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.


  • 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


  • 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


  • 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.