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States of matter 2 changes of phases ppt

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STATES OF MATTER
CHANGES OF PHASES
 CHANGES IN THE STATES OF MATTER
 LATENT HEATS
 VAPOUR PRESSURE
 CRITICAL POINT
 E...
THE FACT OF THE MATTER
What happens when matter changes state?
• The three most familiar states of matter are solid, liqui...
Melting
• Change from a solid to a liquid
• The melting point of a substance is fixed in pure states.
• Impure substances ...
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States of matter 2 changes of phases ppt

  1. 1. STATES OF MATTER CHANGES OF PHASES  CHANGES IN THE STATES OF MATTER  LATENT HEATS  VAPOUR PRESSURE  CRITICAL POINT  EUTECTIC MIXTURES Nabeela Moosakutty Lecturer Dept of Pharmaceutics K.T.N College of Pharmacy
  2. 2. THE FACT OF THE MATTER What happens when matter changes state? • The three most familiar states of matter are solid, liquid, and gas. • A change of state is the change of a substance from one physical form of matter to another. • When a substance undergoes a physical change, it doesnot change its identity, just its appearance. • change a substance from one state to another, energy must be added or removed. • When a substance gains or loses energy, its temperature changes or its state changes. • All matter is made of tiny particles that are in constant motion. During a change of state, the motion of the particles changes. • Particles can break away from each other and gain more freedom to move, or they may attract each other more strongly and have less freedom to move. • During a change of state, a substance gains energy from or loses energy to the environment, but the total amount of energy is conserved.
  3. 3. Melting • Change from a solid to a liquid • The melting point of a substance is fixed in pure states. • Impure substances have a variable melting point. • When heat is applied, the particles are pushed apart. • When a solid is warmed, its particles gain energy and speed up, and the attraction between them decreases. Eventually they slide past one another. • The temperature at which a substance changes from a solid to a liquid is called its melting point. • Example: When ice turns to water. The temperature remains at 0 until all of the solid substance is melted. CHANGING STATES Melting, Freezing, Evaporation & boiling, Condensation and Sublimation
  4. 4. Freezing • The change from a liquid to a solid. • When a liquid is cooled, its particles have less energy, they slow down, and they lock into the fixed arrangement of a solid. • The temperature at which when a liquid freezes is called the “freezing point” • For most substances, the “freezing point” is the same as the “melting point”.
  5. 5. EVAPORATION & BOILING • Evaporation is the process in which particles of a liquid leave the surface as a vapour. • When a liquid is heated, the particles move faster and collide with each other. When the particles acquire sufficient energy, they break free of the surface and escape The rate of evaporation depends on: • The nature of the liquid • The temperature • The amount of exposed surface • Boiling is the process by which a liquid is freely converted to a gas or vapour. • When a substance is heated, the temperature rises until it reaches the boiling point. • When boiling has started, the temperature remains steady. • Evaporation takes place at the surface, but boiling takes place throughout the liquid.
