Slide 2 CH: 10 THE VITAL ROLE OF WATER ON EARTH ONE OF THE MOST
IMPORTANT INGREDIENTS FOR LIFE ! By: Ms. Thompson Slide 3 M IND M
AP I NTRODUCTION (KWL) P.358 Slide 4 W HAT 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. Thompsons travel photos ) Slide 5 D ISTRIBUTION 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 planets water is
fresh water. About 1% of that is available to us as fresh water.
Slide 6 Slide 7 FIND THE WATER... Slide 8 Slide 9 W ATER C YCLE W
ATER ON EARTH CAN BE FOUND IN 3 STATES - SOLID, LIQUID, AND GAS
Evaporation Condensation Precipitati on Slide 10 CATCHING CLOUDS IN
A BOTTLE EXPERIMENT http://www.youtube.com/watch?v=E8AvfXar9zs
Slide 11 E ND D ISCUSSION Q UESTIONS 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 your skin feel cold. Slide 12 MAGIC EGG
http://www.youtube.com/watch?v=f2H3xsTR7rg&feature=endscre
en&NR=1 When an egg is placed in fresh water, it doesnt
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. Slide 13 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. Slide 14 A REAS OF SALINITY
Salt deposits are left behind when evaporation and freezing occurs.
Equator : greater salt North and South Poles : greater salt Near
coastlines : less salt and diluted. Slide 15 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. Slide 16 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 -4C, which would be the new freezing/melting point.
The higher the concentration of salt, the lower the freezing point
drops. Slide 17 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. Slide 18 WHERE PEOPLE FLOAT LEISURELY DEAD SEA Slide 19
THE DEAD SEA Slide 20 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. Slide 21 DEAD SEA FACTS The extreme salinity of the water
excludes any animal or vegetable life. 8.6 times saltier than the
ocean and one of the worlds saltiest bodies of water. 417 meters
below sea level and lowest point of earth surface Slide 22
HOMEWORK: 10.2 CYU 1-11 Quiz is on Thursday, June 7 th. Slide 23
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. Slide 24 V EGETATION Slide 25 D EVELOPMENT Slide 26
Slide 27 C ITES LISTED
http://www.worsleyschool.net/science/files/saltan
dfreezing/ofwater.html
http://www.worsleyschool.net/science/files/saltan
dfreezing/ofwater.html Salt and the freezing point of water website
Slide 28 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.
