1. Water and Seawater Ever wonder why temperature extremes are found at places far from the ocean, while those close to the ocean are moderated? worldbook.com

2. Winter in South Dakota…and Long Island http://www.polarbearclub.org/polarbears/gallery_c.htm

3. Water and Seawater The mild climates found in coastal regions are made possible by water’s unique thermal properties These and other properties of water, which stem from the arrangement of its atoms and how its molecules ‘stick’ together, give water the ability to store vast quantities of heat, to stick together, and to dissolve almost anything

4. Some general chemistry…. Water is a molecule – A molecule is a group of 2 or more atoms held together by mutually- shared electrons – Water consists of 1 Oxygen atom and 2 Hydrogen atoms (H 2 O)

5. Some general chemistry…. An atom is the smallest unit of matter; contains protons (+), electrons (-) and neutrons (=) The protons and neutrons are located in the atom’s nucleus An element contains a specific set of protons and electrons www.dkimages.com/discover/Home/Science/ Physics-and-Chemistry/Matter/Atoms-and-Molecules/ Atoms-and...-197.html Nucleus: protons (+), neutrons (=) electrons

6. General chemistry continued Elements in their pure form are quite rare in nature; instead they frequently combine to form compounds A compound consists of 2 or more elements The electron arrangement determines the chemical properties of an element – Atoms whose shells are incomplete tend to interact with other atoms to gain, lose, or share electrons

7. My name is bond, ionic bond If an atom has 1 electron too many, it will donate that electron to an atom that is 1 electron short (of a complete outer electron shell) The donation of this electron, and its acceptance results in 2 charged atoms, or ions – The donating element has a (+) charge, having 1 more proton than it does electrons – The accepting element has a (-), having 1 more electron than it does protons

8. Na Sodium atom Transfer of electron Cl Chlorine atom Na + Sodium ion Cl – Chloride ion Sodium chloride (NaCl) + – Formation of an ionic bond The electrical attraction between the 2 ions (Na + and Cl - ) holds them together

9. My name is bond, covalent bond Two atoms may also share electrons When atoms share their outermost electrons, they form covalent bonds The resulting compound is called a molecule The resulting bond is very strong Elements in need of 4 electrons, and those with only 1 electron to share (=Hydrogen) frequently form covalent bonds

11. Water is covalently bonded Water (H 2 O) is a covalently-bonded molecule, in which Oxygen shares its electrons with 2 Hydrogen atoms (completes the outer electron shells of both the Hydrogen atoms and the Oxygen atom)

12. (–) O HH (+) A water molecule is a polar molecule The oxygen atom in water is highly electronegative; it attracts the shared electrons much moreso than does the Hydrogen atoms, so the shared electrons spend more time near the Oxygen than the Hydrogen atoms

13. Water is a polar molecule A polar molecule results from the unequal distribution of electrical charges Atoms in a covalently-bonded molecule are in a constant ‘tug-o-war’ for their shared electrons An atom with a high electronegativity (its attraction for shared electrons) can pull electrons towards its nucleus and away from the other, sharing atom

14. Recall that in a water molecule, two hydrogen atoms share electrons with an oxygen atom, completing the outer shell of all 3 atoms O H H

15. But the electrons do not spend an equal amount of time with hydrogen as they do oxygen + + + ++ + + + + + O H H

16. This is because oxygen has 8 protons in its nucleus, while hydrogen only has 1 Remember that opposites attract. The difference in positive charges pulls the shared electrons toward oxygen, and away from the two hydrogen atoms + + + ++ + + + + + O H H

17. The abundance of electrons near oxygen makes the oxygen atom in a water molecule slightly negative Likewise, the 2 hydrogen atoms become slightly positive since their shared electrons spend so little time near them + + + + + + + + + + (-) (+)

18. A water molecule is said to be polar in that it has two ends of opposing charges: a slightly positive charge near the hydrogen atoms, and a slightly negative charge near the oxygen atom O H H (- ) (+)

