27 - Colligative Properties - 1 - Chemistry

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Colligative Properties

Electrolytes

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-

Substance whose aqueous solution conducts electricity.

Ions carry the electric current, MUST HAVE IONS.

Non-electrolytes – do not conduct electricity, do not break into ions.

Colloids

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-

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“Gluelike”

Elmer’s glue is a colloid (do not always need a glue however)

Mixture of 2 phases of matter: continuous and dispersed phases

Between solution and suspension

Has subcategories: o

Aerosols – liquid or solid in a gas

Fog (liquid), smoke (solid) o

Foams – gases in liquids or solids

Shaving cream, whipped cream (liquids), marshmallows (solid) o

Emulsions – liquids in liquids

Mayonsaise, milk o

Sols – solids in liquids

Paints, gelatin, clay, jellies (w/ out preserves)

Tyndall Effect: the scattering of light by colloidal or suspended particles

Brownian Motion: the random movement of colloidal particles due to their bombardment

(bumping into collisions) by the molecules of the dispersing medium.

Ex: hitting a balloon to keep it from touching the ground

Suspension

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Heterogeneous mixture that will settle out

Can’t see through it

Will settle

Questions to ask:

1)

2)

Can you see through it? a.

Yes: solution b.

No: colloid OR suspension

Will it settle? a.

b.

Yes: suspension

No: Colloid

Type

Solution

Colloid

Suspension

Colligative Properties

Effect on light

Does not scatter

Scatters

Scatters

Particle size

Less than 1 nm

1 – 100 nm

Greater than 100 nm

Permanence

Permanent

Permanent

Settles out

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Properties determined by the # of particles in solution (rather than the type)

*# of particles of solute in solvent will cause the following* o

Vapor pressure decreases o

Boiling point increases o

Freezing point decreases

Higher vapor pressure

pure solvent

More solute = lower vapor pressure

**type of solute is note important, what is important is how many particles the solute contributes .

Some particles create more particles than other upon dissolving o

Creates more ions

more temperature change

NaCl (s)

Na

+

(aq) + Cl

-

(aq) 2 ions formed

CaCl

2

(s)

Ca

2+

(aq) + 2 Cl

-

(aq) 3 ions formed

C

6

H

12

O

6

(s)

C

6

H

12

O

6

(aq) 1 molecules formed

The change in vapor pressure, freezing and boiling point is directly proportional to the number of particles dissolved.

Distillation

Separates substances with different boiling points.

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