Lecture 1_States of Matter PDF

Faculty of Pharmacy Physical Pharmacy ‫اﻟﺼ ﯿﺪ ﻟﺔ اﻟﻔ ﯿﺰ ﯾﺎﺋﯿﺔ‬ PT202 Credit hour: 3 (2+1) By Dr Noura Hassan Abd Ellah Department of Pharmaceutics and Pharmaceutical Technology (PT)...

Faculty of Pharmacy Physical Pharmacy ‫اﻟﺼ ﯿﺪ ﻟﺔ اﻟﻔ ﯿﺰ ﯾﺎﺋﯿﺔ‬ PT202 Credit hour: 3 (2+1) By Dr Noura Hassan Abd Ellah Department of Pharmaceutics and Pharmaceutical Technology (PT) 2023/2024 1  Faculty of Pharmacy Topic 1: States of Matter _ Solids Matter: It is anything that has mass and occupies space. It exists as gas, liquid or solid. Each state of matter has unique physical properties. The 2 important factors that determine whether a substance exists in gaseous, liquid, or solid state……… Temperature and Pressure Gaseous State.. Ø Gas occupies the entire container. Ø Kinetic energy of a gas is so high. Ø Intermolecular forces are nil. Ø Intermolecular distances are very large. Ideal Gas Law ***Several laws that are significantly used to describe the behavior of ideal gas as follow: -Boyle's Law - Charles' Law - Avogadro's Law - Gay-Lussac's Law Boyle's Law Charles' Law Avogadro's Law Law: Ideal gas law: -State of a hypothetical ideal situation -relates T, P and V of an ideal or a perfect gas R: gas constant Note: Gas volume (V), Pressure (P), Temperature (T), Number of moles (n). 2  Faculty of Pharmacy At standard temperature and pressure (STP), one mole of an ideal gas occupies 22.414 L. The conditions 0°C and 1 atmospheric pressure (atm) are called standard temperature and pressure (STP). Real Gases As T of a gas is lowered and/or its P is increased, the ideal gas law is not followed because the volume of gas is not negligible and intermolecular forces do exist. Van der Waals equation for real gases is written as: a & b: constants for deviations from ideal behavior. a: accounts for the cohesive forces between the gas molecules b: accounts for the incompressibility. a/V2: accounts for the internal pressure per mole Liquid state. Like a gas, liquid take the shape of the container. However, unlike a gas, a liquid may not always fill every space in the container. Gas Liquid Vapor pressure In case of liquids: -Kinetic energy is not distributed evenly among molecules. -Some molecules acquire more energy. Molecules that have sufficient energy to overcome intermolecular attractions can escape to the vapor phase “evaporation”. 3  Faculty of Pharmacy Average kinetic energy of molecules: in vapor state >> in liquid state Therefore, the temperature of liquid falls on evaporation. In condensation: Molecules of liquid in the vapor phase: -Undergo collisions -Transfer their energy to other molecules -Come back to the liquid phase. At dynamic equilibrium, rate of evaporation = rate of condensation. The pressure of the saturated vapor above the liquid is then known as “Equilibrium vapor pressure”. Figure: Representation of dynamic equilibrium condition Solid state. In solid state, the constituent particles atoms, ions, or molecules are packed closely together. Solid Gas Liquid 4  Faculty of Pharmacy ***Some characteristic properties of solids: 1. Rigid, definite shape and volume. 2. Strongest intermolecular attraction forces. 3. Incompressible. 4. Most solids melt on heating, while some undergo sublimation. 5. Higher density as compared to gases. **Based on their structural features, the solids are classified to 3 main types: A) Crystalline Solids B) Amorphous Solids C) Polycrystalline Solids (Polymers) 5  Faculty of Pharmacy A) Crystalline Solids Crystalline solids, in which the molecules are packed in a definite order. The temperature at which the crystal lattice breaks is the melting point of the crystal. Crystal lattice: Symmetrical 3D arrangement of atoms inside a crystal. All crystals are made up of repeating units called unit cells. Seven primitive unit cells such as: 1- Cubic: such as sodium chloride 2- Hexagonal: 3- Orthorhombic: 4- Tetragonal: such as urea 5- Rhombic: such as iodine 6- Monoclinic: such as sucrose 7- Triclinic: such as boric acid 6  Faculty of Pharmacy Types of crystalline solids: Crystalline solids may be classified into the following four types based on the nature of bonds: Type Constituent Nature of bonds Appearance Melting Example point 1) Molecules -weak attraction Soft and compressible Low Dry ice Molecular forces “van der (water), crystals Waals forces”. wax, -Hydrogen bonding Iodine 2) Ions Strong Hard & brittle, High Salts as: Ionic electrostatic forces NaCl. crystals (+ve & -ve ions) 3) Atoms Covalent bonds Hard & Incompressible Very Diamond Covalent High & quartz crystals 4) Atoms Metallic bonds. -Soft or hard variable Nickel, Metallic -Metallic luster Copper crystals -Converted into sheets and wires (Malleable). In crystalline solids, we will discuss: *Polymorphs *Solvates/Hydrates *Salts/Cocrystals 7  Faculty of Pharmacy *Polymorphism (polymorphs) Polymorphism is the ability of a compound to crystallize as more than one crystalline species with different internal lattices. This means that an element existing in 2 or more physical forms (Polymorphs- polymorphic form) Different polymorphs (polymorphic form) may have different: - Melting points - Solubilities - X-ray diffraction patterns - Chemical stability and may spontaneously convert from a metastable form to a stable form. These changes affect the drug development by altering a drug's bioavailability and related parameters. Examples of polymorphism: 1- Chloramphenicol palmitate exists in 3 crystalline polymorphic forms (A, B and C), the more soluble form B has higher bioavailability. 