The document discusses the molecular structure and properties of water. It notes that water is a polar molecule, with slightly positive and negative ends due to the uneven sharing of electrons between the oxygen and hydrogen atoms. This polarity allows water molecules to form hydrogen bonds with each other and other polar substances. The hydrogen bonding between water molecules gives water many unique properties that help to moderate Earth's temperature and make it suitable for life, including its high heat capacity, ability to change state from solid to liquid to gas, and ability to dissolve many other substances.

2.  SC.912.L.18.12 Discuss the special
properties of water that contribute to Earth's
suitability as an environment for life:
cohesive behavior, ability to moderate
temperature, expansion upon freezing, and
versatility as a solvent.

3. It is a very stable.
Polar molecule: It has a “+” and
“–” end. This polarity has a large
impact on the properties of water.

4. <<The molecular structure of
water, showing its polarity.
Oxygen and Hydrogen are
bonded together by sharing
electrons, but the oxygen atom
“pulls” the shared e- closer to
it, creating negative and
positive sides of the water
molecule. This polarity
accounts for many of the
properties of water>>

5.  Because of the electron arrangements in the water
molecule, a polarity results that allows water to
form hydrogen bonds with one another and other
polar substances.
Polar substances are HYDROPHILIC (water-loving)
Nonpolar ones are HYDROPHOBIC (water-dreading)
and are repelled by water.

6.  Life began in water
 About ¾ of Earth is covered
in water.
 All living things need water
 Your cells are approximately
70-95% water
 Water is the “universal
solvent” because it can
dissolve many things!

8. #1. Hydrogen Bonding: caused by
the oxygen end (-) attracted to
the hydrogen end (+) of another
H2O.
Weak bond

9. H2O sticks to itself causing surface
tension

10.  Is defined as the property of the
surface of a liquid that allows it
to resist an external force, due
to the cohesive nature of the
water molecules.

11. H2O sticks to other material

12. #4 Capillary action: helps
H2O rise against gravity from
roots to leaves in plants.
#5 Density: ice is less dense
than water causing it to
float.

13. The floating ice slows the
freezing process by insulating
the water underneath, which
contributes to the moderate
temperatures on earth.
The layer of ice prevents many
lakes from freezing solid,
allowing fish and other
organisms to survive under the
ice.

14. water ice

15. Water is considered an universal solvent
because it can dissolve many substances.
 Ions and hydrophilic solutes dissolve easily
in water.
The solvent properties of water are greatest with respect to polar
molecules because "spheres of hydration" are formed around the
solute molecules.

16.  It means that water takes longer
to heat up and to cool down.
 Water in a pond will stay
relatively the same from day to
night.
 Bodies of water near cities take
longer to heat up and longer to
cool down than do land masses
 These cities will tend to have less
extreme temperatures than
inland cities.
This property of water is one
reason why states on the coast and
in the center of the United States
can differ so much in temperature
patterns. A Midwest state, such as
Nebraska, will have colder winters
and hotter summers than Oregon,
which has a higher latitude but has
the Pacific Ocean nearby.

17.  Coolant
 Retains heat (Good insulator)
 Resists sharp changes in temp.
 Expands when it freezes & floats.
 Dissolves many things (Universal solvent)
 Key to biological processes
 Maintains homeostasis.
<<Homeostasis is the ability of living things to maintain a steady state of balance
despite changing conditions. Ex.: Steady internal temperature in warm blooded
animals no matter the temperature of their environment.

18. Solutions:
Solute: substance
that is being
dissolved (salt)
Solvent: dissolves
the solute (ex.
Water)
Suspensions:
Substances that
separate into tiny
pieces but don’t
dissolve.

19. Indicates concentration of H+
The lower the pH #, then the
more H+
pH means “potential of the H+ “
0-6 Acid, 7 = neutral, 8-14=base

20. Strong Acids = pH of 0 to 3

21. Strong Bases have a pH of 11 to 14
Contain fewer H+ ions

22. Water molecule dissociates
(separate) into H+ and OH- in
solutions.
H
O H+ + OH
2
-
Hydrogen Ion
Acid
Hydroxide
Ion Base

23.  A salt is an ionic compound formed when an
acid reacts with a base.
Example: NaOH +HCl ——> NaCl +H2O.
 Many salts dissolve into ions that serve key
functions in cells.
 Ex. Nerve function is dependent on Na+, K+,
Ca+ ions.

24. pH can affect chemical reactions
necessary to support life.
Buffers:
Produced by body
 used to prevent sharp, sudden
changes in pH (neutralization).
Maintain homeostasis.

25. Q1: What is water? How would you
best describe what water is in
chemical terms?
Q2: Explain the physical phases of
water.
Q3: Water is a polar molecule. What
does that mean?

26. ANY QUESTIONS?