Introducing

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IntroducingColligative Properties
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Colligative Properties

• Colligative properties are
• Observed or measured physical
• properties that change when a solute
• is added to a solvent to make a solution.

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These colligative properties are

• Vapor Pressure
• Boiling Point
• Freezing Point

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Vapor (Gas) Pressure

• The pressure within a solution pushing out
  because it wants to evaporate!
• Atmospheric pressure usually prevents this from
  happening by pushing back down.
• But when vapor pressure and atmospheric
  pressure are equal, it boils!

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Boiling Point

• Point at which vapor pressure (pushing up) equals
  atmospheric pressure (
• Heat is only needed to get vapor pressure up high
  enough to equal the downward push of atmospheric
  pressure!
• pushing down).

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Freezing Point

• Temperature is a measure of kinetic energy of
  particles.
• Low temp. low kinetic energy
• Particles slow down, get close together and
  solidify

kinetic energy of solids
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• Colligative Properties Change when a solute is
  added to a solvent to make a solution!

• Solute particles INTERFERE with the solvent
  particles!
• Adding the solute changes the vapor pressure,
  boiling point, and freezing point!

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• What kinds of solutes affect colligative
  properties?

Doesnt matter what the solute is, it matters
how many particles! Ionic compounds have a
greater effect! They split up into more particles
(ions) when dissolved! Ex NaCl, KNO3, CaCl2,
CuSO4, KCl, MgBr2 Organic and covalent
compounds have less of an effect. They dont
split up when dissolved! Ex C12H22O11, C6H12O6
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• Many Ionic Compounds are called electrolytes
  because their aqueous solutions can conduct an
  electric current.
• Ionic solutes break apart and
• always produce more than
• one ion which makes the
• number of solute particles
• increase.

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Ionic Solutes dissociate into
2 moles of ions

• NaCl ?
• MgCl2 ?
• Na3PO4 ?

1 Na1 1 Cl-1
1 Mg2 2 Cl-1
3 moles of ions
3 Na1 1 PO4-3
4 moles of ions
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• The solutes below are placed into
• water. What happens to these
• solutes as they begin to dissolve?
• C6H12O6 ?
• C12H22O11 ?
• They dissociate one molecule at a
• time!

1 mole of particles
1 C6H12O6
1 C12H22O11
1 mole of particles
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Okay, the solute particles interfere so how do
colligative properties change?

• Add the solute and.
• Vapor Pressure decreases ?
• (solute particles interfere with the upward
  pressure)
• Boiling Point Increases ?
• (solute particles interfere with upward pressure)
• Freezing Point decreases ?
• (solute particles interfere with particles
  getting close)

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• 3 Types of Mixtures
• SOLUTIONS,
• COLLOIDS, and
• SUSPENSIONS

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Solutions (we know this!)

• Mixtures with smallest particles dissolved
• Solute disappears to the eye - homogeneous
• Particles do not settle out
• Examples windex, koolaid, steel

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Colloids

• Mixtures with medium particle size
• Solute particles cannot be seen homogeneous/
  cloudy
• Particles do not settle out
• Examples fog, milk

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suspensions

• Mixtures with large particle size
• Solute particles can be seen heterogeneous
• Particles will settle out (float or sink)
• Examples cereal, Italian dressing, pulpy OJ