States of Matter

1
States of Matter
Chapter 2
Dr. Mohammed Suleiman
2
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
3
Repulsive and Attractive Forces
As two atoms or molecules are brought closer
together, the opposite charges and binding forces
in the two molecules are closer together than the
similar charges and forces, causing the molecules
to attract one another.
The negatively charged electron clouds of
molecules largely govern the balance
(equilibrium) forces between the two molecules
When the molecules are brought so close that the
outer charge clouds touch, they repel each other
like rigid elastic bodies
4
Repulsive and Attractive Forces
Repulsion and the intermolecular 3D structure
1,2-Dimethylcyclopentans
Has two conformation
cis
trans
The trans conformation is energetically favored
due to the a minimization of the repulsive force
5
Intermolecular Forces
Intermolecular forces are attractive forces
between molecules.
Intramolecular forces hold atoms together in a
molecule.

• 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 boiling
point melting point DHvap DHfus DHsub
Generally, intermolecular forces are much weaker
than intramolecular forces.
6
Intermolecular Forces
Cohesion is the intermolecular attraction between
like molecules
Adhesion is an attraction between unlike molecules
Hg
H2O
7
Types of attractive Intermolecular Forces
Types of inter. Forces

• Keesom forces (Dipole-dipole)

Van der Waal forces

• Dipole-induced dipole

• Dispersion (London forces)

• Ion-dipole

• Hydrogen bonding

Depending on the phase of a substance, the nature
of Chemical bonds, and the type of element
present, more than one type of inter. can be
present between the molecules
8
Permanente dipole
Peptide bond
?-
?
9
Intermolecular Forces
Dipole-Dipole Forces
Attractive forces between polar molecules
Max. attractive interaction
In liquid polar molecules are not held as rigidly
as in solid
10
Intermolecular Forces
Ion-Dipole Forces
Attractive forces between an ion and a polar
molecule
11
Interaction Between Water and Cations
in solution
Hydration is one example of ion-dipole
interaction
12
Intermolecular Forces
Dispersion Forces
Attractive forces that arise as a result of
temporary dipoles induced in atoms or molecules
He atom or Non-polar molecule
ion-induced dipole interaction
He atom or Non-polar Molecule
dipole-induced dipole interaction
13
Induced Dipoles Interacting With Each Other
Instantaneous dipole it lasts for tiny fraction
of second
This type of interaction is responsible for the
condensation of non-polar gases as He and N2
14
Dispersion Forces
Benzene
Orbital overlap
15
Intermolecular Forces
Dispersion Forces depends on
1. Charge on the ion and the strength of the
dipole
2. Polarizability is the ease with which the
electron distribution in the atom or molecule can
be distorted.

• Polarizability increases with
• greater number of electrons
• more diffuse electron cloud
• (i.e. large atom)

Dispersion forces usually increase with molar
mass.
16
What type(s) of intermolecular forces exist
between each of the following molecules?
HBr
HBr is a polar molecule dipole-dipole forces.
There are also dispersion forces between HBr
molecules.
CH4
CH4 is nonpolar dispersion forces.
SO2
SO2 is a polar molecule dipole-dipole forces.
There are also dispersion forces between SO2
molecules.
17
What type(s) of intermolecular forces exist
between the following of the following pairs (a)
HBr and H2S (b) Cl2 and CBr4 (c ) I2 and NO3-
(d) NH3 and C6H6 ?
(a) HBr and H2S
Both are polar
H---Br
Therefore, the intermolecular forces present are
Dipole dipole forces ,as well as dispersion
forces
18
(b) Cl2 and CBr4
Both are nonpolar
Only dispersion forces between these molecules
c) I2 and NO3-
I2
is homonuclear diatomic molecule and therefore
nonploar
NO3- anion
The forces between both are
Ion-induced dipole
and
dispersion forces
19
(d) NH3 and C6H6
NH3 is polar
C6H6 is nonpolar
The forces dipole-induced dipole forces and
dispersion forces
20
Intermolecular Forces
Hydrogen Bond
The hydrogen bond is a special dipole-dipole
interaction between they hydrogen atom in a polar
N-H, O-H, or F-H bond and an electronegative O,
N, or F atom.
A B are N, O, or F
21
Intermolecular Forces
Hydrogen Bond
The average strength of a hydrogen bond is quite
large 40kj/mol
Hydrogen bond have powerful effect on the
structure and Properties of many compounds
The strength of a hydrogen bond is determined by
the coulomb Interaction between the lone-pair of
the electronegative atom and the hydrogen nucleus.
Fluorine is more electronegative than oxygen
HF(l) have stronger hydrogen bond than H2O(l)
22
Which of the following can form hydrogen bonds
with water? CH3OCH3, CH4, F- , HCOOH, Na
No electronegative elements (F, O or N ) in
either CH4 an Na
CH4 can not form hydrogen bond
Na can not form hydrogen bond
CH3OCH3, F-, and HCOOH can form hydrogen bond
23
Which of the following species are capable of
hydrogen bonding among themselves? (a) H2S (b)
C6H6 (c) CH3OH
CH3OH only
24
Intermolecular Forces
Hydrogen Bond
Water
Unusual properties of water

