Chemical And Physical Features of Seawater

1. Chemical And Physical Features of Seawater Chapter 3

2. Warm up 9/12 Ridges and Trenches!! 1. In a complete sentence, compare and contrast ridges and trenches by the plate boundary at which they occur 2. Name the 2 major ridges of the Pacific and Atlantic Oceans 3. At which geologic feature is seafloor created? 4. At which trench is seafloor destroyed?

3. Warm Up 2/11 • In a complete sentence, describe the differences between passive and active margins. • Would point A fall on a passive margin? Why or why not?

4. Agenda 2/11 – 4th Block • Start talking about Ch.3 ~ 10 minutes • In lab groups, begin lab questions & design model ~ 40 minutes 9:15-10:09-4th Block10:09-10:15-Change10:15-12:15-3rd Block/Lunch (30 min. per lunch)12:15-Dismiss from 3rd Block (Students will return from 4th lunch to 3rd block at 12:10).

5. Salinity and Density Lab • What is meant by “mass”? • The weight in grams of your solution • What is meant by “volume”? • The amount of space your solution occupies, measured here in millileters

7. Salinity and Density Lab • Will be working in assigned groups • Each group will assign a leader responsible for directing members and a recorder for writing data table

8. Salinity and Density Lab • Each group needs: • five beakers (between 250ml and 400ml) labeled A-E with tape • One 150ml beaker for water measurement • One 25ml graduated cylinder • Salt • Scale • Scoop/spoon • Lab sheet [DO NOT WRITE ON] • Calculator • Separate paper for recording data, conclusion answers

9. Lab 9/18 Salinity and Density • Each group will need to construct their own data table to submit. • Each group will need to: • answer Conclusion questions 1 & 2, and 4 • create a graph of their data.

10. Homework – due Friday http://science.nasa.gov/earth-science/oceanography/physical-ocean/salinity/ • How does salinity affect movement of ocean currents? • Is it true that the ocean stores more heat in its upper meter than the entire atmosphere stores? Why or why not? • How can ocean salinity be measured? • What factors can affect salinity readings? • Where is the saltiest area in the open ocean? Why is it so salty?

12. Warm Up 2/18 • 1. Place the layers of the earth in order from inside  outside • 2. Identify the layer of the earth that contains convection currents. • 3. Identify the layer of the earth that contains tectonic plates. • 4. What is one important toxic substance released from hydrothermal vents?

13. Agenda 2/18 • Continue Ch.3 … density/salinity lab tomorrow • Review for Ch.2 … Exam tomorrow!

14. Bill Nye Water

15. Water- a unique compound • Water is a polar molecule (slightly charged) • molecules are attracted to one another – hydrogen bonds. • only substance to exist naturally in all 3 states of matter!

16. Hydrogen Bonds between water molecules Oppositely charged ends attracted each other like poles on a magnetic POLAR MOLECULE

17. Three States of water

18. Three State of Water • Solid (ice) • Liquid (water) • Gas (vapor)

19. Three States of Water • Heating Water • H2O molecules in constant motion • Adding enough energy = the hydrogen bonds break & H2O boils • Evaporation : molecules breaking hydrogen bonds and escaping liquid phase TEMPERATURE = MOLECULAR MOVEMENT

20. Water in its liquid state

21. Three States of Water • Cooling Water • Decrease in temperature = decrease in molecular speed • In cooler temps, molecules move slower and pack close together • Volume decreases without changing the mass = denser TEMPERATURE = MOLECULAR MOVEMENT D = Mass Volume

22. Three States of Water • Decreasing temperatures increases density • Why coldest water in the ocean sinks • However, when water gets cold enough to form ice, hydrogen bonds separating molecules lengthen, increasing volume. 1 2 1 4 D = Mass Volume Density = Density = > 0.5 0.25

23. ICE WITH LONGER HYDROGEN BONDS Ice formation

24. Three States of Water • Cooling Water • H2O cools so much that hydrogen bonds overcome molecular movement, fixing molecules in 3D pattern • Crystals: solids that consist of 3D fixed patterns

25. Three states of Water • Water is less dense as a solid than as a liquid • Floating ice insulates water and keeps it warm enough to support life! This is why ice floats!!!!!!!!!

