REVIEWER IN GENERAL CHEMISTRY II
LESSON 1.1 : Kinetic Molecular
Model of Liquids and Solids

Phase
-
A homogeneous part of a system in
contact with other parts of the
system, but separated from these
other
parts
by
well-defined
boundaries.
Intermolecular forces

attractive forces. However, the
molecules can move past one
another freely. Liquids can flow, can
be poured and assumes the shape of
its container.
In a solid, molecules are held tightly
in position with virtually no freedom of
motion. There is even less empty
space in a solid than in a liquid.
Solids are almost incompressible and
possess definite shape and volume.
PROPERTIES
OF MATTER
are attractive forces between
molecules.
Kinetic Molecular Theory:
1. All matter is made of tiny particles.
2. These particles are in constant
motion.
3. The speed of particles is proportional
to temperature.
-Increased temperature means
greater speed.
4. Solids, liquids, and gases differ in
distances between particles, in the
freedom of motion of particles, and in
the extent to which the particles
interact.
The Condensed State: Liquids and
Solids:


In liquids, the molecules are so close
together that there is very little empty
space between them. Liquids are
much more difficult to compress and
they are much denser at normal
conditions.
Molecules in a liquid are held
together by one or more types of
GAS
VOLUME/SHAPE
Fixed volume;
fixed
shape (regardless
of size
and shape of
container)
Fixed volume;
assumes shape
of occupied part
of container.
Assumes
volume and
shape of
container
DENSITY
High
High
low
COMPRESSIBILITY
Cannot be
appreciably
compressed
Cannot be
appreciably
compressed
Easy to
compress
Vibration in place
Random,
medium speed,
limited distances
Random,
fast, cover
large
distances
Intramolecular forces
- hold atoms together in a molecule.
SOLID
MOLECULAR BEHAVIOR
LIQUID
MOTION OF
PARTICLES
For gases:

An increase in temperature results in
increased kinetic energies of gases
dissolved in liquids. This increased
motion enables the dissolved gas to
break intermolecular forces with the
solvent, and escape the solution.
Note: When a solid melts, or a liquid boils,
the particles move away from each other. As
they do, intermolecular forces of attraction
are broken. The stronger the intermolecular
forces to be broken, the larger the amount of
energy needed to break them, hence, the
higher the melting point for solid to liquid
transformation, and boiling point for liquid to
gas transformation.
REVIEWER IN GENERAL CHEMISTRY II
The different types of intermolecular forces
are the following:
-
1. Dispersion forces
-
-
-
-
-
These forces of attraction result
from temporary dipole moments
induced in ordinarily nonpolar
molecules.
These forces are present
between all types of molecules
due to the movement of
electrons.
As electrons move around the
nucleus, an uneven distribution
causes
momentary
charge
separations.
Dispersion forces may be the
weakest of intermolecular forces
that can exist between two
molecules.
The larger the atoms present,
the stronger the dispersion
forces.
because some elements are
more electronegative than others
are.
Stronger than the dispersion
forces because polar molecules
have a permanent uneven
distribution of electrons.
The larger the dipole moment,
the stronger the attraction
4. Hydrogen Bond
-
-
A special type of dipole-dipole
interaction between the hydrogen
atom in a polar bond, such as N‒H,
O‒H, or F‒H, and an electronegative
O, N, or F atom.
Hydrogen bonds between water
molecules are particularly strong.
2. London Dispersion Force
-
-
Due to electron repulsion, a
temporary dipole on one atom can
induce a similar dipole on a
neighbouring atom. This will cause
the neighbouring atoms to be
attracted to one another.
It is significant only when the atoms
are close together.
The weakest intermolecular force
Sometimes called an induced dipoleinduced dipole attraction
London forces are the attractive
forces
that
cause
nonpolar
substances to condense to liquids
and to freeze into solids when the
temperature is lowered sufficiently.
