INDEX specific heat

In this section we discuss some important chemical properties of water which make this molecule very unique water has a high surface tension, a high specific heat index and it is the only substance found on Earth at all three states, gas, liquid and solid. There are only few molecules with similar properties like water. The amount of water in the oceans of the Earth is estimated at about 1.4 x 10 kg. Comparing this with the amount of water estimated on Venus (2 x 10 kg) we see that Venus is a dry planet, however, there is still a huge quantity of water there. 

Thermal Properties. Thermal properties include heat-deflection temperature (HDT), specific heat, continuous use temperature, thermal conductivity, coefficient of thermal expansion, and flammability ratings. Heat-deflection temperature is a measure of the minimum temperature that results in a specified deformation of a plastic beam under loads of 1.82 or 0.46 N/mm (264 or 67 psi, respectively). Eor an unreinforced plastic, this is typically ca 20°C below the glass-transition temperature, T, at which the molecular mobility is altered. Sometimes confused with HDT is the UL Thermal Index, which Underwriters Laboratories estabflshed as a safe continuous operation temperature for apparatus made of plastics (37). Typically, UL temperature indexes are significantly lower than HDTs. Specific heat and thermal conductivity relate to insulating properties. The coefficient of thermal expansion is an important component of mold shrinkage and must be considered when designing composite stmctures. 

Boiling point Specific gravity Refractive index Specific heat Heat of polymerisation... 

The transition between crystalline and amorphous polymers is characterized by the so-called glass transition temperature, Tg. This important quantity is defined as the temperature above which the polymer chains have acquired sufficient thermal energy for rotational or torsional oscillations to occur about the majority of bonds in the chain. Below 7"g, the polymer chain has a more or less fixed conformation. On heating through the temperature Tg, there is an abrupt change of the coefficient of thermal expansion (or), compressibility, specific heat, diffusion coefficient, solubility of gases, refractive index, and many other properties including the chemical reactivity. 

Temperature, Heat capacity. Pressure, Dielectric constant. Density, Boiling point. Viscosity, Concentration, Refractive index. Enthalpy, Entropy, Gibbs free energy. Molar enthalpy. Chemical potential. Molality, Volume, Mass, Specific heat. No. of moles. Free energy per mole. 

Both kinetic and thermodynamic approaches have been used to measure and explain the abrupt change in properties as a polymer changes from a glassy to a leathery state. These involve the coefficient of expansion, the compressibility, the index of refraction, and the specific heat values. In the thermodynamic approach used by Gibbs and DiMarzio, the process is considered to be related to conformational entropy changes with temperature and is related to a second-order transition. There is also an abrupt change from the solid crystalline to the liquid state at the first-order transition or melting point Tm. 

Tg can be determined by studying the temperature dependence of a number of physical properties such as specific volume, refractive index, specific heat, etc. First-order transitions, such as the melting of crystals, give rise to an abrupt change or discontinuity in these properties. However, when a polymeric material undergoes a second-order transition, it is not the primary property (the volume), but its first derivative with respect to temperature, (the coefficient of expansion), which becomes discontinuous. This difference between a first and second-order transition is illustrated in Figure 10. 

Octahedral sulphur is a brittle solid of hardness approximately 2-3 the colour is lemon-yellow at the ordinary temperature but darkens somewhat on warming, whilst at —50° C. it almost disappears, leaving the solid practically colourless 6 the refractive index for sodium light is 2-08,7 the mean specific heat is 0-170,8 and the coefficient of cubic... 

The anhydrous salt yields yellowish-white crystals of density2 7-3 at 15° C. and melting point 3 1042° C. The specific heat is 4 0-0728 and the molar heat 05-4. The index of refraction is 2 2-14. It is insoluble in water, aqueous ammonia and in solutions of ammonium salts,5 and only slightly soluble in aqueous alkali or brine.6 It is decomposed when heated with hydrogen chloride,7 forming lead and arsenic chlorides, and in hot nitric acid it dissolves to form arsenic acid and lead nitrate, the latter being precipitated if the acid is sufficiently concentrated.8... 

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

During the increase of the heat production rate, the succession of populations was very rapid, the strains isolated at different incubation times never clustered at a similarly high level. The values of index of utilization of small molecules (amino acids, carbohydrates, alcohols) showed a net tendency to decrease and reach a minimum indicating physiological specialization, paralleled by the maximum value of the specific heat dissipation rate q. ... 

For a number of properties in this group, including density, specific heat capacity, refractive index, etc., X attains its limiting value Xx already at molar mass below the real macromolecular range. For these properties the configuration of the structural unit alone is the preponderant factor determining the property. 

The degree of flammability of a polymeric material may be predicted from its chemical structure. One of the most valuable criteria in fire research, the so-called limiting oxygen index (LOI) may be estimated either from the specific heat of combustion or from the amount of char residue on pyrolysis. Since both quantities can be determined if the chemical structure is known, also the LOI can be estimated. An approximate assessment of the LOI value direct from the elementary composition of the polymer is also possible. 

Estimate the specific heat of combustion of polycarbonate and its limiting oxygen index by means of Eq. (26.3). 

References are appended to investigations of the properties of dilute aqueous solutions of sodium chloride, including the molecular depression of the freezing-point8 and elevation of the boiling-point,9 vapour-pressure,10 density,11 viscosity,12 refractive index,13 specific heat,14 diffu-... 

References are appended to investigations of the solubility of sodium bromide in organic solvents,2 and to others dealing with such properties of its aqueous solutions as specific heat,3 density,4 refractive index,8 vapour-pressure,6 molecular depression of the freezing-point7 and elevation of the boiling-point,8 electrical constants,9 and the influence of sulphur dioxide on the solubility of the bromide.10... 

Other properties of aqueous solutions investigated are density,3 refractive index,4 molecular elevation of the boiling-point,6 vapour-pressure,6 specific heat,7 and electric conductivity.8 References are also appended to work on the compressibility,9 the solubility in organic solvents10 and sulphurous acid,11 the molecular weight in liquid sulphur dioxide,11 the electric conductivity in acetone12 and dilute alcohol,13 the non-existence of polyiodides,14 isomorphism with potassium iodide,15 and the formation of a double salt with silver iodide.16... 

It shows a huge fhistration index of 150 with a spin freezing Tf = 3.4 K for a sample with 90% coverage of the pyrochlore slabs by Cr +. Several anomalous properties appear in the specific heat that are still not understood in detail bnt point to the possible involvement of spin singlets in the ground state... 

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