Lecture 4 (Ch. 5 of text) Properties of Seawater (Part I)

1. Lecture 4 (Ch. 5 of text) Properties of Seawater (Part I) Biology is wet and dynamic - Random walks in biology 1983,byH. C. Berg The most common molecule on the Earth - water Soup as salty as the seawater

2. Learning Objectives 1. Understand the nature of the water molecule and its uniqueproperties and how these are altered by the presence of salt in solution. Review of following terminologies: Atoms Temperature Heat Specific Heat Thermodynamics Internal Energy and Entropy 2.Know the types of materials that are dissolved in sea water, their importance and how they vary with time. 3. Explain variations in salinity, temperature, and pressure within the sea and how they alter the chemical and physical properties of the ocean.

3. Atomic Structure (Ch.5.1) • The smallestunit of a substance that retains all of its chemical properties • Subatomic particles include protons, neutrons, and electrons • A stable atom of an element is electrically neutral • An ion is an atom with either positive- (excess protons) or negative- (excess electrons) charged • Atoms that chemically bonded to another (either same type or different one) comprise a molecule • An element has isotopes due to its varied no. of neutrons in nucleus

4. Periodic Table 稀土元素 錒系元素 More likely to gain electrons and be negatively charged More likely to loose electrons and be positively charged The charge of an ion is the single most important reason for its ability to bond with other elements

5. Basic physical notions (Ch. 5.2) H2O: the only substance that can co-exist naturally as a gas, liquid, and solid states on the Earth’s surface 聚合體 States of Matter (e.g. water) Thermodynamics: the kinetic theory of heat

6. Phase diagram for water

7. a mercury thermometer Precisely, what does the temperature reading mean? Why does the hot-air balloon move upward?

8. it is a measure of the average translational kinetic energy associated with the disordered microscopic motion of atoms and molecules. It is measured in (Celsius, Kelvin, and Fahrenheit). using  Kinetic temperature definition State variables What is temperature?

9. Concept of Entropy (熵) Thermal Equilibrium = Maximum Entropy dS = dQrev = 0; dQrev : heat being reversibly qqqqqqqqqadded or removed T

10. However, the concept of temperature is complicated by internal degrees of freedom Box is solid (Constant volume) Heat: 1) Represents the transfer of energy from high to low temperature. Therefore, heat has units of Energy 2) An object does not possess "heat"; the appropriate term for the microscopic energy in an object is internal energy. Q Heat may be defined as energy in transit from a high temperature object to a lower temperature object.

11. State variables What is Internal Energy? Internal energy = Measure of the Kinetic energy and potential energy on atomic and molecular scales.

12. There is a difference between Temperature and Internal Energy k = 1.38x10-23 J/◦K

13. Change of Internal Energy

14. First Law of Thermodynamics Temperature Pressure

15. Specific Heat Capacity? Amount of energy needed to raise temperature of unit volume of water by one degree C. Units: energy/(mass * degree)

16. Flow chart of thermodynamics http://hyperphysics.phy-astr.gsu.edu/hbase/heacon.html#heacon

17. Flow chart of thermodynamics http://hyperphysics.phy-astr.gsu.edu/hbase/heacon.html#heacon

18. Facts: – Water has one of highest heat capacities ccknown, makes water excellent heat cctransfer material – Allows ocean currents to modulate global ccclimate

19. The amazing water molecule (Ch. 5.3) Liquid/gas state only Plus high heat capacity (thermal inertial) and solvent power (Covalent bond) 共價鍵結 (hydrogen bonding) (in electricity)

20. Water is a powerful solvent – for example Sodium Chloride Rock SALT Ionic bond Cation Anion 陽離子 陰離子 Cation: in greek, downward, descend;anode 陽極 Anion: in greek, go up, ascend; cathode 陰極

21. 外層覆蓋物 Hydration: Water (as solvent) dissolves salts (as solute) by surrounding the atoms in the salt molecule and neutralizing the ionic bond holding the molecule together.

22. All solid-state substances sink in their own liquids, except the water ! Mickey’s ears loosen when entering the ice house (109.50 )

24. Properties of Seawater • Salinity • Temperature • Density • Pressure

25. Salinity: the total weight in grams of dissolved salt in 1 KG of seawater expressed as ‰ (part per thousand PPT)

26. Another factor contributing to the dissolution of salts is acidity

27. Sources for acidity in the ocean Carbonic Acid Bicarbonate Ion (重碳酸鹽離子)

28. Example: Orthoclase (正長石) Kaolinite Dissolved Silica

29. Major constituent (conservative ions) of Seawater (c.f. Table 5.1) Seawater Rivers (鉀) 35 PPT 0.088 PPT

30. Sources of Salt in Seawater Weathering and erosion of rocks on land Rate of supply of salts from rivers: 1015 grams/year ! 陽離子交換 落塵

31. Surprisingly, The Ocean DOES NOT get saltier at least during the past 1.5 billion years The "steady state" results from the removal rate of salts from the ocean being equal to the input rate. This balance holds because the removal rate of salts is related to their concentration, and increases when their concentration increases

32. Sinks of Salt in Seawater Removal of salt from seawater occurs by (1)inorganicprocess, such as a. evaporation-precipitation loop through the formation of supersaturated solution, b. wind, c. adsorption, and (2) organicprocess such as diatoms having silica shells and forams with carbonate shells that are precipitated from the uptake of Si4+ and Ca2+ from seawater (Ch. 4) 石膏

33. The equilibrium state of salinity of seawater gives a hint toward the grand sedimentary cycle in geologic time frame

34. If rivers are the primary supply of salts. Why is CALCIUM and BICARBONATE so little in seawater? Seawater Rivers 35 PPT 0.088 PPT

35. … different processes removing different elements HCO3 and Ca are used biologically very rapidly (non-conservative) Na and Cl are removed very slowly, by absorption on clay particles (conservative) Elements have different residence times, decided by reactive speed and demanding by ocean biota (see Table 5.8)

36. Residence time the average time a component spends in a system (such as monthly stipend in your account). C = total amount r = the removal rate (units of [C]/time)

37. slow absorption removal Rapid biological removal

38. The ocean gets thoroughly stirred, by currents, every ~1,600 years,. This is called themixing timeof the ocean: the time it takes the ocean to mix thoroughly Salts stay in seawater much longer than 1,600 years Salt well mixed  Constant proportion of relative constituents salts of seawater

39. The Hydrological Cycle

40. Surface Salinity (which season?) Evaporation −Precipitation Subsidence regions (c.f. Fig.5-12 of text)

41. Spread out of Mediterranean seawater

42. Effects of salinity on the properties of water

43. Chemical/physical structure of the oceans (Ch.5.5)

44. January Winter July Summer July-January Summer-Winter

45. Why is the deep ocean cold?

46. Transfer of Heat to the Ocean (heat flux) Absorption of solar radiation decreases rapidly with depth

47. Vertical Structure of Temperature Thermocline

49. Vertical Structure of Temperature Outstanding question: what sets the depth of the thermocline?

50. Salinity How do the water masses move? c.f. Fig.5.13b Temperature