-
o
o
o
3. Dipole-Dipole Forces
-
-
are attractive forces between
polar molecules (molecules that
possess dipole moments)
In polar molecules, the electrons
are
unevenly
distributed
A molecule will be polar if:
o
-
One or more terminal atoms
differ from each other.
At least one polar bond is
present.
The terminal atoms are not
symmetrically arranged
The molecule has one slightly
positive end and one slightly
negative end.
A molecule will be nonpolar if:
REVIEWER IN GENERAL CHEMISTRY II
o
o
o
All of the terminal atoms (or
groups) are the same
All of the terminal atoms (or
groups)
are
symmetrically
arranged around the central
atom
The terminal atoms (or groups)
have the same charges
o
o
LESSON 1.2: Properties of Liquids
and Intermolecular Forces
Note: The properties of liquids that were
observed are consequences of the interactions of
particles that make up the liquid.
-
o
o
-
Two types of forces are
involved in capillary action:
o
Surface tension
o
The measure of the elastic force
in the surface of a liquid. It is the
amount of energy required to
stretch or increase the surface of
a liquid by a unit area.
These intermolecular forces tend
to pull the molecules into the
liquid and cause the surface to
tighten like an elastic film or
“skin”.
liquids
that
have
strong
intermolecular forces also have
high surface tension
o
-
Cohesion is the intermolecular
attraction between like molecules
(the liquid molecules).
Adhesion is an attraction between
unlike molecules (such as those in
water and in the particles that make
up the glass tube).
Viscosity
o
A measure of a
resistance to flow.
o
The greater the viscosity, the
slower the liquid flows
The larger the molecule, even if
it is nonpolar, the stronger the
intermolecular forces and the
greater the viscosity compared
to nonpolar substances made up
of small molecules.
Viscosity
decreases
as
temperature increases
o
Capillary action
o
The tendency of a liquid to
rise in narrow tubes or to be
drawn into small openings.
o
also known as capillarity, is a
result of intermolecular attraction
between the liquid and solid
materials.
Surface tension causes the film
of water to contract and pulls the
water up the tube
When the cohesive forces
between the liquid molecules are
greater than the adhesive forces
between the liquid and the walls
o
o
of the container, the surface of
the liquid is convex.
When the cohesive forces
between the liquid molecules are
lesser than the adhesive forces
between the liquid and the walls
of the container, the surface of
the liquid is concave.
When both adhesive and
cohesive forces are equal, the
surface is horizontal
o
-
Vapor
o
-
A gaseous substance that
exist naturally as a liquid or
solid at normal temperature
Vaporization
o
-
fluid’s
The change of phase from
liquid to vapor (gaseous
phase).
Vapor pressure of a liquid
REVIEWER IN GENERAL CHEMISTRY II
o
o
o
o
o
o
The equilibrium pressure of a
vapor above its liquid; that is,
the pressure exerted by the
vapor above the surface of
the liquid in a closed
container.
The greater the number of
gaseous particles, the greater
the pressure exerted by the gas.
The equilibrium vapor pressure
is the maximum vapor pressure
of a liquid at a given temperature
and that it is constant at a
constant
temperature.
It
increases with temperature.
substances
with
weak
intermolecular forces, the energy
requirement is easy obtained
from collisions with other
molecules and absorption of
energy from the surroundings.
Many molecules can vaporize,
resulting in a high vapor
pressure
For molecules with strong
intermolecular forces, gathering
enough energy may not be as
easy, and register low vapor
pressures.
The stronger the intermolecular
forces of attraction, the lower the
vapor pressure of a liquid.
Note: the pressure of a gas is directly proportional
to the number of gas particles present.
Which means that…
 As the temperature increases, the vapor
pressure of water also increases.
 When temperature is high, more
molecules have enough energy to
escape from the liquid.
 At a lower temperature, fewer molecules
have sufficient energy to escape from the
liquid.
-
Boiling point
o
The temperature at which a
liquid boils. The boiling point of a
liquid when the external pressure
o
o
-
is 1 atm is called the normal
boiling point.
