The Extraordinary Properties
of Water
Where there’s life……there’s water!!!
Water
• A water molecule (H2O), is made up
of three atoms --- one oxygen and
H
two hydrogen.
O
H
Water is Polar
• Having positively and
negatively charged
sides.
• The oxygen end “acts”
negative
• The hydrogen end
“acts” positive
•The term “POLARITY” means the molecule has an
uneven distribution of electrons
What are
the
Properties
of Water?
The Universal Solvent
Properties of Water
• Cohesion
• Adhesion
Cohesion – “Co” means
“With or Together”
• Attraction between similar substances
( why water is attracted to itself)
• Due to Hydrogen bonds
Cohesion
• Produces a surface film on water called
• surface tension that allows insects to
walk on water and leaves to float.
• Surface Tension - a measure of the
strength of water’s surface
Adhesion
• Attraction of H2O to
different substances.
• Due to hydrogen
bonds
• Ex:paper towels soak
up water, meniscus in
a graduated cylinder.
Adhesion Also Causes Water to …
Form spheres &
hold onto plant
leaves
Attach to a
silken spider
web
Both Cohesion and Adhesion
Causes
Capillary Action
Capillary action gives
water the ability to “climb”
structures
High Specific Heat
• Amount of heat needed to raise the
temp of 1g of H2O 1° C.
• Water has a very HIGH specific
heat.
• Crucial in temperature stability in
living systems to maintain
homeostasis.
High Heat of Vaporization
• Amount of energy to convert 1g
water from a liquid to a gas.
• Called vaporization or evaporation
High Heat of Vaporization
• As water evaporates, it removes a
lot of heat with it (cooling effect).
• Ex: evaporation of sweat from the
body
Water is Less Dense as a Solid
• Ice is less dense
as a solid than as
a liquid –
therefore it floats
• Other materials
contract when
they solidify, but
water expands.
Water is Less Dense as a Solid
•Which is ice and which is water?
Water
Ice
Water is a Solvent
• Solvent: any substance that dissolves
other substances.
• Water is a very versatile solvent
• Other polar substances dissolve easily in
water.
Solution
• Mixture of 2 or more substances.
• Evenly distributed
+
+
MIXTURE
Materials composed of 2 or more elements
or compounds that are physically mixed
but not chemically combined.
Hydrophilic (“water-loving” )
• substances that dissolve easily in
water are known as water soluble.
• Examples: salts, polar compounds
(sugar).
Hydrophobic (means “water-fearing”)
• substances that do not dissolve
easily in water separate and are
known as insoluble..
• Examples: oils, fats, lipids, waxes.
• These substances are non-polar.
Acids, Bases and pH
One water molecule in 550 million
naturally dissociates into a
Hydrogen Ion (H+) and a Hydroxide
Ion (OH-)
H2O 
H+
Hydrogen Ion
Acid
+ OH
-
Hydroxide Ion
Base
The pH Scale
• Ranges from 0 to 14
• Measures strength of
an acid or base by
concentration of H+
ions and OH- ions.
• Pure Water has a pH
level of 7.
• Substance
that contains
high
concentration
of H+ ions.
• pH of acids
range from 06
• Strong acids
have a pH of
1-3
Acids
• Substance that have
lower
concentrations of
H+ ions thus
increasing OH- ions
• Bases have a pH
value range from 8
to 14.
• Strong Bases have a
pH of 11 to 14
Bases
Buffers
• Weak acids or bases that react with
strong acids or bases to prevent sharp,
sudden changes in pH (neutralization).
• Produced naturally by the body to
maintain homeostasis
Weak Acid
Weak Base