2- Cacao butter: it exists in 4 polymorphic forms, the unstable gamma form (melting at 18°C), the alpha form (melting at 22°C), the beta prime form (melting at 28°C), and the stable beta form (melting at 34.5°C). 3- The most common example indicating difference in properties of polymorph is the contrast between a graphite and a diamond, both of which are composed of crystalline carbon. 8  Faculty of Pharmacy ****A crystalline solid can incorporate other compounds into the lattice to produce new crystalline material. *Solvates/Hydrates When solvent is incorporated into the lattice àSolvate When water is incorporated into the lattice àHydrate The hydrated forms may be monohydrate (1 water molecule) and dihydrate (2 water molecule). A compound not containing any water within its crystal is termed anhydrous. *Salt/Cocrystals When acid or base is incorporated into the lattice àSalt. Multicomponent crystal, in which different components held together in the lattice (in a stoichiometric ratio) by intermolecular forces à Cocrystals B) Amorphous Solids Amorphous solids have no organized structure. In this respect, they resemble liquids. However, their rigidity and cohesiveness allow them to retain a definite shape and considered to be solids. 9  Faculty of Pharmacy Examples of amorphous solids: Polymers such as polystyrene Drug as cefuroxime axetil Foods such as cotton candy The lack of molecular order in amorphous solids has a significant effect upon the physical and chemical properties. Amorphous is less stable than crystalline Amorphous is more soluble than crystalline C) Polycrystalline In certain crystalline solids, the crystals are very fine, and solids give an impression of being amorphous ……… Such fine crystalline solids are known as polycrystalline solids. Types of solid On basis of arrangement Crystalline Solids Amorphous solids Definition Packed in a definite order No organized structure (Regular arrangement) (Irregular arrangement) Example NaCl, diamond, graphite cefuroxime axetil Characteristics 1. True solid 1. Pseudo solid or supercooled liquids 2. Sharp melting point 2. No sharp melting points 3. Molecules in crystals are held by 3. Soften on heating and gradually begin strong intermolecular forces to flow like liquids 4. Anisotropic in nature (different 4. Isotropic in nature (same properties in properties in different direction) different direction) 10  Faculty of Pharmacy Liquid Crystal State - A 4th state of matter is…..…….. Liquid crystal state or mesophase. The liquid crystal state is a state of matter between the crystalline solid and liquid states. Crystalline Liquid : Liquid crystal state: solid: - Regular Liquid motion arrangement overcomes the Increased molecular of intermolecular motion overcomes molecules. forces the weaker forces -Fixed And molecules positions by move into but molecules remain intermolecular random bound by the forces. positions. stronger forces. This results in: This results in: -Molecules are arranged in layers -Within each layer, molecules are in random positions. ………..…. Molecules can slide around each other ………...…. Layers can slide over each other ---------------------------This molecular mobility produces the fluidity in liquid crystal state. 11  Faculty of Pharmacy Changes in the State of Matter Liquefaction of Gases Any gas can be liquefied by decreasing temperature or increasing pressure. Critical temperature: It is the highest temperature at which liquefaction of gas occurs. Critical pressure: It is the minimum pressure required to liquefy the gas at its critical temperature. Critical volume: It is the volume occupied by a mole of gas at critical temperature and pressure. When temperature of gas is reduced, it loses some of its kinetic energy. If pressure is applied to the gas, the molecules are brought within the sphere of van der Waals interaction forces and thus pass into liquid state. The methods used in liquefaction of gases include: 1. Faraday's method 2. Linde's method 3. Claude's method Reference: Gaurav K. Jain, Farhan J. Ahmad, Roop K. Khar. Theory and Practice of Physical Pharmacy, First Edition. Chapter 1: States of Matter. Elsevier 12