The boiling point is related to
molar heat of vaporization: the
higher ΔHvap , the higher the
boiling point
The boiling points of substances
often reflect the strength of the
intermolecular forces operating
among the molecules. At the BP,
enough energy must be supplied
to overcome the attractive forces
among molecules before they
can enter the vapor phase.
Molar heat of vaporization
(ΔHvap)
o
The energy (usually in kilojoules)
required to vaporize 1 mole of a
liquid at a given temperature.
Note: The heat of vaporization may be
considered a measure of the strength of
intermolecular forces in a liquid.
 If the intermolecular attraction is strong, it
takes a lot of energy to free the molecules
from the liquid phase and the heat of
vaporization will be high.
LESSON 1.3: The Unique
Properties of Water
a.
Water is a good solvent
o A unique property of water is its
ability to dissolve a large variety
of chemical substances. It
dissolves salts and other ionic
compounds, as well as polar
covalent compounds such as
alcohols and organic substances
that are capable of forming
hydrogen bonds with water
b. Water has a high specific heat
o Specific heat is the amount of
heat or energy needed to raise
REVIEWER IN GENERAL CHEMISTRY II
o
o
c.
d.
the temperature of one gram of a
substance by 1oC.
Water can absorb a large
amount of heat even if its
temperature rises only slightly.
To raise the temperature of
water,
the
intermolecular
hydrogen bonds should break.
The converse is also true; water
can give off much heat with only
a slight decrease in its
temperature. This allows large
bodies of water to help moderate
the temperature on earth.
The boiling point of water unusually high
o Many compounds similar in
mass to water have much lower
boiling points.
o The strong intermolecular forces
in water allow it to be a liquid at a
large range of temperatures.
Solid water is less dense, and in fact
floats on liquid water
o
the molecules in solid water
are actually farther apart
than they are in liquid water
o When solid water forms, the
hydrogen bonds result in a
very open structure with
unoccupied spaces, causing
the solid to occupy a larger
volume than the liquid.
o This makes ice less dense
than liquid water, causing ice
to float on water.
APPLICATION:
1. Arrange these substances in order of
increasing rates of evaporation
o
Lowest Rate - acetic acid, water,
ethanol, acetone - Highest Rate
2.
Arrange these substances in order of
increasing boiling point temperature
o
Lowest Boiling Point - acetone,
ethanol, water, acetic acid - Highest
Boiling Point
Arrange these substances in order of
increasing intermolecular forces.
o
Lowest IMF - acetone, ethanol,
water, acetic acid – Highest IMF
4. Rank these forces in terms of their
relative strengths: hydrogen bonding;
dipole-dipole; induced dipole induced
dipole (dispersion), and covalent bonds.
o Covalent bonds >>> hydrogen
bonding > dipole-dipole > induced
dipole-induced dipole (dispersion)
3.
LESSON
2.1:
Intermolecular
Forces of Liquids and Solids;
Solids and their Properties
Vocab:
Crystal or crystalline solid - A solid material
whose components, such as atoms, molecules or
ions, are arranged in a highly ordered
microscopic structure.
 Molecular crystal
A solid composed of molecules held together by
van der Waals forces (dispersion force, dipoledipole attraction, hydrogen bonding).
 Ionic crystal
A solid that consists of positively and negatively
charged ions held together by electrostatic
forces.
 Network solid or covalent network crystal
A solid that may be a chemical compound (or
element) in which atoms are bonded
by covalent bonds in a continuous network
extending throughout the material.
 Crystal lattice
The regular repeating structure of a crystalline
solid.
 Unit cell
The smallest subunit of a crystal lattice that can
be repeated over and over to make the entire
crystal
REVIEWER IN GENERAL CHEMISTRY II
How is a solid described in
terms of the Kinetic
Molecular Theory?
a. Average kinetic energy
b. Distance among particles
c. Arrangement/order of particles
d. Attractive forces between particles