The extraordinary properties of Water

• Cohesion• Adhesion

• High Specific Heat

• High Heat of Vaporization

• Less Dense as a Solid

http://www.realeyz.com/photo/macro/photos/leaf_drops.jpg

CohesionCohesion is the property of water that causes it to be attracted to itself.

•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.

Surface Tension

Water strider

Capillarity Water molecules will “tow”

each other along when in a thin glass tube.

AdhesionAttraction between molecules of different substances

Ex: glass and water

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.

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

Did you ever wonder: How does water move from roots to leaves when a tree doesn’t have a heart to pump the water?

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 ScaleMeasurement of the concentration of hydrogen ions

Acid:High concentration of [H+](or hydronium ion);low conc. of [OH-]

Base:High [OH-](a.k.a. hydroxide ion);low [H+]

pH = -log [H+]

Stomach Acid = pH 2

Homeostasis

• Steady state

• Constant physiological condition of cells, organisms global ecosystems– a. Makes a good insulator– b. Resists temperature change– c. Universal solvent– d. 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.phy-astr.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