Transcript Properties of Ocean Water

Properties of Ocean
Water
What is ocean water made of?
 Water!
 Other
substances:
Salts – including
NaCl –
KCl –
CaCl2
MgCl2
con’t next page
 Other
substances in Ocean water
Organic matterliving and dead animals and
plants
Dissolved gases
CO2
O2
N2
Why are dissolved gasses important
and how did they get there?
 CO2
 O2
– what produces it, uses it?
– what produces it, uses it?
 N2 –
 Fish
what produces it, uses it?
tank
vs. natural ocean
Gases and solids dissolve in
ocean water…..
 What
affects the solubility?
 Temperature?
 Solids

Ex: sugar in water
 Gases

are more soluble in _____ water.
are more soluble in _____ water.
Ex: what happens to a warm bottle of soda?
What does this mean for
oceans?
 Gases
 In


dissolve better in colder areas
surface layer of oceans, there can be…
More oxygen, carbon dioxide in polar areas
Less oxygen, carbon dioxide in tropical areas
What is salinity?
 The
total amount of dissolved salts in
seawater.
Salinity

1 % is 1 in 100 (familiar with this)

But salinity is usually expressed
• in parts per thousand 0/00
• 1 o/oo is 1 in 1000

Ex: 3.3 % is 3.3 percent = same as
• 33 o/oo, 33 parts per thousand

Ocean water is avg 3.5% OR _______ o/oo.
How can salinity in the ocean
change?
 Let’s
think about a beaker of fresh
water…………………let’s add salt
 The
salinity is a certain o/oo
 How can we change the salinity in the
beaker?
Two ways to change salinity…
 Change
the amount of dissolved
substances

add/remove salt
 Change

the amount of water molecules
add/remove water
How can we decrease the
salinity?
 Add
fresh water!!
 What
natural processes add water to the
oceans?

Precipitation

River and stream run-off

Snow/glacier melting
Can also remove/lose salt..
 Waves
breaking
on land
 salt particles go
into the
atmosphere.
How can we increase the
salinity in the beaker?
 Remove
water?.............How?
 What
natural processes remove water
from the oceans?

Evaporation
• Leaves salts behind
• At the beach, ocean water evaporates off your arm
and leaves salt on your skin

Freezing – same idea, ice is fresh water
Adding salt to Sea Water
 1.
erosion from continental rock
 2. volcanic eruptions (land and in the
ocean)
 3. from the atmosphere
 Which
has the quickest, biggest effect on
salinity?


Add/remove fresh water?
Add/remove salt?
It’s the fresh water!
 That

can happen quickly
Precipitation, etc
Also large volumes of water can be added and
removed quickly!
On the other hand, it takes a long time for more
salt to enter the oceans or to be removed
naturally!
Salinity of ocean has not
changed for millions of years
 How
can this be?
 Within
large areas of ocean, a lot of mixing
 Even
though there are changes with the
seasons,


The average salinity is steady
Additions/deposits are used by marine plants,
animals
How salty is the ocean?
Salinity variesopen ocean (far from land)
33-38 o/oo
 Salinity

EXTREMES
Baltic Sea 10 o/oo
Why?
Water here is
brackishfresh water
mixes with
sea water
More salinity extremes
 The
Red Sea 42 o/oo
Why?
 The


Red Sea is located in a tropical area
high evaporation
limited open ocean circulation.
 got
its name because of a type of algae
called Trichodesmium erythraeum which is
found in the sea. When these blooms of
algae die off, they appear to turn the bluegreen color of the ocean to a reddishbrown.
More….extremes!!!
 Inland
Bodies of Water

Great Salt Lake 280 o/oo

Dead Sea 333 o/oo
How about the salinity of the water
we drink?
 Tap
water .8 o/oo
 Good Tasting water .6 o/oo
 Bottled water .3 o/oo
 Distilled water zero!
What areas of the world have the
greatest variation in salinity?
______________ Areas

hot and rainy!
Tropical Areas
 ___
salinity – hotter so more evaporation
salinity – rainy season – increased
precipitation
 ___
_________Areas
Polar Areas
salinity –in winter –increased
freezing
 ____
salinity – in summer- increased
melting of snow
 ___
_________Areas
Coastal Areas
 ___
salinity – receives river/stream run-off
What does it matter that salinity changes or
that the ocean is salty at all?
 Does
the salinity affect the properties of
ocean water?
 Let’s review water’s properties





Surface tension
Phase change – freezing/boiling point
Heat capacity
Solubility
density
Density
 Demo:

Egg sinks in fresh water
Egg floats in salty water

What does this mean?

• Sink vs float is related to density of object
compared to the liquid it’s in

Salty water is MORE DENSE than fresh water
Phase change, freezing/boiling
 Why
do we sprinkle salt on icy roads?
 Salt melts the dangerous ice
 What does the salt do to the freezing point
of water?
 It reduces the freezing point
 In other words, water stays liquid at lower
temperatures, below 0C
Solubility
 That’s
why we have salts and stuff in the
ocean in the first place!!
 The
water itself dissolves SOOO many
substances
 It
all ends up in the oceans!
Surface tension
 Re-doing


the penny dropper lab?
Would salt have same effect as soap?
Scientists study surface tension of ocean
water
• Affects marine life
• Affects foaminess, mixing of air into ocean water
Heat capacity
 Addition
of salt does not affect water’s
heat capacity

Still high compared to other substances
Heat capacity of the huge volume of oceans
affects
movement of energy within the oceans
transfer of energy to air – land - oceans
Summary
Freezing Point
Boiling Point
Surface tension
Dissolving
power
Special
Behavior?
Heat capacity
Water ( H2O)
Importance to Ocean
0C
32 F
100C, 212 F
Highest of all liquids
Dissolves more
substances than any other
liquid
Floats as solid, becomes
less dense
Highest of all solids and
liquids except ammonia
Salts in ocean decrease
freezing point
Latent heat of
fusion
Highest except ammonia
Latent heat of
evaporation
Thermal
expansion
Highest of all substances
Temp of max density
decreases w/ increasing
salinity
Controls drop formation, etc.
Universal solvent; dissolves
many minerals, etc into
ocean
makes marine life possible
Prevents extreme ranges in
ocean temperature; heat
transfer by currents is large
Acts as thermostat at
freezing point because of
gain or loss of latent heat
Important in heat transfer to
the atmosphere
Freshwater and dilute
seawaters reach max density
at temp above freezing pt.
What effect does this all have on the
movement of ocean water?
 If
salty water is more dense…..
 If
cold water is more dense……
 Bill
Nye will help explain it!
 http://www.youtube.com/watch?v=w_8mw1HYFg