States of Matter SB

States of matter
Prof. Mirza Salman Baig
Assistant Professor in Pharmaceutics
AIKTC, School of Pharmacy, New Panvel
Affiliated to University of Mumbai (INDIA)
Latent heat, vapour pressure,
Boiling point, Sublimation,
Critical point,
Eutectic mixtures,
Gases, aerosols – inhalers,
Relative humidity,
Liquid complexes, Liquid crystals,
Glassy states, solid crystalline,
Amorphous & polymorphism

The Latent heat
• All the heat energy supplied to a crystalline solid at its melting
point utilize into melting, and none of it goes into raising the
temperature this is known as Latent heat.
• When energy is absorbed as heat by a solid or liquid during the phase
transformation, the temperature of the object does not rise.
• The thermal energy cause the mass to change from one phase, or
state, to another without rise in temperature

The Latent heat
• The latent heat associated with melting a solid or freezing a liquid is
called the heat of fusion.
• The latent heat associated with vaporizing a liquid or a solid or
condensing a vapor is called the heat of vaporization.
• The latent heat is normally expressed as the amount of heat (in units
of joules or calories) per mole or unit mass of the substance
undergoing a change of state.

Evaporation
• When a liquid is placed in an open vessel, it
evaporates.
• The molecules of a liquid move with different kinetic
energies.
• Those molecules which possess higher kinetic
energies manage to overcome the intermolecular
forces holding them in a liquid and thus escape from
the liquid surface as vapors.
• The process by which the molecules of a liquid go
into the gaseous state is called vaporization or
evaporation.

Condensation
• If the liquid is placed in a closed
vessel, the vapors escape into the
empty spaces above the liquid but
as the concentration of the liquid
molecules in the empty spaces
increases the molecules strike on
the walls of the vessel and get
converted back into liquid. This
process is called as condensation.

Equilibrium (Condensation ⇌ Evaporation)
• Thus a dynamic equilibrium is
established between the liquid and
vapor at a given temperature.
• Now the concentration of the vapour
in the space above the liquid remains
unchanged with the lapse of time.
This vapour will exert a definite
pressure at equilibrium.
• The pressure exerted by the vapor in
equilibrium with the liquid is called as
vapor pressure.

FACTORS AFFECTING VAPOUR PRESSURE :
• (1)Nature of the liquid : The vapour pressure exerted by a liquid
depends on its nature. Liquids with a low boiling point will have a
high vapour pressure.
• (2)Intermolecular forces of attraction : Liquids with weak
intermolecular forces of attraction evaporate faster and then have a
high vapour pressure.
• (3)Temperature : If the temperature of the liquid increases, the
vapour pressure also increases. An increase, in temperature increases
the kinetic energies of more molecules and hence more of them leave
the liquid thereby increasing the vapour pressure.

METHODS FOR MEASURING VAPOUR PRESSURE
• A sufficient amount of liquid whose vapor
pressure is to be determined is placed in
the bulb connected to a mercury
manometer.
• A part of the liquid evaporates. The system
is then maintained at a fixed temperature
for enough time for equilibrium.
• The difference in the levels of mercury in
the manometer is equal to the vapor
pressure of the liquid.

The Boiling point
• If a liquid is placed in an open container and heated until the vapor
pressure equals the atmospheric pressure, the liquid starts to boil and
escape into the gaseous state.

The temperature at which the vapor pressure of the liquid equals the
external or atmospheric pressure isknown as the boiling point
.
The absorbed heat used to change the liquid to vapor (at constant
temperature i.e., boiling point) is called the latent heats of vaporization.
The Boiling point

• The temperature at which the vapor pressure of the liquid equals an
atmospheric pressure of 1 atm is called normal boiling point
• At higher elevations, the atmospheric pressure decreases and the
boiling point is lowered.
• At a pressure of 700 mm Hg, water boils at 97.7°C; at 17.5 mm Hg, it
boils at 20°C.
• The change in boiling point with pressure can be computed by using
the Clausius–Clapeyron equation.
The Boiling point

