Specific heats of solids and liquids

We shall show in the next paragraph that the vapour pressure constants play an important part in the calculation of chemical equilibria in gases. The first problem which Nernst had to solve after the discovery of his theorem was therefore the calculation of at least the approximate value of C for as many simple substances as possible. For this purpose he made use of the theorem of corresponding states, and assumed further that the specific heat of solid and liquid bodies diminishes to a small but finite value (viz. nx 1 5, where n is the number of atoms in the molecule) as the temperature is lowered. On the evidence of the measurements published up to that time he also assumed that the molecular specific heat of gases and vapours is a linear function of the temperature which approaches the value 3-5-l-7ixl-5 at very low temperatures. In this way he arrived at the vapour pressure formula... 

DETERMINATION OF THE TRUE SPECIFIC HEAT OF SOLID AND LIQUID SUBSTANCES BY THE MICROCALORIMETER OF E. 

Selected Physical Property Data (molecular weights, specific gravities of solids and liquids, melting and boiling points, heats of fusion and vaporization, critical temperature and pressure, standard heats of formation and combustion)... 

Regnault s later research was almost exclusively in physics the specific heats of solids and gases, densities and compressibilities of gases, properties of steam, etc., and his results in this field are very accurate. He became professor of physics in the College de France and director of the porcelain factory at Sevres (1854). In the war of 1870 his son was killed in battle and his laboratory at Sevres was deliberately wrecked and his papers destroyed by the Prussian army. His chemical publications are on Dutch liquid, etc., the aldehydene theory (see p. 355), the identity of equisitic and maleic acids, the action of steam on heated metals and sulphides, sulphonaphthalic acid, and the action of sulphur trioxide on organic substances,methyl sulphate, mineral combustibles, alkaloids, diallage, potassium and lithium micas, the action of chlorine on Dutch liquid, sulphuryl chloride and sulphamide, chlorides of carbon, determination of carbon in cast iron and steel, action of chlorine on ethers, sulphuryl chloride, report on the Marsh test, respiration (with... 

This remarkable result has been verified by experimental measurements of specific heats at very low temperatures, viz., in liquid air and liquid hydrogen (cf. references in Chap. I.). It was formerly believed that the specific heats of solids approached small positive limiting values at the absolute zero, but the form of the curve at very low temperatures alters appreciably, and it may be inferred that the specific heat is vanishingly small at... 

A steam calorimeter was perfected by J. Joly (1886) and used for the accurate determination of specific heats of solids, liquids, and gases. In principle this apparatus consists of a balance, with the specimen hung from one pan and surrounded by an enclosure that can be flooded with steam. The mass of moisture condensing on the specimen, multiplied by the heat of vaporization of water, gives the quantity of heat imparted to the specimen. 

Yet another cause for deviation from Eotvos s law may be found in Bom and Courant s theory1 of the motions of the molecules of liquids, which follows the lines of Debye s theory of the specific heat of solids. Assuming three degrees of freedom for the motions of the molecules, they obtained good agreement with experiment for several liquids for which the constant is about 2-1. If the number of degrees of freedom is n, the constant is altered on their theory in the ratio (n/3). ... 

As with gases, data for the heat capacities of solids and liquids come from experiment. The temperature dependence of CP for solids and liquids can also be expressed by equations of the form of Eq. (4.4). Data for a few solids are given in Table 4.2, and for a few liquids, in Table 4.3. Data for specific heats (CP on a unit-mass basis) of many solids and liquids are given by Perry and Green.I... 

Of course, as stated earlier, matter can change form. Cool liquid water and it becomes solid ice. Heat it and it becomes a gas. None of these changes of state involve chemical reactions. Water, ice, and steam are just different states of the same substance, H20. Now, let us return to the question that opened this chapter and make it more specific. What holds solids and liquids together Why do the molecules not fly apart as they do in gases ... 

The specific heats of incompressible substances depend on temperature only. Therefore, the change hi the internal energy of solids and liquids can be expressed as... 

In the solid state, the specific heat of oils and fats shows little change as molecular weight varies. An increase in specific heat can be observed with increased unsaturation. In the liquid state, specific heat increases shghtly with molecular weight but decreases shghtly with less unsaturation. In general, there is little variation among natural oUs and fats (21). 

The specific heat at constant volume of solids and liquids cannot be measured directly. With the aid of thermodynamics, however, it is possible to deduce an equation connecting the specific heat at constant volume with the coefficient of expanT sioii, the compressibihty and the specific heat at constant pressure c, (see Chapter V.). 

Argon.—The heat of evaporation at the boiling-point, the heat of fusion, and the specific heat of solid argon down to T = 17 8 are given in a paper recently published by Eucken (105) the vapour pressures of solid and liquid argon have been determined by Travers, and recently, in greater detail, by Crommelin. ... 

Cps, Cpi, Cp = specific heats of solid, liquid, and vapor, respectively... 

The densities of solids and liquids are commonly expressed in either grams per cubic centimeter (g/cm ) or grams per milliliter (g/mL). The densities of some common substances are listed in TABLE 1.6. It is no coincidence that the density of water is 1.00 g/mL the gram was originally defined as the mass of 1 mL of water at a specific temperature. Because most substances change volume when they are heated or cooled, densities are temperature dependent, and so temperature should be specified when reporting densities. If no temperature is reported, we assume 25 °C, close to normal room temperature. 

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