Transcript CH: 10 the vital role of water on earth

CH: 10
THE VITAL ROLE OF WATER ON EARTH – ONE
OF THE MOST IMPORTANT INGREDIENTS FOR
LIFE!
By: Ms. Thompson
MIND MAP INTRODUCTION (KWL)
P.358
WHAT YOU WILL LEARN ...
You will ...

Describe the distribution of water on Earth

Illustrate the water cycle
Explain how water shapes the landscapes
(stay tuned for Ms. Thompson’s travel photo’s  )

DISTRIBUTION OF WATER: 70% OF THE
SURFACE IS COVERED IN WATER

Use a pie graph to illustrate your understanding
of the distribution of water on Earth.
About 97%
of this water is
found in oceans

Only 3% of the
planet’s water is
“fresh water.”
About 1% of that
is available to us
as fresh water.
FIND THE WATER ...
FIND THE WATER ...
WATER CYCLE
WATER ON EARTH CAN BE FOUND IN 3 STATESSOLID, LIQUID, AND GAS
Condensation
Precipitati
on
Evaporation
CATCHING CLOUDS IN A BOTTLE
EXPERIMENT
http://www.youtube.com/watch?v=E8AvfXar9zs
END DISCUSSION QUESTIONS
Explain what would happen to the water cycle if the
oceans covered only 25% of the planet.
A lot less water would be evaporating; therefore, there
would be a lot less water moving through the cycle
(e.g.,
less precipitation to refill water supplies).
Explain why you feel cold after coming out of a warm
swimming pool on a hot, sunny day. (Hint: think of
water and the transfer of heat).
The water absorbs heat as it evaporates. It takes some
of
the heat from your body. As the water evaporates, it
makes
MAGIC EGG
http://www.youtube.com/watch?v=f2H3xsTR7rg&feature=endscre
en&NR=1
When an egg is placed in fresh water, it doesn’t displace
enough water, and is more dense than the water around it.
This creates unbalanced forces that send the egg to the
bottom of the cup.
Adding salt, causes the salt crystals to break down into
molecules and fill the space between the water molecules.
The solution now has more mass in the same volume which
changes the density of the water. When you add an egg it still
displaces the water, but now floats instead of sinking.
FRESH VS. SALT WATER


Sodium ions (Na +) and chloride ions (CI-) add
up to more than 85% of all the dissolved solids in
the ocean. When combined, they form a compound
call sodium chloride (NaCI)- SALT
Salt water differs from fresh water in several
major ways. The main one is in its salinity. This
characteristic gives ocean water a different
density, freezing point, and boiling point than
fresh water. Even though salt water and fresh
water are connected, they play different roles in
the water cycle.
AREAS OF SALINITY
Equator: greater salt
North and South Poles: greater
salt
Near coastlines: less salt and
diluted.
Salt deposits are left behind
when evaporation and freezing
occurs.
FREEZING POINT
Adding salt disrupts the equilibrium. The salt molecules
dissolve in the water, but do not attach easily to the solid
ice. There are fewer water molecules in the liquid because
some of the water has been replaced by salt. This means
that the number of water molecules able to be
captured by the ice (frozen) goes down, so the rate of
freezing goes down.
The rate of melting of the ice is unchanged by the presence
of the salt, so melting is now occurring faster than
freezing. So the ice eventually melts.
FREEZING POINT CONT.

In order to return the system to equilibrium, where the
number of molecules of water that are freezing is equal to
the number of ice molecules that are melting (this is the
freezing/melting point), we must lower the temperature
sufficiently to make the water molecules slow down
enough so that more can attach themselves to the
ice.

In our example, this point is reached at -4°C, which would
be the new freezing/melting point. The higher the
concentration of salt, the lower the freezing point drops.
BOILING POINT



Why do you add salt to water?
Aside from flavour, salt is added to water because it
increases the boiling point of the water, meaning your
water will have a higher temperature when you add the
pasta, so it will cook better. That's how it works in theory.
In reality, you would need to add 230 grams of table salt to
a liter of water just to raise the boiling point by 2° C. That
is much more salt than anyone would care to have in their
food.
WHERE PEOPLE FLOAT LEISURELY
DEAD SEA
THE DEAD SEA
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The Dead Sea is not really a sea, it is actually a land locked
lake between Israel and Jordon.
Since there is no outlet, the water in the Dead Sea
evaporates depositing the dissolved minerals, and since it
has no place to go, the dissolved salt minerals continue to
accumulate and be concentrated in the sea.
DEAD SEA FACTS
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
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The extreme salinity of the water excludes any
animal or vegetable life.
8.6 times saltier than the ocean and one of the
world’s saltiest bodies of water.
417 meters below sea level and lowest point of
earth surface
HOMEWORK: 10.2 CYU 1-11

Quiz is on Thursday, June 7th.
SOURCES OF FRESH WATER

Water makes its long journey back to the ocean, pulled along
by gravity. The flow is called run-off. The amount of run-off
can lead to the flooding of surrounding land and washing
away top soil from fields. Fast moving rivers can also be
harmful to aquatic animals.
Run-off is affected in the following ways
- Nature of the ground material: rock versus soil
- Amount of rain: saturated grounds= increase in run-off as
the ground can not absorb any more.
- Length of rain: saturation leads to run-off
- Slope of land: steeper land= faster run-off, and less
absorption
- Amount of vegetation: little vegetated areas will have a
greater amount of run-off
- Amount of development: developed areas will lead to an
increase in run-off because the water is channelled into storm
sewers.
VEGETATION
DEVELOPMENT
CITES LISTED
http://www.worsleyschool.net/science/files/saltan
dfreezing/ofwater.html
 Salt and the freezing point of water website

CAN ANY GOOD COME FROM A SEWER?
A microbe can be turned into a fuel cell. A microbial fuel cell could be
developed to clean water at waste treatment plants, and generate
modest amounts of electricity as a bonus.