Sublimation
• Sublimation is the transition of a substance directly from the solid to
the gas phase, without passing through the inter-mediate liquid
phase.
• Sublimation is caused by the absorption of heat which provides
enough energy for some molecules to overcome the attractive
forces of their neighbors and escape into the vapor
• Sublimation occur at low pressure

The Phase diagram (for water)
• The simplest phase diagrams are
pressure-temperature diagrams of a
single simple substance, such as water.
• The axes correspond to
the pressure and temperature.
• The phase diagram shows, pressure-
temperature space, the lines of
equilibrium or phase boundaries
between the three phases of solid, liquid
and gas

The Phase diagram (for water)
• The phase diagram shows three distinct curves :
• The vapour pressure curve along which the liquid and vapour coexist in
equilibrium.
• The melting/fusion curve along which the solid ice and liquid water are in
equilibrium.
• The sublimation curve along which solid ice and vapour are in equilibrium.
• These curves are also called as phase boundaries.
• The point at which all the three curves meet is called as the triple point.
• Thus triple point is that point at which all the phases solid, liquid and gas
coexist in equilibrium

The critical point
• Thus the critical point is that temperature and pressure at which
liquid and vapour exist as one phase.
• The critical point is different from triple point
• Above the critical point the fluid is called as supercritical fluid.

Supercritical fluids
• The density of supercritical fluids is about threeorders of
magnitude greater than that of gas; therefore, the dissolving power
is increased for supercritical fluids, because as density increases
more solute–solvent interactions will occur.
• Since supercritical fluids have great dissolving power, they are
used in a number of ways for purification, extraction,
fractionation, and recrystallization of a wide host of material

EXAMPLES OF SCF
SOLVENT
MOLECULAR
WEIGHT
CRITICAL
TEMPERATURE
CRITICAL
PRESSURE
CRITICAL
DENSITY
g/mol K (atm) g/cm3
Carbon dioxide
(CO2)
44.01 304.1 7.38 0.469
Water
(H2O)
18.015 647.096 22.064 0.322
Methane
(CH4)
16.04 190.4 4.60 0.162
Acetone
(C3H6O)
58.08 508.1 4.70 0.278
Supercritical fluid examples

Advantages of SCF
1.SCFs have solvating powers similar to liquid organic solvents, but with
higher diffusivities, lower viscosity, and lower surface tension
2.Since the solvating power can be adjusted by changing the pressure or
temperature separation of analytes from solvent is fast and easy.
3.By adding modifiers to a SCF (like methanol to CO2) its polarity can be
changed for having more selective separation power.
4.In industrial processes involving food or pharmaceuticals, one does not
have to worry about solvent residuals as you would if a "typical" organic
solvent were used.
5.Candidate SCFs are generally economic, simple and safe.
6.Disposal costs are much less and in industrial processes, the fluids can be
simple to recycle.

Eutectic mixture
Salol + Thymol

• A eutectic system is a homogeneous mixture of substances that melts
or solidifies at a single temperature that is lower than the melting
point of either of the constituents.
• The eutectic temperature is the lowest possible melting temperature
over all of the mixing ratios for the involved component species.
• These mixtures can be explained with the help of a phase diagram.

Salol Thymol
Phase diagram
There are four regions:
(i) a single liquid phase,
(ii) a region containing
solid salol and a conjugate
liquid phase,
(iii) a region in which
solid thymol is in
equilibrium with a
conjugate liquid phase,
and
(iv) a region in which both
components are present as
pure solid phases.

The eutectic point
• The lowest temperature at which a liquid phase can exist in the
salol–thymol system is 13◦C, and this occurs in a mixture containing
34% thymol in salol.
• This point on the phase diagram is known as the eutectic point
• The eutectic point is the point at which the liquid and solid phases
have the same composition (the eutectic composition).

