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 interfacesphysical chemical interfacephases solidliquidgasvacuum

Phenomena in Surface Chemistry 1.Wetting, Spreading and Penetration 2.Foam Breaking in Aqueous Systems 3.Solubilization 4.Rheological Effects in Surfactant Phases

Assignment-6 Group Presentation G10 : Group Presentation G9 : Foam breaking and its application G10 : Solubilization and its application G11 : Rheology and its application (5 min)

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

Assignment-7 1.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. 3.Report is due on September 15, (10 points) Individual Report

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

1. Gas-Liquid and Liquid-liquid Interfaces

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

Surface Tension as a Force  caused by the attraction between the moleculesmolecules of the liquid by various intermolecular forcesintermolecular forces

Surface Tension as Surface Excess Free Energy.,

Capillary Rise Method where h = the height the liquid is lifted,  la = the liquid-air surface tension (J/m² or N/m)surface tension θ = contact anglecontact angle ρ = density of liquid (kg/m 3 )density g = acceleration due to gravity (m/s²)accelerationgravity r = radius of tube (m)radius Determination Methods

The Ring Method  = where  =constant (Du Nouy tensiometer)

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

Surface tension (mN m -1 ) ofsome liquids 0 o C 20 o C 40 o C 60 o C 80 o C 100 o C H 2 O Ethanol Acetone Toluene Benzene Hg (0 o C) 480 Ag (970 o C) 800 NaCl (1080 o C) 94 AgCl (452 o C) 125 Intermolecular forces

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

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

Interface Tension and Spreading

Spreading Coefficient, S in Water at 20 o C liquid B n-hexadecane 72.8-( ) = Drop on water surface n-octane 72.8-( ) = Spreading n-octanol 72.8-( ) = Spreading against inpurity S =

Use the following data of the surface/interface tensions (mN m -1 ) at 20 o C A B  A  B  AB H 2 O C 6 H H 2 O CCl H 2 O Hg H 2 O C 8 H 15 OH predicts the spreading behavior of B on A

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

Surface Tension of Some Alcohols in Water at 20 o C

Surfactants in solution Micelle formation when C > CMC

CMC determination CMC = critical micelle concentration

Effect of Temperature on Surface tension T  Pure liquid Surfactant solution

Gibbs isotherm  is known as surface concentration (mol/m 2 ) C is the concentration of the substance in the bulk solution. R is the gas constantgas constant T the temperaturetemperature Effect of Concentration on Surface tension Adsorption On surface