CHAPTER 12: LIQUIDS AND SOLIDS
A. IMFs and States of Matter (Section 12.1)
1. At a given temperature, the magnitude of intermolecular forces (IMFs) determines the phase of matter:
a. If the IMFs are too weak to hold the particles together, the substance is a gas. b. If the IMFs are strong enough to hold the particles together, the substance will be a liquid or solid.
 Referred to collectively as the

2. There are three IMFs we consider in pure substances:
a.
 Present in all compounds.
b.
 Present only in polar molecules.
c.
 Present only when H is bonded directly to
B.

Review of Lewis Structures, VSEPR, and Polarity
1. To draw a Lewis Structure:
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a. Determine the total number of valence electrons in the molecule.
b. Determine the central atom; place outer atoms around central atom.
c. Draw a single bond between the central and outer atoms.
d. Place remaining electrons, in pairs, around the outer atoms until their octet is satisfied.
 Start with highest EN element first.
e. Any remaining electrons go on the central atom.
f.

Check to make sure all atoms have their octets.
 If the central atom does not have an octet, use multiple bonds.

2. VSEPR Review
# edomains

# nonbonding domains EDG

MG

Bond
Angles

Hybridization

2

0

Linear

Linear

180°

sp

3

0

Trigonal Planar

Trigonal Planar

120°

sp2

3

1

Trigonal Planar

Bent

<120°

sp2

4

0

Tetrahedral

Tetrahedral

109.5°

sp3

4

1

Tetrahedral

Trigonal
Pyramidal

<109.5°

sp3

4

2

Tetrahedral

Bent

<109.5°

sp3

2

# e- domains

# nonbonding domains EDG

MG

Bond
Angles

Hybridization

5

0

Trigonal
Bipyramidal

Trigonal
Bipyramidal

120°, 90°

sp3d

5

1

Trigonal
Bipyramidal

See-Saw

5

2

Trigonal
Bipyramidal

T-Shape

5

3

Trigonal
Bipyramidal

Linear

6

0

Octahedral

Octahedral

90°

sp3d2

6

1

Octahedral

Square
Pyramidal

6

2

Octahedral

Square Planar

3. Molecules can be either polar or nonpolar:
a.

Polar (dipole):
 A polar molecule must have at least one polar bond!

b.

Nonpolar (no dipole):
 Molecule with polar bonds can still be nonpolar!

c.

Determine if the center of positive & negative charge are in the same place.  Make sure to take the account! into

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C.

Properties of Liquids (Section 12.2)
1. Surface Tension-

a.

Forces that must be overcome to increase the surface area of a liquid.

b.

Due to an unequal pulling of the molecules at the surface of the liquid.

c.

As IMFs increase, surface tension

d.

The attraction of a substance to itself is known as
 All forces holding liquid together.

e.

The attraction of a substance to another substance is known as
 Forces attracting a liquid to another surface.

2. Capillary Action
a.

For a liquid in a vessel, the relative magnitudes of cohesion and adhesion to the vessel affect its behavior:
 If the magnitude of adhesion is greater than cohesion, the liquid is drawn up the walls, forming a meniscus. o This is the basis of capillary action.
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 If the magnitude of cohesion is greater than adhesion, the liquid is drawn toward itself, forming a meniscus. b.

Capillary action occurs when a liquid creeps up or down a capillary tube (caused by adhesion between liquid and the glass) until gravity forces eventually stop it.

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3. Viscositya.

As IMFs increase, viscosity.
 Viscosity low when molecules can easily slide past one another (weak intermolecular forces). o Oil has

b.

viscosity, gasoline

.

Measured by
, which measures flow time through a capillary tube required for a specific volume of liquid.
 Society of Automotive Engineers (SAE) developed viscosity scale for automobile oil. o Higher number oils have higher viscosities.

SAE 40 Oil

SAE 10 Oil

4. Vapor Pressure
a.

Often, molecules in a liquid will have enough energy to vaporize spontaneously. 6

 Vaporization o Molecules of liquid have distribution of

o As T increases fraction of molecules with sufficient KE increases, and evaporation rate increases. o Since only high energy molecules are escaping,