Videos from sea floor

1. Videos from sea floor • http://www.youtube.com/watch?v=hmMlspNoZMs • http://www.youtube.com/watch?v=rFHtVRKoaUM

2. Do Now • Use your textbook to look up and write down the definitions to the following terms • Heat capacity • Latent heat of melting • Latent heat of evaporation

3. Chemical and Physical Features of Seawater and the World Ocean Chapter 3

4. Surface Tension • http://www.youtube.com/watch?v=2suY9h7xnKg

5. Hydrogen Bonds • Attractions between water molecules • Weak • Temperature reflects average speed of the molecules • D=m/v • As sea water gets colder, it gets more dense.

6. Less Dense Frozen

8. Melting Ice • Takes a lot of heat. • Hydrogen bonds have to be broken. • The amount of heat required to melt a substance is called the latent heat of melting • http://www.youtube.com/watch?v=MpDJmRydR04

9. Heat capacity • The amount of heat it takes to raise a substances temperature by a given amount. • Water has a high heat capacity

10. Latent heat of evaporation • Water absorbs a great deal of heat when it evaporates.

11. Universal Solvent • Water is very good at dissolving salts • Charged atoms or groups of atoms are known as ions • Salts have much stronger electric charges than the opposite end of the water molecule. • Bonds between ions are stronger than hydrogen bonds

12. Water dissolves salt

13. Seawater • Characteristics of seawater are due to the nature of pure water and solutes • Weathering • Volcanoes • Hydrothermal vents.

14. Salt composition • Seawater contains a little of almost everything, most of the solutes are made up of a small group of ions • 6 ions compose over 99% of the solids dissolved in seawater • Sodium chloride accounts for 85%

15. Salinity • The total amount of salt dissolved in seawater • How is it expressed? • Parts per thousand • Because of the electrical charges ions are good conductors of electricity • Electric conductivity of seawater therefore reflects salt concentration • Practical salinity units (psu)

16. Salinity on organisms • Organisms are affected by total amount of salt and the type of salt • Examine salts left after evaporation

17. Table 3.1

18. Rule of constant proportions • William Dittmar – chemist analyzed samples from the Challenger expedition. • Found that percentage of the various ions in seawater remained constant even though the total amount of salt varied from place to place • Oceans are chemically well mixed • Varies by addition or subtraction of pure water

19. Average Salinity • 35 0/00 • Open ocean varies little between 33 0/00 and 37 0/00 • The variation mostly depends on evaporation and precipitation

20. Red Sea • The Red Sea is very salty • About 40 0/00 • Salinity affects the density of water like temperature • Salty water is more dense than freshwater • Discovery Ed Red Sea clip

21. Salt water • Freezes at a lower temperature that freshwater • Oceans are less prone to freezing than lakes and rivers are • Temperature varies more in the ocean than salinity • Open ocean range is about -2 degrees C and 30 degrees C

22. Do Now

23. Measuring temp. and salinity • Specially designed bottles and thermometers on a wire to the desired depth • A weight known as a messenger is released to slide down the wire. • Temperature profile

24. Temperature profile

25. CTDs • Conductivity, temperature and depth in the water column • Used along with other instruments. • Bathythermographs – measure temp but not salinity

26. Complications w/ samples • What are some complications that scientists may face when collecting samples? • Hmm.. • Trying to get samples from multiple sites • Weather and climate variability

27. Solutions • What are some solutions to these problems? • Hmm… • Instruments could drift with the currents