States of matter
Gaseous state

States of matter
1. Gaseous state
2. Liquid state
3. Solid and crystalline state
4. Liquid crystalline state

Gas general properties
• Gases can be expanded infinitively, therefore gases can fill containers
and take their volume and shape.
• Gases diffuse and mix evenly and rapidly.
• Gases have much lower densities than liquids and solids (There is a
lot of free space in a gas, therefore; It is the most compressible state
of matter).

Gas general properties
• Gas molecules travel in random paths and collide with one another
and with the walls of the container in which they are confined
• Hence, gas exerts a pressure (a force per unit area) expressed in
dynes/cm2, atmospheres or in mmHg (1 atm = 760 mmHg = 760
Torr).
• Gases have volumes that is expressed in liters or cubic centimeter
(1 cm3 = 1 mL).
• The temperature involved in the gas equations is expressed by the
absolute or Kelvin scale [0°C = 273.15 K (Kelvin)].

Ideal gas
• Ideal gas is a gas where no intermolecular interactions exist
and collisions are perfectly elastic, and thus no energy is
exchanged during collision.
• The properties of the ideal gas can be described by the
general ideal gas law, which are derived from Boyle, Charles
and Gay-Lussac laws

Ideal gas Boyle’s law
• Boyle’s law states that “the volume
and pressure of a given mass of gas
is inversely proportional”
• when the pressure of a gas
increases, its volume decreases
• P ∝ 1/v
• P =k/v
• P1V1 = P2V2
• P: pressure, K: constant,
• V: volume

Ideal gas Charles law
• Charles law states that “the
volume and absolute
temperature of a given mass of
gas at constant pressure are
directly proportional”
• when the temperature of a gas
increases, its volume increases as
well
• V ∝ T or V = k T
• V1/T1=V2/T2
• T: temperature in Kelvin

Ideal gas Gay-Lussac law
• The law of Gay-Lussac states that “the
pressure and absolute temperature of
a given mass of gas at constant
volume are directly proportional”
• when the temperature of a gas
increases, its pressure increases as
well
• P ∝ T or P = k T
• P1/T1 = P2/T2

Ideal gas Combined gas law
• Boyle, Gay-Lussac and Charles law can be combined to
obtain the equation
𝑷 𝟏 𝑽 𝟏
𝑻 𝟏
=
𝑷 𝟐 𝑽 𝟐
𝑻 𝟐
Where,
V = volume (dm3)
P= Pressure (atm.)
T= Temperature (K)

Combined gas law: Example 2
• A sample of methane CH4 has a volume of 7.0 dm3 at a temperature
of 4°C and a pressure of 0.848 atm. Calculate the volume of
methane at a temperature of 11°C and a pressure of 1.52 atm.

Ideal gas
General ideal gas law
• General ideal gas law (also called equation of state) relates the
specific conditions, that is, the pressure, volume, and temperature of
a given mass of gas.

Ideal gas
General ideal gas law: Molar gas constant
• The volume of 1 mole of an ideal gas under standard conditions of
temperature and pressure (i.e., at 0°C and 1 atm) has been found by
experiment to be 22.414 liters.
• Substituting this value in general ideal gas law:

Ideal gas
General ideal gas law: Molecular weight
• The approximate molecular weight of a gas can be determined by use
of the ideal gas law:
Where,
g= no. of grams of gas
M= molecular wt. of gas

Ideal gas
Kinetic Molecular Theory
1. Kinetic molecular theory explains the behavior of gases according to the
ideal gas law:
2. Gases are composed of particles called atoms or molecules, the total
volume of which is very small (negligible) in relation to the volume of
the space in which the molecules are confined.
3. Gas molecules exert neither attractive nor repulsive forces on one
another.
4. The particles exhibit continuous random motion. The average kinetic
energy, E, is directly proportional to the absolute temperature of the gas,
E =
𝟑
𝟐
RT.
5. The molecules exhibit perfect elasticity; there is no net loss of speed or
transfer of energy after they collide with one another and with the walls of
the confining vessel.

