Properties of Water

1
Properties of Water
2
W-A-T-E-R

• More than 70 of the earths surface is covered
  with water (H20)

3
WATER

• Atomic Structure 2 hydrogen atoms bonded to 1
  oxygen atom
• The hydrogen side slightly positive ()
• The oxygen side slightly negative (-)

4
WATER A Polar Molecule

• Water Molecules are POLAR! WHY?
• Because there is an uneven distribution of
  electrons between the oxygen and hydrogen atoms
• ? Results in water molecules being attracted to
  each other, forming bonds?called Hydrogen bonds

5
Why is Polarity So Important?

• It allows water to dissolve many substances
  including other polar molecules and ionic
  compounds

6
Water Molecules are Held Together by Hydrogen
Bonds

• Hydrogen bonds are weak bond between a hydrogen
  atom in one molecule and a negatively charged
  region of another molecule
• Hydrogen bonds are strong enough to cause water
  to cling to itself and other substances

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Hydrogen Bonding
8
Hydrogen Bonding

• http//www.northland.cc.mn.us/biology/Biology1111/
  animations/hydrogenbonds.html
• Animation of water binding through H bonds

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Two properties of water result from Hydrogen
Bonding

• Cohesion- attraction of molecules of the same
  substance (ex. water attracted to water)
• gt Surface tension- cohesion of water
  molecules at the surface of a body of
  water ex. bug walking on water

10
Two properties of water result from Hydrogen
Bonding

• Adhesion attraction between molecules of
  different substances
• (ex. Water molecules attracted to a glass)
• gt Capillary Action- the adhesion
  of water molecules another
  substance moving up against gravity

11
How is Hydrogen Bonding related to Temperature?

• Hydrogen bonding makes water able to absorb a lot
  of heat before it gets hot and changes
  temperature because hydrogen bonds must break in
  order for the temperature to change
• This is called having a
• high specific heat

12
Water also has a unique density

• Solid water is LESS DENSE than liquid water
• ex. Ice floats (icebergs)
• Ponds freeze from top down

13
In your notes, answer the following

• Read about hydrogen bonds in section 2.2 then
  explain why the water behaves in the manners
  explored in the class activities.
• Using the following terms below explain how they
  can be related to the demonstrations that you
  attempted yesterday.
• a. Cohesion
• b. Adhesion
• c. Surface Tension - the attraction of molecules
  to each other on a surface creating a barrier
  between the molecules.