1. How Ocean Water Differs from Fresh Water
10.2

2. Objectives List the ways salt water differs from fresh water
Describe what salinity is and how it affects ocean waters
Describe the characteristics between ocean water and fresh water in terms of density, freezing point and boiling point
The role of both fresh and ocean water

3. Salinity
If the oceans are constantly being filled up with fresh water, as the water cycle shows, why is ocean water not clear and fresh?
The amount of salt dissolved in water is called salinity

4. Salinity Ocean water’s salinity = 200X greater than fresh water
Average salinity of oceans is 35 parts per thousand
Oceans at equator (evaporation) and poles (ice) have the highest salinity (removing water increases salinity)
Ocean locations near rivers have low salinity, due to addition of fresh water

5. Composition of Water
Salt water is composed of minerals dissolved during run-offs occurring over millions of years
Volcanic eruptions also release minerals from inside Earth
Sodium ions (Na+) and chloride ions (Cl-) are most common solids in ocean water
Na+ ions and Cl- ions > 75% of all solids in ocean water
Mixed and joined in the ocean, NaCl is chemical name for salt

6. Composition of Water Near the continents
freshwater from rivers empties into the oceans
since the river waters are fresh water (little salt), it dilutes the ocean water near the continents

8. Where Does the Salt Come From?
Land
Rain falls on the land and makes it way to streams and rivers
When water travels through the ground , it picks up materials (such as salt). We call these materials dissolved solids.
Eventually these materials get into the oceans
In the oceans, the dissolved solids are well mixed because the water is moving constantly

9. Dissolved solids are in the ground
Dissolved solids are in the ground. As the water seeps from the ground into streams and rivers, it carries the solids with it. Eventually they end up in the oceans.

10. Density of Salt Water
Density = how tightly packed the molecules are in an object
Less dense always floats on more dense
Eg. warm air rises above cool air, and oil floats on water
We float better in salt water than fresh water

11. Where Does the Salt Come From?
Volcanoes
Undersea volcanoes spew materials into the water
On land, volcanoes spew materials into the atmosphere (these materials condense in clouds and are returned to the oceans when it rains)
Under water volcano
African volcano

12. Lava going into the ocean at Hawaii’s Volcanoes National Park

13. Freezing Point of Salt Water
Salt water has slightly different properties than fresh water
Salt water freezes at –1.9 ºC

14. Freezing Point of Salt Water
This is why we add salt to the gravel when the trucks sand the roads in the winter time
The salt lowers the temperature of freezing causing the ice to melt!