1. 1

2. < 0o C - ice; 0o C - 100o C – liquid; > 100o C - steam
2

3. 3

4. • Water consists of an Water is a Polar Molecule
oxygen atom bound to -has oppositely charged
two hydrogen atoms
by two single covalent ends
bonds.
– Oxygen has
unpaired & paired
electrons which
gives it a slightly
negative charge
while Hydrogen has
no unpaired
electrons and shares
all others with
Oxygen
– Leaves molecule
with positively and
negative charged
ends 4

5. Water molecules form Hydrogen
bonds
slightly positive
charge
hydrogen bond
between (+) and (-)
areas of different
water molecules
slightly negative
5
charge 5

6. 6
6

7. Water’s Properties
• Cohesion
• Adhesion
• Capillarity
• High Specific Heat
• High Heat of Vaporization
• Density
• Solvent
• Transparent
7

8. Adhesion
– Adhesion refers
to attraction to
other
substances.
 Water is
adhesive to
any substance
with which it
can form
hydrogen
bonds.
8

9. Cohesion
• Water clings to polar
molecules through
hydrogen bonding
– Cohesion refers to
attraction to other
water molecules.
 responsible for
surface tension
 a measure of the
force necessary to
stretch or break
the surface of a
liquid
9

10. 10

11. 11

12. water evaporates from
Capillary action leaves = transpiration
adhesion,
cohesion and
capillary action
water taken up by
roots
12

13. •trees have specialized structures to transport water:
xylem and phloem “plumbing”
• water molecules are “dragged” from the roots to the
top of the tree by capillary action and cohesion:
hydrogen bonds help water molecules to each other 13

14. High Specific Heat
– High specific heat
 Amount of heat that must be
absorbed or expended to change
the temperature of 1g of a
substance 1o C.
14

15. Impact of water’s high specific heat ranges from
the level of the whole environment of Earth to that
of individual organisms.
• A large body of water can absorb a The Earth is over
large amount of heat from the sun in
75% water!
daytime and during the summer, while
warming only a few degrees.
• At night and during the winter, the
warm water will warm cooler air.
• Therefore, ocean temperatures and
coastal land areas have more stable
temperatures than inland areas.
• The water that dominates the
composition of biological organisms
moderates changes in temperature
better than if composed of a liquid
15
with a lower specific heat.

16. High Heat of Vaporization
– High heat of vaporization
 Amount of energy required to change
1g of liquid water into a gas (586
calories).
 large number of hydrogen bonds
broken when heat energy is
applied
16

17. • As a liquid evaporates, the
surface of the liquid that remains
behind cools - Evaporative
cooling.
• Evaporative cooling moderates
temperature in lakes and ponds
and prevents terrestrial
organisms from overheating.
• Evaporation of water from the
leaves of plants or the skin of
animals removes excess heat.
17

18. “Universal” Solvent
• A liquid that is a completely homogeneous
mixture of two or more substances is called a
solution.
– A sugar cube in a glass of water will eventually
dissolve to form a uniform mixture of sugar
and water.
• The dissolving agent is the solvent and the
substance that is dissolved is the solute.
– water is the solvent and sugar the solute.
• In an aqueous solution, water is the solvent.
• Water is not really a universal solvent, but it is
very versatile because of the polarity of water
molecules.
18

19. • Water is an effective
solvent as it can form
hydrogen bonds.
– Water clings to
polar molecules
causing them to be
soluble in water.
 Hydrophilic -
attracted to
water
– Water tends to
exclude nonpolar
molecules.
 Hydrophobic -
repelled by water 19

20. • Water transports molecules dissolved in it
– Blood, a water-based solution, transports
molecules of nutrients and wastes
organisms
– Nutrients dissolved in water get
transported through plants
– Unicellular organisms that live in water
absorb needed dissolved substances
20

21. Solid water (ice) is less dense than liquid
• Ice is less dense than water: the molecules are
spread out to their maximum distance
Density = mass/volume
same mass
but a larger
volume 21

22. Oceans and lakes don’t freeze solid
because ice floats
 water expands as it
solidifies
 water reaches
maximum density at
4-degrees C
 water freezes from
the top down
 organisms can still
live in the water
underneath the ice
during winter 22

23. Water is Transparent
• The fact that water is clear allows light to
pass through it
– Aquatic plants can receive sunlight
– Light can pass through the eyeball to
receptor cells in the back
23

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