1. Ocean Water Vs. Fresh Water How are they different?
Ch 10.2

2. Ocean water has more salt so it has a higher salinity
The Salinity of Water
Have you ever tried drinking ocean water? It is very salty!!! Ocean water is about 200x saltier than fresh water! The amount of salt in the water is known as salinity.
Ocean water has more salt so it has a higher salinity

3. The Salinity of OCEAN WATER
The salinity of salt water is not the same everywhere in the world....
At the equator....
-temperatures are high
- water evaporates in the oceans
- this leaves salt behind (water is more salty!)
Equator

4. The Salinity of OCEAN WATER
At the North and South Poles
- temperatures are low and water freezes
- this leaves salt behind as well
- water has high salinity

5. The Salinity of OCEAN 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
River water
(fresh water)
Ocean water
(salt water)

6. Composition of Salt Water
Salt is the main component of salt water
What is salt made of...?
Salt is made of two ions
Chloride ions (Cl-)
Sodium ions (Na+)
These ions form Sodium Chloride (or salt)

7. Where Does the salt come from?
From the 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

8. 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.

9. Where Does the salt come from?
(2) 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

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

11. Density of salt water D = m/V Recall that density = mass/ volume
Salt water is denser than freshwater because of the particles of NaCl!
D = m/V
Density (salt water) = 1027 kg/cm3
Density (freshwater) = 1000 kg/cm3
NaCl increases the mass of water

12. Density of salt water
Because salt water is denser than freshwater, you will float more easily in very salty oceans or seas!

13. Freezing point of salt water
Normally water freezes at 0°C
Adding salt to water causes the freezing point to lower (-1.9°C )
So the freezing point of salt water is LOWER than fresh water.
This is also why we add salt to the roads in the winter!

14. Understanding Check How much saltier is ocean water than fresh water?
Why do the world’s oceans contain so much more salt than fresh water does?
Name two main dissolved solids found in ocean water
Why is the freezing point of salt water lower than that of fresh water?