Physical Pharmacy Lecture 1 PDF

Physical Pharmacy  01 State of matter syllabus 02 Thermodynamics 03 Solutions of non-electrolytes 04 Solution of electrolytes 05 Ionic equilibria 06 Buffer& isotonic solution  All matter is composed of small particles...

Physical Pharmacy  01 State of matter syllabus 02 Thermodynamics 03 Solutions of non-electrolytes 04 Solution of electrolytes 05 Ionic equilibria 06 Buffer& isotonic solution  All matter is composed of small particles Matter (atoms, molecules, or ions) Matter exists in different physical forms under different conditions. For example: water exists as ice (solid), as liquid water and as steam (gaseous water).  the form of matter characterized by rigidity; a solid is solid relatively incompressible and has fixed shape and volume. the form of matter that is a relatively incompressible fluid; liquid a liquid has a fixed volume but no fixed shape (takes the shape of container). the form of matter that is an easily compressible fluid; gas a given quantity of gas will fit into a container of any size and shape.  Particle Properties Phase Proximity Energy Order Volume shape Solid close little ordered definite definite Liquid close moderate diordered definite indefinite Gas far apart a lot very indefinite indefinite disordered  State of matter The molecular comparision of liquid, solid and gas  does not have a defined shape or volume has defined shape and does not and take up all the space in a container lose its shape take the shape of the container  measuring matter mass volumes using balance using or scale measuring cup ?  v Forces can be attractive or repulsive vAll matter is held depending on whether together by force. like or unlike charges vThe force between are closer together. atoms within a molecule v Adhesion is the force is a chemical or of attraction between intramolecular force. molecules of different vThe force between substances while cohesion is the force molecules is a physical of attraction between or intermolecular force. molecules of the same substance  Repulsive and Attractive forces Ø On the atomic or molecular scale, all particles exert both attractive and repulsive forces on each other. Ø If the attractive forces between two or more atoms are strong enough to make them into unit with own observable properties, we call the result a "molecule" and refer to the force as a "chemical bond". Ø If the attractive forces between two or more atoms are not strong enough to bind them into a new molecular unit, so we call this force a non-bonding attraction. Ø The shape shows how repulsive and attractive forces affect the potential energy in opposite ways: repulsions always raise this energy, and attractions reduce it. The shape passes through a minimum when the attractive and repulsive forces are exactly in balance (equilibrium state). As we stated above, all particles exert both kinds of forces on one another. At equlibrium, repulsive force between the atoms becomes equals to the attractive force. electrostatic force sharing of electrons v Ionic bonding is the electrostatic force of attraction between positively and negatively charged ions (between non-metals and metals). v These ions have been produced as a result of a transfer of electrons between two atoms with a large difference in electro negativities. v All ionic compounds are crystalline solids at room temperature. v NaCl is a typical example of ionic bonding. v Covalent bonding takes place between atoms with small differences in electronegativity which are close to each other in periodic table (between non-metals and non-metals). v The covalent bonding is formed by sharing of electrons (i.e., s and p electrons) between atoms rather than by electron transfer. v This bonding can be attained if the two atoms each share one of the other’s electrons.  entermolecular forces of the three state of matter Intermolecular Forces = between molecules the intermolecular The average kinetic energy of the attractive forces are strong gas molecules is much larger than enough to lock molecules in the average energy of the Liquids place (high order). attractions between them.. the intermolecular Gases Solids attractive forces are strong enough to hold the molecules close together, but without much order. It depend on the temperature  16 kJ/mol (to separate molecules) - The strengths + + - of intermolecular forces are generally weaker than either ionic or 431 kJ/mol (to break bond) covalent bonds.  Polarity The dipoles can be formed as a result of unbalanced distribution of electrons in asymettrical molecules. This is caused by the location of a few more electrons on one side of the nucleus than on the other. 5 * It is a weak bond, with a typical strength 1-10 Kcal/mole. * It occurs between molecules. * T he explanat ion o f t h e s e w e a k f o rc e s o f attraction is that there are fluctuation in the electron density of all molecules and these cause small dipoles within the molecules. It is these dipoles that attract one molecule to another. They are called van der Waals' forces. Small, weak interactions between molecules  Types of Van der Waals Forces 1) dipole-dipole, (Van der Waals-Keesom force) Force between two permanent dipoles 2) dipole-induced dipole, (Van der Waals-Debye force) Force between a permanent dipole and a corresponding induced dipole 3) dispersion , (London dispersion force or Van der Waals-London force) Force between two instantaneously induced dipoles Are the forces that occur between two molecules with permanent dipoles. (Two polar molecules align so that + and - are matched (electrostatic attraction)( An example of this can be seen in EX: HCl Ex: fluromethane (CH3F) EX: KBr K Br K Br  B-Dipole-Induced Dipole A dipole can induce (cause) a temporary dipole to form in a non-polar molecule The molecules then line up to match + and - charges C-London Dispersion Forces A temporary dipole forms in a non-polar molecule… which leads to… a temporary dipole to form in ANOTHER non-polar molecule Dispersion is the ONLY intermolecular attraction that occurs between non-polar molecules  London Dispersion Forces e- e- e- e- e- e- + e- Cl-Cl e- e- e- e- - + e- Cl-Cl e- e- e- e- - + e- non-polar non-polar - TEMPORARY DIPOLE INDUCED DIPOLE Dispersion (weakest and very short-lived) Types of intermolecular forces (between neutral molecules): London dispersion forces: (instantaneous dipole moment) also referred to as van der Waal’s forces  Review To remember Dispersion between two non-polar molecules Dipole – Dipole between two polar molecules Dipole – Induced Dipole b/w a polar & a non- polar molecule Thank you