The Water Planet The Blue Pl anet •Most of the Earth’s surface is covered by water (71%) •97% of this water is salt water •3% of this water is fresh water
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The Water Planet The Blue Planet Most of the Earth’s surface is covered by water (71%) 97% of this water is salt water 3% of this water is fresh water.
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Slide 1
The Water Planet The Blue Planet Most of the Earths surface is
covered by water (71%) 97% of this water is salt water 3% of this
water is fresh water
Slide 2
Theres just not as much as wed like, and not all the sources
are accessible. Plenty of water exists at the poles, for instance,
but its frozen and located far from population centers. We can
condense water vapor from the atmosphere by artificial means, but
only at an astounding cost. Most of the fresh water we rely on
comes from underground aquifers and rivers. Human primarily need
fresh water
Slide 3
Slide 4
Why study water? as the human population increases, the demand
for fresh water will increase. Most of the habitable area of Earth
is water
Slide 5
Waters unique properties Water is a POLAR molecule
Slide 6
Unique properties of water Waters polarity allows it to bond to
other water molecules Notice the hydrogen bonds resulting from the
slightly positively charged hydrogen part of one water molecule
attracted to the slightly negatively charged oxygen part of another
water molecule.
Slide 7
Effects of hydrogen bonds Liquid Water. The most important
characteristic of hydrogen bonds is their ability to make water a
liquid at room temperature. Cohesion: Because hydrogen bonds
attract water molecules to each other, water molecules tend to
stick together. Adhesion: Water also sticks to other materials due
to its polar nature. This is called adhesion. Capillary Action:
Combination of cohesion and adhesion example: water moves up
trees
Slide 8
Effects of hydrogen bonds Surface Tension cohesion at surface
of water skin like surface Important for small organisms like this
water strider or plankton
Slide 9
Why does ice float? Effects of hydrogen bonds
Slide 10
Ice is less dense than water because the molecules form a
lattice structure as the substance freezes. The small iceberg in
the sea demonstrates this property as the it slowly melts and
floats along the surface.
Slide 11
This "open lattice structure" of water molecules is shown for
solid ice. Open space between the molecules illustrates why ice is
less dense than liquid water.
Slide 12
3 Density layers of the Ocean Surface zone - Temperature
relatively constant here because waves and currents continually mix
the water 2% of ocean Thermocline- - separates warm surface water
from cool deep waters rapid temperature changes with depth. 18%
ocean Below the thermocline is the deep zone layer. This layer is
cold, dense. 80% ocean
Slide 13
a. If ice sank, the ocean would be entirely frozenor at least
substantially coolerbecause water would not be able to retain as
much heat. b. The Earths climate would be substantially
colderperhaps too cold for life at all. c. Ice allows animals like
polar bears to float and hunt for food and build dens. It is a
critical part of their habitat
Slide 14
Seawater is a solution, just like tea coffee or lemonade!
Solvent = Water is called the universal solvent as many substances
dissolve in it. Solute = the substance that dissolves Ex: salt,
sugar, Solution = a uniform mixture of two or more substances Ex:
tea, coffee, lemonade, Solubility of a substance is its ability to
be dissolved in a solvent Saturated = when no more solute will
dissolve in the solvent, it is saturated.
Slide 15
Effects of hydrogen bonds Water is a great solvent
Slide 16
Salinity the measure of the amount of dissolved salts in water
Salinity includes the total quantity or concentration of all
dissolved salts. This is the sodium chloride and everything
else.
Slide 17
Measure Salinity? How well does water conduct electricity Ratio
of the conductivity of the sample compared to the conductivity of a
standard solution of potassium chloride (KCl).
Slide 18
Salinity Salinity is expressed in parts per thousand because
even very small variations are significant. The oceans average
salinity is 35 The abbreviation stands for parts per thousand, so
35 means 35 parts per thousand. Note: To convert parts per thousand
into percent, you divide by 10, so that 35 = 3.5%
Slide 19
Why is the Sea Salty? How does salt get into the sea? From
land, carried by streams and rivers through erosion From inside the
earth through volcanos and hydrothermal vents on the seafloor From
the atmosphere particles are carried by wind and deposited into the
ocean. Does Salt ever leave the ocean? Salt remains in the ocean
unless they become incorporated into the sediments and rocks on the
seafloor.
Slide 20
Salinity varies within ocean Surface ocean salinity varies with
the season and with the weather, particularly with rainfall and
evaporation : Rainfall decreases salinity by adding fresh water.
Evaporation increases salinity by removing fresh water. Freshwater
input from rivers lowers salinity.
Slide 21
The solubility varies with temperature of the water. As
temperature increases, so does its solubility. More evaporation in
tropical regions results in more evaporation of water vapor,
therefore increasing the salinity at the surface. Most areas of
high salinity found near equator. Most areas of low salinity found
near poles.
Slide 22
Slide 23
Salinity in the ocean varies Brackish water = mixture of fresh
and salt water Has a salinity somewhere between salt water and
fresh water. Typically found in estuaries, areas where rivers meet
the sea. Salinities in estuaries vary from 1 40 psu. Varies with
the temperature and season.
Slide 24
What is an estuary? An area where fresh water and seawater mix
Organisms which live there must be able to live in a variety of
salinity levels, depending on the amount of rain and evaporation
Example: Indian River lagoon
Slide 25
Density Density = mass / volume D=m/ v Vol. is usually
expressed in g/cm 3 for a solid and g / mL for liquids.
Slide 26
Slide 27
In what three states of matter does water exist ? The process
of changing from one state of matter to another is called a phase
change.
Slide 28
What did we learn about the freezing point of sea water
compared to the freezing point of fresh water? Fresh water freezes
at 0* Celsius Seawater typically freezes at -2* Celsius
Slide 29
Because dry ice is way colder than regular ice! It changes
directly from a solid to a gas when heated above -78*C. This
process is known as sublimation. What is dry ice? Solid CO 2
Slide 30
How does the boiling point of fresh water compare to the
boiling point of sea water? Fresh water boils at 100* C Sea water
boils at a higher temp., typically 102* C or more.
Slide 31
Phase change diagram showing water's state of matter
Slide 32
What is buoyancy? The principle of buoyancy states that an
object immersed in a gas or liquid is buoyed up by a force equal to
the weight of the gas or liquid displaced. The upward force that
keeps materials afloat in fluids.
Slide 33
The buoyant force is what pushes upward on objects in water.
This force opposes weight, the force that pulls objects downward,
toward the center of the Earth.
Slide 34
Neutral buoyancy is the ability to maintain position is the
water column; not floating or sinking Example: a jellyfish
Slide 35
Osmosis process of water moving across a membrane from areas of
high water concentration to areas of low water concentration.
Slide 36
Osmoregulation = balancing the amount of water that enters or
leaves cells Necessary because shrinking or swelling of cells can
be dangerous for animals. Sea turtles drink sea water but close to
their eyes they have special organs called salt glands like your
tear ducts that constantly pump the salt out of their body!
Slide 37
Osmoregulation Fresh water fish Marine fish Freshwater fish
experience the opposite problem. If it was not for osmoregulation,
their cells would be constantly taking on water, like your skin
cells in the bath. Instead, freshwater fish produce a lot of dilute
urine, which gets rid of excess water in their systems. Because of
the process of osmosis, many bony fish in the ocean lose water to
their highly saline environment. In order to stay hydrated, they
drink a lot of seawater and secrete the salts through specialized
cells and excrete concentrated urine.