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Review

• 1. What type of bond holds an individual water
  molecule together?
• 2. What type of bond connects water molecules to
  each other?

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WATER
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Importance of water

• The Molecule That Supports All of Life
• Water is the biological medium here on Earth
• All living organisms require water more than any
  other substance

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Water Facts

• Three-quarters of the Earths surface is
  submerged in water
• The abundance of water is the main reason the
  Earth is habitable

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H2O

• Water is made up of Hydrogen and Oxygen
• Water is a polar molecule, one end has a positive
  charge and one end has a negative charge.

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Waters Polarity

• The polarity of water molecules
• Allows them to form hydrogen bonds with each
  other
• Contributes to the various properties water
  exhibits

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Properties of water

• Five emergent properties of water contribute to
  Earths fitness for life
• Storage of Energy
• Cohesion
• Adhesion
• Density of Ice
• Universal solvent

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Storage of Energy

• Water absorbs heat more slowly and retains this
  heat energy longer than other substances.
• Ie. A boiling pot of water takes a long time to
  cool down.
• Oceans help maintain Earths temperatures
• Organisms release heat through water evaporation.
  Water helps maintain homeostasis.
• Ie. sweating

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Cohesion

• Cohesion is an attraction between substances of
  the same kind
• Is due to hydrogen bonding
• Causes surface tension

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Adhesion

• Adhesion is an attraction between different
  substances.
• Helps pull water up through the microscopic
  vessels of plants called capillary action

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Density of Ice

• Solid water, or ice
• Is less dense than liquid water so it floats
• Insulates water organisms below ice layer
• The hydrogen bonds in ice
• Are more ordered than in liquid water, making
  ice less dense (crystal lattice)

WATER
ICE
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The Universal Solvent

• Called the universal solvent since so many
  substances dissolve in water
• A solution is a mixture in which one or more
  substances are evenly distributed in another
  substance.

Ionic compounds and polar molecules dissolve best
because of H2Os polarity
Nonpolar molecules, such as oil, do not dissolve
well in water.
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Acids and Bases

• Water can dissociate into hydrogen/ hydronium
  ions (H or H3O) and hydroxide (OH-) ions
• Compounds that form hydrogen/ hydronium ions when
  dissolved in water are called acids.
• Compounds that reduce the concentration of
  hydrogen ions in a solution are called bases.

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The pH Scale

• Scale goes from 0-14 with 7 neutral
• Difference of 10X in hydrogen ion concentration
  between any two pH values

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Acid Precipitation

• Refers to rain, snow, or fog with a pH lower than
  pH 5.6
• Is caused primarily by the mixing of different
  pollutants with water in the air

It can damage life in Earths ecosystems.