  6. 6. Condensation • The change from a gas to a liquid. • The particles lose energy and move closer together as the gas cools therefore increasing the attraction between them. Sublimation When a substance changes directly from a solid to a gas without going through the liquid state examples of substances that sublime are iodine and ammonium chloride Deposition It is the change in statefrom a gas directly to a solid Rate of Diffusion • Solids -> Very Slow • Liquids -> Slow • Gases -> Rapid
  7. 7. CHANGING STATES
  8. 8. PHASE EQUILIBRIA & THE PHASE RULE
  9. 9.  A phase is defined as any homogeneous and physically distinct part of a system which is separated from other parts of the system by interfaces.  A part of a system is homogeneous if it has identical physical properties and chemical composition throughout the part. A phase may be gas, liquid or solid. A gas or a gaseous mixture is a single phase. Totally miscible liquids constitute a single phase. In an immiscible liquid system, each layer is counted as a separate phase. Every solid constitutes a single phase except when a solid solution is formed. A solid solution is considered as a single phase. Each polymorphic form constitutes a separate phase. PHASE DEFINITION
  10. 10. Examples The number of phases in a system is denoted P 1.Liquid water,pieces of ice and water vapour are present together. The number of phases is 3 as each form is a separate phase. Ice in the system is a single phase even if it is present as a number of pieces. 2.Calcium carbonate undergoes thermal decomposition The chemical reaction is: CaCO3(s)  CaO(s) + CO2 (g) Number of phases = 3 : This system consists of 2 solid phases, CaCO3 and CaO and one gaseous phase, that of CO2. 3.Ammonium chloride undergoes thermal decomposition. The chemical reaction is: NH4Cl(s) NH3 (g) + HCl (g) Number of phases =2 This system has 2 phases, one solid, NH4Cl and one gaseous, a mixture of NH3 and HCl 4.For a liquid system, according to the solubility to decide whether a system consists of one phase or of two. a solution of sodium chloride in water is a singlephase. A pair of liquids that are partially miscible or immiscible is a two-phase system(P=2) 5.A gas, or a gaseous mixture is a single phase. P=1
  11. 11. COMPONENTS The number of components of a system at equilibrium is the smallest number of independently varying chemical constituents using which the composition of each and every phase in the system can be expressed Examples Counting the number of components 1. The sulphur system is a one component system. All the phases, monoclinic, rhombic, liquid and vapour – can be expressed in terms of the single constituent – sulphur. 2. A mixture of ethanol and water is an example of a two component system. We need both ethanol and water to express its composition.
  12. 12.  Phase Equilibrium: A stable phase structure with lowest free-energy (internal energy) of a system, and also randomness or disorder of the atoms or molecules (entropy)  Any change in Temperature, Composition and Pressure causes an increase in free energy and away from Equilibrium thus forcing a move to another‘state’  Phase diagram or (Equilibrium Phase Diagram) It summarizes the conditions at which a substance exists as a solid, liquid, or gas. Or It is a “map”of the information about the control of phase structure of a particular material system.  The relationships between temperature and the compositions and the quantities of phases present at equilibrium are represented. PHASE EQUILIBRIUM & PHASE RULE
  13. 13. General Phase diagram
  14. 14. Key features • The major features of a phase diagram are phase boundaries and the triple point. • Phase diagrams demonstrate the effects of changes in pressure and temperature on the state of matter • At phase boundaries, two phases of matter coexist (which two depends on the phase transition taking place). Phase boundary: The line in a phase diagram that indicates the conditions under which two (transitioning) states of matter exist at equilibrium. • Triple point is the point on the phase diagram at which three distinct phases of matter coexist in equilibrium. Key terms • Critical point – the point in temperature and pressure on a phase diagram where the liquid and gaseous phases of a substance merge together into a single phase. Beyond the temperature of the critical point, the merged single phase is known as a supercritical fluid • Fusion(melting) (or freezing) curve – the curve on a phase diagram which represents the transition between liquid and solid states • Vaporization (or condensation) curve – the curve on a phase diagram which represents the transition between gaseous and liquid states • Sublimation (or deposition) curve – the curve on a phase diagram which represents the transition between gaseous and solid states • Critical temperature- it is the temperature above which the liquid state of a substance no longer exist regardless of pressure • Critical pressure- it is the pressure required to bring about liquefaction at the critical temperature
  15. 15. PHASERULE  J W Gibbs formulated the phase rule It is a general relation between the variance F, the number of components C, and the number of phases P, at equilibrium for a system of any composition  It’s a relation to determine the least number of intensive variable (independent variable that do not depend on the volume or the size) that can be changed without changing the equilibrium state of the system or The least number required to define the state of the system, which is called DEGREE OF FREEDOM F F = C  P + 2  For a system in equilibrium Phase rule  The degrees of freedom or variance F of a system is defined as the minimum number of variables such as  temperature  pressure  concentration
  16. 16. EXAMPLES 1. A gaseous mixture of CO2 and N2. Three variables: pressure, temperature and composition are required to define this system. This is, hence, a trivariant system. 2. A system having only liquid water has two degrees of freedom or is bivariant. Both temperature and pressure need to be mentioned in order to define the system. 3. If to the system containing liquid water, pieces of ice are added and this system with 2 phases is allowed to come to equilibrium, then it is an univariant system. Only one variable, either temperature or pressure need to be specified in order to define the system. If the pressure on the system is maintained at 1 atm, then the temperature of the system gets automatically fixed at 0oC, the normal melting point of ice.
