Cohesive force/energy

The transformation of bulk Hquid to sprays can be achieved in many different ways. Basic techniques iaclude applying hydraulic pressure, electrical, acoustic, or mechanical energy to overcome the cohesive forces within the Hquid. 

The fundamental principle of Hquid disiategration Hes ia the balance between dismptive and cohesive forces. The common dismptive forces ia atomizer systems iaclude kinetic energy, turbulent fluctuation, pressure fluctuation, iaterface shearing, friction, and gravity. The cohesive forces within the Hquid are molecular bonding, viscosity, and surface tension. 

For cavitation to occur in a liquid, it has to overcome the natural cohesive forces present in the liquid. Any increase in these forces will tend to increase the threshold pressure and hence the energy required to generate cavitation. In highly viscous liquids, severe attenuation of the sound intensity occurs and the active cavitating zone gets reduced substantially. Moholkar et al. [56] have confirmed this fact with experiments with different liquids and reported that for highly viscous liquids, cavitational effects are not observed. 

However, there are only two decisive parameters - the basicity which assists to swelling process and the is molar volume, which opposites to this process taking into account the needed energy and the negotiation of the cohesion forces have only insignificant influence and the exclusion of this parameter from the calculations practically does not worsen the equation... 

When a solvent undergoes a small isothermal volume expansion, it does work against the cohesive forces which causes a change in the internal energy E of the solvent. The internal pressure is given by the relation (Dack, 1976)... 

The three kinds of forces described above, collectively known as the cohesive forces that keep the molecules of liquids together, are responsible for various properties of the liquids. In particular, they are responsible for the work that has to be invested to remove molecules from the liquid, that is, to vaporize it. The energy of vaporization of a mole of liquid equals its molar heat of vaporization, Ay//, minus the pressure-volume work involved, which can be approximated well by Rr, where R is the gas constant [8.3143 J K" mol" ] and T is the absolute temperamre. The ratio of this quantity to the molar volume of the liquid is its cohesive energy density. The square root of the cohesive energy density is called the (Hildebrand) solubility parameter of the liquid, 8 ... 

Even at low temperature some molecules may overcome the energy barrier of the cohesive forces and escape from the sohd or hquid state into the gaseous phase. 

Harkins defines two terms, the work of cohesion We which is the work done when a bar of liquid of unit cross sectional area is pulled apart against the cohesive forces. It is thus numerically equal to twice the sur ce energy of the liquid. The work of adhesion Wa is similarly defined as the work required to pull apart a composite bar consisting of half of one liquid and half of the other, at the place of junction. 

As has been pointed out by O Keeffe and Hyde (1985), the cation lattices of many of these structures are found in the structures of metal crystals, the delocalized conduction electrons, which provide the cohesive force, concentrating in the cages where their potential energy is lowest (Zuo et al. 1999). These low potential cages therefore also provide good sites for anions. 

Measurement of the free energies of monolayer desorption from the rates of desorption depends on whether equilibrium exists between the monolayer and a thin region of solution immediately beneath the film. The relation which tests this condition (Equation 8) must correctly predict the dependence of the rate constant for desorption, k8, on 7r. For the sulfate, phosphonate, and carboxyl films in this study Equation 8 is obeyed within the range of experimental error (2 to 5%). Therefore, it is reasonable to assume that the necessary equilibrium condition does exist. The cohesive forces in the monolayer follow directly from the evaluation of the free energies of desorption. 

Enhancement of Eu3+ fluorescence has also been observed [612] when incorporating Tb3+ ion in Eu3+ doped tungstate host lattice. The degree of enhancement is proportional to the Tb3+ ion concentration. The mechanism of energy transfer in this case may probably involve interaction with Tb3+ affecting the cohesive force operating on Eu3+. 

Structurally, a more specific definition would be that a molecule is a local assembly of atomic nuclei and electrons in a state of dynamic siahility. The cohesive forces are electrostatic, but. in addition, relatively small electromagnetic interactions may occur between (he spin and orbital motions of (he electrons, especially in the neighborhood of heavy nuclei. The intcrnuclear separations are of the order of 1-2 x 10" meter, and the energies required to dissociate a stable molecule into smaller fragments... 

The like-dissolves-like rule reflects the fact that attractions between solute molecules and some attractions between solvent molecules must be replaced by solute-solvent attractions when a solution forms. If the new attractions are similar to those replaced, very little energy is required for the solution to form. For example, when the main cohesive forces in a solute are hydrogen bonds, the solute is more likely to dissolve in a... 

The contribution from the energy required for the change in volume against the internal cohesive forces acting between the constituent particles of a substance. 

The cohesive force between solid surfaces and the surface energy of solids." Ibid., 13 (7th Ser.) 853-862. 

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