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2-4-PhaseEquilibriumGeneric.pdf

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2-4-PhaseEquilibriumGeneric.pdf

  1. 1. PHASE AND PHASE EQUILIBRIUM Dr. L.T.M. Muungo, PhD
  2. 2. TOPICS ❑ Introduction ❑ Gibbs phase rule ❑ Cooling curve ❑ Classification of equilibrium diagtams
  3. 3. Introduction: One of the most important objective of engineering metallurgy is to determine properties of material. The properties of material is a function of the microstructure which depend on the overall composition and variable such as pressure and temperature. Hence to determine the phase present in the material system , an equilibrium or phase diagram is plotted. Equilibrium diagram or phase diagram is a graphical representation of various phase present in material system at various temperature and composition point. All the phase diagrams have temperature as the ordinate as the ordinate(Y-axis) and percentage composition by weight as the abscissa(X-axis)
  4. 4. Uses of equilibrium or phase diagram: The equilibrium diagram is used to obtain following information: 1. It shows the various phase present at different composition and temperature. 2. It indicate solid solubility of one element in other. 3. It shows the temperature range over which solidification or liquidification of material system occurs. 4. It indicate the temperature at which different phase start to melt.
  5. 5. Basic Terms: 1. System: The substances that isolated and unaffected by their surrounding are known as system. It may be composition of solid, liquid , gases or the combinations and may have metals and nonmetals separately or in any combination. A system is capable of changing its composition, temperature, pressure, density etc. 3. Phase: It is a physically and chemically composition of a substance(system), separated from the other portion by a surface and an interface. Each portion have different composition and properties. In a equilibrium diagram, liquid is one phase and solid solution is another phase. 3. Variables: A particular phase exists under various condition of pressure and temperature and composition. These parameters are known as the variables of the phase.
  6. 6. Basic Terms: 4. Component: These are the substances, element or chemical compound whose presence is necessary and sufficient to make a system. A pure metal is one component system whereas and alloy of metals is a two-component(binary) system etc. 5. Alloy: It is a mixture of two or more elements having metallic properties. In the mixture, metal is in the large proportion and the other can be metal and non-metals.
  7. 7. GIBB’S PHASE RULE Gibbs phase rule establishes the relationship between the number of variable (F), the number of element (C), and the number of phases(P). It is expressed mathematically as follows: P + F = C + 2 ……….(I) Where, P = Number of phases in system F = Number of variables that can be change independently without effecting number of phases C = Number of elements 2 = It represent any two variables amongst temperature, pressure and composition
  8. 8. GIBB’S PHASE RULE In general all equilibrium diagram studied at constant pressure, hence Gibb’s phase rule is modified to” P + F = C + 1 ……….(II) Phase rule helps to determine maximum number of phase present in an alloy system under equilibrium conditions at any point in phase diagram. The phase rule can also be used to determine the degree of freedom that can be changed
  9. 9. GIBBS FREE ENERGY FOR THERMODYNAMIC STABILITY OF PHASES Gibb’s free energy for thermodynamic stability of phases describes the amount of energy that released or consumed when a phase is created from other phase. Gibb’s free energy of formation ( Gf ) is relative value allows us to compare energies of different phases. So by the conventions the value of Gf for pure metal or element is assumed zero. The phase having lowest value of Gibb’s phase energy is a stable phase.
  10. 10. GIBBS FREE ENERGY FOR THERMODYNAMIC STABILITY OF PHASES and temperature. Gibb’s free energy of any phase varies with the pressure The fundamental relation between them is given as, G = E + p V – T S G = E + p V – T S G= Gibb’s phase energy in J/mole E= Internal energy in J/mole P= Pressure in Pascal V = volume in cm3/mole T= Temperature in degree S= Entropy is J/ deg-mole
  11. 11. GIBBS FREE ENERGY FOR THERMODYNAMIC STABILITY OF PHASES At high temperature phase with high entropy are very stable because TS term in equation has negative sign. Similarly at high pressure, phase with high volume are unstable because pV term has positive sign. The Gibb's free energy tells us whether a reaction will takes place.
  12. 12. Solid solution and Compound The element present in the alloy in the largest portion is referred as base metal or parent metal or solvent and the other elements are referred as alloying element or solute. Solid solution is a type of alloy in which the atoms of alloying element are distributed in the base metal and both have similar crystal structure. The composition of alloying element may vary but the structure should be similar to base metal.