19. Water is a polar molecule The bonds that exist between 2 polar molecules are called hydrogen bonds - very weak (compared to ionic and covalent) but collectively are very strong Hydrogen bonds

20. O H H (-) (+) O H H (-) (+) Water: Cohesion O H H (-) (+) O H H (-) (+) O H H (-) (+)

21. I’m getting thirsty… Hydrogen bonds make water cohesive; its molecules tend to ‘stick’ together This cohesion allows plants to transport water and nutrients from their roots to their leaves (think of a giant redwood) Water has an extremely high surface tension (the measure of the difficulty to stretch or break the surface of a liquid)

22. A water strider walks on water …and let’s not forget Jesus Christ Superstar, er, Lizard http://www.youtube.com/watch?v=45yabrnryXk&feature=related

23. Water, water everywhere Water’s hydrogen bonds moderate temperature – Water is able to absorb a great deal of heat energy without an increase in temperature because of its hydrogen bonds – Heat must be absorbed to break hydrogen bonds and heat is released when hydrogen bonds form – To increase temperature of water, heat energy must first disrupt the hydrogen bonds; when water is cooled, more hydrogen bonds form

24. Water: Heat Capacity HEAT

25. Water: Heat Capacity HEAT

26. Water: Heat Capacity We experience the benefits of water’s high heat capacity every time we sweat. Our body provides the heat to evaporate water from a liquid to a gas (water vapor), keeping us cool This is the same reason why dogs pant and pigs wallow in the mud! H2OH2O

27. How much heat required to induce evaporation

28. Water is a moderator of climate

29. Hurricane path: Camille 1969

30. Day minus night temperature difference

31. Water’s amazing properties Water exists in all phases (gas, liquid, solid) on Earth Jeopardy question: What is the molecular formula of ice??? Because of hydrogen bonds, ice is less dense than water – This prevents lakes, ponds, and even the ocean from freezing solid; fish, dolphins, walruses very grateful

33. Thank you Hydrogen Bonds!!!

34. Water is the solvent of life Because of water’s polar properties (its hydrogen bonds), water is an incredible solvent A solvent is the dissolving agent of a solution, a liquid consisting of uniform mixture of 2 or more substances The substance that is being dissolved is called a solute

35. Ion in solution Salt crystal

36. Seawater Just how salty is seawater? The oceans contain enough salt to cover the entire planet with a layer more than 500 feet thick (the height of a 50-story skyscraper)! (but we have a lot of ocean….) The total amount of solid material dissolved in water is a measure of its salinity

37. Salinity of seawater The salinity of seawater is typically 3.5% A salinity of 3.5% indicates that seawater contains 96.5% pure water and 3.5% solutes The major solutes of seawater are chlorine, sodium, sulfur, magnesium, calcium, and potassium (=99% of the dissolved solutes), but >80 other elements have also been identified in seawater

38. Major dissolved components in seawater

39. Salinity of seawater Sodium and Chlorine make up 85% of the solutes found in seawater! Salinity is typically expressed in parts per thousand A salinity of 3.5% is equivalent to 35‰ 35‰ seawater has 35 grams of salt in every 1000 grams of seawater But where does all this salt come from???

40. Could you please pass the salt? Rivers supply most of the ‘salt’ to the oceans Volcanic activity on land and underwater contributes to the amount of ions in seawater The weathering of rocks by rainwater contribute sodium, magnesium and calcium (remember water is an incredible solvent!) Out-gassing through volcanoes and rift vents provide carbon dioxide, chlorine, sulfur, hydrogen, fluorine, nitrogen and water vapor

41. The ocean as an Earth tea Some of the ocean’s solutes are hybrids of the weathering and outgassing processes; table salt (NaCl) Recent evidence suggests that mid-oceanic rifts increase the content of calcium and potassium of seawater, but may decrease the content of magnesium and sulfur – Water circulating through new ocean floor at these sites is apparently stripped of these elements

42. The Principle of Constant Proportions When samples from the Challenger expedition were analyzed, the salinity of seawater changed slightly from location to location, but the relative amounts of ions did not vary significantly – Regardless of the salinity of seawater, the ratio of solutes remain constant – How could this be so?

