Transcript Ocean Water Vs. Fresh Water How are they different?

Ocean Water Vs.
Fresh Water
How are they different?
Ch 10.2
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
The Salinity of OCEAN WATER
• The salinity of salt
water is not the same
everywhere in the
world....
(1)At the equator....
-temperatures are high
- water evaporates in the oceans
- this leaves salt behind (water is
more salty!)
Equator
The Salinity of OCEAN WATER
(1)At the North and
South Poles
- temperatures are low
and water freezes
- this leaves salt behind
as well
- water has high salinity
The Salinity of OCEAN WATER
(1) 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)
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)
Where Does the salt come
from?
(1)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
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.
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
Lava going into the ocean at Hawaii’s Volcanoes
Density of salt water
• Recall that density = mass/
volume
D = m/V
• Salt water is denser than
freshwater because of the
particles of NaCl!
Density (salt water) = 1027 kg/cm3
Density (freshwater) = 1000 kg/cm3
NaCl increases the mass of water
Density of salt water
• Because salt water is denser than
freshwater, you will float more easily in
very salty oceans or seas!
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!
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?