Chapter 10 Interface (Surface) Phenomenon

1. Chapter 10 Interface (Surface) Phenomenon Phase Homogeneous system one phase Heterogeneous system two or more phase 10.1 Interface Interface, surface

2. Volume surface Mass surface • Result in the tendency • Liquid surface is to become as small as possible • Physical and Chemical adsorption Dispersity

4. 10.2 Surface Tension 10.2.1. Surface Tension Surface work Wr = dAs  unit J·m-2＝N·m·m-2＝N·m-1，  -- surface tension

5. dl L F  (a) dl dl L L Ｆ   (b) (c)

6. L  dl

7. 10.2.2 Surface Energy of Dispersion System dU = TdS - pdV +dAs + BdnB dH = TdS + Vdp +dAs + BdnB dA =-SdT - pdV +dAs + BdnB dG =-SdT + Vdp +dAs + BdnB  Unit surface free energy

9. 10.2.3 Temperature Dependence of Surface Tension T ,   — p  

10. 10.3 Curved Surface 10.3.1 Excess Pressure of Curved Surface

11. x +dx y+dy dz y x dz r2 r1 O2 O1 r: curvature radius Young -Laplace equation r1 = r2 = r，

12. convex： r>0,  p >0， p1>pg concave：r<0  p <0, p1< pg plane： r=0  p =0， p1= pg

13. Kelvin equation 10.3.2 Saturated Vapor Pressure of Curved Surface pr*——Saturated vapor pressure of curved liquid surface p* ——Saturated vapor pressure of plane， MB——molar mass ； B——volume mass σ——surface tension； r——curvature radius convex(droplet)： r>0, ln(pr*/p*)>0， pr*>p*； concave(bubbles)： r<0, ln(pr*/p*)<0， pr*<p*。

14. • • • • • P(r>0) • • • g • • • • • • p（r=0） • • • p(r<0) g • • • • l • • • g • • • • • l l pr*(convex)>pr*(plane)>pr*(concave) Ｆ (convex）＜Ｆ（ plane）＜Ｆ（ concave）

15. 3 2 {Pr} 1 10-1 100 101 102 103 Saturated vapor pressure of curved liquid surface r /nm 298.15 K convex plane concave

16. 10.3.3 Metastable State Supersaturated vapor Supersaturated solution Superheated liquid Superhcooled liquid dG=－SdT+Vdp+dAs dGT,P＝dAs>0 v ∝r2exp(-Br2)

17. 10.3.4 Wetting (a) adhesion wetting

18. (b) dipping wetting

19. (c) spreading wetting Spreading coefficient

20.  < 90—wetting；  > 90—unwetting； Contact angle Young’s equation

21.  <90( >90)  >90( <90) ＝180-θ

22. r  R  h 10.3.5 Capillary Phenomenon

23. Ⅰ {} Ⅱ Ⅲ {c} 10.4 Surface adsorption of solution 10.4.1 Surface tension of solution

24. h h 体相  V  h1 h1 h0 Surface phase S1 h0 h0 界面层S Surface layer S2 AS h2 h2 V   (a) practice system (b) c ~ h (c) Gibbs model 10.4.2 Surface adsorption of solution Positive adsorption，negative adsorption Surface excess B

25. Ⅰ {} Ⅱ {c} (I)，B<0，negative adsorption； (II、III)，则B >0， positive adsorption 。 10.4.3 Gibbs equation Gibbs equation

26. hydrophile lipophile COO- CH3(CH2)7=CH(CH2)7 H+ Structure characteristic of a surfactant 4. Surfactants

27. Surface film of unimolecular layer Associated colloid(micell)

28. Critical micell concentration Increase dissolution

29. anionic surfactants e.g.soap RCOONa cationic surfactants Ionic surfactants C18H37NH3+Cl- Amphoteric surfactants Surfactants R-NH-CH2COOH Nonionic surfactants e.g. R[CH2OCH2]nCH2OH

30. Wetting action Emulsification , dispersed action Foaming action , do away with foam Washing action

31. kink terrace impurity adsorbed atom step dislocation 10.5 The extent of adsorption 10.5.1 Solid surface adsorption, adsorbate, adsorbent

32. 10.4.2 Physical adsorption and chemical adsorption

33. H H H b b H a Cu Cu Cu X Cu Cu Cu {E} D Ea a 0 Hc= -33.5kJ 55.4kJ Hp H H C Cu Cu Cu H H Cu Cu H H Cu Cu {r}

34. Adsorption quantityΓ m——mass of solid ； V——volume of adsorbed gas at T.p T fixed, Γ = f (p) Adsorption isotherm p fixed, Γ = f (T) Adsorption isobar pΓ fixed, p = f (T) Adsorption isostere {Γ} {p} (a) (b) (c) (d) (e) 10.4.3 Adsorption curve

35. A(g) + M(surface) A ka M kd 10.4.4 Langmuir isotherm Langmuir assumption (i) Adsorption cannot proceed beyond monolayer coverage. (ii)All site are equivalent and the surface is uniform ( that is , the surface is perfectly flat on a microscopic scale) . (iii)The ability of a molecule to adsorb at a given site is independent of the occupation of neighboring sites. (iv)At equilibrium, the rates of adsorption and desorption of molecules from the surface are equal. ka :rate coefficient of adsorption kd :rate coefficient of desorption

36. equilibrium constant of adsorption Langmuir isotherm Coverage of surfaceθ υa= ka (1-θ）p υd= kd θ at equilibrium，υa=υd， ka (1-θ)p ＝kdθ

37. {Γ} (a) (i)bp<<1， θ＝bp (ii)bp>>1， θ＝1 V——volume of adsorbate adsorbed by solid at T,p V∞——volume of adsorbate corresponding to complete monolayer coverage

38. Mixed adsorption A、B Dissociation adsorption A2 + 2* 2（A – *）

39. 10.4.5 The BET isotherm BET isotherm