Specific heat capacity INDEX

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. 

Where i ) is porosity, C is mass-specific heat capacity and p is density, and the index tof applies to total rock, mtx to solid rock matrix and por to pore filling fluid. 

Chemical name (lUPAC) Surface tension Y(T)=A-BT Surface tension (293.15K) Thermal conductivity (293.15K) Specific heat capacity Latent enthalpy vaporization Refractive index (589nm) UV cut- off Relative electrical permittivity (293.15K) Dipole moment Henry s law constant Vapor pressure (293.15K)... 

Thermophysical Properties of Matter (14 volumes), by Touloukian, Y.S., Kirby, R.K., Taylor, R.E. Lee, T.Y.R. (eds.)(1970-1977). New York, IFI/Plenum Press. Thermal conductivity (vol. 1-3), Specific heat capacity (4-6), Thermal radiative properties, and thermal diffusivity (10), Absolute and Dynamic Viscosity (11), Coefficients of Thermal Expansion (12-13) and index (14). 

Above a critical value, some properties (density, specific heat capacity, refractive index) are independent on molar masses. 

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. 

At temperatures below 1 K, the ratio of the constant pressure heat capacity Cp of the glass relative to the Debye heat capacity CDebye of a solid increases [124], Consequently, we introduce a quantity R2 defined as the ratio of Cp(glass) to that of the Debye heat capacity CDebye(solid) [124], Specifically, if R2 is normalized as R2 = (Cp/CDebye) lmn ] / [(Cp/coebye)rnax], then a correlation is observed between this quantity and the fragility index [124],... 

The aforementioned macroscopic physical constants of solvents have usually been determined experimentally. However, various attempts have been made to calculate bulk properties of Hquids from pure theory. By means of quantum chemical methods, it is possible to calculate some thermodynamic properties e.g. molar heat capacities and viscosities) of simple molecular Hquids without specific solvent/solvent interactions [207]. A quantitative structure-property relationship treatment of normal boiling points, using the so-called CODESS A technique i.e. comprehensive descriptors for structural and statistical analysis), leads to a four-parameter equation with physically significant molecular descriptors, allowing rather accurate predictions of the normal boiling points of structurally diverse organic liquids [208]. Based solely on the molecular structure of solvent molecules, a non-empirical solvent polarity index, called the first-order valence molecular connectivity index, has been proposed [137]. These purely calculated solvent polarity parameters correlate fairly well with some corresponding physical properties of the solvents [137]. 

The other group of properties are the intensive properties these are characteristic of the substance (or substances) present, and are independent of its (or their) amount. Temperature and pressure are intensive properties, and so also are refractive index, viscosity, density, surface tension, etc. It is because pressure and temperature are intensive properties, independent of the quantity of matter in the system, that they are frequently used as variables to describe the thermodynamic state of the system. It is of interest to note that an extensive property may become an intensive property by specifying unit amount of the substance concerned. Thus, mass and volume are extensive, but density and specific volume, that is, the mass per unit volume and volume per unit mass, respectively, are intensive properties of the substance or system. Similarly, heat capacity is an extensive property, but specific heat is intensive. 

Because the specific volume of polymers increases at Tg in order to accommodate the increased segmental chain motion, Tg values may be estimated from plots of the change in specific volume with temperature. Other properties such as stiffness (modulus), refractive index, dielectric properties, gas permeability. X-ray adsorption, and heat capacity all change at Tg. Thus, Tg may be estimated by noting the change in any of these values such as the increase in gas permeability. 

Melting involves a change from the crystalline solid state into the liquid form. For low-molecular-weight (simple) materials, melting represents a true first-order thermodynamic transition characterized by discontinuities in the primary thermodynamic variables of the system such as heat capacity, specific volume (density), refractive index, and transparency. Melting occurs when the change in free energy of... 

The transition from a glass to a rubberlike state is accompanied by marked changes in the specific volume, the modulus, the heat capacity, the refractive index, and other physical properties of the polymer. The glass transition is not a first-order transition, in the thermodynamic sense, as no discontinuities are observed when the entropy or volume of the polymer is measured as a function of temperature (Figure 12.2). If the first derivative of the property-temperature curve is measured, a change in the vicinity of is found for this reason, it is sometimes called a second-order transition (Figure 12.2). Thus, whereas the change in a physical property can be used to locate Tg, the transition bears many of the characteristics of a relaxation process, and the precise value of can depend on the method used and the rate of the measurement. 

The first coefficient describes the most common case, namely how much entropy AS flows in if the temperature outside and (also inside as a result of entropy flowing in) is raised by AT and the pressure p and extent of the reaction are kept constant. In the case of the secmid coefficient, volume is maintained instead of pressure (this only works well if there is a gas in the system). In the case of J = 0, the third coefficient characterizes the increase of entropy during equilibrium, for example when heating nitrogen dioxide (NO2) (see also Experiment 9.3) or acetic acid vapor (CH3COOH) (both are gases where a portion of the molecules are dimers). Multiplied by T, the coefficients represent heat capacities (the isobaric Cp at constant pressure, the isochoric Cy at constant volume, etc.). It is customary to relate the coefficients to the size of the system, possibly the mass or the amount of substance. The corresponding values are then presented in tables. In the case above, they would be tabulated as specific (mass related) or molar (related to amount of substance) heat capacities. The qualifier isobaric and the index p will... 

There are various methods of the glass transition temperature evaluation based on temperature dependence of polymer physical properties in the interval of glass transition 1) specific volume of polymer at slow cooling (dilatometric method) 2) heat capacity (calorimetric method),3) refraction index (refractometric method) 4) mechanical properties 5) electrical properties (temperature dependence of electric conductivity) or maximum of dielectric loss 6) NMR ° 7) electronic paramagnetic resonance, etc. 

Effects of molar mass on mrmerous physical properties of macromolecules -let Its call them O - such as heat capacity, specific volume, thermal expansion coefficient, refractive index, and so om can be expressed with Equation (1). 

The chemical and therefore structural nature of the polymer determines Tg. For most commercial polymers, values lie in the range — 100 °C to 250 °C as illustrated in Table 1.1. The value can be >250°C (e.g. in thermosets) but decomposition often occurs before it is reached. Tg can be determined by any technique which shows a change in a particular property of the polymer with temperature, e.g. density, modulus, heat capacity, refractive index, dielectric loss, X- and j8-ray adsorption, gas permeability, proton and NMR. The value of Tg can be obtained from plots of the magnitude of this property against temperature and is indicated by a break in linearity. Figure 1.4 shows modulus (i.e. strength) v. temperature and Figure 1.5 specific volume v. temperature for a typical polymer. 

The index of comparison is the heat absorption capacity, in BTU per second, for each pound of engine thrust, which is one way of lumping the specific heat, allowable temperature rise, and the proportionate amount of propellant flow at maximum specific impulse, It can be seen that hydrogen is attractive as a coolant,... 

It is well known that corrosion processes are enhanced if there are high levels of impurities in the water. Therefore, to keep the level of impurities low, an ion exchange purification system has been employed since startup in the MIR reactor coohng pool. This system includes a heat exchanger, a pump, two filters with a total capacity of 800 L, a flowmeter, shut-off valves and other fittings. The filters are filled with Russian made nuclear grade ion exchange resins KU-2-8 (cationic) and AV-17-8 (anionic) in the ratio of 2 1. This system provides reduction of the specific p activity by more than a factor of 10. When this index drops to a factor of 2, the resin is replaced otherwise, as a rule, it is replaced once a year. 

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