Solids characteristic properties

Spectroscopy, or the study of the interaction of light with matter, has become one of the major tools of the natural and physical sciences during this century. As the wavelength of the radiation is varied across the electromagnetic spectrum, characteristic properties of atoms, molecules, liquids and solids are probed. In the... 

Hydrazinoselenazoles are solids, often in the form of crystals. They possess the characteristic properties common to hydrazines, especially as... 

The commonest form of phosphorus, and the one which is usually formed by condensation from the gaseous or liquid states, is the waxy, cubic, white form o -P4 (d 1.8232 gcm at 20°C). This, paradoxically, is also the most volatile and reactive solid form and thermodynamically the least stable. It is the slow phosphorescent oxidation of the vapour above these crystals that gives white phosphorus its most characteristic property. Indeed, the emission of yellow-green light from the oxidation of P4 is one of the earliest recorded examples of chemiluminescence, though the details of the reaction... 

Only a handful of substances are gases under normal conditions of temperature and pressure. Of the hundred or so elements, most are normally solids two or three are liquids. As for compound substances, more than a million have been prepared by chemists, yet, more than 99% of these are liquids or solids, each with distinctive and characteristic properties. It is no surprise, then, that there is great variety among all of these substances. Rather, it is remarkable that they can be classified into a small number of types and that the wealth of information represented by the diversity of all of these compounds... 

The distances between atoms in a molecule are characteristic properties of the molecule and can give us information if we compare the same bond in different molecules. The chief methods of determining bond distances and angles are X-ray diffraction (only for solids), electron diffraction (only for gases), and spectroscopic methods, especially microwave spectroscopy. The distance between the atoms of a bond is not constant, since the molecule is always vibrating the measurements obtained are therefore average values, so that different methods give different results. However, this must be taken into account only when fine distinctions are made. 

The elements can be divided into categories metals, nonmetals, and metalloids. Examples of each appear in Figure U. Except for hydrogen, all the elements in the left and central regions of the periodic table are metals. Metals display several characteristic properties. For example, they are good conductors of heat and electricity and usually appear shiny. Metals are malleable, meaning that they can be hammered into thin sheets, and ductile, meaning that they can be drawn into wires. Except for mercury, which is a liquid, all metals are solids at room temperature. 

Rheological studies explore the flow of a material as an external force acts upon it. This flow depends not only on the magnitude and directionality of the external force, but also on the molecular composition and structure of the material that experiences the force. In this chapter, we will focus on the flow behavior of molten polymers, as it relates to their molecular structure. It is important to note that the molecular characteristics that determine a molten polymer s behavior also define the polymer s solid state behavior. Therefore, many of the concepts introduced in this chapter will reappear in Chapter 8, Solid State Properties of Polymers., ... 

We most often encounter polystyrene in one of three forms, each of which displays characteristic properties. In its pure solid state, polystyrene is a hard, brittle material. When toughened with rubber particles, it can absorb significant mechanical energy prior to failure. Lastly, in its foamed state, it is versatile, light weight thermal insulator. 

Perhaps the common characteristic of all contributions to this volume is the permanent concern about the intimate relationships between the structural and electronic properties. Indeed, the careful design of increasingly complex molecular and supramolecular architectures allows us now to anticipate many molecular and solid state properties, but the final solid state structures are always the results of many competing interactions. The resulting electronic properties of these radical assemblies, whether conductivity or magnetism, are always very sensitive to minute modifications of their solid state structures and one of the main difficulties through... 

X-ray diffraction studies are usually carried out at room temperature under ambient conditions. It is possible, however, to perform variable-temperature XPD, wherein powder patterns are obtained while the sample is heated or cooled. Such studies are invaluable for identifying thermally induced or subambient phase transitions. Variable-temperature XPD was used to study the solid state properties of lactose [20], Fawcett et al. have developed an instrument that permits simultaneous XPD and differential scanning calorimetry on the same sample [21], The instrument was used to characterize a compound that was capable of existing in two polymorphic forms, whose melting points were 146°C (form II) and 150°C (form I). Form II was heated, and x-ray powder patterns were obtained at room temperature, at 145°C (form II had just started to melt), and at 148°C (Fig. 2 one characteristic peak each of form I and form II are identified). The x-ray pattern obtained at 148°C revealed melting of form II but partial recrystallization of form I. When the sample was cooled to 110°C and reheated to 146°C, only crystalline form I was observed. Through these experiments, the authors established that melting of form II was accompanied by recrystallization of form I. 

Figure 14 Schematic representation of the microphase separation of block copolymers. The left graph shows atomic-scale details of the phase separation at intermediate temperatures, and the right graph shows a lamellar phase formed by block copolymers at low temperatures. The block copolymers have solid-like properties normal to the lamellae, because of a well-defined periodicity. In the other two directions, the system is isotropic and has fluid-like characteristics. From reference 54.

Equation 1 implies that solubility is independent of solvent type, and is only a function of the equilibrium temperature and characteristic properties of the solid phase. In real systems the effect of non-ideality in the liquid phase can significantly impact the solubility. This effect can be correlated using an activity coefficient (y) to account for the non-ideal liquid phase interactions between the dissolved solute and solvent molecules. Eq. 1. then becomes [7,8] ... 

Most tanks store liquid rather than gases or solids. Characteristics and properties such as corrosiveness, internal pressures of multicomponent solutions, tendency to scale or sublime, and formation of deposits and sludges are vital for the tank designer and the operator of the tank and are discussed herein. Excluded from the discussion are the unique properties and hazards of aerosols (qv), unstable liquids, and emulsions (qv). A good source of information for liquid properties for a wide range of compounds is available (2). 

Occasionally, some residual homopolar bonds remain in metals, for example a small per cent of the molecules Li—Li, Na—Na, etc. are found in the vapours of these metals, analogous to the hydrogen molecule, but there is no trace of them in the solid state. The most characteristic property of metals, in which the smallest potential difference produces an electric current, is their electrical conductivity. Since no transport of mass takes place in a metallic conductor, a metal must contain free electrons, from which it follows that positive ions must also be present. The picture of a metal is thei efore one in which the lattice is composed of positive ions held together by electrons which move freely in the space between. It is as though the ions were cemented together by an electronic gas. 

A gel can be viewed as a container of solvent made of a three dimensional mesh [9,10]. In a dried state, a gel is a solid material. However, a gel swells until it reaches the swelling equilibrium when a solvent is added. The solvent molecules are kept in the three dimensional mesh and the combination of the mesh and the solvent molecules creates a world having characteristic properties which will be described later. This world can be either isolated from (isochore) or linked to (isobar) its surrounding world by changing the population, i.e. the solvent molecules. 

In this and the following two chapters, we will focus on solid-aqueous solution and solid-air exchange involving natural sorbents. We will try to visualize the sets of molecular interactions involved in each of the above-mentioned sorption processes. With such pictures in our minds, we will seek to rationalize what makes various sorption mechanisms important under various circumstances. Establishing the critical compound properties and solid characteristics will enable us to understand... 

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