Guided Notes about Guided Notes about SeawaterSeawater

Chapter 15, Section 2Chapter 15, Section 2

1. Seawater is a solution of 1. Seawater is a solution of about about 96.5% water and 3.5% dissolved 96.5% water and 3.5% dissolved saltssalts. The most abundant salt in . The most abundant salt in seawater is seawater is sodium chloride (NaCl)sodium chloride (NaCl). .

2. Most elements on Earth are 2. Most elements on Earth are present in seawater in the form present in seawater in the form of of ionsions..

Define salinity and state how it is Define salinity and state how it is expressed :expressed :

Salinity is a measure of the amount of dissolved salts in seawater. It is expressed as grams of salt per kilogram of water, or parts per thousand.

4. The sources of salts in seawater 4. The sources of salts in seawater are are volcanicvolcanic eruptions and the eruptions and the weatheringweathering of crustal rock of crustal rock..

5. Salts are removed from seawater 5. Salts are removed from seawater through through precipitationprecipitation near arid, near arid, coastal regions. Marine organisms coastal regions. Marine organisms also remove also remove ionsions from seawater to from seawater to build their build their shells, bones, and teethshells, bones, and teeth..

6. Seawater is denser than freshwater 6. Seawater is denser than freshwater because because salt ions are heavier than salt ions are heavier than water moleculeswater molecules. The density of . The density of seawater varies depending on its seawater varies depending on its salinity and temperaturesalinity and temperature. .

7. Variations in salinity also cause the 7. Variations in salinity also cause the freezing pointfreezing point of seawater to be of seawater to be lower than freshwater. Seawater lower than freshwater. Seawater freezes at freezes at -2-2˚C˚C

8. The average surface temperature of 8. The average surface temperature of ocean water is ocean water is 15 degrees Celcius15 degrees Celcius, , but temperatures decrease but temperatures decrease significantly with significantly with depthdepth, so that deep , so that deep ocean water is always cold, even in ocean water is always cold, even in tropicaltropical oceans. oceans.

3 layers of the ocean, based upon 3 layers of the ocean, based upon temperature variations: temperature variations:

•Warm, sunlit surface layer, 100 m. thick

•A transitional layer, the thermocline, in which temperatures decrease rapidly with depth.

•The bottom layer is cold and dark, with near freezing temperatures