Condensed-phase phenomenon

Of course, condensed phases also exliibit interesting physical properties such as electronic, magnetic, and mechanical phenomena that are not observed in the gas or liquid phase. Conductivity issues are generally not studied in isolated molecular species, but are actively examined in solids. Recent work in solids has focused on dramatic conductivity changes in superconducting solids. Superconducting solids have resistivities that are identically zero below some transition temperature [1, 9, 10]. These systems caimot be characterized by interactions over a few atomic species. Rather, the phenomenon involves a collective mode characterized by a phase representative of the entire solid. 

The introductory remarks about unimolecular reactions apply equivalently to bunolecular reactions in condensed phase. An essential additional phenomenon is the effect the solvent has on the rate of approach of reactants and the lifetime of the collision complex. In a dense fluid the rate of approach evidently is detennined by the mutual difhision coefficient of reactants under the given physical conditions. Once reactants have met, they are temporarily trapped in a solvent cage until they either difhisively separate again or react. It is conmron to refer to the pair of reactants trapped in the solvent cage as an encounter complex. If the unimolecular reaction of this encounter complex is much faster than diffiisive separation i.e., if the effective reaction barrier is sufficiently small or negligible, tlie rate of the overall bimolecular reaction is difhision controlled. 

For very fast reactions, the competition between geminate recombmation of a pair of initially fomied reactants and its escape from the connnon solvent cage is an important phenomenon in condensed-phase kinetics that has received considerable attention botli theoretically and experimentally. An extremely well studied example is the... 

When the two phases in contact are condensed phases and the entire volume is taken up by incompressible substances, positive adsorption of one component must be attended by negative adsorption (desorption) of other components. This phenomenon is called adsorptive displacement. 

It was concluded that turbulent flow following the reaction was responsible for the phenomenon in gas. There is no convincing evidence to show that there is or is not turbulence in the flow following the reaction in condensed phase expls. The decay zone in such expls has be n observed only when the deton front has been allowed to become divergent... 

Vapor-solid and vapor-liquid transformations (condensation of a gas, or its reverse, evaporation) can fractionate elements and sometimes isotopes. Each element condenses over a very limited temperature range, so one would expect the composition of the condensed phase and vapor phase to change as a function of the ambient temperature. Many of the chemical fractionations that took place in the early solar system are due, in one way or another, to this phenomenon. It is convenient to quantify volatility by use of the 50% condensation temperature, that is, the temperature by which 50% of the mass of a particular element has condensed from a gas of solar composition. Table 7.1 lists the 50% condensation temperatures for the solid elements in a gas of solar composition at a pressure of... 

Returning to the idea of molecular structure, it is implied that isolated small molecules have no rigid structure or shape, and acquire this property only in condensed phases. The best documented example of such behaviour is the NH3 molecule, but the phenomenon is certainly more general. The important implication is that shape is an attribute of molecules with appreciable mass. There is no need for shape when dealing with the small isolated entities of atomic physics, and for this reason it does not feature in traditional formulations of quantum theory. 

Soret effect — When a temperature gradient is applied to an homogeneous mixture of two or more components there is a partial separation of the components by -> migration along the temperature gradient. This phenomenon, known as Soret effect, occurs in condensed phases (i.e., liquids and solids) [i]. Another term that is used to describe the Soret effect is thermo diffusion, which has been observed for either mixtures of gases or liquids and solid solutions [ii]. For electrolytic solutions in a temperature gradient, ions move from a location... 

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