The Kinetic-Molecular Theory
• Kinetic-molecular theory explains the
different properties of solids, liquids, and
gases, and describes particle behavior in
terms of particles in motion
• Atomic composition affects chemical &
physical properties
The Kinetic-Molecular Theory (cont.)
GAS
• Gases consist of small particles separated
by empty space.
• Gas particles are too far apart to experience
significant attractive or repulsive forces.
The Kinetic-Molecular Theory (cont.)
• Gas particles are in constant random
motion.
• An elastic collision is one in which no kinetic
energy is lost.
The Kinetic-Molecular Theory (cont.)
• Kinetic energy of a particle depends on
mass and velocity.
• Temperature is a measure of the average
kinetic energy of the particles in a sample of
matter.
• Absolute Zero = -273 oC
or 0 K
Explaining the Behavior of Gases
• Great amounts of space exist between gas
particles.
• Compression reduces the empty spaces
between particles.
Gas Pressure
• Pressure is defined as force per unit area.
• Gas particles exert pressure when they
collide with the walls of their container.
Gas Pressure (cont.)
• The particles in the earth’s atmosphere
exert pressure in all directions called air
pressure.
• There is less air pressure at high altitudes
because there are fewer particles present,
since the force of gravity is less.
Gas Pressure (cont.)
• Barometers are
instruments used
to measure
atmospheric air
pressure.
Gas Pressure (cont.)
• Manometers measure gas pressure in a
closed container.
Gas Pressure (cont.)
• The SI unit of force is the newton (N).
• One pascal(Pa) is equal to a force of one
Newton per square meter or N/m2.
• One atmosphere is equal to 760 mm Hg or
101.3 kilopascals (kPa).
Gas Pressure (cont.)
Pg. 407
Section 12.1 Assessment
The average of kinetic energy of particles
in a substance is measured by its ____.
A. mass
B. density
D
A
0%
C
D. pressure
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. temperature
Intermolecular Forces
• Attractive forces between molecules cause
some materials to be solids, some to be
liquids, and some to be gases at the same
temperature.
Intermolecular Forces (cont.)
• Dipole-dipole forces are attractions
between oppositely charged regions of
polar molecules.
Intermolecular Forces (cont.)
• Hydrogen bonds are special dipole-dipole
attractions that occur between molecules
that contain a hydrogen atom bonded to a
small, highly electronegative atom with at
least one lone pair of electrons, typically
fluorine, oxygen, or nitrogen.
IMF
Hydrogen Bonds
Dipole-Dipole
Induced Dipole
(aka dispersion force)
H bonded to N, O or F
(type of dipole-dipole)
∂ - end attracted to a
∂+ end of a polar
molecule
VERY weak attraction
between non-polar
covalent molecules
Intermolecular Forces (cont.)
Section 12.2 Assessment
A hydrogen bond is a type of ____.
A. dispersion force
B. ionic bond
C. covalent bond
D
C
A
0%
B
D. dipole-dipole force
A. A
B. B
C. C
0%
0%
0%
D. D
Section 12.2 Assessment
Which of the following molecules can
form hydrogen bonds?
A. CO2
B. C2H6
D
A
0%
C
D. H2
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. NH3
12.3 Liquids and Solids
Liquids:
• are closely packed in a fixed
volume, not in a fixed position.
• are much denser than gases because of
the stronger intermolecular forces holding
the particles together
• need large amounts of pressure to
compress into very small amounts.
Liquids (cont.)
• Fluidity is the ability to flow and diffuse;
liquids and gases are fluids.
• Viscosity is a
measure of the
resistance of a liquid
to flow and is
determined by the
type of intermolecular
forces, size and
shape of particles,
and temperature.
Liquids (cont.)
• Surface tension is the
energy required to
increase the surface
area of a liquid by a
given amount.
• Surfactants
are
compounds
that lower the
surface
tension of
water.
Liquids (cont.)
• Adhesion is
the force of
attraction
between
molecules
that are
different.
(WATER 
CONTAINER)
• Cohesion is the force
of attraction between
identical molecules.
(WATER WATER)
•Capillary action is
the upward
movement of liquid
into a narrow
cylinder, or
capillary tube.
12.3 Liquids and Solids
Solids:
• contain particles with strong attractive
intermolecular forces that vibrate in a fixed
position.
• are more dense than liquids.
• An exception-Ice is not more dense than
water.
Plasma- The Fourth State of Matter
• Greater than 5000 0C
• Collisions break up atoms to make positive
ions and electrons.
• Most of the universe is plasma
Section 12.3 Assessment
The viscosity of a liquid will increase as:
A. particle size decreases
B. temperature decreases
C. intermolecular forces decrease
D
C
A
0%
B
D. particle size increases
A. A
B. B
C. C
0%
0%
0%
D. D
12.4 Phase Changes That Require Energy
p. 425
Phase Changes That Require Energy (cont.)
• The melting point of a crystalline solid is the
temperature at which the forces holding the
crystal lattice together are broken and it
becomes a liquid.
• Molecules are freer to move as solid
liquidgas
Phase Changes That Require Energy (cont.)
p. 426
Once over the hump
of KE, substance can
vaporize
Phase Changes That Require Energy (cont.)
• Vaporization is the process by which a
liquid changes to a gas or vapor.
• Evaporation is vaporization only at the
surface of a liquid.
Phase Changes That Require Energy (cont.)
