Matter physical states

Intermolecular forces are responsible for the existence of several different phases of matter. A phase is a form of matter that is uniform throughout in both chemical composition and physical state. The phases of matter include the three common physical states, solid, liquid, and gas (or vapor), introduced in Section A. Many substances have more than one solid phase, with different arrangements of their atoms or molecules. For instance, carbon has several solid phases one is the hard, brilliantly transparent diamond we value and treasure and another is the soft, slippery, black graphite we use in common pencil lead. A condensed phase means simply a solid or liquid phase. The temperature at which a gas condenses to a liquid or a solid depends on the strength of the attractive forces between its molecules. 

The processes that govern the formation of ash particles are complex and only partially understood (Figure 7.12). The mineral matter in pulverized coal is distributed in various forms some is essentially carbon-free and is designated as extraneous some occurs as mineral inclusions, typically 2-5 pm in size, dispersed in the coal matrix and some is atomically dispersed in the coal either as cations on carboxylic acid side chains or in porphyrin-type stmctures. The behavior of the mineral matter during combustion depends strongly on the chemical and physical state of the mineral inclusions. 

The earlier assumption that Luna was a body which had been captured by the Earth can now be regarded as relatively unlikely. The same is true for the double planet hypothesis , according to which Luna and the Earth were formed at the same time from condensing primordial matter (Taylor, 1994). There are, however, still disagreements on the point in time at which the collision occurred and on the masses and the physical states of the heavenly bodies involved (Halliday and Drake, 1999). 

A dynamic equilibrium is a situation in which two (or more) opposing processes occur at the same rate so that no net change occurs. This is the kind of equilibrium that is established between two physical states of matter, e.g., between a liquid and its vapor, in which the rate of evaporation is equal to the rate of condensation in a closed container ... 

Conditions imposed on a process (or a set of equations for that matter) may cause the unit physical states to move from a two-phase to a single-phase operation, or the reverse. As the code shifts from one module to another to represent the process properly, a severe discontinuity occurs in the objective function surface (and perhaps a constraint surface). Derivatives or their substitutes may not change smoothly, and physical property values may jump about. 

Food materials (ingredients or whole systems) can be composed of matter in one, two, or all three physical states solid (crystalline or amorphous or a combination of both), liquid, and gas. The crystalline state is an equilibrium solid state, whereas the amorphous glassy state is nonequilibrium solid state. The main transitions that occur between the physical states of materials of importance to foods are summarized by Roos and Karel (1991) and Roos (2002). The most important parameters affecting the physical state of foods, as well as their physicochemical properties and transition temperatures, are temperature, time, and water content (Slade and Levine, 1988 Roos, 1995). Pressure is not included in this list, as food materials usually exist under constant pressure conditions. 

The notion of standard enthalpy of formation of pure substances (AfH°) as well as the use of these quantities to evaluate reaction enthalpies are covered in general physical chemistry courses [1]. Nevertheless, for sake of clarity, let us review this matter by using the example under discussion. The standard enthalpies of formation of C2H5OH(l), CH3COOH(l), and H20(1) at 298.15 K are, by definition, the enthalpies of reactions 2.3,2.4, and 2.5, respectively, where all reactants and products are in their standard states at 298.15 K and the elements are in their most stable physical states at that conventional temperature—the so-called reference states at 298.15 K. 

There have been a number of improvements in techniques, and more convenient models have been formulated however, the basic approach of the pseudopotential total energy method has not changed. This general approach or standard modd is applicable to a broad spectrum of solid state problems and materials when the dec-trons are not too localized. Highly correlated electronic materials require more attention, and this is an area of active current research. However, considering the extent of the accomplishments and die range of applications (see Table 14.3) to solids, dusters, and molecules, this approach has had a major impact on condensed matter physics and stands as one of the pillars of the fidd. 