26. Water: Latent Heat • Latent heat of melting: the amount of energy needed to melt ice • Ice requires a lot of heat to melt because of hydrogen bonds • Reverse is true: a lot of heat must be removed from liquid H2O to freeze it  This is why it takes a long cold spell to freeze a large body of water Bill Nye

27. Water: Latent Heat • Heat capacity : a substances ability to store energy • AKA “specific heat” : the amount of heat required to raise a ‘unit mass’ of a substance by 1° temperature • H2O has a very high heat capacity!!!! • Means it can absorb heat without large jumps in temperature • Provides stable environment for marine organisms

31. Ocean can absorb 1000 times the heat energy as the atmosphere without changing temperature, and even IT’S heating up! Ocean Warming

32. Water: “The Universal Solvent” • Water can dissolve more substances than any other natural compound • Especially salts! • Due to polarity, or charge, of molecules

33. Solubility

34. Water Relationships #1 1. Density & Salinity • Increasing salinity increases density • Why? Increasing the amount of dissolved material increases mass, but volume stays same Pure water has a density of 1.0 g/ml. Average density of ocean water at the surface is 1.025 g/ml.

35. Wednesday 2/19

36. Water Relationships #2 2. Density and Temperature: INDIRECTLY PROPORTIONAL • Temperature greatly affects the density of water. • Review: • Decrease in temperature = decrease in molecular speed • Cooling down causes molecules to pack closer together, reducing volume, and thus, increasing density TEMPERATURE = MOLECULAR MOVEMENT TEMPERATURE = MOLECULAR MOVEMENT Proportional relationship true until water becomes ice

37. Water Relationships #3 3. Density and Buoyancy • Buoyancy: upward force exerted by a fluid that opposes the weight of an immersed object • The more dense the liquid, the more force it exerts upward Example: The Dead Sea or Great Salt Lake Dead Sea Float

38. Predictions for how the egg will float? Buoyancy of Water Demonstration • Set up the following observation table in your notes:

39. Water Relationships • Review: temperature affects density of water • Review: salinity affects density of water • THEREFORE… salinity and temperature affect ocean water. • Temperature in open ocean varies between 28° to 86°F WAIT … At what temperature does pure water freeze? How can ocean water be 28° and still liquid?? Salt lowers the freezing point of water!!!!

40. Warm Up 9/20 • The winter of 1984-85 was particularly cold in Europe. The northern part of the Black Sea froze, which is rare. The Adriatic Sea, located to the east, had just as cold a winter but never froze. The Black Sea has an unusually low salinity at 18%. What would you guess about the salinity of the Adriatic?

42. Buoyancy Lab Questions – Write Question first. Use complete sentences. • Which type of water exerted a greater buoyant force on your boat? Why? • How would increasing the salinity of the water affect the buoyancy of your boat? • In which type of water would your boat be more buoyant: cold saltwater or warm saltwater? Why? • What is the relationship between temperature and density? • Describe the role molecular movement plays in the relationship between density and temperature. • What is the relationship between density and buoyancy? • What changes would you make to your boat or water to increase its buoyancy?

43. Seawater • Solids dissolved in seawater present due • Weathering of rocks on earth • Release of minerals from interior earth at hydrothermal vents • Na+ and Cl- make up 85% of dissolved solids

44. Seawater • Salinity: total amount of salt dissolved in seawater • # of grams NaCl/1,000 grams H2O • expressed in PSU (practical salinity units)  same as ‰ (parts per thousand … 1/1000) • Example: If we evaporated 1,000 grams of seawater and were left with 35 grams of salt, our seawater’s salinity in PSU or parts per thousand would be ______________. 35 ‰

45. Salinity of seawater- 35‰

46. Salinity • Rule of constant proportions: the proportions of salts in the ocean remains constant. • Chemistry of ocean is well-mixed and relatively constant. • Ions added and removed continuously and simultaneously HOW? Precipitation, evaporation, runoff!!!

47. Sea Surface Temperatures of the World Ocean

48. Dissolved Gases • Three most important: 1. Oxygen 2. Carbon Dioxide (80%) 3. Nitrogen • Gases dissolve more easily in colder water! • Gas exchange between the ocean and the atmosphere occurs at the surface

49. Dissolved Gases • O2 concentration in water strongly affected by organisms present • Photosynthesis • Respiration • Low dissolved O2 levels leave ocean susceptible to depletion • Oxygen minimum layer: 1600 ft. deep layer of ocean where levels are virtually zero. But life still survives!!!!!!!!!!

50. Biogeochemical Cycling • Photosynthesis, Respiration, and Nitrogen cycles provide important substances for life to thrive