  17. 17. Degrees of Freedom = What you can control What the system controls  F = C + 2 P Can control the no. of components added and P & T System decided how many phases to produce given the conditions A WAY OF UNDERSTANDING THE GIBBS PHASE RULE: THE DEGREES OF FREEDOM CAN BE THOUGHT OF AS THE DIFFERENCE BETWEEN WHAT YOU (CAN) CONTROL AND WHAT THE SYSTEM CONTROLS
  18. 18. ONE-COMPONENT SYSTEMS Phase diagram ofwater Curve O -C Sublimatio nDeposition Curve O-A Vaporization Condensation Curve O -B Melting Freezin g
  19. 19. A) AT THE TRIPLE POINT: P = 3 (SOLID, LIQUID, AND GAS) C= 1 (WATER) P + F = C + 2 F = 0 (NO DEGREE OF FREEDOM) B) LIQUID-SOLID CURVE P = 2 2+F = 1 + 2 F= 1 One variable (T or P) can be changed For One component system (C=1) : 3 conditions may arise when P=1, P=2 and P=3 C) LIQUID P =1 So F =2 Two variables (T and P) can be varied independently and the system will remains a single phase
  20. 20. TWO COMPONENT EUTECTIC SYSTEMS Figure shows the simplest of two component phase diagrams. The components are A and B, and the possible phases are pure crystals of A, pure crystals of B, and liquid with compositions ranging between pure A and pure B. Compositions are plotted across the bottom of the diagram. Note that composition can be expressed as either a percentage of A or a percentage of B, since the total percentage must add up to 100. (Compositions might also be expressed as mole fraction of A or B, in which case the total must add up to 1). Temperature or pressure is plotted on the vertical axis. For the case shown, we consider pressure to be constant, and therefore have plotted temperature on the vertical axis. The curves separating the fields of A + Liquid from Liquid and B + Liquid from Liquid are termed liquidus curves. The horizontal line separating the fields of A + Liquid and B + Liquid from A + B all solid, is termed the solidus. The point, E, where the liquidus curves and solidus intersect, is termed the eutectic point. At the eutectic point in this two component system, all three phases, that is Liquid, crystals of A and crystals of B, all exist in equilibrium. Note that the eutectic is the only point on the diagram where this is true.
  21. 21. Two component system C=2 When P=1 Degree of freedom F = C – P + 2 F = 2 – 1 + 2 = 3 Where two component systems (solid and liquid phases only) are present then, the effect of pressure can be neglected Condensed system: solid / liquid System with the absent vapor phase (gas phase) is called condensed system Remaining variables temperature and concentration Hence, experimental measurements of temperature an concentration in condensed systems are carried out under atmospheric pressure, given that the F is reduced by one Then rule of the reduced phase as F’ = C – P + 1 F = 2 – 1 + 1 = 2 bivariant So reduced phase rule is more convenient to apply to the two component solid/ liquid condensed system When P=2 Then F’ = C – P + 1 F’ = 2 – 2 + 1 = 1 monovariant When P=3 (at eutectic point) F’ = C – P + 1 F’ = 2– 3 + 1 = 0 non variant
  22. 22. A eutectic mixture is defined as a mixture of two or more components which usually do not interact to form a new chemical compound but, which at certain ratios, inhibit the crystallization process of one another resulting in a system having a lower melting point than either of the components. Eutectic mixture formation is usually, governed by following factors: (a)components must be miscible in liquid state and mostly immiscible in solid state (b)Intimate contact between eutectic forming materials is necessary for contact induced melting point depression (c)the components should have chemical groups that can interact to form physical bonds such has intermolecular hydrogen bonding etc. (d)the molecules which are in accordance to modified VantHoff’s equation can form eutectic mixtures. Eutectic mixtures, can be formed between Active Pharmaceutical Ingredients (APIs), between APIs and excipients or between excipients; thereby providing a vast scope for its applications in pharmaceutical industry • During pre-formulation studies- Testing foreutectic mixture formation can help in anticipation of probable physical incompatibility between drug and excipient molecules • Eutectic mixtures are commonly used in drug designing and delivery processes for various routes of administration Eutectic mixture Pharmaceutical Application