  13. 13. Solid solution and Compound Solid solution Substitutional solid solution Interstitial solid solution Regular Random Or Or Ordered Disordered
  14. 14. 1) Substitutional solid solution In substitutional solid solution, atoms of alloying element occupy the atomic size of base metal. They are further classified as: (a) Regular or ordered substitutional solid solution: ( )In this type, the substitution of atoms of alloying element is in definite order in the base metal matrix. ( )Examples: Ni-Al solid solution below 400 C.
  15. 15. Ni (solvent) Al (solute)
  16. 16. (b) Random or disordered substitutional solid solution: In this type, substitution of alloying elements is in any random order in the base metal matrix. Example: Alpha brass Copper solvent Zinc solute
  17. 17. (2) Interstitial solid solution: In Interstitial solid solution, the atoms of alloying elements occupy the interstitial sites of base metal. This type of solution is formed when atomic size of alloying element is much smaller compared to that of the base metal. Example: Fe-C Iron (solvent) Carbon (solute)
  18. 18. Hume - Rothery’s Rules for Solid Solubility Solid solution is an alloy of two or more element wherein the atomic crystal structure of alloying element (solute) is same as that of the base metal matrix (solvent). The solubility limit of the solute in the solvent ( of the alloying element in base metal matrix) is governed by certain factors. These governing factors are known as Hume- Rothery’s rules for solid solubility. These governing factor are as follows.
  19. 19. ❑Group work discussional questions: ❑ Give a detailed descriptive account of Interfacial Phenomena ➢Give a detailed descriptive account of Applications of surface-active agents ➢Give a detailed descriptive account of Electric Properties of Interfaces ➢Explain the process of Interface tension ➢Explain the process of micelle formation in each favourable environment ➢Give a descriptive account of the phases of matter with logical relevance to state of medicines as they are taken for their respective therapeutical values ➢Describe some key phase changes of materials substance when exposed to some environmental conditions . ➢Describe the role of contact angle during the wetting process of a material substance ➢Describe the GIBB’S Phase rule as used quantitative in characterization of pharmaceutical material dynamics ➢Describe some practical applications of Gibb’s and Hume - Rothery’s Rules for pharmaceutical material dynamics ➢Differentiate the role of adsorption process of a material substance in surface and interfacial tension ➢State and explain the factors that have direct adsorptive effect on surface and interfacial tension process ➢State and explain some of the medical and pharmaceutical applications of named surface active agents.
  20. 20. Hume - Rothery’s Rules for Solid Solubility 1. Atomic size: .Alloying elements having similar atomic size as that of the base metal matrix have better solid solubility. . For a favorable solid solution formation, the difference of atomic size of solute and solvent should be less than 15 %. 2. Chemical affinity: .Element having lower chemical affinity have greater solid solubility. .Element having higher chemical affinity have the tendency of formation of compound and hence restrict formation of solid solution. . In general, the alloy elements located closer in the periodic table have higher solid solubility.
  21. 21. Hume - Rothery’s Rules for Solid Solubility 3. Relative valency: Metals having lower valency have more solubility for metals having higher valency. Hence, for better solubility, the base metal selected should be one that has lower valency as compared to that of alloying elements. 4. Crystal structure: As mentioned earlier, solid solution is an alloy of element having similar crystal structure. Difference in crystal structure limits the solid solubility of elements.
  22. 22. Cooling Curves cooling curve is the graphical plot of phases of element on temperature v/s time. The resulting phase during solidification is different for various alloy composition. The most common coolingcurves are: 1. For pure metals 2. For binary solid solution(alloy) 3. For eutectic binary alloy 4. For off-eutectic binary alloy
  23. 23. 1. Cooling Curves for Pure Metals F=1 F=0 F=1
  24. 24. Region AB represent liquid state, solidification starts at B and continue until C, region CD represent solid state. Application of Gibb’s phase rule in various regions: (1) Region AB P + F = C + 1 1 + F = 1 + 1 Therefore, F = 1 Thus F = 1 means that only one variable i.e temperature can be varied without changing the liquid phase of the system.
  25. 25. (2) Region BC P + F = C + 1 2 + F = 1 + 1 Therefore, F = 0 Thus F = 0 means that no variable amongst temperature and pressure can be varied with out changing the Liquid + Solid phase of system. If the temperature is increased the metal goes into liquid state and if the temperature is lowered it goes into solid state. (3) Region CD P + F = C + 1 1 + F = 1 + 1 Therefore, F = 1 Thus F = 1 means that only one variable i.e temperature can be varied without changing solid phase of system.