• High dielectric constant

• Abnormal low vapor pressure

• High boiling point

25
Hydrogen Bond
Salicylic acid and Iter. Itra. Hydrogen bonding
ASPIRIN
Hydrogen fluoride HF
26
The Bond Energy
Its a measure of the strength of the bonds
H bond is relatively weak (2 to 8 kcal/mole) are
much weaker than the covalent bond (100kcal/mole)
and ionic bond (gt 100kcal/mole)
Energies associated with molecular and ionic
interaction
Interaction (kcal/mol) Interaction (kcal/mol) Interaction (kcal/mol) Interaction (kcal/mol) Interaction (kcal/mol)
Compound Orientation Induction Dispersion Total Energy
H2O 8.69 0.46 2.15 11.30
HCl 0.789 0.24 4.02 5.05
HI 0.006 0.027 6.18 6.21
NaCl --- --- 3.0 183
27
The Three States of Matter
Phase homogenous part of a system with well
defined boundary
2 phases
Energy (heat)
Solids with higher vapor pressure, as iodine and
camphor, can pass directly to the gaseous phase
without melting (sublimation)
Certain asymmetric molecules frequently exhibit
fourth phase, termed (mesophase), which lies
between the liqiud and crystalline states called
liquid crystalline state
28
Freeze Drying (Lyophilization)
is a dehydration process typically used to
preserve a perishable material or make the
material more convenient for transport.
Freeze-drying works by freezing the material and
then reducing the surrounding pressure and adding
enough heat to allow the frozen water in the
material to sublime directly from the solid phase
to the gas phase.
29
Freeze Drying (Lyophilization)
Freeze drying is used is industry and pharmacy
for the manufacturing heat-sensitive drug
Freeze dried Cafe
Water soluble medicines
30
The Three States of Matter
Gaseous state
Gases are in constant random motion
Pressure
(force mass x acceleration)
Units of Pressure
1 pascal (Pa) 1 N/m2 1 atm 760 mmHg 760
torr 1 atm 101325 Pa
31
Ideal Gas Equation
The Three States of Matter
Gaseous state
Charles law V a T (at constant n and P)
Avogadros law V a n (at constant P and T)
R is the gas constant
PV nRT
32
The conditions 0 0C and 1 atm are called standard
temperature and pressure (STP).
Experiments show that at STP, 1 mole of an ideal
gas occupies 22.414 L.
PV nRT
R 0.082057 L atm / (mol K)
33
The Three States of Matter
Gaseous state
The molar gas constant R
PV nRT
R PV/nT 1atm (L) / Mol(K)
At STP condition ( 0 C and 1atm) it was found
experimentally that 1 mol of any gas occupy
22.414 L
R 0.082 L . atm /mol . K
1J Kg m2/s2 1Nm
1 dyn 1 gcm/s² 10-5 kgm/s² 10 µN
R 8.314 J/mol K
1 joule 107 erg
1 cal 4.184 J
and
R 1.987 cal/mol deg
34
In the assay of ethyl nitrite spirit, the nitric
oxide gas that is liberated from a definite
quantity of spirit and collected in a gas burret
occupies a volume of 30 mL at a temperature of
20C and a pressure of 740 mmHg. Assuming that
the gas is ideal, what is the volume at 0C and
760 mmHg ?
Synthesis of ethyl nitrite Used for cold Flu
However FDA has blocked over-the-counter sales of
this same remedy, known in the USA as sweet
nitrite or sweet spirit of nitre since 1980
35
What is the volume of 2 moles of an ideal gas at
25C and 780mmHg?
36
What is the volume (in liters) occupied by 49.8 g
of HCl at STP?
T 0 0C 273.15 K
P 1 atm
PV nRT
V 30.7 L
37
Density (d) Calculations
m is the mass of the gas in g
M is the molar mass of the gas
Molar Mass (M ) of a Gaseous Substance
d is the density of the gas in g/L
38
If 0.3 g of ethyl alcohol in the vapor state
occupies 200 mL at a pressure of 1atm and a
temperature of 100C, what is the molecular
weight of ethyl alcohol? Assume that the vapor
presser behaves as and ideal gas
39
Kinetic Molecular Theory of Gases

