Temperature Does Not Change During a Change of State

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Temperature Does Not Change During a Change of
State

• Heat of Fusion
• Energy applied is used to change the state from
  solid to liquid (and vice versa), so temperature
  remains constant.
• It takes energy to keep breaking or forming
  bonds.
• Heat of Vaporization
• Energy applied is used to change the state from
  liquid to gas (and vice versa), so temperature
  remains constant.
• It takes energy to keep breaking or forming bonds.

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Sublimation

• Some materials change directly from a solid to a
  gas.
• State change from Solid directly to a Gas.
  Liquid state is skipped under normal
  circumstances.
• Particle bonds break completely when heated to
  a certain point.
• Sublimation vs. Deposition

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Diffusion

• The movement of particles from an area of high
  concentration to an area of low concentration.
• Requires no energy.
• Spreads particles out evenly.
• Occurs faster in the gaseous state than in the
  liquid state.
• Why does Oxygen enter our bodies?
• How can diffusion be speeded up?

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Evaporation
Ordinary evaporation is a surface phenomenon -
some molecules have enough kinetic energy to
escape. If the container is closed, an
equilibrium is reached where an equal number of
molecules return to the surface. The pressure of
this equilibrium is called the saturation vapor
pressure.
In order to evaporate, a mass of water must
collect the large heat of vaporization, so
evaporation is a powerful cooling mechanism.
Evaporation heat loss is a major climatic factor
and is crucial in the cooling of the human body.
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Evaporation vs Boiling
Ordinary evaporation is a surface phenomenon -
since the vapor pressure is low and since the
pressure inside the liquid is equal to
atmospheric pressure plus the liquid pressure,
bubbles of water vapor cannot form. But at the
boiling point, the saturated vapor pressure is
equal to atmospheric pressure, bubbles form, and
the vaporization becomes a volume phenomena.
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Electronegativity
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Electronegativity

• Linus Pauling
• Electronegativity is defined as
• The power of an atom in a molecule to attract
  electrons to itself.
• There is a numerical scale that lists the
  Electronegativity of all elements.
• Excluding the noble gases, the values tend to
  increase as you move to the right and up.
• The values tend to decrease as you go down and to
  the left.
• This is used to determine the ionic magnitude of
  a bond.

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Some Numerical Electronegativities
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Using Electronegativity

• One can tell the type of bond two atoms will form
  by calculating the difference between the two.
• Ionic, Polar Covalent, or Pure Covalent
• Ionic EN gt 2.0
• Ionic/Polar Covalent EN Between 1.6 and
  2.0
• Polar Covalent EN between 0.2 and 1.6
• Pure Covalent EN lt 0.2

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EN Between 1.6 and 2.0

• If a metal is involved
• Ionic
• If only nonmetals are involved
• Polar Covalent