  26. 26. 2. Cooling Curves for Binary solid solution (alloy)
  27. 27. Region AB represent liquid state, solidification starts at B and continue until C, region CD represent solid state. Application of Gibb’s phase rule in various regions: (1) Region AB P + F = C + 1 1 + F = 2 + 1 Therefore, F = 2 Thus F = 2 means any two variables temperature and composition can be varied without effecting liquid phase of the system.
  28. 28. (2) Region BC P + F = C + 1 2 + F = 2 + 1 Therefore, F = 1 Thus F = 1 means that only one variable i.e temperature can be varied without changing Liquid + Solid phase of system. (3) Region CD P + F = C + 1 1 + F = 2 + 1 Therefore, F = 2 Thus F = 2 means any two variables temperature and composition can be varied without effecting solid phase of the system.
  29. 29. 3.Cooling Curves for Eutectic binary alloy L F=2 Temperature c L+s1+s2 F=0 S1+S2 F=1 Time
  30. 30. Eutectic alloy is the one that undergoes eutectic reaction during cooling. Eutectic reaction can be stated as: Liquid1 Constant Temperature Solid + Solid2 1 Thus, eutectic alloy when cooled forms two different solid phases. Fig. shows typically cooling curve for binary eutectic alloy. A binary eutectic alloy thus has two element which are completely soluble in liquid state but entirely insoluble in the solid state. Region AB represent liquid state, solidification starts at B and continue until C, region CD represent solid state containing.
  31. 31. Application of Gibb’s phase rule in various regions: (1) Region AB P + F = C + 1 1 + F = 2 + 1 Therefore, F = 2 Thus F = 2 means any two variables temperature and composition can be varied without effecting liquid phase of the system. (2) Region BC P + F = C + 1 3 + F = 2 + 1 Therefore, F = 0 Thus F = 0 means that no variable amongst temperature and pressure can be varied with out changing the Liquid + Solid phase of system. If the temperature is increased the metal goes into liquid state and if the temperature is lowered it goes into solid state.
  32. 32. (3) Region CD P + F = C + 1 2 + F = 2 + 1 Therefore, F = 1 Thus F = 1 means that only one variable i.e temperature can be varied without changing solid state of system.
  33. 33. 4.Cooling Curves for off-Eutectic binary alloy L F=2 L+S1(or S2) F=1 Temperature c L+s1+s2 F=0 S1+S2 F=1 Time
  34. 34. Eutectic reaction occurs for a definite composition and definite temperature. In the composition of alloy differs from the eutectic composition, it is referred as off-eutectic alloy. Off-eutectic alloys with composition less than eutecti composition are called hypo-eutectic alloys and those with composition more than eutectic composition are called hyper-eutectic alloys. During cooling of off-eutectic alloy, either of the two solids separate out earlier depending on whether the alloy is hypo or hyper eutectic alloy. The pre-separated solid referred as pro-eutectic phase. Fig. shows typically cooling curve for off-eutectic binary alloy. Region AB represent liquid state, solidification starts at B , region BC represent solidification either or, region CD represent solidification of both and, region DE represent solid state of entire system.
  35. 35. Application of Gibb’s phase rule in various regions: (1) Region AB P + F = C + 1 1 + F = 2 + 1 Therefore, F = 2 Thus F = 2 means any two variables temperature and composition can be varied without effecting liquid phase of the system. (2) Region BC In this region, either or start separating out by solidification. P + F = C + 1 2 + F = 2 + 1 Therefore, F = 1 Thus F = 1 means that only one variable i.e temperature can be varied without the solid state of the system.
  36. 36. (3) Region CD In this region, the other starts separating out by solidification P + F = C + 1 3 + F = 2 + 1 Therefore, F = 0 Thus F = 0 means that no variable amongst temperature and composition can varied without changing the Liquid + Solid state of the system. (4) Region DE P + F = C + 1 2 + F = 2 + 1 Therefore, F = 1 Thus F = 1 means that only one variable i.e temperature can be varied without changing the Solid state of the system.
