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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 3 Chemical and Physical Features of the Oceans Why.

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Presentation on theme: "Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 3 Chemical and Physical Features of the Oceans Why."— Presentation transcript:

1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 3 Chemical and Physical Features of the Oceans Why study this?

2 Part One: The Waters of the Ocean Water makes up 80% of most marine organisms. 95 % in jellyfish! Makes life possible!

3 Water: Three States Solid Liquid Gas Water is the only substance that occurs in all 3 states within the range of surface temperatures on Earth.

4 The Unique Nature of Pure Water H 2 O Covalent bonds Water is polar Allows for weak hydrogen bonds to form between different water molecules. Reason for many of waters unique properties Fig. 2.1 Opposites attract

5 The Unique Nature of Pure Water Molecules heated, move quicker, bonds break until evaporation. Molecules cool, move slower Water becomes denser as it cools, molecules closer, same mass, less volume. Freezes when molecules locked into a fixed crystal by hydrogen bonds. Fig. 2.2

6 Water and Ice Fig. 2.2 Solid water is less dense than liquid water. Insulates the water below so that it doesn’t freeze. Ice forms on top allowing organisms to live underneath the ice

7 Heat Capacity Hydrogen bonds must be broken before molecules can begin to move around Water melts at higher temperature & absorbs a lot of heat when it melts and great deal of heat must be removed to freeze it = high heat capacity.

8 Heat Capacity In melting ice, added heat breaks more hydrogen bonds than increasing molecular motion, so the temp of ice-water mixture remains at 0° Adding heat goes into melting the ice not raising temperature. Ex: Ice keeping drinks cold High heat capacity, therefore marine organisms not affected by temperature changes in atmosphere

9 Fig. 2.2 Heat and Water Molecular structure changes with temp. 1) In ice, H bonds hold molecules in a hexagonal pattern, in a crystal 2) Heat added, ice warms up, molecules move quicker until break free of crystal structure. Ice melting 3) While ice is melting, added heat absorbed by H bonds, not by increasing the temp. 4) When ice completely melted, additional heat causes temp to rise. 5)Some molecules fast enough to break all bonds and evaporate. At 100 degrees C, all h bonds broken, water boils and evaporates.

10 Fig. 3.3

11 Water as a Solvent Dissolves more things than any other natural substance, esp. salts called the universal solvent Salts made of opposite charged particles (ions) and conduct electricity Fig. 2.2 wat

12 Water as a Solvent In water, strong ion charges attract water molecule, water molecules surround the ions and pull them apart =dissociation Dissociation Video Fig. 2.2 wat

13 Water as a Solvent -Seawater Characteristics of seawater due to nature of pure water and materials dissolved in it Dissolved solids due to weathering of rocks on land & hydrothermal vents Rain and snow

14 Water as a Solvent -Seawater Sodium chloride account for 85% of all solids dissolved, Na and Cl Salinity is total salt dissolved in seawater Measurement Parts per thousand, 30-35 g/mL, 1.020-1.025

15 Challenger Expedition William Dittmar Wrote papers on composition of seawater Rule of constant proportions salinity varies, but not percent composition of ions

16 Seawater Removal and addition of water, changes salinity. How? Avg. 35 ppt and between 33-37 ppt in open ocean.

17 Salinity fluctuations Oceans well mixed, salinity varies as a result of addition/removal of fresh water, rather than removal/addition of salt.

18 Salinity, temperature, and density Get denser as it gets saltier, colder, or both Ocean temp varies -2° to 30°C (28-86°F) Temps below 0°C possible because saltwater freezes at colder temps. Density controlled more by temperature than salinity Are exceptions therefore salinity & temp need to be measured to determine density


20 Trace Elements and Dissolved gases Trace elements: Nitrogen Phosphorus, and Iron Needed to make amino acids, nucleic acids (DNA) Sulfate, Magnesium, Calcium, Potassium, Bromide, Bicarbonate, Fluoride O 2, CO 2 and N 2 in atmosphere and sea surface Gas exchange happens between the surface and atmosphere

21 Trace Elements and Dissolved gases Oxygen Necessary for respiration Most oxygen is released into the atmosphere Carbon Dioxide Necessary for photosynthesis 80% of gasses is carbon dioxide 50 times more CO2 stored in oceans than in atmos. Important topic in global climate change Gas dissolves better in colder water

22 Transparency Sunlight can penetrate, but it’s affected by the material suspended in the water Important to the photosynthetic organisms

23 Transparency Seawater is transparent, but not all colors penetrate as well. blue is best, red is worst

24 Transparency Runoff makes coastal waters less transparent than open ocean. Plankton and algae blooms can affect water transparency Simple instrument to test water clarity, Secchi disk

25 Pressure Sea level = 1 atm or 14.7 pounds per square inch (psi) On land, organisms are under 1 atm. Marine organism have the pressure of the atmosphere and water

26 Pressure Added weight of water column Each 10 meters (33 ft) = another atmosphere Ex: 33 ft down = _____ atm of pressure. Ex: 66 ft down = ______atm of pressure.

27 Pressure Effects Increase pressure/depth, gases compress. Causes gas-filled structures to shrink or collapse Decrease pressure/depth, gases expand Head in middle taken to 2000 ft, head on left taken to 3000 ft

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