States of matter....3 .pptx

STATES OF MATTER & PROPERTIES OF
MATTER
Ms. Punam Dilip Bagad
Assistant Professor, Dept. of Pharmaceutics
GES’s Sir Dr. M. S. Gosavi College of Pharm. Edu. & Research,
Nashik-422005, INDIA
1

Content as per syllabus
 State of matter, changes in the state of matter,
 Latent heats, vapour pressure, sublimation critical point, eutectic
mixtures,
 Gases, Liquefaction of gases, aerosols– inhalers,
 Relative humidity, liquid complexes, liquid crystals, glassy states, solid
crystalline, amorphous(Methods of crystal analysis: X-Ray Diffraction,
Bragg‟s equation)
 Polymorphism (Definition, Different shapes of polymorphs, Example
and its Pharmaceutical applications, Brief introduction of Detection
techniques).
3

Sublimation
 Sublimation is the transition of a
substance directly from the solid to
the gas phase, without passing
through the intermediate liquid phase.
 Carbon dioxide is an example of a
material that easily undergoes
sublimation
 As shown the phase diagram for
water, low pressures are required for
sublimation to take place.
4

Sublimation
 Solid sublimes only when the pressure of the vapour is below the triple point
of that substance.
 Camphor naphthalene P dichlorobenzene and iodine have triple point
pressure below 1 atm.
 A number of substances including camphor, menthol, naphthalene, etc.,
exhibit the phenomenon of sublimation. Other substances such as ices can
also be forced to exhibit the phenomenon of sublimation by varying the
temperature and pressure; the process being adopted during freeze drying of
heat labile substances
5

Sublimation
 Sublimation is an endothermic phase transition that occurs at temperatures
and pressure below a substance’s triple point in its phase diagram.
 Sublimation is a phase change and heat energy must be added to the frozen
product for it to occur.
 In thermodynamics, the triple point of a substance is the temperature and
pressure at which the 3 phases coexist in thermodynamics equilibrium.
6

Examples of Sublimation process:
a) Freeze- drying process
Sublimation in freeze drying process can be described simply as:
 Freeze: The product is completely frozen, usually in a vial, flask or tray.
 Vacuum: The product is then placed under a deep vacuum, well below the triple point
of water.
 Dry: Heat energy is then added to the product causing the ice to sublime
Examples of substances undergoes Sublimation:
a) Dry ice is actually solid, frozen carbon dioxide, which happens to sublimate
or turn to gas at -78.5°C
b) Iodine
7

Advantages of Sublimation
a) Main advantage of sublimation is for purification process. It is
preferred over crystallization process.
b) The minimum amount of product is lost.
c) Solvents are not used.
d) Most traces of any solvent in compound are effectively eliminated.
e) When the substance weighs less than 100 mg the best method for
purification is sublimation.
8

DISAdvantages of Sublimation
a) Recovery may not be complete- the fumes may be blown away.
b) Non-sublimable agent may decompose under heat.
9

Desublimation & Deposition
 Desublimation refers to the process in which a gas changes directly to a solid
without going through the liquid state. The reverse of deposition is
sublimation and hence sometimes deposition is called desublimation.
 Deposition is an exothermic reaction. Deposition as a change of state often
occurs in nature.
 One example of deposition is the process by which, in sub-freezing air,
water vapor changes directly to ice without first becoming a liquid.
 Deposition is used widely to create materials in industry, especially to apply
a thin coating to materials used for cutting or shaping.
 Much research is ongoing in the field of chemical vapor deposition,
especially in the area of materials used to cover polymers, and finding
materials that are less harmful to the environment.
10

Caffeine isolation and Purification by direct sublimation
process:
 Sublimation is a process used to isolate a natural product from other undesired
compounds, and thes purify it by a direct phase change of that product from a solid
to a vapor.
 Crude caffeine is extracted from coffee, and contains many impurities that may
have been separated with it such as tannic acids (carboxylic acid-containing
constituents).
 Pure caffeine has a lower boiling point than the rest of the impurities that make it
crude. Therefore, it will undergo the direct phase change before the rest of the
impurities.
 By condensing the evaporated caffeine over a controlled area, we can separate and
collect it from the impurities.
12

CRITICAL POINT
 The concept of critical point can be understood by plotting the phase
diagrams.
 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, in pressure-temperature space, the
lines of equilibrium or phase boundaries between the three phases of solid,
liquid and gas.
13

CRITICAL POINT
 The phase diagram shows three distinct curves:
(i) The vapour pressure curve along which the liquid and vapour coexist in
equilibrium.
(ii) The melting/fusion curve along which the solid ice and liquid water are in
equilibrium.
(iii) The sublimation curve along which solid ice and vapour are in equilibrium.
(iv) These curves are also called as phase boundaries.
14

