Introductory Chemistry: Concepts & Connections 4th Edition
Introductory Chemistry: Concepts & Connections 4th Edition
Concepts & Connections
4th Edition by Charles H. Corwin
Christopher G. Hamaker, Illinois State University, Normal IL
© 2005, Prentice Hall
Properties of Liquids
• Unlike gases, liquids do not respond dramatically
to temperature and pressure changes.
• We can study the liquid state and make 5 general
1. Liquids have a variable shape, but a fixed
• Liquids take the shape of their container
2. Liquids usually flow readily.
• However, not all liquids flow at the same rate.
Properties of Liquids Continued
3. Liquids do not compress or expand significantly
• The volume of a liquid varies very little as the
temperature and pressure change.
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 will form a homogeneous mixture.
Intermolecular Bond Concept
• An intermolecular bond is an attraction between
molecules, whereas intra molecular bonds are
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
• 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: dispersion
forces, dipole forces, and hydrogen bonds.
• 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
• This creates a temporary dipole
and two molecules with
temporary dipoles are attracted
to each other.
Dispersion Forces Continued
• Dispersion forces are the weakest intermolecular
• 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
– The more electrons in a molecule, the stronger the
• 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.
• Hydrogen bonds are a special type of dipole
• 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.
Physical Properties of Liquids
• There are 4 physical properties of liquids that we
can relate to the intermolecular attractions present
in the molecules:
– Vapor Pressure
– Boiling Point
– Surface tension
• 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 condensation.
• When the rates of evaporation and condensation
are equal, the pressure exerted by the gas
molecules above a liquid is called the vapor
Vapor Pressure Continued
• The stronger the intermolecular forces between
the molecules in the liquid, the less molecules
escape into the gas phase.
• As the attractive force between molecules
increases, vapor pressure decreases.
Vapor Pressure Comparison
• Lets compare water and ether.
– Water has strong intermolecular attractions and ether
has only weak intermolecular attractions.
• At 0C, neither has a significant vapor pressure.
• At 35C, ether has a significant vapor
pressure and water does not.
Vapor Pressure vs. Temperature
• As the temperature
increases, the vapor
pressure of a liquid
• Again, the stronger
lower the vapor
pressure at a given
• The normal boiling point of a substance is the
temperature where 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
• The viscosity of a liquid is a liquid’s resistance to
• Viscosity is the result of an attraction between
• The stronger the intermolecular forces, the higher
• The attraction between molecules at the surface of
a liquid is 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.
Properties of Solids
• Unlike gases, solids do not respond dramatically
to temperature and pressure changes.
• We can study the solid state and make 5 general
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,
Properties of Solids Continued
3. Solids do not compress or expand to any degree
• Assuming 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
• 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
• There are three types of crystalline solids
examples of which are shown below:
– Ionic solids like NaCl, (a)
– Molecular solids like H2O, (b)
– Metallic solids like Cu, (c)
• 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
• A crystalline molecular
solid has molecules
arranged in a particular
• In water, H2O, the
molecules are arranged
in a regular threedimensional structure.
• Other examples of crystalline molecular solids are
table sugar, C12H22O11, and sulfur, S8.
• 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.
General Properties of Solids
Changes of Physical State
• Heat is necessary to raise the temperature and
change the physical state of a substance.
• Specific heat is the amount of heat required to
raise 1.00 g of a substance 1C.
• Water is the reference and its specific heat is
• The specific heats of ice and steam are about half
that of liquid water.
Solid/Liquid Phase Changes
• As a solid melts, the temperature is constant until
all of the solid is changed to liquid.
• The amount of heat required to melt 1.00 g of
substance is called the heat of fusion (Hfusion).
For water, the heat of fusion is 80.0 cal/g.
• When a liquid changes to a solid, the heat change
is the heat of solidification (Hsolid).
• The value of Hfusion is the same as the value of
Liquid/Gas Phase Changes
• As a liquid vaporizes, the temperature is constant
until all of the liquid is changed to gas.
• The amount of heat required to vaporize 1.00 g of
substance is called the heat of vaporization
(Hvapor). For water, the value is 540 cal/g.
• When a gas changes to a liquid, the heat change is
the heat of condensation (Hcond).
• The value of Hvapor is the same as the value of
• We can graph the amount of energy required to
change the temperature and physical state of a
• The heating curve
for water is shown
• As energy is added
Energy from Heating Curves
• We can use the heating curve and heat values for
water to calculate how much energy is required to
change the temperature of a sample of water.
• The amount of energy required to raise the
temperature of a substance is calculated using the
heat = (specific heat) × (change in temperature) × (mass of sample)
• The amount of energy required to change the state
of a substance is calculated as follows:
heat = (Hxxx) × (mass)
• How much energy is required to raise 25.5 g of
ice at –5.0C to steam at 100.0C?
• Looking at the heating curve for water, there are
1) Heating of solid ice from –5.0C to 0.0C
2) Melting of ice at 0.0C
3) Heating of liquid water from 0.0C to 100.0C
4) Vaporization of water at 100.0C
• The total energy is the sum of the energy in steps
1) through 4). Calculate the energy for each step.
1) (25.5 g) × [0.0 – (–5.0)]C × (0.50 cal/g×C) = 64 cal
2) (25.5 g) × (80.0 cal/g) = 2040 cal
3) (25.5 g) × [100.0 – 0.0)]C × (1.00 cal/g×C) = 2550 cal
4) (25.5 g) × (540 cal/g) = 13,800 cal
• The total energy is:
64 cal + 2040 cal + 2550 cal + 13800 cal =
Structure of Water
• Lets 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
Properties of Ice
• Water is a one of the few substances that is less
dense as a solid than as a liquid.
• As water freezes, the hydrogen bonds organize the
water molecules into a three-dimensional structure
where the molecules are farther apart in the liquid.
• Liquid water has a
density of 1.00 g/mL
while ice has a density
of 0.917 g/mL.
Physical Properties of Water
• Water has unusually melting and boiling points,
especially compared to the other hydrogen
compounds of Group IVA/16.
• This is due to
which is present in
water but not present
in H2S, H2Se, or
Chemical Properties of Water
• Water can undergo an electrolysis reaction to
produce hydrogen and oxygen:
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
CO2(g) + H2O(l) → H2CO3(aq)
• A hydrate is a crystalline ionic compound that
• 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
CuSO45H2O(s) → CuSO4(s) + 5 H2O(l)
• There are three types of intermolecular bonds:
– Dispersion forces
– Dipole forces
– Hydrogen bonds
• Dispersion forces are the weakest and hydrogen
bonds are the strongest.
• These intermolecular attractions affect the
physical properties of substances.
• There are 5 properties of liquids that are affected
by intermolecular bonds:
– Vapor pressure decreases as intermolecular forces
– Boiling point increases as intermolecular forces
– Viscosity increases as intermolecular forces increase
– Surface tension increases as intermolecular forces
• There are 3 types of crystalline solids:
– Ionic solids
– Molecular solids
– Metallic solids
• Energy is required to raise the temperature of a
• Water displays many unique properties due to the
presence of strong hydrogen bonds.