Internal energy symbol

The quantity AU JV° is the internal energy of vaporization per unit volume and is called the cohesive energy density (CED) of component i. The square root of the CED is generally given the symbol 6j for component i. 

The systems of interest in chemical technology are usually comprised of fluids not appreciably influenced by surface, gravitational, electrical, or magnetic effects. For such homogeneous fluids, molar or specific volume, V, is observed to be a function of temperature, T, pressure, P, and composition. This observation leads to the basic postulate that macroscopic properties of homogeneous PPIT systems at internal equiUbrium can be expressed as functions of temperature, pressure, and composition only. Thus the internal energy and the entropy are functions of temperature, pressure, and composition. These molar or unit mass properties, represented by the symbols U, and S, are independent of system size and are intensive. Total system properties, J and S do depend on system size and are extensive. Thus, if the system contains n moles of fluid, = nAf, where Af is a molar property. Temperature... 

In this book, elastic strain and plastic deformation will be differentiated by both words and symbols. Elastic strain is given the usual symbols e and y for extensional and shear elastic strains, respectively. For plastic shear deformation. 8 will be used, e and 8 are physically different entities, e and y are conservative quantities which store internal energy. 8 is not conservative. The work done to create it is dissipated as heat and structural defects. 

Absolutely everything possesses energy. We cannot see this energy directly, nor do we experience it except under certain conditions. It appears to be invisible because it is effectively locked within a species. We call the energy possessed by the object the internal energy , and give it the symbol U. 

No symbol has been approved by the IUPAC for dissociation energy in the chemical thermodynamics section [13]. Under Atoms and Molecules, either El or D is indicated. The latter is more common, and IUPAC recommends Do and De for the dissociation energy from the ground state and from the potential minimum, respectively. Because the bond energy concept will be omnipresent in this book and can be explored in a variety of ways, some extra names and symbols are required. This matter will be handled whenever needed, but for now we agree to use DUP for a standard bond dissociation internal energy and DHj for a standard bond dissociation enthalpy, both at a temperature T. In cases where it is clear that the temperature refers to 298.15 K, a subscript T will be omitted. 

Figure 13. Fitted cubic curves representing solute internal energy with respect to the d f distance, corresponding to the precursor and the successor complexes, e symbol represents an electron inside an electrode. (Reprinted from Ref. 64.)...

Figure 3.16. Population distribution b0 (a) and rotational alignment b2/b0 (b) plotted vs. the internal energy. As in Figure 3.15, Boltzmann population distributions are linear in such plots. The different symbols correspond to different spin-orbit states of NO. From Ref. [170].

We cannot measure the total energy of a system all we can do is measure changes in energy. If a system does 15 J of work, it has used up some of its store of energy, and we say that its internal energy has fallen by 15 J. To denote this change, we write AU = —15 J. Throughout thermodynamics, the symbol AX means a difference in a property X ... 

Some texts use the symbol U for the energy, and some texts call it the internal energy. Also, one should be aware that some texts define the energy function as being equal to (dQ — dW). This depends upon the sign convention used for work. 

Symbol potential energy on a Bom-Oppenheimer surface (i.e. in a PES diagram) is denoted in Chapter 2 by E. Other common designations are V (origin obscure) and PE, and sometimes U, but this latter is best reserved for internal energy. Equation potential energy is the integral over the relevant distance of the force, itself usually a function of distance. 

Symbol Helmholtz free energy is denoted in chemistry by A (German Arbeit, work), in physics by F, free energy. Equation A U — TS, where U = internal energy, T = Temperature, S = entropy. 

It has also been explained before, that a part of internal energy of a system can be utilized at constant temperature to do useful work. So, this fraction of internal energy which is isothermally available is called the work function of the system. It is denoted by the symbol A. The exact nature of the functions will be clear as follows ... 

Let symbols without subscripts refer to the solid and symbols with subscript w refer to the water. Heat transfer from the solid to the water is manifested by changes in internal energy. Since energy is conserved, AU = —At/, . If total heat capacity of the solid is C (= mC) and total heat capacity of the water is C w (= mwCw), then ... 

Figure 23. Excess internal energy and EOS of Kr for several reduced densities along the isotherms T = 273 and 348 K. AS only (dotted lines), AS+AT contribution (solid lines), symbols...

It is important to mention briefly the issues of notation and units. A glossary of frequently used symbols is given in Appendix A. Note that the definition of thermodynamic work used here is the work done on a system (e.g., dw = -p dV). As a result, the first law of thermodynamics has the form dE= dq + dw. Note also that E is used for the thermodynamic internal energy and U for the potential energy instead of the lUPAC choices of... 

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