CRITICAL POINT
 The phase boundary between liquid and gas does not continue indefinitely.
Instead, it terminates at a point on the phase diagram called the critical point.
Thus, at the critical point, the liquid and gaseous phases become
indistinguishable. In water, the critical point occurs at around
Tc = 647.096K (373.946 °C)
Pc = 22.064 MPa (217.75 atm)
ρ= 356 kg / (m3)
 Thus the critical point is that temperature and pressure at which liquid and
vapour exist as one phase. Above the critical point the fluid is called as
supercritical fluid.
 For most substances, the solid-liquid phase boundary (or fusion curve) in the
phase diagram has a positive slope so that the melting point increases with
pressure.
16

CRITICAL POINT
 This is true whenever the solid phase is denser than the liquid phase. The
greater the pressure on a given substance, the closer together the molecules
of the substance are brought to each other, which increases the effect of the
substance's intermolecular forces.
 Thus, the substance requires a higher temperature for its molecules to have
enough energy to break out of the fixed pattern of the solid phase and enter
the liquid phase. A similar concept applies to liquid-gas phase changes.
 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. For water, triple point is at a temperature of 0.01°C
(273.16° K) and 0.006 atm (0.0006 Mpa).
17

Kinetic molecular THEORY OF GASES
 Maxwell and Boltzmann in 1859 developed a mathematical theory to explain
the behaviour of gases. It is based on the concept that gas is made of a large
number of molecules in a perpetual motion. This theory is therefore called as
kinetic theory of gases.
 The theory is based on the following assumptions :
1. A gas consists of extremely small discrete particles dispersed throughout the container.
2. Gas molecules are in constant random motion with high velocities.
3. Gas molecules can move freely, independent of each other.
4. There is no loss of kinetic energy of a molecule during a collision.
5. The pressure of a gas is due to the striking of gas molecules on the walls of the container.
6. The average kinetic energy of molecules is the same at a given temperature.
18

 A gas that confirms to the assumptions of the kinetic theory of gases is called
as ideal gas.
 An ideal gas also obeys the gas law PV = RT at all pressures and
temperatures.
 A real gas however shows deviations from the above theory. e.g. hydrogen,
nitrogen, oxygen, etc.
 The extent to which a real gas deviates from the ideal behaviour is expressed
in terms of a new parameter called as compressibility factor Z. It is given
as:
Z=PV/RT
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 The deviations from ideality is expressed by a plot of Z vs P. For an ideal gas
Z = 1 and is independent of temperature and pressure. However for a real
gas the deviations from ideal behaviour depends on pressure and
temperature.
 By lowering the temperature and increasing the pressure a gas can be
liquefied. The gas molecules lose their kinetic energy at lower temperatures
and the slow moving molecules are converted into liquid by aggregating due
to attractions between them.
 The same effect is produced due to increase in pressure. The gas molecules
come closer by compression and coalesce to form liquid.
 This phenomenon of liquefaction of a gas can be used for the purpose of
drug delivery in the form of aerosols.
20

Liquefaction of gases
 Liquefaction of gases means converting of gases into liquids. The sequence
of steps involved in this process is described below.
 The principles of liquefaction can be understood under 3 things:
 Critical conditions
 Joule-Thomson’s effect
 Inversion temperature
21

Critical constants
 A gas can be liquefied by: lowering a temperature or by increasing a
pressure.
 At low temperature, gas molecules looses kinetic energy and start moving
slowly. This facilitate aggregation into attraction between them and gas gets
converted into liquid.
 At high pressure, volume is decreased and molecules come closer to each
other and then attractive forces cause liquefaction.
 Andrew’s (1869) studied pressure temperature conditions for several gases
& he described these conditions as follows: critical temperature, critical
pressure and critical volume.
22

Critical constants
 Critical temperature (Tc): Critical temperature is the temperature above
which a gas can not be liquefied, no matter how great the pressure applied is.
 Critical pressure (Pc): Critical pressure is the minimum pressure required to
liquefy a gas at its critical temperature.
 Critical volume (Vc): Critical volume is the volume occupied by a one mole
of gas at a critical temperature and critical pressure.
 Tc, Pc & Vc are collectively called as critical constants
 At Tc & Pc: liquid and gases states become identical and indifferentiable and
this state is called as critical state.
 The smooth merging of gaseous state with liquid state is called as critical
phenomenon.
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 If a gas is cooled below its critical temperature, less pressure is sufficient to
liquefy it.
 Critical pressure is also the highest vapour pressure that a liquid can have.
 In other words, as the temperature is increased sufficiently, a value is
reached above which it is impossible to liquefy a gas irrespective of the
amount of pressure applied.
 Molecules possess sufficient kinetic energy so that no amount of pressure
can bring them with in the range of attractive forces that cause the particles
to stick together. Thus, the effect of temperature is more important than the
pressure.
24