Real gas
• Real gases do not interact without energy exchange, and therefore do
not follow the laws of Boyle, Charles, and Gay-Lussac.
• Real gases molecules are not composed of infinitely small and
perfectly elastic non-attracting spheres.
• They are composed of molecules of a finite volume that tend to
attract one another.
• The significant molecular volume and the intermolecular attractions
between gas molecules affect both the volume and the pressure of
the real gas, respectively.

Real Gas
• Van der Waals Equation: The influence of non-ideal behavior of gas is
greater when the gas is compressed (At high pressure and low
temperature).
• Pressure correction: Real pressure = Ideal pressure + inward pull
• Volume correction: Real volume = Ideal volume – volume occupied by
gas molecules

Real Gas
• Van der Waals Equation: The van der Waals equation is a modified
ideal gas equation that considers the factors that affect the volume
and pressure of a real gas.
• The term a/V2 accounts for the internal pressure per mole resulting
from the intermolecular forces of attraction between the molecules;
b accounts for the excluded volume, which is about four times the
molecular volume.

Principle
• Liquefaction of a gas can be achieved by applying pressure on it and
keeping the temperature below the critical temperature.
• When the pressure is reduced, the molecules expand, and the liquid
reverts back to the gaseous state.
• Aerosols are based on this principle of reversible change of state on
the application and release of pressure.

Propellant
• In pharmaceutical aerosols a drug is dissolved
or suspended in a propellant (a material that
is liquid under the high pressure inside the
container but forms a gas under normal
atmospheric conditions).
• Part of the propellant exists as a gas and
exerts the pressure necessary to expel the
drug, whereas the remainder exists as liquid
and provides a solution or suspension vehicle
for the drug

The Aerosol container
• The container is designed in such a
manner that on depressing a valve,
some of the drug-propellant mixture
is expelled out due to the excess
pressure inside the container.
• The propellant used in such products
are generally fluorinated
hydrocarbons although gases such as
nitrogen and carbon-di-oxide and also
being used.

Filling of the container
• The aerosol containers are filled either by cooling the propellant and
drug to a low temperature within the container which is then sealed
with the valve.
• Alternatively, the drug is sealed in the container at room temperature
and the required quantity of propellant is forced into the container
under pressure.
• In both the cases, when the container is at room temperature, part
of the propellant is in the gaseous state and exerts pressure
necessary to extrude the drug while the remaining is in the liquid
state and provides a solution or suspension vehicle for the drug.

INHALERS
• These are the devices used to generate the aerosols of solid
particles.
• These are of following types:
• Metered dose inhalers (MDI)/Pressurised metered dose inhalers
(pMDI).
• Dry Powder Inhalers (DPI).
• Nebulisers.

Metered dose inhalers
(MDI)
• These aerosols are specifically
designed to deliver a fixed dose of
the drug, every time the valve is
actuated.
• This modification is done by using a
metering valve as a component of
the aerosol package.
• These type of inhalers are widely
used to improve drug delivery into
the nasal passages and the
respiratory tract.
•

Metered dose inhalers (MDI)
Advantages :
• (1) It delivers a specified amount
of dose.
• (2)Portable and compact.
• (3)No product contamination
and easy to use.
• (4)Dose to dose reproducibility
is high.
Disadvantages :
• (1)More pharyngeal deposition
than deposition in lungs.
(2)Patient counseling regarding
the way to use it is needed.

LIQUID COMPLEXES
• Complex liquids or liquid complexes are
materials intermediate between
conventional liquids and solids, displaying
fluid-like as well as solid-like
behavior. (Example: polymeric melts,
Foams)
• Many of these systems are disordered and
strongly heterogeneous with large
fluctuations on a wide range of length and
time-scales. Furthermore many

Liquid complexes
• These are binary mixtures that have a coexistence between two phases:
solid-liquid (suspensions or solutions of macromolecules such as
polymers), solid-gas (granular), liquid-gas (foams) or liquid-liquid
(emulsions).
• They exhibit unusual mechanical responses that are applied stress or
strain due to the geometrical constraints that the phase coexistence
imposes.
• The mechanical response includes transitions between solid-like and
fluid-like behavior as well as fluctuations.
• Their mechanical properties can be attributed to caging, and clustering on
multiple length scales.
• Shaving cream is an example of a complex fluid. Without stress, the foam
appears to be a solid: it does not flow. However, when adequate stress is
applied, shaving cream flows easily like a fluid.

