States Of Matter

Presented By
Swati Mittal
 Objectives of the lecture
After completion of this chapter, the students should be
able to:
Describe the solid state , crystallinity, solvates and
polymorphism
Understand phase equilibria and phase transitions between
the three main states of matter
Understand the phase rule and its application to different
systems containing multiple components.
 STATE OF MATTER
MATTER
• Anything that occupies space and has mass.
• Include things we can see and touch (water, trees) as well as things we can’t see
(air).

THREE STATES OF MATTER

All substances/matter can exist in 3 states : solid, liquid and gas.
●

Solid - molecules are held close together in an orderly fashion with little
●

freedom of motion.

Liquid - molecules are close together but are not held so rigidly in position
●

and can move fast one another.

Gas - molecules are separated by distances that are large compared with the size
●

of the molecules.
The three states of matter are interconvertable.

 The physical properties of a substance depends on the state of the substance.

When a substance undergoes a change in state, many of its physical
properties change.
 Comparison of Gases, Liquids and Solids
 Gases are compressible fluids. Their molecules are widely separated.
 Liquids are relatively incompressible fluids. Their molecules are more tightly packed.
 Solids are nearly incompressible and rigid. Their molecules or ions are in close contact
and do not move.

In order for molecules to exist in aggregates in gases, liquids

and solids Intermolecular forces must exist
 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 repulse one another.
Solids
 SOLIDS & CRYSTALLINE STATE
Pharmaceutical Drugs: more than 80% are solid formulations
 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.
 Classification of Solids

Crystalline Amorphous

 Amorphous
A unit cell is the basic repeating structural unit of a crystalline solid.

lattice
point
At lattice points:
• Atoms
• Molecules
• Ions

Unit Cell Unit cells in 3 dimensions

The crystal lattice of sodium chloride NaCl

Na Cl
 Melting point of crystalline solids
 The temperature at which a liquid passes into the solid state is known as
the freezing point.
 heat of fusion: the heat required to increase the interatomic or
intermolecular distances in crystals, thus allowing melting.
 Crystalline solids
• The units that constitute the crystal structure can be atoms, molecules, or ions.
The sodium chloride crystal, consists of a cubic lattice of sodium ions
interpenetrated by a lattice of chloride ions, the binding force of the crystal being
the electrostatic attraction of the oppositely charged ions.

•In diamond and graphite, the lattice units consist of

atoms held together by covalent bonds.
• In organic compounds, the molecules are held together by van der Waals forces
and hydrogen bonding, which account for the weak binding and for the low
melting points of these crystals.

• ionic and atomic crystals in general are hard and brittle and have high melting
points

• molecular crystals are soft and have relatively low melting points.
 Molecular weight, type of intermolecular bonds and molecular
configuration, all can affect melting and freezing point of compounds.
 In the picture below even number chains have higher melting points
compared to odd number chains (No, of carbons)
 Polymorphism
• When a substance exists in more than one crystalline form, the different form are
designated as polymorphs and the phenomenon as polymorphism.
• Polymorphs have different stabilities and may spontaneously convert from the
metastable form at a temperature to the stable form.
• carbon: diamond in a cubic (tetrahedral lattice
arrangement )

• Graphite in sheet of a hexagonal lattice

 Depending upon their relative stability, one of the several polymorphic
form will be physically more stable than others.
 Stable polymorph represents the lowest energy state, has highest melting
point and least aqueous solubility.

 Metastable form represent the higher energy state, have lower melting point
and high aqueous solubility
.
 Metastable form converts to the stable form due to their higher energy
state.
 Metastable form shows better bioavailability and therefore preferred in
formulations.
 Only 10% of the pharmaceuticals are present in their
metastable form.
 Amorphous Solids
 They differ from crystalline solids in that they tend to flow when
subjected to sufficient pressure over a period of time, and they do
not have definite melting points.
 Whether a drug is amorphous or crystalline has been shown to affect
its therapeutic activity.
 the crystalline form of the antibiotic novobiocin acid is poorly
absorbed and has no activity, whereas the amorphous form is readily
absorbed and therapeutically active.
 This is due to the difference in the rate of dissolution
Latent Heat
Latent heat (also known as latent energy or heat of transformation) is
energy released or absorbed, by a body or a thermodynamic system,
during a constant-temperature process.