1. A gas is composed of molecules that are separated
   from each other by distances far greater than
   their own dimensions. The molecules can be
   considered to be points that is, they possess
   mass but have negligible volume.
2. Gas molecules are in constant motion in random
   directions, and they frequently collide with one
   another. Collisions among molecules are
   perfectly elastic.
3. Gas molecules exert neither attractive nor
   repulsive forces on one another.
4. The average kinetic energy of the molecules is
   proportional to the temperature of the gas in
   kelvins. Any two gases at the same temperature
   will have the same average kinetic energy

40
Kinetic Molecular Theory of Gases
For the last postulates, the following
fundamental kinetic equation is derived
Where P is the pressure and V the volume occupied
by any number n of molecules of mass m and
velocity
We can obtain the root mean square velocity
usually written as
Because nm/V is equal to density (d), we can write
41
What is the root mean square velocity of oxygen
(molecular weight 32) at 25C (298K) ?
42
The van der Waals Equation for Real Gases
Deviations from Ideal Behavior
1 mole of ideal gas
Repulsive Forces
PV nRT
Attractive Forces
43
The van der Waals Equation for Real Gases
Effect of intermolecular forces on the pressure
exerted by a gas.
44
The van der Waals Equation for Real Gases
Van der Waals equation nonideal gas
(
)
P (V nb) nRT
45
A 0.193 mole of sample of ether was confined in a
7.35 L essel at 295 K. Calculate the pressure
produced using (a) the ideal gas equation (b) the
van der Waal equation. (the van der Waal value of
a for ether is 17.38 L2 atm/mol2 the b value is
0.1344 L/mol
46
Calculate the pressure of 0.5 mol CO2 gas in a
fire extinguisher of 1 liter capacity at 27 C
using the ideal gas eqn. and the van der Waal
eqn. (the van der Waal constants ( a b) can be
calculated from the critical Temperature Tc and
the critical pressure Pc)
47
The Three States of Matter
The Liquid state
Effect of Temperature on Kinetic Energy
Methods of achieving Liquefaction
1. Use freezing mixture
Subject a gas into intensive cold using a
freezing mixture
2. Diabetic expansion
The gas is expands so rapidly that no heat
enters the system
T2 gt T1
The work done to bring expansion comes on the
expense of the gas heat energy as a result the
gas T falls
Repeating the process many times cause the gas to
liquefies
3. Joule-Thomson effect
Highly compressed nonideal gas expands into a
region of low p The T decrease results from the
energy expended in overcoming the attraction
force b/w molecules
4. High p in closed camber at T lt Tc
48
The Three States of Matter
The Liquid state
The critical temperature (Tc) is the temperature
above which the gas cannot be made to liquefy, no
matter how great the applied pressure.
The critical pressure (Pc) is the minimum
pressure that must be applied to bring about
liquefaction at the critical temperature.
49
Aerosols
Gases can be liquefied under high pressure in a
closed container as log as its kept below Tc.
The drug is dissolved or suspended in a
propellant a material which is L under the p
condition of the container and its gas under
atmospheric conditions
e.g. of propellant CFCs and HFCs
Ethyl chloride is used as antiseptic when sprayed
into skin it freezes the tissue so that it can be
used as local anesthesia
50
The equilibrium vapor pressure is the vapor
pressure measured when a dynamic equilibrium
exists between condensation and evaporation
51
Molar heat of vaporization (DHvap) is the energy
required to vaporize 1 mole of a liquid at its
boiling point.
P (equilibrium) vapor pressure
T temperature (K)
R gas constant (8.314 J/Kmol)
Vapor Pressure Versus Temperature
52
Alternate Forms of the Clausius-Clapeyron Equation
At two temperatures
or
53
The vapor pressure of diethyl ether is 401 mmHg
at 18 C. Calculate its vapor pressure at 32C ?
( ?Hvap 26.0 kJ/mol for diethyl ether)
54
The vapor pressure p1 of water at 100C is 1 atm
what is the vapor pressure at 120C. ( take ?H as
9720 cal/mol at this pressure range)
55
Boiling point
The boiling point is the temperature at which the
(equilibrium) vapor pressure of a liquid is equal
to the external pressure.
The normal boiling point is the temperature at
which a liquid boils when the external pressure
is 1 atm.
56
Properties of Liquids
a) Surface tension
Surface tension prevents the paper clip from
submerging
Water striders use surface tension to walk on the
surface
57
Properties of Liquids
a) Surface tension
is the amount of energy required to stretch or
increase the surface of a liquid by a unit area.
Pulled downward to side
Pulled in all directions
Strong intermolecular force high
surface tension
Water has the strongest surface tension among
liquids
58
Properties of Liquids
a) Surface tension
Capillary action an example on surface tension
Cohesion is the intermolecular attraction between
like molecules
Adhesion is an attraction between unlike molecules
Hg
H2O
59
Properties of Liquids
b) viscosity
is a measure of a fluids resistance to flow.
Strong intermolecular forces
High viscosity
Viscosity decreases with increasing the liquid
temperature
60
Solids and the crystalline state
A crystalline solid possesses rigid and
long-range order. In a crystalline solid, atoms,
molecules or ions occupy specific (predictable)
positions.
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
• Atoms
• Molecules
• Ions

