1. Chemistry of the Oceans
Section 1: Water

2. Water Chemical formula of water: H2O
Hydrogen and Oxygen are held together with covalent bonds.
How is a covalent bond different than an ionic bond?
Covalent bonds between oxygen and hydrogen.

3. Water
Polarity – water is polar because of an uneven distribution of electrons between oxygen and hydrogen, resulting in a opposite charges on different ends of the molecules.
Electrons hang out more often near around the oxygen atom.
Slightly Negative (-)
Slightly Positive (+)
Water molecules are polar – they have a positive and a negative end.

4. Water Hydrogen bonds from between the positive and negative charges.
Hydrogen bonds are not as strong as ionic or covalent bonds.
Hydrogen bonding gives water many unique properties:
Solid, Liquid and Gas States
Surface Tension
High Heat Capacity
Viscosity

5. States of Water
Earth is the only place where water exists in all three states.
Solid (ice)
Liquid
Gas (Water Vapor or Stream)
The amounts of solid, liquid and gaseous water is constantly changing.
The total amount of water on Earth remains constant.
What percentage of the Earth’s water is saltwater?

6. States of Water The temperature determines how fast molecules move.
Colder Temperature = molecules move slower
Most substances become more dense the colder they get because the molecule need less room to move.
Water is the exception (it becomes less dense when it freezes)
Why? Water molecules slow down it colder temp. allowing for more hydrogen bonding to take place.
Looking at the diagram, Why does ice float?

7. Viscosity Viscosity: a liquids tendency to resist flowing
Thick liquids like syrup or honey have high viscosity.
Thin liquids like alcohol have low viscosity.
Hydrogen bonding causes water has high viscosity (it is difficult for animals to move through water)
Many small marine animal float because water to too viscous to swim through.
Would it be easier to swim through a pool full water or a pool full of syrup? Why?

8. Surface Tension
Surface Tension: a measure of how difficult it is to break the surface of a liquid.
Hydrogen bonding causes water to have high surface tension.
All the molecules at the surface of a body of water are connected to each other with hydrogen bonds.
The causes the surface of the water to act as a protective film or skin.
For anything to sink, it must first break the hydrogen bonds on the surface.
Explain how the basilisk lizard can run on water even though it is more dense.

9. Heat Capacity
Heat Capacity: The amount of heat need to raise 1 gram of water 1 oC.
Water has a very high heat capacity because of hydrogen bonding.
It takes a long time for water to heat up and cool down.
Most marine organism are cold-blooded because the temperature of the oceans does not rapidly change.
Water helps regulate the temperature on Earth.
Explain why the ocean water is still cold on hot summer days.

10. Acids, Bases and pH Water molecules sometimes split apart to from ions
Animation
Water molecules sometimes split apart to from ions
H H+ + OH-
Water Hydrogen ion + Hydroxide ion

11. Acids, Bases and pH Bases Acids Produce H+ ions in solution
Produce OH- ions in solution
If [OH-] > [H+] then the solution is basic
pH greater than 7
Acids
Produce H+ ions in solution
If [H+] > [OH-] then the solution is acidic.
pH less than 7
Neutral Solution: [OH-] = [H+]; pH = 7; Ex - water

12. Acids, Bases and pH
Buffers: A solution that prevents sharp and sudden changes in pH.
Ex. Blood has several buffers that maintain a pH of 7.4
If the pH in our bodies changes, it will affect the chemical reactions inside our cells.
What is homeostasis and why are buffers important for homestasis?

13. Acids, Bases and pH pH: (power of Hydrogen) as in Hydrogen ions
Measures the H+ concentration in solution: [H+]
It is a log scale, so it increases by powers of ten.
Ex: A solution with a pH of 1 is ten times more acidic then a solution with a pH of 2.

14. Section 2: Temperature, Light, Pressure and Sound in the Ocean
Temperature and Water
The colder temperature increase the density of water. (This causes downwelling in the arctic)
Thermocline: the layer of water that shows a large amount of temperature change with depth.
Looking at the diagram, describe the area of the main thermocline.

15. Light and Water How are the two types of light different?
How are they similar?
Different wavelength = different colors.
All objects either reflect or absorb visible light.
Red objects reflect red light and blue objects reflect blue.
Black objects absorb all colors of light.
White reflects all colors of light.
Explain why a plant would die if you only shined a green light on it?

16. Light and Water The sun gives off white light (contains all colors)
These colors are absorbed at different rates.
Red light is absorbed first.
Blue light is absorbed last.
Why colors would you see 65 meters below the surface?
Why are most small fish and crabs red?

