Colligative Properties

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Colligative Properties
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What Are Colligative Properties?

• Physical Properties that depend on the number of
  solute particles
• Do NOT depend on the identity of the solute
  particles

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The Colligative Properties

• Vapor Pressure Lowering
• Boiling Point Elevation
• Freezing Point Depression

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Vapor Pressure

• The pressure given off by liquid particles in a
  container that have escaped the liquids surface
  and turned into a gas.

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Vapor Pressure Equilibrium

• Particles from the liquid go into the gas state
  as they evaporate.
• Gas particles turn into liquid again as they
  cool.
• This happens at the same timeif it happens at
  the same rate it is in equilibrium

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Vapor Pressure Lowering

• When a solute is added to the solvent, the of
  solvent molecules near the surface decreases
  because the solute particles get in their way.
• This keeps the solvent particles from turning
  into gas particles.

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Vapor Pressure Lowering

• Sothere are less gas particles above the
  solution exerting pressure.
• This is lowered vapor pressure.

The Vapor Pressure of a Solution is Lower than
that of the Pure Solvent
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Intermolecular Forces

• High intermolecular forces means low vapor
  pressure
• The particles are closely held onto so they cant
  be released into gas state

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Atmospheric Pressure

• Pressure of the air in the room over a solution

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Boiling Point

• Boiling is when
• Vapor Pressure Atmospheric Pressure
• Liquid turns into gas

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Boiling Point Elevation

• Adding solute lowers vapor pressure (more solute
  blocks the particles from turning into gas.so
  less pressure)
• This makes it harder to boilso higher boiling
  point

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Boiling Point Elevation

• Ethylene glycol (a solute) in antifreeze allows
  cars a higher operating temperature because it
  lowers the vapor pressure of the water by raising
  the boiling point.

13
Freezing Point

• The temperature at which the vapor pressures of
  the solid and liquid phases are the same.

14
Freezing Point Depression

• The solute particles get in between the solvent
  particles.
• The solute messes with the attractive forces that
  make it a solid (freezing).
• This keeps the solution from freezing and thus
  lowering the freezing point

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Freezing Point Depression

• The freezing point of water is 0C, but that
  freezing point can be lowered by adding a solvent
  such as salt. This helps the ice to melt on the
  roads by lowering the temperature that the water
  will freeze to ice.