GLASSY STATES
• Glass is a state of matter which combine
some properties of crystals and some of
the liquids but are distinctly different from
both.
• Glasses have the mechanical rigidity of
crystals, but the random disordered
arrangement of molecules that
characterizes liquids.
• Glasses are usually formed by melting
crystalline materials at very high
temperatures.
• When the melt cools, the atoms are locked
into a random (disordered) state. Hence,
they can not form a perfect crystal
arrangement

GLASSY STATES
• As a liquid (at the melting temperature, Tm) is cooled from a high
temperature, it may either crystallize or become super cooled.
• The particles (atoms, molecules or ions) forming crystalline materials are
arranged in orderly repeating patterns, extending to all three spatial
dimensions.
• The structures of crystalline solids depend (predictably) on the chemistry of
the material and the conditions of solidification
• Super cooled liquids, on the other hand, demonstrate a rather different
behavior. Upon cooling below the Tm, their particles progressively lose
translational mobility, so that around the so called glass transition
temperature (Tg)

Types of glassy states
• Glassy states of polymers
• It consists of polymers which have been cooled below the glass
transition temperature (Tg).
• Glassy states of inorganic compounds
• It consists of inorganic compounds of multivalent elements. They
have the most thermostable chemical structure. e.g. Silicon dioxide

Liquid Crystal
• Some organic molecules do not melt to give liquid directly
• They pass through intermediate state known as ‘liquid crystal state’
• These substance have long rod-shaped molecules
• E.g. p-oxyanisole
• Liquid crystal have structure between liquid and crystalline solid.
• As Liquid molecules can move randomly and solid crystal have ordered and fixed
arrangement while liquid crystals are arranged parallel to each other and they
can flow.
• Hence, liquid crystals have fluidity of liquid and optical property of solid

Types of liquid crystals
• Nematic liquid crystal: They
have molecules parallel to each
other like soda straw but they
are free to slide or roll
individually
• Smectic liquid crystal: The
molecules in this type are also
arranged parallel but these are
arranged in layers. The layers can
slide on each other.
• Cholesteric liquid crystal: Like
nemetic they also have
molecules parallel but arranged
in layers. Due to sliding of layers
it form spiral structure.

Pharmaceutical applications of LC
• Many small molecular pharmaceutical active compounds have been demonstrated to
form LC mesophases e.g. Itraconazole hydrochloride is an antifungal drug which forms
chiral nematic phases.
• Large molecular pharmaceutical active compounds are also known to form LCs; some
common examples of them are cyclosporine, calcitonin, amylin, nafarelin, detirelix and
leuprolide.
• Some of the pharmaceutical excipients such as hydroxypropyl cellulose, ethyl cellulose
and cellulose acetate have also displayed LC phases
• Liquid crystalline state of lipids have been used as a model to mimic the biological
systems.
• In various foods, pharmaceutical and biotechnical applications, the liquid crystalline
phases formed by surfactants in aqueous medium represent useful host systems for
drugs, amino acids, peptides, proteins and vitamins.
• Colloidal smectic nanoparticles are emerging as a carrier system for lipophilic drugs due
to their liquid crystalline nature..

Relative Humidity
• Relative Humidity may be defined as the ratio of amount of water
vapor in the air at a specific temperature to the maximum amount
that the air could hold at that temperature, expressed as a
percentage.

Relative Humidity
• In other words, it is the ratio of the actual water vapour pressure to
the saturation water vapour pressure at the prevailing temperature.
• The amount of water vapour the air can hold increases with
temperature. Relative humidity therefore decreases with increasing
temperature if the actual amount of water vapour stays the same.

