Thermal molecular movements

Thermal molecular movements furthering the formation of a dispersed state with freely movable molecules, that is, a gaseous state. 

The ideal gas law (1.8) describes the macroscopic properties of a system of gas particles that solely interact through random, elastic impacts in the ideal gas the thermal molecular movements dominate, and the gas properties are independent of intermolecular forces. 

The van der Waals equation (1.11) describes the macroscopic properties of a real gas where the intermolecular forces and thermal molecular movements are in mutual balance. From a molecular point of view the real gas is a transition state between the ideal gas and the condensed, liquid and solid states. 

Figure 4.3. A ball changing from jumping to a state of rest is an example of an irreversible process. The ball s organized movement is spontaneously transformed into beat, i.e. disorganized, thermal molecular movements in the ball and its foundation. The opposite process, that disorganized molecular movements are spontaneously transformed into an organized, macroscopic movement, is not known.

The polypeptide chain in the native protein is folded into a compact structure, which strongly limits the freedom of molecular movement. The arrangement in space of each atom in the protein molecule is fixed and does not change with time in the absence of thermal collisions with other atoms in a protein and solvent molecules. From the thermodynamic point of view, the... 

For a Tg to occur in crosslinked systems, there must be sufficient molecular mobility to affect the macroscopic physical modulus of the material. As the effective molecular weight, between the crosslinks decreases with increasing crosslink density, the thermal activation required to induce sufficient molecular movement, seen by a Tg, is commensurably increased. 

Since antigen(s) and antibodies are located in different sites (layers, reservoirs) at the beginning of the experiment, in all cases one or both have to move so that they meet in the gel in concentrations and proportions suitable to give a visible precipitate. The cause of this movement may merely be the thermal molecular agitation which results in diffusion. Alternatively, one or two of the reagents may migrate as a result of an electric field (electrophoresis). In the latter case, diffusion, which cannot... 

In this chapter, I discuss the phenomenon of molecular orientation induced by photoisomerization whereby experiment merges with theory to assess molecular movement during isomerization. The theory unifies photochemistry with optics, and it provides rigourous analytical tools for powerful quantification of coupled photoisomerization and photo-orientation. Experiments on spectrally distinguishable isomers detail the mechanisms of chromophore reorientation during photo- and thermal isomerization. In particular, I... 

The theory of molecular diffusion has been developed based on the theory of Brownian motion. Molecular diffusion is defined as the net action of molecules to minimize a concentration gradient. In other words, diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached. This molecular movement is caused by random thermal movement of each molecule. 

The distance between the dipoles depends largely on the position of the poles in the molecule (i.e., on steric molecular influences) and on thermal vibrational movements. The force of attraction between the dipoles accordingly decreases sharply with increasing temperature. 

In order to generate motion, a molecular-level machine requires an energy source. Therefore spontaneous molecular movements caused by thermal energy including the demonstration of the rotation of a single molecule on a surface, have nothing to do with the concept of a molecular-level machine. 

We outline briefly the physical basis of the Arrhenius equation as applied to atomic or molecular movements in a solid. All viscoelastic effects, including large strain effects (see Gtapter S), are due to thermally activated movements of segments of macromolecules under imposed mechanical stress. There is no question of the stress generating molecular movements which, in the absence of the stress, would not take place. What in fact occurs is that molecular movements or jumps occur spontaneous, and it is the function of the stress to bias them so that th no longer occur in random directions. This results in a molecular flux which leads to time-dependent mechanical strain. 

Thermal expansion. Coefficients of thermal expansion are frequently represented by a single figure. This is inadequate for plastics in general, and for composites it is positively misleading. Because molecular movement inereases with temperature, so does the expansion coeffieient. In fibrous composites, the coefficient at any temperature is directionally dependent unfortunately in tabulated data the figure presented is nor-... 

As stated above, Tg is the temperature at which the thermal energy of the chains is sufficient to overcome the barriers to rotation and molecular movement. Tg is also dependent on the rate or frequency at which it is... 

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