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Ocean Chemistry Study Guide


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                                    Ocean Chemistry – Chapter 6 Study Guide

   1. Define Chemical Property. Give an example.

   2. Define Physical Property. Give an example.

   3. What contribution to Chemistry did Robert Boyle make? (See textbook)

   4. What is the Periodic Table? What are periods on the Periodic Table? What are groups on the Periodic Table?

   5. How many known elements are there? Remember that we talked about a couple that are known but have not
      been officially added to all Periodic Tables.

   6. Know: The major elements in seawater are : Sodium (Na), Magnesium (Mg), Potassium (K), Calcium (Ca),
      Strontium (Sr), Boron (B), Carbon (C), Fluorine (F), Sulfur (S), Chlorine (Cl), and Bromine (Br).

   7. Know: The biologically important elements in seawater are: Iron (Fe), Silicon (Si), Phosphorus (P), Nitrogen (N)
      and Oxygen (O).

   8. The early Greek philosophers (500 BC) counted 4 basic elements from which they believed everything else was
      made. What were these four elements?

   9. In 1783, Henry Cavendish determined that water was not a simple element. What did he discover?

   10. In the early 1800’s, Sir Humphrey Davey actually discovered the correct formula for water. What is it?

   11. How many atoms make up a single water molecule? Define an atom.

   12. What is the Atomic number of an element? What is the Atomic mass of an element?

   13. How many electrons does one atom of hydrogen possess? How many electrons does one atom of oxygen
14. Hydrogen carries its electron in a single energy shell around its nucleus. This is not true for oxygen. How does it
    carry its electrons?

15. Atoms are “happy” with their outer electron shells full (with 8 electrons). As stated above, this is not oxygen’s
    natural arrangement of electrons. What does oxygen do to compensate for its lack of a full outer electron shell?
    Why will this make oxygen a negative atom?

16. When 2 hydrogen atoms and 1 oxygen atom combine to form a water molecule, each hydrogen atom shares its
    single electron with the oxygen atom, and the oxygen atom shares one of its electrons with each hydrogen
    atom. What are bonds that form with shared pairs of electrons called?

17. A molecule of water is electrically neutral, but the negatively charged electrons within the molecule are
    distributed unequally. Where do the shared electrons spend most of their time in a water molecule? (around
    the oxygen or the hydrogen?)

18. What is a polar molecule? Is a water molecule a polar molecule?

19. Due to its polarity, water can make weak bonds with itself. What are these bonds called?

20. Water is characterized by an extensive but ever-changing 3D network of hydrogen-bonded molecules. The
    result is an atypical liquid with extraordinary properties. Explain two of these extraordinary properties (think
    about the surface of the water & water’s dissolving ability).

21. Ions surrounded by water molecules are said to be what?

22. The major constituents, by definition, make up the majority of elements in seawater and exert the greatest
    effect on its density. Name the 11 elements that have a concentration greater than 1 part per million (ppm) and
    account for 99.9% (by weight) of the dissolved substances in seawater.

23. An interesting property of the major constituents is the near constancy of their ratios. Because of this
    constancy, the major ions are called conservative elements. What principle is invoked to describe this constancy
    of ratios? Who confirmed this principle in seawater samples?
24. Does the principle described in #23 apply to all constituents found in seawater? If not which ones don’t follow
    this principle? Why?

25. What do we call the elements whose concentrations in seawater are below 1 ppm?

26. We talked about a particular marine organism that concentrates trace elements in its body. Name the animal
    that we discussed. What does this organism do with these concentrated elements?

27. Many gases move readily across the air-sea interface. Three gases are particularly critical to life on earth and to
    the physical and chemical balances within the ocean realm. These gases comprise more than 99% of the gases
    in the atmosphere and the oceans. Name these three gases.

28. Define Saturation Concentration.

29. The saturation concentration level can change because it depends on temperature, salinity and pressure of the
    water. How?

30. The distribution of gases in the ocean depends upon abiotic factors such as temperature, pressure and salinity,
    in addition to biological processes such as photosynthesis, respiration and decay. Explain what role these three
    biological processes play in the distribution of oxygen and carbon dioxide. Be specific about location in the
    water column. Which process affects the surface waters more? Which process affects the deep ocean more?
    And which process occurs throughout the water column?

31. Define: Hypoxic, Anoxic, and Anaerobic.

32. Define supersaturation.
33. Where is the largest deep-basin anoxic environment found? Waters below 100 m at this location are
    permanently anoxic.

34. Oxygen concentrations in the ocean are highest at the surface and reduce with depth down to the O2 minimum
    zone (around 800-1000m). After this point, oxygen levels gradually increase to a concentration above that
    found at the oxygen minimum zone. Explain why this happens.

35. Carbon Dioxide concentrations in the ocean are lowest at the surface and increase with depth. Explain why this

36. Geological evidence available indicates the salt content of the oceans has been very stable for perhaps 1.5
    billion years or more. A system that regulates or matches the inputs and outputs of salts to and from the
    world’s oceans must exist. More importantly, salt must be removed from the ocean each year to approximately
    match the salts added. The salinity of the world ocean reflects a balance between sources of salts, processes
    that add salts to seawater, and sinks of salts, processes that remove salts from seawater. List at least four
    sources of salts. List at least four sinks. (See image from slide 17 of lecture.)

37. What is a hydrothermal vent? When was the first hydrothermal vent discovered?

38. Differentiate between “Black Smokers” and “White Smokers”.

39. What is so intriguing about the “Godzilla” vent chimney in the Pacific Ocean off the coast of Oregon?

40. Define Residence Time (RT).

41. List 5 ions in seawater that have very long residence times (more than 10 million years). List 3 ions in seawater
    that have relatively short residence times (in the hundreds of years). See Table 6.1 in text or slide 18 from
42. Define Cation. Define Anion.

43. Define pH. What does “pH” actually stand for?

44. The pH scale is a logarithmic scale that measures the concentration of the hydrogen ion. This scale ranges from
    0-14. On which end of the scale would you find acids? On which end of the scale would you find bases? What
    pH number represents a neutral substance, like pure water?

45. What is the average pH for acid rain? What is the average pH range of the open ocean?

46. Define Buffer.

47. How does CO2 act as a buffer in the ocean? (See slide 21 from the lecture; describe the reversible chemical
    reactions that occur with CO2 and water.)

48. What is the Keeling Curve? What anthropogenic effects appear to be depicted by this graph?

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