19. Pressure and Water
All organism on land have the weight of the atmosphere pushing on them.
The pressure of the atmosphere is 14.7 pounds per square inch (1 atm = 14.7 psi)
Water is much heavier than air, so the deeper you go, the more pressure.
Pressure causes the gases in the organism’s body to compress.
This limits how deep many organism can dive?

20. Sound and Water
Sound is a type of wave that causes molecules to bump into each other.
Sound move through liquids better that gases because the liquid molecules are closer together and therefore more likely to bump into each other.
The slower the sound moves the further it can travel.
At deeper ocean depths you will find a . . .
Decrease in temperature = decrease in speed of sound
Increase in pressure = increase in speed of sound

21. Sound and Water
SOFAR Channel: a layer of water where the sound travels the furthest.
About 1000 meters – 1500 meters below the surface
The temperature decreases (because of thermocline) slowing the speed of sound.
It is still close enough to the surface so there is not a lot of pressure (which would increase the speed of sound.)
Why do whales “sing” in the sofar channel?

22. Section 3: Contents of Ocean Water
Salt: any substance that consists of negatively charged particles bonded to positively charged particles.
Table Salt (NaCl) is only one example of a salt
The Na atom loses an electron, forming an ion with a positive charge.
The Cl atom gains an electron, forming an ion with a negative charge.

23. Salt Salt crystals dissolve or disassociate in water
The negative end of the water molecules are attracted to Na+
The positive end of the water molecules are attracted to Cl-
Water molecule surround each ion and keep them separated.

24. Salt Salinity: the amount of salt dissolved in water
Ocean water has a salinity of 35 part per thousand (ppt).
How many grams of salt is there in 100 grams of ocean water?
Where did all this salt come from?
Negative ions (Cl-) come from volcanic emission and deep sea hydrothermal vents.
Positive ions (Na+) come from weathered rocks.

25. Salt Ocean water contains many other ions besides Na+ and Cl-.
Rule of Constant Composition: the percentage of each ion dissolved in ocean water will always remain the same.
The salinity (35 ppt) may change with depth and temperature.
The “stuff” dissolved in the water will always be the same.
How would the last column change if the salinity of ocean water decreased from 35 ppt to 32 ppt?

26. Gases Gases as well as salt can be dissolved in seawater.
Gases dissolve better in cold water.
The three main gases in the atmosphere (O2, CO2, N2)are the same as the ocean.
Gas Exchange: gases from the atmosphere get dissolved by surface water vice versa.
What is the only gas that is more common in ocean water than in the atmosphere?

27. Gases Oxygen There is much less oxygen in water than in air.
Oxygen enters the water through the air and through photosynthesis.
What is the equation for photosynthesis?
Oxygen Minimum Zone: area of the water just below the sunlit surface where the oxygen level drops suddenly.
Why does the oxygen level suddenly drop in the oxygen minimum zone?

28. Gases Carbon Dioxide (CO2)
There is 50 times more CO2 in the ocean compared to the air.
Water reacts chemically with sea water to form carbonic acid and bicarbonate.
The bicarbonate keeps the pH level stable around pH 8.
Nitrogen
Mostly enters the water through the atmosphere
Nitrogen is the most abundant gas in the atmosphere

29. Section 4: Human Impacts on Ocean Chemistry
Ocean Acidification
The burning of fossil fuels has caused the amount of CO2 in the atmosphere to increase.
More CO2 is dissolved in the ocean, which creates carbonic acid.
This makes the ocean more acid.
This weakens the shells and exoskeletons of marine life and as a result larger organism experience a drop in their food supply.

30. Overwhelming the Nitrogen Cycle
Nitrogen fertilizer that is applied to farm fields runs into the ocean.
The denitrifying bacteria cannot convert fertilizer back into nitrogen gas (N2) fast enough.
Eutrophication: the nitrogen is absorbed by algae, which leads to excessive algae grow.
The algae dies and decomposes, which uses up all of the oxygen.
Animal population die of lack of oxygen.

31. Climate Change
The Earth’s average global temperature has increased 1.1 oF over the last 100 years.
The sea level has risen on average 1.5mm/year
Sea level rise is not caused by melting ice.
It is cause by the surface water heating up and expanding.
Gases do not dissovle as well in warmer water.
Hypoxic Zones: areas in the ocean with reduced oxygen levels.
Eutrophication is also a cause of hypoxic zones