3 лекция - по&ETH

3 лекция - поÐ

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Lecture №3 1.Topic: Surface phenomenon, having place in living organism. Adsorption. 2.Aim: Form the knowledge about physic-chemistry of the surface phenomena. 3. Plane and thesis of lecture: 3.1. Plane of lecture 1. Surface tension 2.Surface active substance Isotherm of surface tension 3.Surface non active substance. Isotherm of surface tension 4.Surface activity. Rule of Ducle-Traube. 5. Sorption and its kinds 6.Adsorption. Adsorption of strong electrolyte. 7.Chromatography analysis. 3.2. Thesis of lecture All of the liquids and solids are bordered by external surface on which they get in touch with phases of the other structure (water-steam) or another composition (water-benzene). Properties of this substance in that inter-phase surface are differ from the properties of the substance in the bulk of a liquid. For instance , there are two molecules are inn touch: steam (gas) and a liquid. Molecule "B" is in a bulk of the liquid and is surrounded by the other molecules and experiences intermolecular interaction from the other molecules on the radius 10" 9 m. Sum of all intermolecular interactions on "B" molecule is equal to zero F=0 and molecule is in equilibrium state. Molecule "A" experiences interactive forces from the liquid side and from the gas but interaction from the liquid side is more then from the gas so resulting forces from the liquid side pull the "A" molecule into the liquid and F is not equal to zero. This energy of inter-phase surface is called as surface energy. Surface energy is work which is spent for the new surface formation. Work which is spent for the formation of the unit of new surface is called for the liquid as specific surface tension or coefficient of surface tension. It is signed as sigma. Sigma =F/S i.e. coefficient of surface tension is expressed in the units of the work divided to aria unit erg/cm 2 or J/m 2 . Surface tension force tries to keep surface of the liquid till minimum what explains spherical shape of the liquids drops in air. Surface phenomenon is a phenomenon that takes place on or near the surface of a substance or phase. In most cases, the special properties of a surface cause these unique phenomena. Why do some insects succeed in skating on water instead of sinking? Why in some cases, does the water sprinkled on a glass surface collect into drops and in other cases spread like a thin film? Why does water climb up a thin tube? Why can you make bubbles with soapy water and not with tap water? For reasons we will see later on, the surface of a substance has special properties. These surface properties are what allow the strange phenomena we have mentioned. Not only that, but the surface is also the place of contact among different substances. In short, the properties of surfaces are so special and important that there is
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This note was uploaded on 11/29/2011 for the course RWR fref taught by Professor Erf during the Spring '11 term at Audencia Nantes Ecole de Management.

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3 лекция - поÐ

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