On a somewhat larger scale, there has been considerable activity in the area of nanocrystals, quantum dots, and systems in the tens of nanometers scale. Interesting questions have arisen regarding electronic properties such as the semiconductor energy band gap dependence on nanocrystal size and the nature of the electronic states in these small systems. Application [31] of the approaches described here, with the appropriate boundary conditions [32] to assure that electron confinement effects are properly addressed, have been successful. Questions regarding excitations, such as exdtons and vibrational properties, are among the many that will require considerable scrutiny. It is likely that there will be important input from quantum chemistry as well as condensed matter physics. 

On the practical side, we note that nature provides a number of extended systems like solid metals [29, 30], metal clusters [31], and semiconductors [30, 32]. These systems have much in common with the uniform electron gas, and their ground-state properties (lattice constants [29, 30, 32], bulk moduli [29, 30, 32], cohesive energies [29], surface energies [30, 31], etc.) are typically described much better by functionals (including even LSD) which have the right uniform density limit than by those that do not. There is no sharp boundary between quantum chemistry and condensed matter physics. A good density functional should describe all the continuous gradations between localized and delocalized electron densities, and all the combinations of both (such as a molecule bound to a metal surface a situation important for catalysis). 

Under normal conditions, matter can appear in three forms of aggregation solid, liquid, and gas. These forms or physical states are consequences of various interactions between the atomic or molecular species. The interactions are governed by internal chemical properties (various types of bonding) and external physical properties (temperature and pressure). Most small molecules can be transformed between these states (e.g., H2O into ice, water, and steam) by a moderate change of temperature and/or pressure. Between these physical states— or phases—there is a sharp boundary phase boundary), which makes it possible to separate the phases—for example, ice may be removed from water by filtration. The most fundamental of chemical properties is the ability to undergo such phase transformations, the use of which allows the simplest method for isolation of pure compounds from natural materials. 

A phase is defined as a state of matter that is uniform throughout in terms of its chemical composition and physical state in other words, a phase may be considered a pure substance or a mixture of pure substances wherein intensive properties do not vary with position. Accordingly, a gaseous mixture is a single phase, and a mixture of completely miscible liquids yields a single hquid phase in contrast, a mixture of several solids remains as a system with multiple solid phases. A phase rule therefore states that, if a limited number of macroscopic properties is known, it is possible to predict additional properties. 

A temperature-pressure graph showing the various states of matter is a phase diagram. Phase refers to a single homogeneous physical state. Different phases have either different compositions or different physical states. In the preceding figure, there are 3 phases with the same composition solid, liquid, and gas. 

H. Qian, Cycle kinetics, steady state thermodynamics and motors—a paradigm for living matter physics. J. Phys. (Condensed Matter) 17, S3783-S3794 (2005). 

The previous chapter dealt with chemical bonding and the forces present between the atoms in molecules. Forces between atoms within a molecule are termed intramolecular forces and are responsible for chemical bonding. The interaction of valence electrons between atoms creates intramolecular forces, and this interaction dictates the chemical behavior of substances. Forces also exist between the molecules themselves, and these are collectively referred to as intermolecular forces. Intermolecular forces are mainly responsible for the physical characteristics of substances. One of the most obvious physical characteristics related to intermolecular force is the phase or physical state of matter. Solid, liquid, and gas are the three common states of matter. In addition to these three, two other states of matter exist—plasma and Bose-Einstein condensate. 

Ong, N., Jing, T., Wang, Z., Clayhold, J. and Hagen, S., Electronic Properties of YBa2Cus07 in the Normal and Superconducting States. Proc. 1st Asia Pacific Conf. on Condensed Matter Physics, World Scientific, Singapore (1988). 

These ideas are evident in an essay of Lavoisier s from 1773, in which he identifies the three different physical states of matter solid, liquid, and gas. Here he makes the crucial distinction between the physical and chemical nature of substances, which confused the ancients and led to their minimal elemental schemes. The same bod/, says Lavoisier, can pass successively through each of these states, and in order to make this phenomenon occur it is necessary only to combine it with a greater or lesser quantity of the matter of fire. ... 

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