09/04/2014
Stacking Water on a Penny
Properties of Water
Which liquid had more drops added
before falling off?
A Very Unique Substance
Stacking Water on a Penny
Paper Towel
Water is cohesive
Hydrogen bonding
between water
molecules made them
stick together so the
water didn’t fall off the
penny right away
Water taking up the spaces between fibres
in a material is called wicking.
Alcohol doesn’t
hydrogen bond as well
therefore probably
couldn’t put as many
drops on the penny
Paper Towel
Call Me Bond, Hydrogen
Bond
Water is cohesive AND adhesive
Water is attracted to other materials
that have positive and negative
charges… like paper towel
Did you get the paper clip to sit on the
surface? Was it floating?
Its ability to stick to other surfaces
allows water to be absorbed by paper
towel; other water molecules are then
pulled along too through cohesion
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09/04/2014
Call Me Bond, Hydrogen
Bond
The surface of water acts like a skin. The
surface tension is caused by a layer of
water molecules held tightly together by
hydrogen bonds. This is why water forms
drops, and why some insects can skate on
water’s surface.
How Can You Tell a Polar
Molecule From a Polar Bear?
How Can You Tell a Polar
Molecule From a Polar Bear?
Sugar (small molecules) dissolves in water
Was there a difference is the way the water
looked when you added the different
substances?
because both are polar
Makes a solution
Starch is many, many sugar molecules put
together in a chain
Starch does not dissolve well in water. It is
not very polar and the molecules are
relatively large
Makes a suspension
Sweating
Sweating
Water is constantly
Did your wrists feel different?
evaporating from the
surface of our skin
Evaporation requires
heat (to separate the
hydrogen bonds)
Prevents body from
overheating
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09/04/2014
Freezing Water
Freezing Water
While most other materials contract when they
solidify, water expands due to hydrogen bonds
Think of a mosh pit…
In ice, water molecules are actually farther apart
from each other than they are in liquid form
Soap Boat
Soap Boat
Did you get the boat to zip along the surface
of the water?
Soap disrupts hydrogen bonds between
water molecules
Disrupting hydrogen bonds breaks surface
tension at the back of the boat
Surface tension at the front (unaffected by
the soap) pulls the boat forward
Does Diameter Matter?
Does Diameter Matter?
Example of capillary action
Water will rise in narrower tubes due
to adhesion to the tube and cohesion
with other water molecules
Adhesion causes some water
molecules to “climb” the tube, and the
others are pulled along by cohesion.
Where does this happen in the real
world?
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09/04/2014
Capillary Action
Plants!
Responsible for
water getting from
soil to the leaves of
the tallest trees
Pumping water
could not get
water to the top
(past 10 m)
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