 These critical values indicate the extent of intermolecular forces involved in
the liquids.
 In case of gases, such as ammonia, chlorine, sulphur dioxide and carbon
dioxide, which have fairly high critical temperature, application of suitable
pressure alone is sufficient to cause liquefaction.
 Gases such as hydrogen, oxygen, nitrogen and helium have very low
critical temperatures. These cannot be liquefied by simple technique.
Cooling the gas to below its critical temperature and then compressing can
liquefy a gas.
25

Joule-Thomson's Effect
 When a gas is allowed to pass from a high-pressure zone to a low pressure
zone, the gas expands by taking up heat from the surroundings, which
ultimately results in cooling.
 Joule-Thomson's effect offers further support to the view that attractive
forces do exist between gas molecules.
 As the gas expands, the molecules fall apart from one another. For this to
occur work has to be done to overcome the cohesive and attractive forces. In
this process, the kinetic energy of the gas decreases, since it is proportional
to temperature.
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Inversion temperature
 Inversion temperature is defined as the temperature characteristic of a gas
below which only the gas cools when allowed to get expanded. Experiments
have shown that gases become cooler during Joule Thomson's expansion
only if they are below a certain temperature known as inversion temperature.
 At inversion temperature, there is no increase or decrease of temperature of
the surroundings. Above inversion temperature, there is a small rise in
temperature. Below inversion temperature, there is a fall in temperature.
Inversion temperatures of some gases are:
 Hydrogen (H₂) - 80 °C
 Helium (He) - 240 °C
 The gases, therefore, are initially cooled to temperature below these values
for liquefaction.
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Applications
 Liquefied gases as well as compressed gases find important uses.
1. Liquid ammonia and liquid sulphur dioxide are used as refrigerants.
2. Liquid carbon dioxide is used in soda fountains.
3. Liquid air is an important source of oxygen in rockets, jet propelled planes
and bombs.
4. Compressed oxygen is used in welding.
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Methods of liquefaction
 For liquefaction, a gas has to be cooled below its critical temperature.
 Faraday’s method
 Linde’s method
 Claude’s method
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1. Faraday’s method
 If gas is cooled below its critical
temperature, less pressure is sufficient to
liquefy it. E.g. sulphur dioxide, carbon
dioxide, nitric oxide, chlorine, etc.
 The assembly of apparatus for Faraday's
method is shown in Figure. A V-shaped tube
in one arm of which the gas is produced
while in the other, it is liquefied under its
own pressure and with the help of external
cooling. Hydrogen, oxygen and nitrogen
gases cannot be liquefied by this method
when the pressure is raised at 270 MPa.
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2. Linde’s method
 Linde's method: the principle used in this method is Joule-Thomson effect.
 Principle: Air is liquefied based on the fact that a compressed gas on free
expansion produces intense cooling (Joule-Thomson effect).
 At high pressure, the molecules of the gas are very close to each other and
molecular attractions are appreciable. When it is allowed to escape through a
jet into a region of low pressure, the molecules move apart. In doing so the
inter-molecular attraction must be overcome and energy is needed for it. This
energy is taken from the gas itself, which is thereby cooled. This is called
Joule-Thomson effect.
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2. Linde’s method
Working:
 The apparatus used for liquefaction by Linde's method is shown in Figure. Air is
compressed to above 20 MPa (megapascal) and is allowed to pass through a water-
cooled pipe, where heat of compression is removed.
 Then the compressed air is passed through a spiral pipe with a jet at the end through
which the air is issued.
 The free expansion of gases at the jet results in a considerable drop in temperature.
 The cooled air now passes up and cools the incoming compressed gas of the spiral
tube.
 Then it goes again to the compressor. Thus on repeated cycles of compression and
expansion, the temperature becomes low enough to liquefy air.
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2. Linde’s method
Disadvantages: Hydrogen and helium gas cannot be liquefied by Linde's
method, these show negative Joule-Thomson effect at ambient temperature.
33

3. Claude’s method
 Examples of gases that can be liquefied by this method are: ammonia,
helium, nitrogen, air, chlorine, sulphur dioxide and oxygen.
 Principle: Compressed air is allowed to do mechanical work by
expanding the cylinder of an engine. Here the cooling effect produced
is greater than the Linde's method as the gas does work not only by
overcoming the intermolecular forces, but also in driving the engine.
The cooled gas is circulated around the coil carrying the incoming
compressed gas to produce intense pre-cooling.
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3. Claude’s method
Working:
 The apparatus used for liquefaction by Claude's method is shown in Figure.
Compressed gas is passed through a pipe, which bifurcates towards the
pump.
 A part of the gas goes into the cylinder where it expands and does work by
driving the piston back and the gas thus gets cooled.
 This gas goes up the liquefying chamber and cools the down-coming
compressed gas. As a result, the released gas at the jet gets further cooled
and liquefied.
 Any gas escaping liquefaction goes back to the compressor and the whole
process is repeated over and over again.
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States of matter....3 .pptx

States of matter....3 .pptx

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States of matter....3 .pptx