General Chemistry II
Chapter 1 – The Kinetic Molecular Model and Intermolecular Forces of Attraction in
Matter.
What is kinetic Molecular Theory?
All matter is made
of tiny particles.
These particles are The speed of
in constant motion. particles is
proportional to
temperature.
solids, liquids,
gases differ in the
freedom of motion
of their particles
and the extent to
which the particles
interact.
How does Kinetic Molecular Theory Describe Solid, Liquid, and Gases?
Kinetic Molecular Theory
PROPERTY
Arrangement of
Particles
SOLID


Closely
packed
Orderly
LIQUID


GASES
Less closely
packed than
solid
disorderly


Very far apart
disorderly
Kinetic Energy
of Particles

Particles
vibrate and
rotate about a
fixed position.

Particles slide
over each
other

Particles move
about at a
great speed
Particle Motion

Very low

low

high
Attractive
Forces
Between
Molecules

Very strong

strong

Very weak
The kinetic Molecular Theory explains the properties of solids and liquids in terms
of intermolecular forces of attraction and the kinetic energy of the individual
particles.
“PHASES OF MATTER”
 Each physical state of matter is a phase, a physically distinct, homogeneous
part of a system.
 The properties of each phase are determined by the balance between the
potential (stored energy) and kinetic energy (is the energy that it possesses
due to its motion) of the particles.
 The potential energy, in the form of attractive forces, tends to draw particles
together.
 The kinetic energy associated with movement tends to disperse particles.
3 STATES OF MATTER
1.) Solid
2.) Liquid 3.) Gas
KINETIC MOLECULAR VIEW OF THE 3 STATES
GAS
Attractive forces VS. Kinetic Energy
Attractive forces are weak relative to
kinetic energy.
LIQUID
Attractive forces are stronger because
particles have less kinetic energy.
SOLID
Attractions dominate motion. Particles
are fixed in place relative to each
other.
PROPERTIES
Particles are far apart. A
gas has no fixed shape, or
volume.
A liquid can flow and,
change shape,
but has a fixed volume.
A solid has a fixed shape
and volume.
ATTRACTIVE FORCES
 Intramolecular or bonding forces are found within a molecule. The
chemical behavior of each phase of matter is the same because the same
basic particle is present in each case. (The three types of intramolecular
forces are covalent, ionic, and metallic bonding.)
 H2O molecules are present whether the substance is in the solid, liquid, or
gas phase.
 Intermolecular or nonbonding forces are found between molecules. The
physical behavior of each phase of matter is different.
*PROPERTIES OF MATTER/MOLECULAR BEHAVIOR OF 3 STATES OF MATTER
FOUND IN PPT*
Intramolecular Force - force of attraction within the compound.
Compound –
1. Inorganic/ionic - metals + non-metals
- ionic bond/intramolecular
Ex of ionic compound -> NaCl, MgCl2, Ca(NO3)2
2. Covalent/molecular – nonmetals
Nonpolar – the same non-metals
- Di atomic molecule ( Halogens) - F2,Cl2,Br2, I2
- common gases - H2, O2,N2 ,
- symmetry - contains the same terminal atom
- linear hydrocarbons - CH4, C2H6,
- EN difference - below 0.5 or 0
- Linear structure
- no lone pair electron
Polar molecule - OH bonding - dipole
- H bonded to ---- F , O, N
H+F- - - Hydrfluoric acid - dipole (+) (-)
NH3 - ammonia
H2O - water
- CH3OH - methyl alcohol
- no symmetry --
- bent structure - SO2
- shows lone pair electron
polar , non polar , ionic
1. MgCl2 – ionic
2. C2H5OH – polar
3. CH3OH - polar
4. H2- non polar
5. N2- non polar
6. NH3- polar
7. H+Br- - polar
8. SO2 – polar
Polar <2.0
nonpolar <0.5 or 0
Ionic >2.0 or >1.7
Intermolecular forces
 are attractive forces between molecules or particles in the solid or liquid
states.
 Intermolecular forces (IMF) are relatively weaker than the forces within the
molecules forming bonds (intramolecular forces)
 Intramolecular forces holds atoms together in a molecule
Intermolecular forces of attraction:
The intermolecular forces of attraction in a pure substance are collectively knows as
van der Waals forces.
Ion- dipole force
-
-
It acts between an ion (either positive or negative) and a polar
molecule.
This explains the solubility of ionic compounds in water, which is polar
molecule.
The ions and the oppositely charged ends of the polar water molecules
overcome the attraction between ions themselves. Each ion becomes
separated and water molecules cluster around it.
These forces exist when an ion and the partial charge found at the
end of a polar molecule attract each other.
Dipole- a molecule whose ends have opposite charges.
Polar Vs. Nonpolar Molecules
Polar:


Electrons are not equally shared.
One part of the molecule is slightly negative compared to the other side.
Nonpolar:
 There is an equal sharing of electrons.
 There is no slightly negative or slightly positive side of the molecule (no poles)

Dipole-dipole force
-
forces exist between polar molecules. One end of a dipole attracts the
oppositely charged end of the other dipole
This is the attraction of bond dipoles in different molecules.
Polar molecules attract each other when the positive end of one
molecule is attracted to the negative end of another molecule.
London dispersion forces
-
It is the weakest type of intermolecular force.
When two non-polar molecules approach each other, an instanteneous
dipole moment forms.
This form is sometimes called an induced dipole-induced dipole
attraction.
Hydrogen bond
-
-
It is a special and very strong type of dipole – dipole force that
exists between a hydrogen atom bound to a small and highly
electronegative non-metal atom.
Hydrogen bond occurs in polar molecules containing H and any of
highly electronegative elements, in particular Nitrogen, Flourine, and
Oxygen.
Ion-Ion force
-
Ionic bonding (ex. Mg—Cl=ion-ion) (metal+non-metal)
Ionic, H-bonding, Dipole, or London?
DETAILS
ΔEN = 0 - 0.5
BOND
Nonpolar
MOLECULE
Nonpolar
IMF
London
ΔEN = 0.5 - 1.7
ΔEN = 1.7 - 3.2
H + N,O,F
Symmetrical
molecule (any
ΔEN)
Polar
Ionic
Polar
---
Polar
Ionic
polar
nonpolar
Dipole-dipole
Ionic
H-Bonding
London
Different types of Intermolecular Forces from Weakest to strongest
Weakest to strongest
o
o
o
o
o
LONDON DISPERSION FORCE - Weakest
DIPOLE-DIPOLE FORCE
HYDROGEN BONDING
ION-DIPOLE FORCE
ION-ION FORCE - strongest