Pharmshala

Discover the art of Pharmacy

States of Matters

  • Matter- anything that has mass and occupies space

There are three states of matter:-

  1. Solid
  2. Liquid
  3. Gas

SOLIDS :- Definite shape and size. High density particles closely packed. Force of attraction between particles are maximum. Incompressible.

LIQUIDS :- Definite volume but take the shape of container. Force of attraction between particles is less than solids and more than gases. Incompressible.

GASES :- Do not have definite shape and volume. Particles are at sufficient distance from each other. Least force of attraction between molecules. Highly compressible.

  • Temperature and pressure are 2 important factors which determines the state of substance.
  • Liquid crystals- State of molecule between liquid and crystalline state.
  • Supercritical fluids- State of molecule between liquid and gases.
  • Examples of Compressed gas – Aerosol, deodorant, inhalers.
  • Vander Waals forces
    • They are the weakest intermolecular forces.
    • These forces are the sum of attractive and repulsive electrical forces between atoms and molecules.
    • Solids held together by these forces have lower melting point and are softer than those held together by ionic, covalent, metallic bond
    • They include London forces, dipole – dipole forces and dipole induces dipole forces.
  • London / dispersion forces
    • They are weak, temporary attractive forces, that result when e– in 2 adjacent atoms occupy positions that make the atom form temporary dipole.
  • Because of constant motion of e– ,an atom or molecule can develop instantaneous dipole, when its e– are distributed unsymmetrically about the nucleus . A second atom B can be distorted by appearance of dipole in atom A ( because e– repel each other) which leads to an electrostatic attraction between molecules
    • London forces increase with – increase in number of e– in molecules , increase in molecule size, increase in molecule weight.
    • They act on short distance and their magnitude depend on the polarizability of particles.
  • Dipole-Dipole forces
    • They are strong and exist between polar molecule, where positive end of one molecule attract negative end of another molecule
    • Ends of dipole posses partial changes (δ+ and δ- )
    • They are stronger than London forces but weaker than ion dipole forces.
    • These forces increase with – increase in molecular size of molecule, increase in molecular weight of molecule, increase in polarity of molecule.
  • Dipole – Dipole interaction energy between stationary polar molecule (solids) is proportional to 1/r3 and that between rotating polar molecule is proportional to 1/r6, where ‘r’ is distance between polar molecule
    • The angle between 2 faces is Interfacial angle.
    • Eg- KMnO4, NaCl, FeSO4, Benzoic acid, Mohr’s salt
  • Amorphous Solids
    • They have no particular arrangement of molecules and do not occur in characteristic geometrical shape
    • Amorphous solids soften on heating and gradually begin to flow
    • Cleavage of amorphous solid is rough, and the edges obtained are not clear
    • They usually have a range of melting point , due to irregularity in arrangement of molecules.
    • They are isotopic in nature and are also called supercooled liquids
    • Eg-  Polymers such as polystyrene, charcoal, baking powder, talc, window glass, Griseofulvin
    • They get soft on heating and start melting. However they are not liquids as they are bound by high cohesive forces. 
  • Discuss the process of changes in states of matter
  • Matter exists in 3 phases –

Solid, liquid, gas

  • Melting is the process of conversion of state from solid to liquid.
  • Sublimation is when the substance goes directly from solid to gaseous state.
  • Fusion or freezing is when a substance goes from a liquid to solid state, the reverse of melting.
  • Vaporization = Boiling + Evaporation. It is the transition of state from liquid to gas.
  • Deposition occurs when a substance goes from gaseous to solid state, it is the reverse process of sublimation.
  • Condensation occurs when a substance goes from gaseous to liquid state.
  • Triple point –

The point on a phase diagram at which the three state of matter – solid , liquid, gs coexist. It occurs when both the temperature and pressure of the 3 phase of the substance coexist in equilibrium.

  • Critical pint – 

The point in temperature and pressure when the liquid and gaseous phases of a substance merge together into a single phase and are hence indistinguishable.

Beyond the temperature of critical point the merged single phase is called Supercritical fluid and liquidform doesn’t exists.

  • At high pressure and low temperature, the substance is in solid phase .

At low pressure and high temperature, the substance is in gaseous phase.

The liquid phase appears between two region

  • Critical temperature

Temperature above which gas cannot be liquefied irrespective of the pressure applied.

