Properties of Water
Polarity & Hydrogen Bonding
Polar Molecule
Sometimes when
atoms form covalent
bonds, they do not
share electrons equally
• One of the atoms in the
bonds “hogs” the
negatively charged
electrons and becomes
the “negative” side of
the molecule
•
If
electrons
are around
you, you
become
negative!
Polar Molecules Continued
In
other words, one side of the
molecule is “positive” and the
other side of the SAME molecule
is “negative” side
Polar Molecule – H20
For
a water molecule, the
negative side is the
Oxygen and the positive
side in the Hydrogen (the
“ears”)
Polar Molecule – H20
Non-Polar Molecule
A
non-polar molecule is
one that the electrons are
distributed more equally
 There is NO “negative”
or “positive” side
Hydrogen Bonding
 The “positive” side of one
water molecule is
attracted to the “negative”
side of another water
molecule
 These bonds are weak
 Attract water molecules
to each other like
magnets, no electrons are
shared or transferred
Hydrogen Bonding of Water
Water: Covalent Bonds
Vs. Hydrogen Bonds
 Covalent
bonds
form
molecules
 Hydrogen
bonds
form
between
molecules
Water Properties Analysis
1.
Summarize what you believe to be the
reason all these phenomena occur. Use
these to guide your summaries1.
2.
3.
The paperclip floats on water. What is
happening here?
Why did the pepper shoot to the sides and
sink when you added soap to the water.
What’s happening here?
Some people can get 60 drops on Mr.
Lincoln. What’s happening here?
Cohesion
 The tendency
of “like”
molecules to
be attracted
to one
another
 Molecules
“stick” to
each other
Surface Tension –
A Special Type of Cohesion
 Surface
tension due to cohesion of water
 Cohesion of the top layer of the water
Adhesion
 The
sticking
together of
molecules of
different
substances
 Examples: water
adhering to paper,
plastic, or glass
Capillary Action
Capillary Action
 Surface
tension/cohesion and adhesion
 Adhesion of water to the walls of a the
stem cause an upward force on the liquid
at the edges and result in a meniscus
which turns upward
 The surface tension acts to hold the
surface intact, so instead of just the edges
moving upward, the whole liquid surface is
dragged upward (cohesion).
ALL OF WATER’S SPECIAL
PROPERTIES COME
FROM THE FACT THAT
HYDROGEN ‘BONDS’ THAT ATTRACTIONS
BETWEEN THE NEGATIVE
AND POSITIVE SIDES OF
WATER MOLECULES’ –
EXIST 