The Extraordinary Properties of Water

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The Extraordinary Properties of Water
Where theres lifetheres water!!!
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Water

• A water molecule (H2O), is made up of three atoms
  --- one oxygen and two hydrogen.

O
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Water is Polar

• Having positively and negatively charged sides.
• The oxygen end acts negative
• The hydrogen end acts positive
• Causes the water to be POLAR

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Hydrogen Bonds Exist Between Water Molecules

• Weak attraction between H and an
  electronegatively charged atom.
• One hydrogen bond is weak , but many hydrogen
  bonds are strong

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Interaction Between Water Molecules
Negative Oxygen end of one water molecule is
attracted to the Positive Hydrogen end of another
water molecule to form a HYDROGEN BOND
H-Bonds are critical to the structure of water
and therefore determine the properties of water.
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• What are the Properties of Water?

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Properties of Water

• Cohesion

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Properties of Water

• Cohesion
• Adhesion

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Properties of Water

• Cohesion
• Adhesion
• High Specific Heat

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Properties of Water

• Cohesion
• Adhesion
• High Specific Heat
• High Heat of Vaporization

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Properties of Water

• Cohesion
• Adhesion
• High Specific Heat
• High Heat of Vaporization
• Less Dense as a Solid

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Cohesion Co Here

• Attraction between similar substances ( why water
  is attracted to itself)
• Due to Hydrogen bonds

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Cohesion Co Here

• Results in surface tension - a measure of the
  strength of waters surface
• Produces a surface film on water that allows
  insects to walk on the surface of water

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Cohesion
Helps insects walk across water
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Adhesion

• Clinging of H2O to different substances.
• Due to hydrogen bonds with other surfaces that
  have electronegativity such as glass, soil, plant
  tissues, and cotton.
• Ex transpiration in plants, paper towels soak up
  water, water on a penny, meniscus in a graduated
  cylinder.

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Adhesion Causes Capillary Action
Which gives water the ability to climb
structures
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Adhesion Also Causes Water to
Attach to a silken spider web
Form spheres hold onto plant leaves
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High Specific Heat

• Amount of heat needed to raise the temp of 1g of
  H2O 1 C.
• Water has a very HIGH specific heat.
• Crucial in temperature stability in living
  systems to maintain homeostasis.

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High Heat of Vaporization

• Amount of energy to convert 1g water from a
  liquid to a gas.
• Called vaporization or evaporation

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High Heat of Vaporization

• As water evaporates, it removes a lot of heat
  with it (cooling effect).
• Ex evaporation of sweat from the body

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Water is Less Dense as a Solid

• Ice is less dense as a solid than as a liquid
  therefore it floats
• Other materials contract when they solidify, but
  water expands.

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Water is Less Dense as a Solid

• As water freezes, it forms a crystal-like lattice
  by bonding to other water molecules.
• H bonds keep molecules at arms length keeping
  it less dense than liquid water.

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• Water is Less Dense as a Solid
• Which is ice and which is water?

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• Water is Less Dense as a Solid

Water
Ice
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Water as a Solvent

• Water dissolves many substances due to its
  polarity.
• Water is a very versatile solvent
• Other polar substances dissolve easily in water.

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Solution

• Homogenous mixture of 2 or more substances.
• Evenly distributed
• SOLVENT dissolving agent of a solution (water)
• SOLUTE - substance that is being dissolved

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Solution
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Hydrophilic

• water-loving
• substances that dissolve easily in water.
• Examples salts, polar compounds (sugar).
• Also known as water soluble.

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Hydrophobic

• water-fearing
• substances that do not dissolve easily in water
  they instead separate.
• Examples oils, fats, lipids, waxes.
• These substances are non-polar, and are also
  known as insoluble.

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Acids, Bases and pH

• One water molecule in 550 million naturally
  dissociates into a Hydrogen Ion (H) and a
  Hydroxide Ion (OH-)
• Hydrogen Ion
  Hydroxide Ion
• Acid Base

H2O ? H OH-
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The pH Scale

• Measures strength of an acid or base by
  concentration of H ions and OH- ions
• Each pH unit represents a factor of 10X change in
  concentration
• pH 3 is 10 x 10 x 10 (1000) stronger than a pH of
  6

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Acids

• Substance that increases H ions
• Strong acids have a pH of 1-3

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Bases

• Substance that decreases H concentration, thus
  increasing OH- ions
• Strong Bases have a pH of 11 to 14

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Buffers

• Weak acids or bases that react with strong acids
  or bases to prevent sharp, sudden changes in pH
  (neutralization).
• Produced naturally by the body to maintain
  homeostasis

Weak Acid
Weak Base