  • Critical pressure

It is the pressure required to liquefy the gas at its critical temperature

It is the highest vapour pressure a liquid can have.

  • Critical temperature of water = 374° c

Critical pressure of water = 218 atm.

  • Latent heat

The quantity of heat absorbed or released by a substance that is underlying transition of state is called ‘ Latent Heat ‘ or ‘ Heat of Transformaton ‘.

Latent heat of Vaporization – Amount of heat required by liquid to vapourise.

         Eg-   Ice melts or sink, heat absorbed by ice . 

                 Wax solidify or sink, heat released on skin.       

Latent heat is consumed to increase KE and undergo state transition.

  • Aerosol –
  • An Aerosol is a suspension of fine solid particles or liquid droplets in a gas.
  • The Aerosol System depends on the power of compressed or liquefied gas to expel the contents from the container.
  • By pressing the value, excess pressure is created inside container that expels the content of the container. As soon as contents are exposed to atmospheric pressure, they get evaporated and form a fine spra.
  • Vapour pressure

Vapour pressure is pressure executed by gas in equilibrium with a solid or liquid in a closed container at a given temperature . Eg- Water vapour has vapour pressure of 0.03 atm.

  • Latent heat of vaporization.

Latent heat of vapourisation is the amount of heat required to change unit mass of liquid into vapour at its boiling point at a constant temperature.

  • 1 g of ice at 0°c requires 336J energy to convet to 1g of water.
  • Explain mechanism of Transmission of heat.
    • Conduction
      • This mechanism occurs in solids.
      • When particles of matter are in direct contact, heat transfer by means of conduction
      • The adjacent atoms of higher energy liberate against one another, which transfers higher energy to lower energy.
      • That is , atoms of higher intensity and higher heat will vibrate, thereby moving the e– to areas of lower intensity and lower heat.
      • That is , atoms of higher intensity and higher heat will liberate, thereby moving the e– to areas of lower intensity and lower heat.
      • That is atoms of higher intensity and higher heat will liberate , thereby moving the e– to areas of lower intensity and lower heat.
      • Metals are best conductors , fluids and less conductors, than solids due to the fact that they are less dense , i.e. , there is larger distance between atoms.
  • Convection –
    • It occurs in liquids or gases and involves heat transfer between a surface and a liquid or gas in motion.
    • Heat is transferred by the movement of hotter (higher energy) particles away from heat source, carrying the heat, they have gained with them.
    • This can only happen in fluid where particles are free to move about in the space.
    • Hotter fluid is less dense , so will rise due to its greater buoyancy and cooler fluid will take its place, to be heated in turn.
    • Eg- Convection currents in boiling of water.

Radiation

  • It refers to the transfer of heat through empty space . this form of heat transfer occurs without an interveining medium, usually in perfect vacuum.
    • Radiant heat energy is transmitted in form of electromagnetic radiation.
    • Hot objects exist IR radiation from their surface , which then heat up away heat up any matter that absorbs it.
    • Radiant heat passes through IR transparent material

Eg- air, and warms IR absorbent objects that it hits. Black surface tend to exixt and absorb IR radiation best.

  • Heat from sun travel to earth as radiant energy.
  • Gaseous state
    • The intermolecular force of gases are neligible due to the fact that KE of gas is very high and there is large distance between the molecule.
  • A gasat temperature below its critical temperature is called Vapour.
  • Ideal Gas laws
    • Boyle’s law
      • If the temperature and amount (no of molecules) of a gas are held constant , then the pressure of the gas is inversely proportional to its volume.
  • Charles’ law
    • At a constant pressure, the volume of a fixed mass of gas is directly proportional to its absolute temperature.
    • As the T ↑, KE of molecule ↑ , they start moving apart , hence V ↑.
  • Avogadro’s law
    • Volume of an extensive property, which depends on the amount of substance of system.
    • At constant pressure and temperature, equals volumes of all gases contains equal number of molecules.
  • Gay Lussac’s Law
    • At a constant volume , the pressure of a gas is directly proportional to temperature.
  • Ideal gas equation

Cobmbining all the laws , gives ideal gas law which is a state of hypothetical ideal situation.

  • Real Gas Equation
    • If temperature of gas ↓ and pressure ↑ , the ideal Gas Law isn’t applicable as the intermolecular forces exist and volume of gas isn’t negligible.

  a , b = constants

  a = cohesive force between molecules

  b = incompressibility of gas molecule known as excluded volume.

