The States of Matter II Liquids and Solids

Although we live immersed in a mixture of gases that make up Earth s atmosphere, we are more familiar with the behavior of liquids and solids because they are more visible. Every day we use water and other liquids for drinking, bathing, cleaning, and cooking, and we handle, sit upon, and wear solids. 

Molecular motion is more restricted in liquids than in gases and in solids, the atoms and molecules are packed even more tightly together. In fact, in a solid they are held in well-defined positions and are capable of little free motion relative to one another. In Chapter 6, we examine the structure of liquids and solids and discuss some of the fundamental properties of these two states of matter. 

1 The Structure and Properties of Liquids Are Governed by intermoiecuiar interactions 334 

2 Crystaiiine Soiids Can Be Ciassified in Terms of Their Structure and Intermoiecuiar Interactions 341 

3 The Properties of Crystalline Solids Are Determined Largeiy by intermoiecuiar interactions 351 

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Dufour effect Establishment of steady temperature gradient due to fixed concentration gradient. There can be two types of time-invariant states. One such is equilibrium state. In the equilibrium state, thermodynamic variables such as temperature T, pressure P and chemical potentials p, are adjusted in a way so that there is no (i) flow of matter, (ii) flow of energy and current and (iii) occurring in the system. Typical examples are vapour-liquid, liquid-Uquid, solid-liquid and chemical equilibria. However, time-invariant non-equilibrium steady states are also possible when opposite flows are balanced and gradients are maintained constant. 

Class II includes flexible macromolecules. They stay only in the states of liquid and solid, in order to reserve the integrity of chemical bonds. Evaporation of such macromolecules requires so high level of thermal energy that the chemical bonds are actually broken before reaching that level. The molecular flexibility in the liquid mainly comes from the internal rotation of the main-chain C-C bonds. This class includes structural materials of synthetic polymers such as Nylon, PVC, PET, and PC, adhesives such as PVA, epoxy resins and Glue 502, elastomers such as natural rubber, polyurethane, SBS and EPDM (mbber could be regarded as the cross-linked liquid polymers.), biomaterials such as celluloses, starch, silks and wools, and even bio-macromolecules such as DNA, RNA and proteins. The class of flexible macromolecules corresponds to the soft matter defined above. 

Further discussion of the uses of specific gases is given in the remainder of this chapter and in the gas monographs in Part II. The physical world inhabited by mankind largely consists of three states of matter - solid, liquid, and gas. Suffice it to say that the history of gas use is the history of how humans have used compressed gases for the improvement of life. 

In Section II. 1 the heat capacity is considered from the viewpoint of pheno-menolo cal thermod3mamics. In Section II.l.l the usual definitions are ven for the heat capacity Cy or Cp at constant volume V respectively constant pressure and constant quantity of matter. They are valid for thermodynamically simple systems. As far as liquids and solids are concerned (and polymers are alwaj in a condensed state) Cp is the quantity more available from the experiment and Cy that more available from the theory. In consequence, one is always constrained to convert both quantities. Such a conversion is rendered postible by Eq. (25a) if the thermal expansion coefficient a, the isothermal compressit ty x and the volume V (or the mass densitiy) of the system are known. In default of these data the formula (25b) of Nemst and lindemann is often used which, as approximation, follows from (25a). 

The chemical methods can be divided into three types, in accord with three aggregate states of the matter (i) gas phase reactions, (ii) liquid state reactions, and (iii) solid state reactions. 

Leonard Katzin I want to make two comments, one on this last point in relation to the point that Dr. Margerum made about substituents. Chromium (I II) in the hexahyd rated state is quite resistant to penetration of the coordination shell by nitrate ion. Yet if one takes the% violet chromium nitrate hexahydrate in solid state and treats it with liquid tributylphosphate, within a matter of minutes one gets chromium compound in solution by the mechanism of substituting tributylphosphate for water. So this reaction is fast. This initial solution is violet Within the space of an hour or two it is green. And we have had for some years now infrared evidence that this color change is accompanied by penetration of the nitrate ion into the coordination sphere (4). So this again is a matter of the substituent s changing the relationship of the water. 

The sample was initially in a completely liquid state at 37°C. A cooling rate between 0.5 and 4°C/min was chosen. Figure 18 presents the experimental and simulated evolution of the latent heat released by the sample for the four different cooling rates smdied. As forecasted, a mixture of phases II and III was formed. Simulated results were similar to the experimental ones. Simulated curves were interrupted before the end of the crystallization, because calculation stopped when the sample reached 14°C. As a matter of fact, below this temperature, experimental measurements could not be obtained because crystallization kinetics was too fast and crystallization started before the isothermal temperatiue was reached. The slight bump in the experimental curves at slow cooling rates, which is aiso reproduced in the simulated curves, corresponds to a stop in crystallization between 17 and 16°C, because the maximal fraction of solid that can form does not change between these two temperatures. 

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