45. The Principle of Constant Proportions The addition of solutes (“sources”) is balanced by the removal of solutes (“sinks”) The sources = the sinks The rate at which an element is added to the ocean equals the rate at which it is removed (steady state condition) Materials added to the ocean are counteracted by processes that cycle dissolved substances out of seawater

46. How to measure salinity Because the ratio of solutes in seawater is constant, salinity can be measured by chlorinity; the measure of chlorine, bromine and iodine ions in seawater – Easy to measure – Salinity = 1.80655 x chlorinity

47. How to measure salinity Because increases in the amount of dissolved solutes increases the conductivity of water, the salinity of seawater is easily obtained by measuring the electrical conductivity (the ability of a substance to transmit electric current) of seawater – Very accurate

48. Dissolved gases in seawater Gases in the air easily dissolve in seawater at the ocean’s surface Organisms living in the ocean require these dissolved gases to survive The major gases in seawater are: – Nitrogen – Oxygen – Carbon dioxide

49. Dissolved gases in seawater: Nitrogen Nitrogen constitutes ~48% of the dissolved gases in seawater; the upper surface waters of the ocean are saturated (no additional Nitrogen can dissolve) Nitrogen is essential for organisms and can be a limiting factor for phytoplankton Most dissolved Nitrogen is unusable since it exists as N 2 gas, a form that cannot be assimilated by most organisms

50. Dissolved gases in seawater: Oxygen Oxygen constitutes ~36% of the gases dissolved in seawater Oxygen is essential for all aerobic life forms Dissolved oxygen comes from photosynthesis and diffusion from the atmosphere

51. Dissolved gases in seawater Carbon dioxide is very soluble in water and comprises ~15% of the dissolved gases in seawater Because CO 2 combines chemically with water to form H 2 CO 3 (carbonic acid), water can hold a tremendous amount of CO 2 In fact, much more CO 2 moves from the atmosphere into the ocean, than from the ocean to the atmosphere

52. CO 2 is used near the surface and produced at depth O 2 is produced near the surface and used at depth

53. Dissolved gases in seawater Concentrations of oxygen and carbon dioxide vary with depth Moreover, gases dissolve more readily in cold water than warm Cold, polar water contains a greater volume of dissolved gases than warm, tropical water As a result, when deep, cold water is upwelled to the surface, it provides the nutrients many organisms need to survive (we return to this)

54. The Acid-Base Balance Water (H 2 O) can separate to form hydrogen ions (H + ) and hydroxide ions (OH - ), which will be present in equal concentrations in pure water An imbalance of these ions, however, produces an acidic or basic solution An acid is a substance that releases H + ions in solution; a base is a substance that combines with a H + ion in solution

55. The Acid-Base Balance The acidity or alkalinity (basic) of a solution is measured on a pH scale pH measures the concentration of H + ions in solution; an excess of H + ions makes the solution acidic; an excess of OH - ions makes the solution basic (alkaline) Seawater is slightly alkaline with an average pH of 7.8

57. The Carbonate Buffering System If CO 2 readily dissolves into seawater and forms carbonic acid, why is seawater slightly alkaline, and not slightly acidic??? When dissolved in seawater, CO 2 is actually present in different forms; carbonic acid is only 1 of these Some carbonic acid, H 2 CO 3 breaks down to produce H + and the carbonate ion, HCO 3 -

59. The Carbonate Buffering System In this way, carbonic acid and bicarbonate are buffers; if seawater becomes ‘too’ basic, reactions will proceed to produce more H +, increasing the acidity of the solution, and vice versa H 2 O + CO 2  H 2 CO 3  HCO 3 - + H +  H + + CO 3 -2 More complex than other gases Carbonic acid Bicarbonate Carbonate

61. The Ocean is density-stratisfied The density of water depends mainly on its temperature and salinity Freshwater is less dense than salt water Warm water is less dense than cold water Much of the ocean is divided into 3 density zones: – Surface zone – Pycnocline – Deep zone

