Chapter 11
Liquids and Solids
Properties of Liquids
• 
Unlike gases, liquids do not respond dramatically
to temperature and pressure changes.
• 
We can study the liquid state and make five
general observations.
1.  Liquids have a variable shape, but a fixed volume.
• 
Liquids take the shape of their container.
2.  Liquids usually flow readily.
• 
However, not all liquids flow at the same rate.
3.  Liquids do not compress or expand significantly.
• 
The volume of a liquid varies very little as the temperature and
pressure change.
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Properties of Liquids, Continued
4. Liquids have a high density compared to gases.
•  Liquids are about 1000 times more dense than gases.
5. Liquids that are soluble mix homogeneously.
•  Liquids diffuse more slowly than gases, but eventually form a
homogeneous mixture.
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Intermolecular Bond Concept
•  An intermolecular bond is an attraction between
molecules, whereas an intramolecular bond is
between atoms in a molecule.
•  Some properties of liquids, such as vapor pressure,
viscosity, and surface tension, are determined by
the strength of attraction between molecules.
•  Intermolecular bonds are much weaker than
intramolecular bonds.
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Intermolecular Bonds
• 
Recall that a polar molecule has positive and negative
charges concentrated in different regions due to
unequal sharing of electrons in bonds.
• 
This uneven distribution of electrons in a molecule is
called a dipole.
• 
Intermolecular attractions result from temporary or
permanent dipoles in molecules.
• 
There are three intermolecular forces:
1.  Dispersion forces
2.  Dipole forces
3.  Hydrogen bonds
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Dispersion Forces
•  Dispersion forces, or London forces, are the result
of a temporary dipole.
•  Electrons are constantly shifting, and a region
may become temporarily electron poor and
slightly positive, while another region becomes
slightly negative.
•  This creates a temporary dipole,
and two molecules with
temporary dipoles are attracted
to each other.
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Dispersion Forces, Continued
•  Dispersion forces are the weakest intermolecular
force.
•  Dispersion forces are present in all molecules.
•  The strength of the dispersion forces in a molecule
is related to the number of electrons in the
molecule:
–  The more electrons in a molecule, the stronger the
dispersion forces.
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Dipole Forces
•  Polar molecules have a permanent dipole.
•  The oppositely charged ends of polar molecules
are attracted to each other; this is the dipole force.
•  The strength of a dipole force is typically 10% of
a covalent bond’s strength.
•  Dipole forces are stronger than dispersion forces.
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Hydrogen Bonds
•  Hydrogen bonds are a special type of dipole
attraction.
•  Hydrogen bonds are present when a molecule has
an N—H, O—H, or F—H bond.
•  Hydrogen bonds are especially important in water
and living organisms.
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Physical Properties of Liquids
• 
There are four physical properties of liquids that
we can relate to the intermolecular attractions
present in molecules:
1.  Vapor pressure
2.  Boiling point
3.  Viscosity
4.  Surface tension
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Vapor Pressure
•  At the surface of a liquid, some molecules gain
enough energy to escape the intermolecular
attractions of neighboring molecules and enter the
vapor state. This is evaporation.
•  The reverse process is called condensation.
•  When the rates of evaporation and condensation
are equal, the pressure exerted by the gas
molecules above a liquid is called the vapor
pressure.
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Vapor Pressure, Continued
•  The stronger the intermolecular forces between the
molecules in the liquid, the less molecules that
escape into the gas phase.
•  As the attractive force between molecules
increases, vapor pressure decreases.
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Vapor Pressure Comparison
•  Let’s compare water and ether.
–  Water has strong intermolecular attractions, and ether
has weak intermolecular attractions.
•  At 0 °C, neither has a significant vapor pressure.
•  At 35 °C, ether has a significant vapor
pressure and water does not.
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Vapor Pressure Versus Temperature
•  As the temperature
increases, the vapor
pressure of a liquid
increases.
•  Again, the stronger
the intermolecular
attractions, the
lower the vapor
pressure at a given
temperature.
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Boiling Point
•  The normal boiling point of a substance is the
temperature at which the vapor pressure is equal to
the standard atmospheric pressure.
•  As we saw in the previous graph, the stronger the
intermolecular attractions, the higher the boiling
point of the liquid.
•  A liquid with a high boiling point has a low vapor
pressure.
