1.Introduction to surface and colloid chemistry课件.pptVIP

;Physical Chemistry;Plans;Examination;Books;References;Chapter 1;Colloids;What is a Colloid?;The dispersion medium is what the dispersed phase is is dispersed in.;History of Colloids;;Properties of Colloids;It consists of the scattering of light when passing through the colloid due to the reflection of light in every colloidal particle resulting in a visible path of the light in that area, or in every particle through a microscope.;Tyndall effect;The Tyndall effect is evident as a beam of light passes through a colloidal dispersion of water droplets in the atmosphere.;The colloidal particles are kept in suspension due to the continuous impacts they receive from the molecules of the solvent, which results in a random motion. ;Adsorption is a physical or chemical process by which molecules of one substance adhere to the surface of a second substance, in this case to the surface of colloid particles.;Colloids have more specific definitions now, but dyalisis a very effective way to separate the colloid particles from it’s solvent, or , even more useful, to separate different colloidal particles, with different membranes;Electrophoresis;When undisturbed, some colloids will appear and behave as a gel, but when disturbed or acted on by a force it will act like a sol. ;Aerosol Sols Emulsion Foam;Occurs when colloid particles, in the form of a liquid or solid, are dispersed in a gas medium.;Occurs when colloid particles, in the form of solids, are dispersed in a liquid medium. There are four types of Sols: Lyophobic Lyophilic Association Gels;Lyophobic Sols: particles have a surface charge and will remain completely separate from the solvents. Lyophilic Sols: Resembles true solutions and the particles have more affinity with the solvents. Association Sols: A mixture of the two types above.; Lyophilic - solvent-attracting (hydrophilic for H2O) Polar species attracted to water lyophobic - solvent-repelling (hydrophobic for H2O) Non polar species in water Gel- semirigid