61
The crystal lattice of sodium chloride NaCl
Na
Cl
62
Seven Basic Unit Cells
The various crystal forms are divide to basic 7
unit according to its symmetry
iodine
NaCl
urea
iodoform
beryl
sucrose
Boric acid
Be3Al2(SiO3)6
63
Types of Crystals

• Ionic Crystals
• Lattice points occupied by cations and anions
• Held together by electrostatic attraction
• Hard, brittle, high melting point
• Poor conductor of heat and electricity

CsCl
ZnS
CaF2
64
Types of Crystals

• Covalent Crystals
• Lattice points occupied by atoms
• Held together by covalent bonds
• Hard, high melting point
• Poor conductor of heat and electricity

diamond
graphite
65
Types of Crystals

• Metallic Crystals
• Lattice points occupied by metal atoms
• Held together by metallic bonds
• Soft to hard, low to high melting point
• Good conductors of heat and electricity

Cross Section of a Metallic Crystal
66
Polymorphism
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.
67
The most common example of polymorphism
High T and p
diamond
graphite
Diamond is metastable and converts very slowly to
graphite
68
Formation of polymorphs of a compound depend on
several pertaining to the crystallization
process, such as

• Solvent differences

Solvent polarity affect the crystalline structure

• Impurities

May favor a metastable polymorph due to specific
inhibition of growth pattern

• The level of supersaturation from which the
  material is crystallized

Generally the higher the concentration above the
solubility, the more the chance a metastable form
is seen.

• The T and p at which the crystallization is
  carried out

• Geometry of the covalent bonds

are the molecule rigid and planar or free and
flexible

• Attraction and repulsion between cations and
  anions

Fit cations into coordinates that are
energetically favorable
69
Polymorphism and Industry/ Pharmaceutical

• Theobroma oil (caco butter)

Exist in 4 polymorphism Gamma form melt at 18
C Alpha melt at 22C Beta prime form melt at
28C 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
polymorph appeared

• Haloperiodal antipsychotic compound

Differeces in the iter. Forces and hydrogen
bonding cause the polymorphism
70
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 form A
71
solvates
Pharmaceutical synthesis include purification and
crystallization, residual solvent can be trapped
in the lattice. This result on cocrystal or
solvate.
The presence of residual solvent may affect
dramatically the crystalline structure of the
solid depending on the type of inter. molecular
forces that the solvent may have with crystalline
solid
72
Amorphous Solids
An amorphous solid does not possess a
well-defined arrangement and long-range molecular
order.
Amorphous substances, as well as cubic crystal,
are isotropic, that is, they exhibit similar
properties in all direction.
Crystals other than cubic are anisotropic,
showing different characteristics (electronic
conductance, refractive index, crystal growth,
rate of solubility ) in various direction along
the crystal.
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.
73
X-Ray Diffraction
X-ray are a form of electromagnetic radiation
having a wavelength of the order of interatomic
distance about 1.5
An Arrangement for Obtaining the X-ray
Diffraction Pattern of a Crystal.
74
Reflection of X rays from Two Layers of Atoms.
(Bragg Equation)
BC CD
2d sinq
nl
75
Melting point and heat of fusion
Solid-Liquid Equilibrium
The melting point of a solid or the freezing
point of a liquid is the temperature at which the
solid and liquid phases coexist in equilibrium
76
Molar heat of fusion (DHfus) is the energy
required to melt 1 mole of a solid substance.
Latent heat of fusion (DHfus) is the energy
required to melt 1 gram of a solid substance.
77
Clapeyorn equation
Relates the change of freezing or melting point
with pressure change
Where Vl and Vs are the molar volume of liquid
and solid respectively
Molar volume (volume in unit of cm3/mole) is
computed by dividing the gram molecular weight by
the density of the compound
Le Châteliers Principle
States that a system at equilibrium readjusts so
as to reduce the effect of an external stress
78
Effect of Increase in Pressure on the Melting
Point of Ice and the Boiling Point of Water
79
What is the effect of an increase of 1atm on the
freezing point of water (melting point of water)?
80
Given that an increase of pressure of 1atm
reduces the freezing(melting) point of ice by
0.0075 deg. To what temperature is the melting
point reduced when a 40.8 kg person skates across
the ice ?