The extraordinary properties
of Water
• Cohesion
•
•
•
•
Adhesion
High Specific Heat
High Heat of Vaporization
Less Dense as a Solid
Cohesion
Cohesion is the property of water that causes it to be
attracted to itself.
http://www.realeyz.com/photo/macro/photos/leaf_drops.jpg
Surface Tension
•Surface tension measures the strength of water
molecules attracting to one another.
•This property allows insects to walk on the
surface of water and the creation of waves.
Water strider
Adhesion
Attraction between molecules of different
substances
Ex: glass and water
Capillarity Water molecules will “tow” each
other along when in a thin glass tube.
http://staff.um.edu.mt/rlib1/sm/wpe32.jpg
Surface Tension
• Water will make
hydrogen bonds
with other surfaces
such as glass, soil,
plant tissues, and
cotton.
Did you ever wonder: How does water
move from roots to leaves when a tree
doesn’t have a heart to pump the
water?
Cohesion-Adhesion
Theory
-As water evaporates from leaves,
it tugs on the water molecules
below
-Cohesion and adhesion pull water
up and replace missing water
molecules
-Water enters the roots by osmosis
www.emc.maricopa.edu/.../BioBookPLANTHORM.html
High Specific Heat
•Water resists temperature change, both for
heating and cooling.
•Water can absorb or release
large amounts of heat energy
with little change in actual
temperature.
High Heat of Vaporization
• In order for water to evaporate, hydrogen bonds
must be broken. As water evaporates, it removes a
lot of heat with it.
•Thus, the heat of vaporization refers to the
amount of energy required to convert water from a
liquid to a gas.
High Heat of Vaporization
•
Water Vapor Imagery
Courtesty of http://www.goes.noaa.gov/
Water is Less Dense as a Solid
•Which is ice and which is water?
Density of Ice
•Most solids are more
dense than their liquids
•This makes solids sink
•Ice is less dense than
liquid water
•Due to H-Bonds
•Important to life
because bodies of water
freeze top down
•Allows life to survive
below
http://shiftingbaselines.org/blog/images/Iceberg.jpg
Density of water
• If density of object is = to or < than water it
will float.
• Displacement is how steel ships can float
even though the density is greater.
• Density of pure water is 1.0
• Density of pure ice is 0.92.
• Density of sea water is 1.03.
• Icebergs are made of pure water will float with
a ratio of more ice above the surface than that
of an ice cube.
pH Scale
Measurement of the
concentration of hydrogen ions
Acid:
High concentration of [H+]
(or hydronium ion);
low conc. of [OH-]
Base:
High [OH-]
Stomach Acid = pH
(a.k.a. hydroxide ion);
low [H+]
pH = -log [H+]
2
Homeostasis
• Steady state
• Constant physiological
condition of cells, organisms
global ecosystems
– a.
– b.
– c.
– d.
Makes a good insulator
Resists temperature change
Universal solvent
Coolant
• Hot water is a better cleaning agent
because the lower surface tension makes
it a better "wetting agent" to get into pores
and fissures rather than bridging them with
surface tension.
• Soaps and detergents further lower the
surface tension.
Bibliography
• What are some examples of cohesion and adhesion? Asked by
LeRoy. http://www.physlink.com/Education/AskExperts/ae543.cfm.
Viewed online on November 14, 2007.
• Surface Tension of Water. http://hyperphysics.phyastr.gsu.edu/hbase/surten.html#c3. Viewed online on November 14,
2007.
• Water.
http://courseweb.hopkins.k12.mn.us/file.php/432/Biochem/biochem_
lectures_ppt/water.ppt#256,1,Slide 1
• Extroadinary Properties of Water.
http://genbio.biol.vt.edu/tapages/russell/water.ppt