General properties
Solids are much denser than both gases and liquids due to the presence of
very strong intermolecular forces.
Solids are essentially incompressible (small empty spaces) Solids have
definite volume and shape (rigid, not fluid)
Solids have no translational
motion (only vibration)

Crystalline Solids
Crystalline solids, such as sodium chloride, and menthol, are composed of
structural units arranged in fixed geometric patterns or lattices.
Menthol
Sodium Chloride

Crystalline Solids
• Crystalline solids show definite melting points, passing rather sharply from
the solid to the liquid state.
• The morphology of a crystalline form is often referred to as its habit, where
the crystal habit is defined as having the same structure but different outward
appearance.

Crystalline Solids
Types of crystalline solids
The units that constitute the crystal structure can be atoms, molecules, or ions
• Ionic crystals
• Covalent (atomic) crystal
• Molecular crystal
• Metallic crystal
.

Crystalline Solids
Types of crystalline solids: Ionic crystal
Ionic crystal
Lattice units consist of
ions held together by
ionic bonds e.g. NaCl
Ionic and atomic crystals in general are
hard and brittle and have high melting
points, while molecular crystals are
soft and have relatively low melting
points.

Crystalline Solids
Types of crystalline solids: Covalent (Atomic) Crystal
Covalent (Atomic) Crystal
Lattice units consist of atoms
held together by covalent bonds
e.g. diamond

Crystalline Solids
Types of crystalline solids: Molecular Crystal
Molecular Crystal
Lattice units consists of
molecules held together by
van der Waals forces
e.g. Solid CO2

Crystalline Solids
Types of crystalline solids: Metallic crystals
Metallic crystals are composed of positively charged ions in a field
of freely moving electrons. The atoms are held together by
metallic bonding.
Metals are good conductors of
electricity because of the free
movement of the electrons in the
lattice.
Metals may be soft or hard and
have low or high melting points.

Amorphous Solids
Amorphous solids may be considered as supercooled liquids in which the
molecules are arranged in a somewhat random manner as in the liquid
state.
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.
Amorphous Crystalline

Amorphous Solids
• A state of substance that consists of disordered arrangement of molecules or
that do not possess distinguishable crystal lattice, but just strewn in any old
fashion is called as amorphous state.
• Amorphous substances do not have characteristic sharp melting point but they
soften over wide temperature range
• The pharmaceutical advantages of amorphous solid is its higher solubility and
bioavailability.
• Its pharmaceutical disadvantages is its low stability (over time, amorphous
solid may transform to the more stable crystalline state).
• Examples of amorphous drugs are accupril/accuretic used to treat high blood
pressure and intraconazole used as an acne medication

Method to differentiate crystalline and Amorphous
Solid
X-ray diffractionThermo analytical method: Differential
scanning calorimeter (DSC)

Difference between Crystalline and
Amorphous Solids

Difference between
Crystalline and
Amorphous Solids

Polymorphism
• Some elements like carbon (Dimond, graphite) and sulphur exist in more
than one crystalline form which is known as polymorphism
• Diamond is metastable (less stable) form of carbon
• Polymorphs exhibit different-
• Melting points
• Solubility
• Formation of different polymorphs depend upon crystallization conditions
(Level of supersaturation, temperature)

Pharmaceutical significance of polymorphs
• Generally, all the long chain organic compounds exhibit polymorphism
• Eg: Triglyceride tristearin shows
• Low melting point metastable (α)
• Beta prime (β’)
• High melting point Stable beta (β)
• Theobroma (coca butter) shows 4 forms γ, α, β’ and β. For making
suppositories Theobroma should be melted at lowest possible temperature
(33C) so that stable polymorph (β MP 34.5C)) should not destroy.
• Because of difference in solubilities of polymorphs, one may be more active
therapeutically than other. E.g. Sulfameter antimicrobial form II is more
active than Form III.
• Cortisone acetate suspension … out of 5 forms only one is stable in presence
of water. During preparation of suspension stable form should be available to
avoid caking.

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