  37. 37. • Series of cooling curves:
  38. 38. – – Two metals of binary solid solution system are mixed in different portions, melted and then cooled, and a cooling curve is constructed for each composition. The phase diagram shows two distinct phases; one is liquid metal solution and the other is solid solution. – – – – – – – Liquidus is that line Above which the alloy is in liquid state Where solidification starts Solidus is that Below which the alloy is in solid state, and Where the solidification completes. If in a phase diagram, for each changes of phase, adequate time is allowed for the change to complete so that phase change takes place under equilibrium conditions, the phase diagram will be known as equilibrium phase diagram. – Generally, equilibrium conditions are not attained during the solidification of weld and casting, that results in porous, cored material which is usually of very inhomogeneous composition.
  39. 39. • Coring or Dendritic Segregation: – Coring or segregation is the non-uniform distribution of constituents in a metal. – Usually a concentration of certain constituents and/or impurities, arising during freezing and generally instant throughout subsequent operations, is known as segregation. – A cored structure arises from a compositional gradient produced within crystals of a solid solutions by progressive freezing. Dendrites of a copper-tin alloy Ag-26%Sn-5%Cu : Cooled quickly after casting
  40. 40. • Interpretation of phase diagram Following the three useful conclusions are the rules necessary for interpreting phase diagram. Rule -1 : Prediction of phases Rule -2 : Phase Composition Rule -3 : Lever arm principle
  41. 41. • Rule -1 : Prediction of phase – – – – – – – Form a phase diagram, specific information cab be obtained only if a temperature and a composition are specified. For example, the state of the alloy of composition 30% bismuth can be determined only with reference to a certain temp. Thus when this alloy is at 1200°F, point 1 located and when it is at 900°F and 600°F, points 2 and 3 are located respectively. The next step is to determine the phase or phases present at points number 1,2 and 3. Point -1 : with 30% Bi-70%Sb alloy at 1200°F, only one phase, i.e., the liquid solution is present. Point -2 : with the same alloy, but 900°F, two phases are present, i.e., liquid solution and solid solution. Point -3 : with the same alloy, but 600°F, only one phase, i.e., the solid solution is present.
  42. 42. • Rule -2 : Phase Composition – To find out the composition of phases which are stable at given temp. (say 900°F), draw a horizontal line, OP at the given temp. – The projections of the intersections of the isothermal line with the solidus and liquidus respectively, give the compositions of the solid and liquid, which co-exist in equilibrium at the temp. – – Liquid phase (point – P) has the composition roughly 62% bismuth. Solid phase (point - O) has the composition roughly 14% bismuth.
  43. 43. • Rule -3 : Lever Arm Principle – – Beside indicating the number of phases and phase composition the phase diagram also tells the proportion of co-existing phases at any given temp. To determine the relative amount of two phases, erect an ordinate at a point (say 30% Bi) on the composition scale which give the total or overall composition of the alloy.
  44. 44. – The intersection of this composition vertical (AL) and a given isothermal line OP (i.e., point M) is the fulcrum of a simple lever system and OM and MP are two lever arms, The relative lengths of the lever arms multiplied by the amounts of the phase present must balance. – – the amount of a given phase multiplied by its lever arm is equal to the amount of the other phase multiplied by its (i.e., other) lever arm This is called the lever rule. It can also be seen that the proportion of solid corresponds to the length of the segment adjacent to liquidus line, whereas the fraction of liquid corresponds to the length of segment adjacent to the solidus line. The isotherm (line OMP) can be considered as a tie line, since it joins the composition of two phases in equilibrium at a specific temperature. – The lever rule or principle may be expressed mathematically as:
  45. 45. 1) Say at point “Q” in (Liquid + Solid) region in a phase diagram, a line passing through point “Q” and parallel to the base is drawn. The line intersects the liquidus and solidus at points P and R respectively. Can you determine %Solid at point Q if PR is 6 cm and QR is 2.4 cm in length? If answer is YES, determine % Solid and if NO, justify your answer.
