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S urface C hemistry

S urface C hemistry. the study of physical and chemical phenomena that occur at the interface of two phases , including solid - liquid interfaces, solid - gas interfaces, solid - vacuum interfaces, and liquid - gas interfaces. P henomena in S urface C hemistry .

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S urface C hemistry

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  1. Surface Chemistry the study of physical and chemical phenomena that occur at the interface of two phases, including solid-liquid interfaces, solid-gas interfaces, solid-vacuum interfaces, and liquid-gas interfaces

  2. Phenomena in Surface Chemistry Wetting, Spreading and Penetration Foam Breaking in Aqueous Systems Solubilization Rheological Effects in Surfactant Phases

  3. Assignment-6 Group PresentationG9 : Foam breaking and its applicationG10 : Solubilization and its application G11 :Rheology and its application (5 min)

  4. Surface Chemistry in Important Technologies Surface Chemistry in Pharmacy Surface Chemistry in Food and Feed Surface Chemistry in Detergency Surface Chemistry in Agriculture Surface and Colloid Chemistry in Photographic Technology Surface Chemistry in Paints Surface Chemistry of Paper Surface Chemistry in the Polymerization of Emulsion Colloidal Processing of Ceramics Surface Chemistry in Dispersion, Flocculation and Flotation Surface Chemistry in the Petroleum Industry

  5. Assignment-7 Individual Report • Search from Journals or websites to find • some examples of Surface Chemistry in • Important Technologies • 2. Write up a 1 page concise report • in A4 paper. • Report is due on September 15, 2009. • (10 points)

  6. Analysis and Characterization in Surface Chemistry • Measuring Equilibrium Surface Tensions • Measuring Dynamic Surface Tensions • Measuring Contact Angle • Determining Critical Micelle Concentration • Measuring Micelle Size and Shape • Identification of Lyotropic Liquid Crystalline Mesophases • Characterization of Microemulsion Structure • Measuring Particle Size by Light Scattering • Measurement of Electrokinetic Phenomena in Surface Chemistry • Measuring Interactions between Surfaces • Measuring the Forces and Stability of Thin-Liquid Films • Measuring Adsorption

  7. 1. Gas-Liquid and Liquid-liquidInterfaces

  8. Surface Tension,  an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet

  9. Surface Tensionas a Force • caused by the attraction between the molecules • of the liquid by various intermolecular forces

  10. Surface Tension as Surface Excess Free Energy           ,     .

  11. Capillary Rise Method Determination Methods • where • h = the height the liquid is lifted, • la = the liquid-air surface tension (J/m² or N/m) • θ = contact angle • ρ = density of liquid (kg/m3) • g = acceleration due to gravity (m/s²) • r = radius of tube (m)

  12. The Ring Method  = where  =constant (Du Nouytensiometer)

  13. Pendant Drop Method mg = 3acos()  is the surface tension of liquid is the contactangle at which a liquid/vapor interface meets the solid surface. Contact Angle Goniometer.

  14. Surface tension (mN m-1) ofsome liquids 0oC 20oC 40oC 60oC 80oC 100oC H2O 75.64 72.75 59.56 66.18 62.61 58.85 Ethanol 24.05 22.27 20.60 19.01 - - Acetone26.20 23.70 21.20 18.60 16.20 Toluene30.74 28.43 26.13 23.81 21.53 19.39 Benzene 31.60 28.90 26.30 23.70 21.30 Hg(0oC) 480 Ag (970oC) 800 NaCl (1080oC) 94 AgCl (452oC) 125 Intermolecular forces

  15. Surface Tension • Directly depends on intermolecular forces in the solution • Inversely depends on temperature • of metallic liquid > ionic liquid > covalent liquid

  16. Liquid in a Vertical Tube • ls = liquid-solid surface tension • la = liquid-air surface tension • = contact angle Concave Concave Adhesive>>Cohesive Convex Adhesive<<Cohesive Convex

  17. Interface Tension and Spreading

  18. SpreadingCoefficient, Sin Water at 20oC S = S = liquid B n-hexadecane 72.8-(30.0+52.1)= - 9.3 Drop on water surface n-octane 72.8-(21.8+50.8) = + 0.2 Spreading n-octanol 72.8-(27.5+8.5) = +36.8 Spreadingagainst inpurity

  19. Use the following data of the surface/interface tensions (mN m-1) at 20oC A B A B AB H2O C6H6 72.75 28.88 35.0 H2O CCl4 72.75 26.28 45.0 H2O Hg72.75 470 375 H2O C8H15OH72.75 17.0 10.7 predicts the spreading behavior of B on A

  20. Surface Tension of Solution Substances in solution : • Surface activeagent “Surfactant” (<o) hydrophilic part hydrophobic part • Surface inactive agent (>o) such as ionic compounds, acids, bases etc.

  21. Surface Tensionof Some Alcohols in Water at 20oC

  22. Surfactants in solution Micelle formation when C > CMC

  23. CMC determination CMC = critical micelle concentration

  24. Effect of Temperatureon Surface tension  Pure liquid Surfactant solution T

  25. Gibbs isotherm Effect of Concentration on Surface tension Adsorption On surface  is known as surface concentration(mol/m2) C is the concentration of the substance in the bulk solution. R is the gas constant T the temperature

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