Vapor pressure

Vapor pressure or equilibrium vapor pressure is defined as the pressure

exerted by a vapor in thermodynamic equilibrium with its condensed
phases (solid or liquid) at a given temperature in a closed system.
 Sublimation critical point,
The sublimation critical point is that the maximum or minimum pressure
and temperature after which the state of the chemical substance is cannot
be changed. - The sublimation critical point of a chemical called dry ice is -
78.5 oC means dry ice sublimates at this temperature.
The Liquid state
 Boiling

If a liquid is placed in an open container and

heated until the vapor pressure equals the
atmospheric pressure, the vapor
will form bubbles that rise rapidly through
the liquid and escape into the gaseous state.
 The temperature at which the vapor
pressure of the liquid equals the external or
atmospheric pressure is known as the
boiling point.
 The boiling point may be considered the temperature at which thermal
agitation can overcome the attractive forces between the molecules of a
liquid.
Therefore, the boiling point of a compound, like the heat of vaporization
and the vapor pressure at a definite temperature, provides a rough
indication of the magnitude of the attractive forces.
 Heat of Vaporization & critical temperature
• Clausius–Clapeyron Equation:

 where p1 and p2 are the vapor pressures at absolute temperatures T1 and T2, and
∆Hv is the molar heat of vaporization, that is, the heat absorbed by 1 mole of
liquid when it passes into the vapor state.

 Heats of vaporization vary somewhat with temperature.

For example, the heat of vaporization of water is 539 cal/g at 100◦C; it is 478
cal/g at 180◦C,
Gases
 THE GASEOUS STATE
 Under certain condition of pressure & temp., most substances can exist
in any one of the three state of matter.

E.g. water - solid :ice ; liquid : water ; gaseous : steam / water vapor

In gases - molecular motion is totally random, forces of interaction
between molecules are so small, each molecules moves freely and
essentially independently of other molecules.

SUBSTANCES THAT EXIST AS GASES

Under normal condition of pressure & temp. (1 atm , 25oC), elements that
exist as gases are:
 The noble gases (Group 8A elements) : He, Ne, Ar, Kr, Xe, Rn -
monatomic species.
 Hydrogen, nitrogen, oxygen, fluorine, and chlorine - exist as diatomic
molecules : H2, N2, O2, F2, Cl2.
 Allotrope of oxygen, Ozone (O3).
 Compounds that exist as gases are HCl, CO, CO2, NH3, N2O, NO,
NO2, SO2, H2S, HCN, CH4.
 Only O2 essential for our survival. H2S, HCN -
 deadly poisons.
 CO, NO2, SO2, O3 - less toxic. He, Ne, Ar -
 chemically inert.
 Most gases are colorless except F2, Cl2, NO2

General Properties of gas ;

 Compressible
 Have low density (about 2 kg per m3)
 Diffuses quickly (mix thoroughly) Fills up a
 container uniformly
 Exert pressure uniformly on all sides of a container independently
of the height or depth.
• Ideal Gases

• Real Gases
Difference between Ideal gas and Real gas
IDEAL GAS REAL GAS
1. No definite volume Definite volume
2. Elastic collision of particles Non-elastic collisions 2
between Particles
3.No intermolecular attraction force Intermolecular attraction 3
force
4. Does not really exists in the
environment and is a hypothetical gas It really exists in the 4
environment
5. High pressure The pressure is less when
5 Compared to Ideal gas
6.Independent Interacts with others
7.Obeys PV = nRT Obeys p + ((n2 a 7 #
)/V2)(V – n b ) = nRT
Ideal gas law

Molar gas constant:

= 0.08205 liter atm/mole K

= 8.314 × 106 erg/mole K
= 1.987 cal/mole deg
Liquefaction of Gases
 When a gas is cooled, it loses some of its kinetic energy in the form of heat, and
the velocity of the molecules decreases.
 critical temperature: Above which it is impossible to liquefy a gas
irrespective of the pressure applied
 critical pressure: The pressure required to liquefy a gas at its critical temperature
which is also the highest vapor pressure that the liquid can have.
 The further a gas is cooled below its critical temperature, the less pressure is
required to liquefy it.
 The critical temperature of water is 374◦C, or 647 K. and its critical pressure is 218
atm,
Aerosols