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.

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

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?

• 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

Surface Tension

• Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton.

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.