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Water : A Molecule Essential for Life. Thoughts to Ponder……. Why can’t we survive more than a week without water? How do insects walk on water? How does water rise up 300 feet from the roots of a redwood tree? Why does water take so long to boil? Why do oil and water not mix? .

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Presentation Transcript
thoughts to ponder
Thoughts to Ponder……
  • Why can’t we survive more than a week without water?
  • How do insects walk on water?
  • How does water rise up 300 feet from the roots of a redwood tree?
  • Why does water take so long to boil?
  • Why do oil and water not mix?
life is dependent on water
Life is dependent on Water

Why?

Source: http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-earth.html

water has unique properties that arise from its structure
Water has unique properties that arise from its structure

http://www.lenntech.com/images/Water%20molecule.jpg

water is a polar molecule
Water is a Polar Molecule

http://rst.gsfc.nasa.gov/Sect20/water_molecules_con_c_la_784.jpg

hydrogen bond formation
Hydrogen Bond Formation

http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page3.html

strength in numbers
Strength in Numbers!
  • Water molecules, with the hydrogen bonds represented by the dotted lines

Source: www.personal.psu.edu/.../ bonddiagram.gif.

properties of water due to hydrogen bonding
Properties of Water due to Hydrogen Bonding
  • Cohesion / Surface Tension
  • Adhesion
  • High heat capacity
  • Solvent of polar and ionic compounds; creates a hydrophobic effect on nonpolar substances
  • Density of ice less than liquid water
slide9

Cohesion

Water molecules

“stick” together

Creates surface

tension

slide10

Adhesion

Water molecules are attracted to different molecules

Capillarity – a special case that results from the relative attraction of the molecules for each other and the solid surface it’s in contact with

slide11

High Heat capacity

A great deal of E is

needed to break

hydrogen bonds

Temperature changes

are minimized

http://i.telegraph.co.uk/multimedia/archive/01549/perspiration_1549996c.jpg

specific heat
Specific Heat

Specific heat – amount of heat needed to change the temperature of 1g. of a substance 1degree Celsius.

High specific heat allows water to act as a heat sink. Water will retain its temperature after absorbing large amounts of heat, and retain its temperature after losing equally large amounts of heat.

slide13

Universal Solvent

The “Great Dissolver”

Water dissolves polar and ionic substances due to its ability to form hydrogen bonds

slide14

Hydrophobic effect on Nonpolarsubstances

Water cannot dissolve nonpolar substances.

Hydrophobic effect- results when water molecules interact with each other and exclude nonpolar substances

Causes molecules like DNA to fold into their specific shapes

slide15

Density

Ice is less dense then water - it floats

Ponds, lakes, streams, ocean surfaces freeze from the top down.

Aquatic organisms receive insulating protection

slide16

Vaporization

Large amounts of heat E are needed to disrupt hydrogen bonds.

Heat helps water to begin evaporating.

Sweat evaporates using the heat from your body…cools your body down!

slide18

Imagine how life on Earth would change if hydrogen bonding between water

molecules no longer could form