Kinetic Theory of Matter
Matter is made up of particles which are in
continual random motion.
Binding Forces between Molecules
The Three States of Matter:
In order for molecules to exist in aggregates in gases, liquids
and solids Intermolecular forces must exist
What is matter?
Matter is anything that has mass and takes up •
STATES OF MATTER
Based upon particle arrangement
Based upon energy of particles
Based upon distance between particles
States of matter and intermolecular forces: •
Molecules in a gas attract each other, but the attractive forces are weak •
compared with the thermal motion of the molecules so the molecules spread
out evenly to fill the container enclosing them, however if a gas is cooled
, the thermal motion will decrease and the gas will first liquify and then it will
Liquids have sufficient attractive forces to stay in an open container but they •
can still flow. Properties such as viscosity and its inverse fluidity are measures
of the attractive forces in liquids.
E.g., glycols are very viscous, while hexane flows very easily. •
Solids have enough attractive forces called crystal lattice energy that they •
do not even flow, e.g., magnesium stearate is a lubricant needed to ease
movement of drug powder in tableting machine.
Solids and the crystalline state
A crystalline solid possesses rigid and long-range order. In a
crystalline solid, atoms, molecules or ions occupy specific
An amorphous solid does not possess a well-defined
arrangement and long-range molecular order.
A unit cell is the basic repeating structural unit of a crystalline solid.
At lattice points
Unit cells in 3 dimensions
The crystal lattice of sodium chloride NaCl
Seven Basic Unit Cells
The various crystal forms are divide to basic 7 unit according to its symmetry
Characterization of crystalline
materials:A- X- Ray Diffraction:It is photographed on sensitive plate arranged behind
the crystal and by such method the structure of a crystal
may be investigated.
B- Melting point and Heat of fusion
The freezing point or the melting point of a pure
crystalline solid is strictly defined as the temperature
at which the pure liquid and solid exist in equilibrium
Some substances, such as carbon or sulfur, my exist in more
than one crystalline form and are said to be polymorphism.
X-ray are a form of electromagnetic radiation having a wavelength of the order of interatomic
An Arrangement for Obtaining the X-ray Diffraction Pattern of a Crystal.
Some elemental substance such as C and S ,may exist in more than one crystalline form and are
said to be allotropic, which is a special case of polymorphism
Polymorphism are chemically identical, but they may have:
Different stabilities •
May spontaneously convert from metastable form at a temperature to a stabile form.
Different melting point, XRD pattern and different solubility•
Solubility and melting point are very important in pharmaceutical processes including
dissolution and formulation.
Polymorphism and Industry/ Pharmaceutical
Theobroma oil (caco butter)•
Exist in 4 polymorphism
Gamma form melt at 18 °C
Alpha melt at 22°C
Beta prime form melt at 28°C
Stable beta form melt at 24.5 °C
AIDS drug ritonavir•
Was marked in dissolved formulation
until a previously unknown , more stable and less soluble
Haloperiodal antipsychotic compound•
Differences in the inter. Forces and hydrogen bonding
cause the polymorphism
Polymorphism and Industry/ Pharmaceutical
Cortisone acetate •
Exist in at least 5 polymorph
Heating, grinding , water and suspension in water are all factors that affect the interconversion
of these different cortisone acetate forms.
Tamoxifen antiestrogenic & antineoplastic drug•
used for breast cancer
B form (with H bonding is more stable) than
An amorphous solid does not possess a well-defined arrangement and long-range
, and many synthetic plastics)
molecular order.( Ex. Glass, pitch(
Amorphous substances, as well as cubic crystal, are isotropic, that is, they exhibit similar
properties in all direction. (iso= equal)
The differ from crystalline solid in that they tend to flow and don’t have definite melting point.
Crystals other than cubic are anisotropic, showing different characteristics (electronic
conductance, refractive index(RX), crystal growth, rate of solubility ) in various direction along
the crystal. (aniso= un equal)
Amorphous or crystalline & therapeutic activity:
The crystalline from of the antibiotic novobiocin acid is poorly absorbed and has no
activity, where the amorphous form is readily absorbed and therapeutically active, due to
different dissolution rate.
Term for Phase
Heat Movement During
which includes Heat goes into the
liquid as it vaporizes.
Heat leaves the gas
Gas to liquid Condensation
as it condenses.
Heat goes into the
Solid to gas Sublimation
solid as it sublimates.
Effect of Increase in Pressure on the Melting Point
of Ice and the Boiling Point of Water
Intermolecular forces are attractive forces between molecules
1) ionic, 2) dipole - dipole, 3) H-bonding, 4) London forces,
5) covalent (network solids), 6) metallic.
Intramolecular forces hold atoms together in a molecule
(ionic, polar, non-polar).
Intermolecular vs Intramolecular
41 kJ to vaporize 1 mole of water (inter)
930 kJ to break all O-H bonds in 1 mole of water (intra)
“Measure” of intermolecular force
forces are much
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