PHYSICAL PROPERTIES OF WATER

1. PHYSICAL PROPERTIES OF WATER Start here for next exam

2. Origin of ocean and atmosphere • Volcanic eruptions • release water and various gases from molten rock • Retained by Earth's gravity • Earth is big enough

3. Origin of ocean and atmosphere • Water is lost from smaller planets – • moon and Mercury lost their gases and water • Mars - we are looking into water on Mars right now: • exhibits signs of running water, and at some time in its history, it may have had a shallow ocean • don't know where the water went

4. WATER ON MARZ

5. Origin of ocean and atmosphere • Altered by biological activity • Plants release O2 during photosynthesis - CO2 is removed from the atmosphere and combined to form carbon compounds. Most of the carbon is buried in sediment deposits, keeping it out of the ocean and atmosphere.

6. Water • Sea water is a mix of water, salt, and living organisms plus decomposition products • Distinctive properties of water dominate • Limited effect of adding salt • Properties of water (Table 5.1) p 133 • this table is loaded with water information that will help you quite a bit with the next exam.

7. Water cont. • Covalent bonds (Fig 5.2) p 130 T 64 S&A 57 • Polar molecules • give water its unusual properties • asymmetric properties of the water molecules • universal solvent

8. Water cont. • Strong interactions among molecules • 1. hydrogen bonds allow water to store large amounts of heat with small temperature changes • 2. Sun's heating of the ocean surface provides enough energy to break the hydrogen bonds, but not enough to break ionic and covalent bonds

9. Water cont. • 3. evaporation requires heat (sweating) • 4. condensation gives up heat (water on windows in the winter) • 5. states of water under special conditions • 0 degrees without freezing • ice -> gas (sublimation) • boiling at < 100 degrees

10. Water cont • Hydrogen bonding between water molecules affects the structures of ice and water, giving them unusual properties • water vapor act like other gases (no bonding between molecules)

11. States of matter - water • Fig 5.9 p 134 • Gas - molecules act independently • molecules striking the sides of a container exert pressure • add or remove gas to change pressure • increase of decrease temp to change pressure

12. States of matter cont. • Solid - molecules rigidly bound - definite size and shape • will bend or break when enough force is applied • fixed internal structure - atoms vibrate which can be increased with increase temperature • molecules are held together with hydrogen bonds forming six sided rings • less dense than liquid water

13. States of matter cont. • Liquid - mix of structured and unstructured liquids • definite volume • can flow or conform to the shape of the container • atoms and molecules are loosely bonded to each other, but the bonds are easily broken, allowing them to flow • molecules can vibrate - increased with heat

14. States of matter cont. • Density dependent upon temperature and pressure D = M/V (Fig 5.12) p 138 • Volume is the thing that is changed with temperature and pressure (review formula) • M • D/V • Density difference between water and ice allows fish to live in water S&A 60

15. Fig 5.8 p 134Drawing # 2 • Latent Heat of Vaporization Amount of heat needed to rise the temperature of one gram of water changing it from a liquid to a gas. • Heat Capacity (specific heat) Fig 5.7 p 134 • Ability to absorb large amounts of heat without large change in temperature • Density S&A 60 • Mass per unit volume (gm/cc)

16. Temperature effects on water (triple point) (T 67) • Heat capacity - ability to absorb large amounts of heat without large change in temperature • need heat to break the hydrogen bonds then start to increase the temperature of water • heat capacity of water is 1 • water close at hand modulates temperature • ocean surface temp changes very little between day time and night • land surface temp changes more between day time and night

17. Temperature effects cont. • Calorie - amount of heat required to raise temperature of 1 gram of water 1 degree C • Sensible heat - heat detected by our senses (feel, thermometer) heat change results from the increased vibrations of molecules • Latent heat - heat used to break bonds during changes of state with no change in temperature of the system (drawing # 2) Fig 5.8 p 136

18. Temperature effects cont. • Freezing point - 0oC • Boiling point - 100oC • Fig 5.8 p 134 This kind of puts it all into perspective.

19. Temperature effects cont. • Freezing and density of water with T 70 • with increasing salinity, both temp of maximum density and freezing point decrease

20. Kinetic energy • molecules are always in motion. Evaporation leads to cooling of the residual molecules that have lost heat energy to their escaping neighbors. The heat energy is transferred along with the escaped molecules from the liquid water to the gas phase (blowing on your sweat covered skin causes the water to evaporate and cool your skin).

