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• PHYSICAL pharmacy
• By Dr. Ahmed R. Gardouh, Ass. Professor of Pharmaceutics And Pharmaceutical Technology
• physical Pharmacy , A.R.Gardouh, PhD
• Ahmed Rifaat Gardouh,PhD. Department of pharmaceutics &industrial pharmacy, suez canal university.
• By the end of this lecture , the student will be able to

  • Differentiate between types of attraction forces
  • Compare between states of matter
  • Enumerate properties of each state of matter
• The three basic phases of matter are solid, liquid, and gas. Other phases are also considered to exist such as crystalline, glass, & plasma.

  
• The different phases of a pure substance are related to each other in terms of temperature and pressure.

  
• Like a liquid, a gas has no fixed shape, but unlike a liquid, it has little resistance to compression because there is enough space for the molecules to move closer to one another.
• We can use other physical parameters, not just temperature, to produce these phase transitions. For example, we can change a liquid into a gas by decreasing the pressure.
• There are intermolecular forces that exist between molecules for gases, liquids and solids.
• The Intermolecular Forces (forces between molecules) are weaker than Intramolecular Forces (The Chemical Bonds within an Individual Molecule).
• Types of Attractive Forces

  • van der Waals forces
  • Ion-Dipole and Ion-Induced dipole forces
  • Hydrogen bonding

  
• Dipole-Dipole forces (Kessam forces)

  Occur between two molecules with permanent dipoles. They result from the dipole-dipole interaction between two molecules.
• Dipole-induced Dipole Forces (Debye interaction)

  A permanent dipole is capable of inducing an electric dipole in nonpolar molecule (easily polarizable).
• Induced dipole-induced dipole (London Forces)

  Involve the attraction between temporarily induced dipoles in nonpolar molecules (often disappear within an instant).
• Ionic-Dipole Forces (Debye interaction)

  Interaction between a permanent dipole and an ion.
• Ion-induced dipole (London Forces)

  Attraction between an ion and temporarily induced dipoles in nonpolar molecules.
• Hydrogen bonding

  Interaction between a molecule containing H-atom and a strongly –ve atom such as F, O or N.

  
• Intermolecular H-bond: Occurring between 2 or more similar or different molecules.

  
• Intramolecular H-bond: Occur in same molecules, it makes the molecule less energetic and more stable, decrease B.P and M.P.

  
• The Gaseous State


  • Gas molecules travel in random paths, colliding with one another and with the wall of the container in which the gas confined. Therefore, they exert a pressure (force/unit area).
• Boyle's Law

  Relates V and P of a given mass of a gas at constant temperature.
• Gay-Lussac & Charles

  Relates V and T of a given mass of a gas at constant pressure.
• General Ideal Gas Law

  PV = n RT
• Real gases do not follow the laws of Boyles, Gay-Lussac and Charles but ideal gases.
• Molecular Weight


  The approximate M.Wt of a gas can be determined using the equation: M = gRT/PV
• van der Waals equation

  A better approximation to real behavior of gases, with terms for internal pressure/mole and incompressibility of the molecules.
• The Liquid State


  • Liquefaction of gases occurs when a gas is cooled and pressure is applied, bringing the molecules within the sphere of the van der waals interaction forces
  • Liquids are considerably denser than gases and occupy a definite volume
  • The transition from a gas to a liquid and from a liquid to a solid depend on both temperature and pressure

  
• Critical temperature


  The temperature above which a liquid can no longer exist, i.e. can't be in the liquid state.
• Critical pressure


  The pressure required to liquefy a gas at its critical temperature.
• Methods of Achieving Liquefaction

  1. Subjecting it to intense cold by the use of freezing mixture

  2. Cooling effect produced in a gas as it expands
• Vapor pressure of liquids


  Molecules with the highest energies break away from the surface of the liquid and pass into the gaseous state, until a dynamic equilibrium is established between vaporization and condensation.
• Clausius – Clapeyron Equation


  Expresses the relationship between the vapor pressure and the absolute temperature of the liquid.

  
• Latent heats of vaporization


  The quantity of heat taken up when liquids vaporize (i.e. heat absorbed to reach boiling point) and are liberated when the vapor condenses to liquid.
• Boiling point


  The temperature at which the vapor pressure of the liquid equals the external or atmospheric pressure.

  
• Boiling point of a compound can provide a rough indication of the magnitude of the attractive forces between molecules.
• Polar molecules, e.g. EtOH and water, that attached through hydrogen bonds, exhibit high boiling points and high heat of vaporization.
• Solid state has 2 different lattice structure
• Vapor pressure


  The pressure exerted by a vapor in equilibrium with its liquid or solid phase
• The V.P. of the liquid


  Equals the external or atmospheric pressure