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Viscosity
•  The viscosity of a liquid
is a liquid’s resistance to
flow.
•  Viscosity is the result of
an attraction between
molecules.
•  The stronger the
intermolecular forces, the
higher the viscosity.
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Surface Tension
•  The attraction between molecules at the surface of
a liquid it called surface tension.
•  For an object to sink in a liquid, it must first break
through the surface.
•  The stronger the intermolecular attractions, the
stronger the surface tension of a liquid.
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Properties of Solids
•  Unlike gases, solids do not respond dramatically
to temperature and pressure changes.
•  We can study the solid state and make five
general observations.
1.  Solids have a fixed shape and volume.
•  Unlike liquids, solids are rigid.
2.  Solids are either crystalline or noncrystalline.
•  Crystalline solids contain particles in a regular, repeating pattern.
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Properties of Solids, Continued
3.  Solids do not compress or expand to any degree.
•  Assuming there is no change in physical state, temperature
and pressure have a negligible effect on the volume of a
solid.
4.  Solids have a slightly higher density than their
corresponding liquid.
•  One important exception is water; ice is less dense than
liquid water.
5.  Solids do not mix by diffusion.
•  The particles are not free to diffuse in a solid heterogeneous
mixture.
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Crystalline Solids
•  There are three types of crystalline solids,
examples of which are shown below:
1.  Ionic solids, such as NaCl
2.  Molecular solids, such as S8
3.  Metallic solids, such as Cu
4.  Crystalline network solids, such as diamonds
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Ionic Solids
•  A crystalline ionic solid is
composed of positive and
negative ions arranged in a
regular, repeating pattern.
•  In table salt, NaCl, sodium
ions and chloride ions are
arranged in a regular threedimensional structure
referred to as a crystal lattice.
•  Other ionic compounds will have different crystal
lattices.
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Molecular Solids
•  A crystalline molecular
solid has molecules
arranged in a particular
conformation.
•  In sulfur, S8, the
molecules are arranged
in a regular threedimensional structure.
•  Other examples of crystalline molecular solids are
table sugar, C12H22O11, and water, H2O.
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Metallic Solids
•  A crystalline metallic solid is
composed of metal atoms
arranged in a definite pattern.
•  A metallic crystal is made up
of positive metal ions
surrounded by valance electrons.
•  Metals are good conductors of
electricity because electrons are
free to move about the crystal.
•  This is referred to as the “electron sea” model.
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Diamond
•  Diamond is a special type of crystalline solid that
has covalent bonds between large numbers of
atoms.
•  This type of crystalline solid is referred to as a
network solid.
•  Diamond is very hard and has
a very high melting point.
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General Properties of Solids
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Structure of Water
•  Let’s start with the electron dot formula for water.
•  Water has a bent molecular shape and the bond
angle is 104.5°.
•  Water is a polar
molecule that exhibits
strong hydrogen
bonding.
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Chemical Properties of Water
•  Water can undergo an electrolysis reaction to
produce hydrogen and oxygen:
2 H2O(l) → 2 H2(g) + O2(g)
•  Water reacts with active metals to produce
hydrogen and a metal hydroxide:
2 K(s) + 2 H2O(l) → 2 KOH(aq) + H2(g)
•  Water reacts with metal oxides to produce a base:
CaO(s) + H2O(l) → Ca(OH)2(aq)
•  Water reacts with nonmetal oxides to produce an
acid:
CO2(g) + H2O(l) → H2CO3(aq)
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Reactions that Produce Water
•  Water is obtained as a product in several types of
chemical reactions.
–  Combustion reactions:
•  2 C2H2 (g) + 5 O2 (g) → 4 CO2 (g) + 2 H2O (g)
•  C2H5OH (g) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g)
–  Neutralization reactions:
•  H3PO4 (aq) + 3 LiOH (aq) → Li3PO4 (aq) + 3 H2O (l)
–  Dehydration reactions:
•  Water is driven off from a hydrate by heating.
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Hydrates
•  A hydrate is a crystalline ionic compound that
contains water:
CuSO4 ⋅ 5 H2O
•  The dot indicates that water molecules are bonded
directly to each unit of hydrate.
•  Heating a hydrate drives off the water and
produces an anhydrous compound (without
water).
heat
CuSO4 ⋅ 5 H2O(s) → CuSO4(s) + 5 H2O(l)
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