21. Vapor pressure • Tendency of molecules in a liquid to escape into the gas phase

22. Viscosity • liquid property that resists flow (think of honey) • 1. Decreases with increased temperature • 2. Increases with increased salinity • 3. Important for minute organisms

23. Surface tension • measure of the tendency of surface molecules of a liquid to cling together. • in water is due to hydrogen bonding

24. Capillarity • water moving up the tube • water clings to sides of glass

25. Sea salts • six elements comprise 99% of the sea salts • Na, Cl, (most abundant) • Mg, Ca, SO4, K • composition of seawater T69 • (Fig 5.12 Table 5.1)p 138

26. Table 5.5 p 147 • Processes affecting seawater salinity

27. Dissolving Ability - (Fig 5.4 p 133) • Water is called the universal solvent because of its exceptionally good dissolving ability for a wide range of materials. • polar nature - each ion of Na+ and Cl- is surrounded by water molecules

28. Water as a solvent

29. Salinity • total amount of dissolved salts, in parts per thousand 1 kg sea water (0/00) • Conservative elements - generally unreactive, chemically and biologically p 160 Can be used to follow ocean currents, know where water goes (like used by plants), and air/water gas exchange. • Non conservative elements - biologically important p 160 Used to follow chemical and biological processes. Amounts given off in volcanic activity, photosynthesis, etc.

30. Density • ratio of mass to volume D = M/V • affected by state (gas, liquid, or solid), temperature, salinity, and pressure

31. Density cont • Stable density structure - least dense floats on top -returns to its original state after being disturbed (snow globe) • Unstable density structure - a parcel rises or sinks until it reaches a level of comparable density (remember isostasy) • Convection - response to unstable density structure (Lake effect) • Water is most dense at 3.98oC (Fig 5.12) p138

32. Dissolved gas • 1/temp, p/1, 1/vapor pressure (all the gases in the atmosphere are dissolved in sea water to some extent) • Think of your pay check: earnings = 1/50, 50/1, 1/50 which would you like? Remember higher the temperature or vapor pressure, less gas is dissolved. • Composition determined by conditions at the sea surface (equilibrium) • Dissolved oxygen is affected by surface processes

33. Photosynthesisvs. respiration • plants/animals affect amount of CO2 = 0.03% • O2 20.99% • you will see this again

34. Photosynthesis Respiration • Occurs in the presence of light (and chlorophyll in plant cells) • Occurs at all times in cells • Requires energy (light) to make sugar (glucose) • Releases energy from sugar • Complex substances (sugar) are formed from simpler ones. • Complex substances (sugar) are broken down into simpler ones. • Carbon dioxide and water are the raw materials. • Carbon dioxide and water are the waste products. • Oxygen is given out. Oxygen is taken in.

35. Carbon dioxide • complicated chemical behavior (Fig 5.21 p 150) • Interaction with atmosphere at surface • Formation and destruction of carbonate shells • Used in photosynthesis • Destruction of organic matter in deep ocean • Important storage mechanism for carbon dioxide from fossil fuels

36. Carbonate buffering system

37. Acidity and alkalinity • Controlled primarily by carbonate equilibrium in sea water • Buffer, like cream in your coffee (Fig 5.20) p 150 S&A 69

38. Process controlling sea water composition • Constituents derived from volcanic activity to give gases (Cl and SO2) and hot water reacting with volcanic rocks and alteration of rocks at Earth surface temperatures and pressures (weathering) • Constituents removed by reactions with rocks • Biological processes important • Evaporation of sea salts

39. Biological processes important Fig 5.16 p 150 • Evaporation of sea salts • Residence time - the average length of time that water, or another chemical substance, stays in a reservoir p163 • Hydrologic Cycle - (Fig 5.15 p 45) T 68

40. Show overhead of Biogeochemical cycle

41. Biogeochemical cycle • C • N2 • S • O2

42. CO2 cycle

43. Resources from sea water • Salt (NaCl) is the most important • Br2 and Mg • Freshwater for human use - still with condenser like on the factory fishing boat • Ocean is generally not a good source of fresh water.

44. Fin