• In a closed container, the pressure exerted
by a vapor over a liquid is called vapor
pressure.
•In closed
container,
water
leaving/
entering
is equal
Phase Changes That Require Energy (cont.)
• The boiling point is the temperature at
which the vapor pressure of a liquid equals
the atmospheric pressure.
Phase Changes That Require Energy (cont.)
• Sublimation is the process by which a solid
changes into a gas without becoming a
liquid.
Phase Changes That Release Energy
• As heat flows from water to the
surroundings, the particles lose energy.
• The freezing point is the temperature at
which a liquid is converted into a crystalline
solid.
• FYI: Melting point and freezing point are the
same points, just opposite direction of phase
change
Phase Changes That Release Energy (cont.)
• As energy
flows from
water vapor,
the velocity
decreases.
•Deposition is the process
by which a gas or vapor
changes directly to a solid,
and is the reverse of
sublimation.
• The process by
which a gas or
vapor becomes
a liquid is
called
condensation.
Phase Diagrams
• A phase diagram:
• graph of pressure versus temperature
• shows in which phase a substance will
exist under different conditions of
pressure and temperature.
Phase Diagrams (cont.)
• The triple point is the point on a phase
diagram that represents the temperature
and pressure at which all three phases of a
substance can coexist.
p. 429
Phase Diagrams (cont.)
• The phase diagram for different
substances are different from water.
p. 430
Section 12.4 Assessment
The addition of energy to water molecules
will cause them to ____.
A. freeze
B. change to water vapor
D
A
0%
C
D. move closer together
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. form a crystal lattice
Section 12.4 Assessment
The transfer of energy from one object to
another at a lower temperature is ____.
A. heat
B. degrees
D
A
0%
C
D. electricity
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. conductivity
• Assignment #1
• DUE ON Friday, March 19th
– Includes the worksheet labeled assignment
#1
– Also, the following textbook problems:
• Q18, 23, 27, 31-35, 58, 63, 68, 69, 79, 82
Chemistry Online
Study Guide
Chapter Assessment
Standardized Test Practice
Image Bank
Concepts in Motion
Section 12.1 Gases
Key Concepts
• The kinetic-molecular theory explains the properties
of gases in terms of the size, motion, and energy of
their particles.
• Dalton’s law of partial pressures is used to determine
the pressures of individual gases in gas mixtures.
• Graham’s law is used to compare the diffusion rates of
two gases.
Section 12.2 Forces of Attraction
Key Concepts
• Intramolecular forces are stronger than intermolecular
forces.
• Dispersion forces are intermolecular forces between
temporary dipoles.
• Dipole-dipole forces occur between polar molecules.
Section 12.3 Liquids and Solids
Key Concepts
• The kinetic-molecular theory explains the behavior of
solids and liquids.
• Intermolecular forces in liquids affect viscosity, surface
tension, cohesion, and adhesion.
• Crystalline solids can be classified by their shape and
composition.
Section 12.4 Phase Changes
Key Concepts
• States of a substance are referred to as phases
when they coexist as physically distinct parts of a
mixture.
• Energy changes occur during phase changes.
• Phase diagrams show how different temperatures and
pressures affect the phase of a substance.
760 mm Hg is equal to ____.
A. 1 Torr
B. 1 pascal
C. 1 kilopascal
D
C
A
0%
B
D. 1 atmosphere
A. A
B. B
C. C
0%
0%
0%
D. D
A collision in which no kinetic energy is
lost is a(n) ____ collision.
A. net-zero
B. elastic
D
A
0%
C
D. conserved
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. inelastic
Solids with no repeating pattern are ____.
A. ionic
B. crystalline
C. liquids
D
C
A
0%
B
D. amorphous
A. A
B. B
C. C
0%
0%
0%
D. D
What is the point at which all six phase
changes can occur?
A. the melting point
B. the boiling point
D
A
0%
C
D. the triple point
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. the critical point
What are the forces that determine a
substance’s physical properties?
A. intermolecular forces
B. intramolecular forces
D
A
0%
C
D. dispersal forces
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. internal forces
What do effusion rates depend on?
A. temperature of the gas
B. temperature and pressure
of the gas
D
A
0%
C
D. molar mass and temperature
of the gas
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. molar mass of the gas
A sealed flask contains helium, argon, and
nitrogen gas. If the total pressure is 7.5
atm, the partial pressure of helium is 2.4
atm and the partial pressure of nitrogen is
3.7 atm, what is the partial pressure of
argon?
A
D. 7.5 atm
D
0%
C. 1.4 atm
C
B. 6.1 atm
B
A. 1.3 atm
A. A
B. B
C. C
0%
0%
0%
D. D
Adding energy to a liquid will:
A. cause it to form crystal lattice
B. decrease the viscosity
D
A
0%
C
D. increase the velocity of the
particles
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. compress the particles
closer together
Hydrogen bonds are a special type of
____.
A. ionic bond
B. covalent bond
D
A
0%
C
D. dispersion force
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. dipole-dipole force
How many atoms of oxygen are present in
3.5 mol of water?
A. 2.1 x 1024
B. 3.5 x 1023
D
A
0%
C
D. 4.2 x 1024
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. 6.02 x 1023
Click on an image to enlarge.
Table 12.4
Unit Cells
Table 12.5
Types of Crystalline Solids
Figure 12.30 Phase Diagrams
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