  23. 23. During tablet compaction the heat produced in the punch and die cavities may lead to fusion or melting of tablet powder compacts leading to manufacturing defects. Thus knowledge of eutectic points of powder components may help avoid these problems During pharmaceutical analysis, understanding of eutectic mixtures can help in the identification of compounds having similar melting points. Compounds having similar melting points, as a rule will have different eutectic point with a common other component. This knowledge could be used to identify compounds like Ergotamine, Allobarbital etc.  EMLA® (lidocaine 2.5% and prilocaine 2.5%) Cream  EMLA Cream (lidocaine 2.5% and prilocaine 2.5%) is an emulsion in which the oil phase is a eutectic mixture of lidocaine and prilocaine in a ratio of 1:1 by weight. This eutectic mixture has a melting point below room temperature and therefore both local anaesthetics exist as a liquid oil rather than as crystals
  24. 24. Tm: Melting point temperature e: Eutectic Mixture; IDR: Intrinsic Dissolution Rate; AUC: Area Under Curve; PEG: Poly Ethylene Glycol Sl No Eutectic Component s (a,b) Ratio Tm °C (a) Tm °C (b) Tm °C (e) Challenges Findings 1 Curcumin, Nicotinamid e 1:2 181.4 128.3 110.5 Oral route-Low solubility, poor oral bioavailbility 10-fold faster IDR and 6- times higher AUC compared to crystalline curcumin 2 Ibuprofen , Thymol 2:3 76.0 52.0 32.0 Transdermal Route Limited ability to penetrate the skin A flux of 150 mg/ cm / h, 5.9 times the flux from a saturated aqueous solution with thymol pretreated skin and 12.7 times the flux from a saturated aqueous solution across non-pretreated skin 3 Genistein, PEG 460 1:24 305.0 2.0 0.2 Parentral Route Low aqueous solubility, thus formulation difficulty. Could help in solubilization of genistein crystals for injection development APPLICATIONS OF EUTECTIC MIXTURES IN FORMULATION DEVELOPMENT
  25. 25. LATENT HEAT HEAT REQUIRED TO PRODUCE A PHASE CHANGE IS CALLED LATENT HEAT (LH ) Examples: heat of freezing- amount of thermal energy released when liquid freezes Heat of vapourization- amount of thermal energy added to transform liquid into gas Lh of vapourization of water : 540 cal /g Lh of freezing of water : 80 cal /g Heat added or subtracted for a phase change = latent heat x mass Q = Lh x M Where, Q = heat Lh = latent heat M = mass
  26. 26. VAPOUR PRESSURE What is Vapour pressure ? • Vapour pressure is defined as the pressure exerted by a vapour in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system • Vapour pressure is nothing but the tendency of particles to escape from the liquid (or a solid) • At normal temperatures, substance with a high vapour pressure is often referred to as volatile. Characteristics of Vapour Pressure  A pure liquid experiences a greater amount of vapour pressure as against a liquid’s solution  It is inversely proportional to the forces of attraction existing between the molecules of a liquid  It increases with a rise in the temperature. This is because the molecules gain kinetic energy and thus, vapourise briskly  The vapour pressure of a liquid depends on the nature of the liquid. The low- boiling liquid exerts more vapour pressure at a given temperature  Liquids in which the intermolecular forces are weak shows high vapour pressure
  27. 27. Thank You

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