RELATIVE HUMIDITY, Humidity, Wet and Dry Hygrometer, LIQUID COMPLEX, LIQUID CRYSTALS, Types of liquid crystals, GLASSY STATES, Characteristics glassy state, Types of glassy state, What is the Glass Transition Temperature?

1. IIIrd Semesester B. pharmacy
Physical Pharmaceutics-I
Unit-II
State of matter and properties
of matter (Part-6)
(Relative humidity, Liquid Complex and Liquid
crystals)
Miss. Pooja D. Bhandare
(Assistant professor)
Kandhar college of pharmacy

2. RELATIVE HUMIDITY
• Humidity: the amount of water vapor in air
• A ratio between the actual amount of water vapour present in the air
and the maximum amount of water the air can hold at a given
temperature.
• Expressed as a percentage (%)

3. • Formula:
𝑨𝒄𝒕𝒖𝒂𝒍 𝒂𝒎𝒐𝒖𝒏𝒕 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓 𝒗𝒂𝒑𝒐𝒖𝒓 𝒊𝒏 𝒕𝒉𝒆 𝒂𝒊𝒓(𝒈/𝒎𝟑)
𝑴𝒂𝒙𝒊𝒎𝒖𝒎 𝒂𝒎𝒐𝒖𝒏𝒕 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓 𝒗𝒂𝒑𝒐𝒖𝒓 𝒕𝒉𝒆 𝒂𝒊𝒓 𝒄𝒂𝒏 𝒉𝒐𝒍𝒅 (𝒈/𝒎𝟑)
x 100
• Since the latter amount is dependant on temperature, relative humidity is
a function of both moisture content and temperature.

4. Wet and Dry Hygrometer

5. LIQUID COMPLEX
• Complex fluid are binary mixtures that have coexistence between two
phase: Solid- liquid ( suspension or solution of macromolecules such
as polymers), solid-gas ( granular), liquid-gas (Foams) or liquid-liquid
(emulsion).
• They exhibit unusual mechanical responses to applied stress or strain
due to the geometrical constrains that the phase coexistence imposes.

6. • The mechanical responses includes transition between solid like and
fluid like behaviour as well as fluctuations.
• The mechanical properties can be attribute to characteristics such as
higher disorder, caging and clustering on multiple length scales.

7. • Shaving cream is an example of a
complex fluid. Without stress, the
foam appears to be a solid: it does not
flow and can support (very) light
loads.
• However, when adequate stress is
applied, shaving cream flows easily
like a fluid.
• On the level of individual bubbles,
the flows is due to rearrangement of
small collections of bubbles. On this
scale, the flow is not smooth, but
instead consist of fluctuations due to
rearrangements of bubbles and
released of stress.

8. LIQUID CRYSTALS
• A fourth state of matter is called as liquid crystal state or mesophase or
(mesomorphic phase).
• It is the state that occurs between a soild and a liquid.
• It possesses characteristics both liquid and crystalline solids.
• In crystalline solid state the molecule are held in a position by
intermolecular forces
• The particles in a solid move but cannot cross each other because the
attraction of neighbouring atom or molecules are too strong to overcome.

9. • In the liquid state, the molecules move to random positions.
• But in the liquid crystal state , the increased molecular motion
overcomes molecule remains bound by stronger forces.
This produces a molecular arrangement where the molecule is
a layered but within each layer, the molecules are arranged a
random position.
The molecule can slide one around the other , and layers can
slide over one another.

10. This molecular mobility generates fluidity in liquid crystal state.

11. Types of liquid crystals
A. Thermotropic Liquid Crystals: Liquid crystals are said to be thermotropic
if liquid crystalline properties depend on the temperature.
a. Nematic Liquid Crystals: Here the molecules (mesogens) have no
positional order, but they have long-range orientational order.
b. Smectic Liquid Crystals: In this the mesogens have both positional order
and orientational order.
c. Cholestric Liquid Crystal: The cholesteric phases can be defined as a
special type of nematic liquid crystal in which thin layers of the parallel
mesogens have their longitudinal axes rotated in adjacent layer at certain
angle.

12. B. Lytropic Liquid Crystals: Liquid crystals which are prepared by mixing
two or more substances of which one is polar molecule, are know as lytropic
liquid crystals. Example Soap in

13. GLASSY STATES
• Glass is a nonequilibrium, non-crystalline state of matter that appears
solid on a short time scale but continuously relaxes toward the liquid
state.
• Glass is a nonequilibrium, non-crystalline condensed state of matter that
exhibit a glass transition.
• The structure of glass is similar to that of their parent supercooled liquids
(SCL), and they spontaneously relax toward the SCL state. Their ultimate
fate, in the limit of infinite time, is to crystallize.”

14.  Characteristics
Transparency
Solid appearance
Brittleness
Molecule have no order structure
Volume of the system is larger than that of crystalline system with the
same composition

15. • These system are often referred to as:
Amorphous ( i.e disorder) solid (e.g., glass) or
Supercooled liquids(e.g., rubber, leather, syrup).
• Glasses are generally formed by melting crystalline materials at very
high temperatures.
• When the melt cools, the atoms are enclosed in a random(disorder) state
before they can form in a perfect crystalline arrangement.

16. Types:
1. The first type: It is characterized by the cessation of the vibratory movement of rotation
of the molecules in a defined (critical) temperature region. This result in stabilization of
the chain structures of rigidity associated polar molecule( by mean dipole)
2. The second type: It is consists of organic glassy polymerization products. These glass in
the stabilized state have a fibrous structure of rigid valency bonded carbon atom with
small lateral branches in the form of hydrogen atom or more complex radicals.
3. The third type: The third most extensive type of glass state consists of refractory
inorganic compounds of multivalent elements. These glasses in the stabilized state have
the most thermostable chemical structure in the form of three dimensional atomic
valency-bonded spital network.

17.  What is the Glass Transition Temperature?
• The temperature below which a polymer is
hard, brittle and above which it is soft is
called as Glass Transition Temperature.
• The hard or brittle state is called glassy
state
• The soft flexible state is called rubbery
state.

18. THANK YOU!