  Due to ‘a’ P real gas < P ideal gas

  a   = internal pressure per mole

V – b = effective volume of gas molecule that expand freely

  • Liquid state

Properties

  • Molecule of liquid are in state random motion , i.e. they are incompressible and have higher density than gases.
  • The K.E. of molecule  of liquid and vapour pressure of molecule of liquid  ∝ temperature.

When we increase temperature, surface molecule of liquid turns into vapour and exert vapour pressure.

Vapour can convert into liquid below critical temperature when pressure is applied.

  • Force of attraction exists between molecule but aren’t enough to hold molecule in fixed position like solid.
  • Properties of liquid – Viscosity book, surface temperature P. can be explained on basis of intermolecular / attractive forces.

Relationship between V.P. absolute temperature of liquid :-

Clausius Clapeyron Equation

ln P2/P1 = -ΔH/R (1/T2 – 1/T1)

         P1 , P2 = Vapour pressure

         T1 , T2  = Absolute temperature

         ΔH  = Heat of vaporization

  • Solid state

Properties

  • Solids are rigid, have definite shape and size and maintain their volume.
  • They are nearly incompressible and their incompressibility is about 10 times of gases.
  • Due to closel packed particles , diffusion of solids is negligible
  • Most Solid melt on heating while some undergo sublimation.
  • Solid have high density compressed to liquid and gases.
  • Crystalline Solids

They have molecule in definite shape which is epeated again and again called unit cell.

  • Types of crystalline Solid
    • Molecular Crystals
      • The molecule are held by weak attractive forces called Vandu Waal Force.
      • They are soft and incompressible, have low M.P. k low b.p. and are bad conductor of electricity
      • They are volatile.
      • Eg- dry ice, wax, I2 crystals, S.
  • Ionic Crystals
    • They consist of positively charged ions arranged in a regular fashion throughout the crystal in 3D structure.
    • They are held hard and brittle, have very high m.p. and b.p.
    • They are poor conductors of electricity, but when melt, or in solution form, they conduct electricity
    • Eg- NaCl, LiF , CuSO4.
  • Covalent Crystal
    • The particles are bonded together by network of covalent bond.
    • They are hard and incompressible, extremely non-volatile and have very high m.p.
    • They are poor conductors of heat and electricity at all temperatures.
    • Eg- Diamond (Cn), quartz (siO2)
  • Metallic Crystals.
    • Forces present between constituents are metallic bond.
    • They can be soft or hard , good conductor of heat and electricity, posses metallic lusture.
    • They have high reflectivity and are highly ductile and malleable.
    • Eg- Cu, Ni, alloys.
  • Polymorphism
    • It is the ability of a compound to crystallize as more than one crystalline form with different lattics under different conditions.
    • This phenomenon is related to allotophy (phenomenon of an element existing in 2 or more physical forms).
  • Polymorphs have different chemical stability and may spontaneously convert from a metastable from to a stable form.
  • Different polymorphic forms may have different X-Ray diffraction, m.p. , solubility and these changes affect the drug development program by altering a drug’s bioavailability and related parameters.
  • Eg- Chloramphenicol palmitate has A, B and C polymorphs which have different physical, chemical and physiological properties.
  • The formation of polymorphs depends upon level of super-solution, temperature of crystallization, geometry of covalent bonds, solvent difference and impurities.
  • Classical examples of polymorphism –

Contrast between a graphite and diamond, both are composed of crystallized C.

  • Classification of Polymorphs-

Enantiotropic :-                                  

One polymorph can be reversely changed into another by varying temperature and pressure. 

Monotropic :-

one polymorphs is unstable at all temperature and pressures. Eg- Glyceryl stearates.

  • Solvate
    • A stochiometric adduct or molecular complex that has incorporated crystallizing solvent molecule into specific silts within crystal lattice
  • Hydrate
    • When the incorporated solvent is water , the complex is a hydrate .
      • Hemihydrate- hydrated form with molar equation of water corresponding to ½
      • Monohydrate- hydrated form with molar equation of water corresponding to 1.
      • Dehydrate- hydrated form with molar equation of water corresponding to 2.
  • Anhydrous
    • A compound not containing any water within its crystal lattice.
    • During pre-formulation, it is important to identify the polymorphs stable at room temperature and to determine whether polymorphic transition can occur within temperature range.