixed freshwater and saltwater (low salinity of ppt)
Estuary: area where freshwater and saltwater meet
Where river currents meet the ocean
Chesapeake Bay

25. Chemistry of Water: Carbon
Carbon = C
Fundamental element of life
Basis for chemical energy and tissue building
Forms found in the ocean
CO2 dissolves in water to form carbonic acid

26. Chemistry of Water: Nitrogen
Nitrogen = N
Required for:
protein
chlorophyll
nucleic acid
Makes up about 48% of dissolved gases in seawater
To be used gaseous N must be fixed into:
Nitrate (NO3-)
Nitrite (NO2-)
Ammonium (NH4+)

27. Chemistry of Water: Nitrogen
Oxygen = O
Dissolved O levels in seawater vary by
Geographical location
Biotic factors (algae blooms)
Depth
Absence of oxygen is called anoxic

28. Chapter 8 Key Vocabulary
Group 1: Water’s Unique Properties
Group 3: Inorganic Water Chemistry
Polarity
Salinity
Covalent Bond
Brackish Water
Hydrogen Bond
Halite
Cohesion
Brine
Adhesion
Colligative Properties
Viscosity
Osmosis
Surface Tension
Semipermeable Membrane
Density D=M/V (The mass per unit volume of a substance under certain pressure and temperature)
Thermocline
Halocline
Pycnocline
Acid
Group 2: Solutions and Mixtures
Alkaline
Solution
Buffer
Solvent
Group 4: Organic Water Chemistry
Solute
Nutrients
Mixture
Denitrification
Homogeneous
Diffusion
Heterogeneous
Isotonic
Suspension
Hypotonic
Ions
Passive Transport
Universal Solvent
Active Transport
Osmoregulation