62. Temperature & salinity are ~constant Density increases with increasing depth Lies below the pycnocline; density changes little with increasing depth

63. Temperature and Salinity Affect Density The pycnocline’s rapid density increase with depth is due mainly to decreasing water temperature Between the surface zone and the deep zone also lies the thermocline; a zone in which temperature decreases rapidly with depth

67. Temperature and Salinity Affect Density Low salinity can also contribute to the pycnocline, especially in regions where freshwater runoff mixes with the surface water The halocline is a zone of rapid salinity increase with depth

69. The Deep Zone The deep zone constitutes 80% of the ocean volume Water in the deep layer originates at the surface where it cools, becomes more dense, and sinks Very cold water; 1-3°C

71. Temperature and Salinity Affect Density Very cold and/or very salty water sinks to the seabed until it reaches a layer of water that is equally dense – Results from the formation of sea ice, or from a high degree of evaporation The pycnocline traps dense water masses at depth and isolates 80% of the ocean water from surface circulation – Density differences power deep ocean currents (we’ll come back to this….)

72. Hear no evil, see no evil… Light does not penetrate far through the ocean Light is a form of electromagnetic radiation that travels as waves through space, air and water (includes radio waves, infrared, ultraviolet and X-rays Water rapidly absorbs the visible wavelengths of light

73. Let there be light! When light is absorbed by water molecules (e.g., the ocean), the molecules vibrate and light energy is converted to heat Where light penetrates, photosynthesis proceeds; very important! The thin film of sunlit water at the top of the surface zone is the photic zone – <100 meters in open ocean – <40 meters in coastal regions – <600 meters in clear tropical regions

74. Hey, who turned off the lights??? Ocean below the photic zone lies in blackness Except for light generated by living organisms (who ‘dat?!!?), the region is in perpetual darkness This dark water beneath the photic zone is the aphotic zone

75. Water transmits blue light more efficiently than red When light reaches surface waters, some of the energy is converted to heat The top meter of the ocean absorbs nearly all of the infrared radiation that reaches the ocean surface, warming it significantly This top meter also absorbs 71% of red light; the dimming light becomes bluer with depth as the red, orange, and yellow wavelengths are absorbed

76. Wavelength (nm) 10 –5 nm Increasing energy Visible light 650 nm 10 –3 nm 1 nm10 3 nm10 6 nm 1 m 10 3 m 380 400 500 600700 750 Radio waves Micro- waves Infrared X-rays UV Gamma rays

77. Light waves with shorter wavelengths contain more energy and penetrate deeper than those with longer wavelengths. However, by 300 meters, even blue light has been converted into heat

78. Deep-sea shrimp

79. Sound travels much farther than light in the ocean Sound is a form of energy transmitted by rapid pressure changes Sound intensity decreases as it travels through seawater because of spreading, scattering, and absorption – Scattering occurs as sound bounces off bubbles, suspended particles, organisms, the surface, the bottom, or other objects – Sound is also absorbed by molecules into very small amounts of heat (sound is energy!)

80. Did you hear that? Sound travels nearly 5 times faster underwater than on land (in the air) In water, sound is transmitted by water molecules; since water molecules are densely packed (more so than molecules in air), they transmit sound more quickly – Sound causes a chain reaction of molecules bumping into one another in a wave pattern,; closely packed molecules transmit sound more efficiently and as a result, faster

81. Do you hear what I hear? Because of sound’s ability to travel so effectively in water, we can use it to map ocean contours!!! (sound familiar???) And because sound waves travel more efficiently underwater than light waves, aquatic organisms frequently rely on sound (hearing), much more so than light (vision) – Other senses, too

82. A whale of a sound Whales regularly communicate with one another through sound – Breaching – Fin- and Tail- slapping – Bubbles – Vocalizations The larger the whale, the deeper the sound they can produce

83. Talk about singin’ the blues… Blue whales produce deep rumbling sounds; deep, low-pitched sounds that are the loudest noise produced by any animal You will feel a blue whale vocalization before you ever hear it Whale vocalizations can travel over entire ocean basins!!!