  46. 46. • CLASSIFICATION OF EQUILIBRIUM DIAGRAMS – An equilibrium diagram has been defined as a plot of the com-position of phases as a function of temperature in any alloy system under equilibrium conditions. – Equilibrium diagrams may be classified according to the relation of the components in the liquid and solid states as follows: – Components completely soluble in the liquid state, 1. and also completely soluble in the solid state, 2. but partly soluble in the solid state (EUTECTIC REACTION). 3. but insoluble in the solid state (EUTECTIC REACTION). 4. The PERITECTIC Reaction – – Components partially soluble in the liquid state, 1. but completely soluble in the solid state. 2. and partly soluble in the solid state. Components completely insoluble in the liquid state and completely insoluble in the solid state. – A study of these diagrams will illustrate basic principles which may be applied to understand and interpret more complex alloy systems
  47. 47. • TWO METALS COMPLETELY SOLUBLE IN THE LIQUID AND SOLID STATES – A system that illustrates an equilibrium diagram in which there is complete solubility in the liquid and solid states is that of the Antimony- Bismuth system. – – Examples of other such systems are Ni-Cu, Au-Ag, Cr-Mo and W-Mo. Since the two metals (such as Sb and Bi or Ni and Cu, etc.) are completely soluble in the solid state, the only type of solid phase formed will be a substitutional solid solution. – – – the equilibrium diagram consists of two lines only— the liquidus and solidus. Above the liquidus there Is a uniform liquid solution for any alloy in the series, while below the solidus there is a single solid solution of any alloy. Between the liquidus and solidus, both liquid and solid solutions co-exist.
  48. 48. – – – Consider an alloy containing 30% Bismuth and 70% Antimony .As the liquid alloy cools, the freezing starts at about 1080°F (582°C) (liquidus line). The composition of the solid formed and liquid at any point say 2(M) can be found from the equilibrium diagram as explained under section. As cooling continues, a stage (i.e., point N) reaches when the whole mass is solid and further cooling will bring the solid to the room temperature.
  49. 49. – Actually the solidification of a liquid alloy of this type consists of two processes: I. a) Formation of crystals in the melt (at say point S), b) Growth of crystals (just as at point M). II. Homogenization of the composition in various parts of each crystal a) By diffusion between core and encasement. b) By diffusion between core and melt.
  50. 50. • EUTECTIC SYSTEM – In an eutectic reaction, when a liquid solution of fixed composi- tion, solidifies at a constant temperature, forms a mixture of two or more solid phases without an intermediate pasty stage. This process reverses on heating. – In eutectic system, there is always a specific alloy, known as eutectic composition, that freezes at a lower temperature than all other compositions. – – At the eutectic temperature, two solids form simultaneously from a single liquid phase. The eutectic temperature and composition determine a point on the phase diagram called the eutectic point.
  51. 51. – Binary alloy eutectic system can be classed as: 1. One in which, two metals are completely soluble in the liquid state but are insoluble in each other in the solid state. 2. two metals are completely soluble in the liquid state but are partly soluble in each other in the solid state.
  52. 52. 1. Two metals completely soluble in the liquid state but completely insoluble in the solid state. – Technically, no two metals are completely insoluble in each other. However, in some cases the solubility is so restricted that for practical purposes they may be considered insoluble.
  53. 53. • Alloy-3: 80% Cd and 20% Bismuth. – As the temperature falls to T1, crystal nuclei of pure Cd begin to form. Since pure Cd is deposited, it follows that the liquid becomes richer in Bi; the composition of liquid move s to left 3’ and as indicated by the diagram, no further Cd deposits until temperature falls to T2. – – At T2 more Cd is deposited and dendrites begin to develop from the already formed nuclei. The growth of the Cd dendrites, on the one hand, and the consequent enrichment of the remaining liquid in Bi, on the other, continues until the temperature has fallen to 140°C, the eutectic temperature in this case. – The remaining liquid then contains 40% Cd and 60% Bi, the eutectic composition.
  54. 54. • • Alloy-1: 20% Cd and 80% Bi – Contrary to alloy 3, in this case crystal of pure Bi form first, enriching the melt with Cd. – The composition of the melt (or liquid) moves to right until Ultimately the point E is reached and the remaining liquid solidi-fies as eutectic (40% Cd and 60% Bi). Alloy-2: 40% Cd and 60% Bi (eutectic alloy) – – – No solidification occurs until the melt reaches the eutectic temperature (140°) At the eutectic temperature, the two pure metals crystallize together to give a characteristically line aggregate known as eutectic. Eutectic consists of alternate layers of Cd and Bi which form at the eutectic temperature (140°C in this case).
