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Water
Amazing Stuff!
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1. Water is a Polar Molecule!
• Like the earth has
poles, so a water
molecule has “poles”.
• It has ____________
and negative poles.
This is called polarity.
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Why does water form?
In a water molecule two
hydrogen atoms form single
covalent bonds with an oxygen
atom.
The bonds are formed to
create a “stable” molecule.
Oxygen needs 2 more
electrons to be stable.
Hydrogen needs 1
more electron to be
stable.
*Gives water more
structure than other
liquids*
2. Water is the “Universal Solvent”
• Because water molecules
have a positive side and a
negative side, any atom with
a positive or negative charge
will be attracted to it. In fact,
water is a universal solvent.
This means water can
dissolve other chemicals to
form a ________________.
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3. Adhesion: Water Sticks to Things!
• The polarity of water
causes its positive side to
stick to ______________
things and its negative
side stick to positive
things (Opposites
___________________.
Water is attracted to
other charged molecules.
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4. Cohesion: Water sticks to itself!
• Because water is polar,
molecules of water are
attracted to other
_________________
molecules! This makes
water stick together.
• Soap stops the
cohesion!
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5. Cohesion Causes Surface Tension
Because water is cohesive,
water molecules make a
_____________ on the
top of water. Thus water
bugs and paper clips can
float on water even
though they should (and
will!) sink.
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Surface tension makes paper clips
float!
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But surface tension is different from
buoyancy… which is described by
Archimede’s Principle.
Buoyancy is the
___________ force
that keeps things
afloat. The net upward
force is equal to the
amount of the weight
of water displaced by
the object.
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6. Water defies gravity! (sometimes)
• Because water is
_________________
(sticky), it can climb a
paper towel or the
stem of a plant. This is
called capillary action.
• Plants rely on this
quality to get water to
their leaves.
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Only water is found _____________
as a SOLID, LIQUID, and GAS on Earth!
While all elements will
change states, only
some compounds will.
Water changes state
within a very narrow
range, allowing it to
snow, rain, and
evaporate… all on the
same day!
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7. Ice is less dense
than liquid water!
Solids are usually more
dense than liquids because
their molecules are closer
together. Liquids are more
dense than gases… but not
for water. Water forms a
___________________
structure which makes ice
(solid water) less dense than
liquid water.
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Solid
Organized
Liquid
Disorganized
Gas
Free Floating
Water “grows”
when freezing:
1. This causes potholes on road
and weathering of rocks.
2. It prevents water from freezing from the bottom up.
Ice forms on the surface first—the freezing of the
water releases heat to the water below creating
insulation. This makes transitions between seasons
less abrupt.
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8. Water holds onto
Heat and won’t let it go!
• The amount of heat that a
substance can “hold” is called
Heat Capacity.
• Three-fourths of the earth is
covered by water. The water
serves as a large heat “sink” (or
bank) responsible for:
1. Prevention of temperature fluctuations that are outside the
range suitable for life.
2. Coastal (Beach) areas having a mild climate
3. A more stable marine (water) environment
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7. Water Moderates Temperatures on
Earth
Water stabilizes air temperatures by absorbing heat from warmer air and releasing
heat to cooler air. Water can absorb or release relatively large amounts of heat with
only a slight change in its own temperature.
Celsius
Fahrenheit
100oC
Water Boils
212oF
37oC
Human Body Temp
98.6oF
23oC
Room Temp
72oF
0oC
Water Freezes
32oF
-273oC
Absolute Zero
-459oF
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Sources:
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http://fizyka.phys.put.poznan.pl/~pieransk/Physics%20Around%20Us/Surface%20tension%2002.jpg
http://www.polytechconsultants.com/images/surftens.jpg
http://quest.nasa.gov/space/teachers/microgravity/image/66.gif
http://gallery.hd.org/_tn/std/natural-science/_more2006/_more01/meniscus-on-water-surface-tension-supporting-steelpaperclip-in-drinking-glass-tumbler-beaker-6-AJHD.jpg
http://www.diracdelta.co.uk/science/source/a/r/archimedes%20principle/image004.jpg
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Review for Quiz
SOLUTE
SOLVENT
SOLUBILITY
Solubility – ability of Liquid to Dissolve Solid
Miscibility