  55. 55. EX. The following data is for Pb-Sn alloy system : (Lead-Tin Solder) Melting point of lead (Pb) - 327ºC Melting point of Tin (Sn) - 232ºC Eutectic alloy is formed at 183ºC with 62% Sn –38% Pb Maximum solid solubility of tin in lead at 183ºC –19% Maximum solid solubility of lead in tin at 183ºC –3% Maximum solubility of tin and lead at room temperature is negligible. (1) Draw the phase diagram with the help of above data and label all the points, lines and regions on it. (2) For 70%Pb – 30%Sn alloy composition, determine the amounts of proeutectic and eutectic constituents at room temperature.
  56. 56. 2. Two metals completely soluble in the liquid state, but only partly soluble in the solid state
  57. 57. – Since most metals show some solubility for each other in the solid state, this type is the most common and, therefore, the most common alloy system. – – Metals such as Pb-Sn and Pb-Sb are partly soluble in each other in the solid state. Fig. shows the Tin-Lead equilibrium diagram with micro-structures (of course) obtained under non-equilibrium condition of solidification. I. Tin will dissolve up to maximum of 2.6% Pb at the temperature, forming the solid solution α. II. Lead will dissolve up to a maximum of (100-80.5) i.e. 19 .5% tin at the eutectic temperature, giving the solid solution β. III. Slope of BA and CD indicate that the solubility of Pb in Sn (α) and that of Sn in Pb (β) decrease as temperature falls –.Consider an alloy of composition Z (70% Pb-30% Sn). As the melt temperature falls to T1, dendrites of composition Y will deposit.
  58. 58. – – The alloy solidifies as a solid solution until at 183°C, the last layer of solid to form is of composition C (80.5% Pb-19.5% Sn). The remaining liquid which has the eutectic composition (38% Pb-62% Sn) then solidifies by depositing, in the form of a eutectic, i.e., alternate layers of α and β, of compositions B and C respectively. – – – If cooled slowly to room temperature the compositions of the solid solutions α and β will follow the line BA and CD, i.e., α will become progressively poorer in lead and β in tin. Take another alloy of composition Z' (95% Pb-5% Sn). When cooled slowly, solidification starts at R and is complete at P, the resultant solid being a homogeneous single phase, the β solid solution. As the alloy cools, the solvus line is reached at point Q. The β solution is now saturated in tin. Below this temperature, under conditions of slow cooling, the excess tin must come out of solution. Since tin is soluble in lead, the precipitate does not come out as the pure metal tin, but rather the α solid solution.
  59. 59. • Peritectic reaction:
  60. 60. – – – – It is the reaction that occurs during the solidification of some alloys where the liquid phase reacts with a solid phase to give a solid phase of different structure. Assuming very slow rates of cooling, the peritectic reaction will occur only in those Pt-Ag alloys that Contain between 12 and 69% silver (Ag). Consider a liquid (melt) of composition Z, i.e., containing 25% Ag. Solidification commences at T1 and dendrites of α, initially of composition W, begin forming. Selective crystallization of α continues down to Tp, the peritectic temperature; when the alloy reaches. this temperature, it is composed of solid α-dendrites of composition B and liquid of composition D in the proportion α : liquid = RD : RB.
  61. 61. • Eutectoid Transformation: – Eutectoid reaction is an isothermal reversible reaction in which a solid phase (usually solid solution) is converted into two or more intimately mixed solids on cooling, the number of solids formed being the same as the number of component in the system.
  62. 62. • Peritectoid Transformation: – The peritectoid reaction is the transformation of two solid into a third solid.
  63. 63. Any Questions
  64. 64. ❑ Define the following terms: [solid, liquid, gas, pure substance, compound, mixture, element, heterogeneous mixture, homogeneous mixture, extensive properties, intensive properties, chemical properties, physical properties, density, color, texture, conductivity, malleability, ductility, boiling point, melting point, flammability, corrosiveness, volatility, pounding, tearing, cutting, dissolving, evaporating, fermenting, decomposing, Exothermic, endothermic, mass, density, gravity, adhesive force, cohesive force, interface, adsorption, catalyst, dipole, physisorption, Chemisorption, hydrophilic, hydrophobic, detergent, surfactant, surface tension, adsorbate, adsorbent, etc] ❑Respond to the following questions: ➢What is viscosity and its relationship with fluids ➢What are surface and Inter-facial tension forces and respective association with activities of a substance material with surface area ➢How is a chemical change different from a physical change at the surface of a material ➢What is contact angle of a substance and its significant role when two materials surface are in contact ➢What is a detergent and justified reasons for its variable composition ➢What is the micelle made up of in terms of its physical form and shape ➢What are some of the practical uses of surface agent material

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