Heat of melting

Environmental Aspects. More than two-thirds of aluminum cans are recaptured and returned for recycling into more cans. Because of the heat of melting, the use of post-consumer recycled cans is safe for beverage contents. Not only does recycling save on mass of materials, it also saves the energy of manufacture from aluminum ore (see Recycling, nonferrous metals). 

This is of exactly the same form as eqn. (5.10) and AH is simply the "latent heat of melting" that generations of schoolchildren have measured in school physics labs." We now take some water at a temperature T < T, . We know that this will have a definite tendency to freeze, so Wf is positive. To calculate Wf we have Wf=- A A, and H = U + pV to give us... 

In principle the heat required to bring the material up to its processing temperature may be calculated in the case of amorphous polymers by multiplying the mass of the material (IP) by the specific heat s) and the difference between the required melt temperature and ambient temperature (AT). In the case of crystalline polymers it is also necessary to add the product of mass times latent heat of melting of crystalline structures (L). Thus if the density of the material is D then the enthalpy or heat required ( ) to raise volume V to its processing temperature will be given by ... 

Variations in cooling load can be provided from the latent heat of melting of ice or a frozen eutectic. Ice can be formed by allowing it... 

The difference between the energy of a substance in liquid form and its energy in solid form is usually much smaller than the difference between the energies of the liquid and gaseous forms. For example, consider the heat of melting a mole of ice,... 

The heat accompanying the phase change (2) is 1.44 kcal/mole. This is much less than the molar heat of vaporization of water, 10 kcal/mole. Table 5-II contrasts the melting points and the heats of melting per mole (the molar heat of melting, or the molar heat of fusion) of the same pure substances listed in Table 5-1. 

Once again, we find an extreme range among the properties of these substances. The molar heats of melting vary from 0.080 kcal/mole for... 

Table 5-II. the melting points and heats of melting of some pure...

We have, in this chapter, encountered a number of properties of solids. In Table 5-II, we found that melting points and heats of melting of different solids vary widely. To melt a mole of solid neon requires only 80 calories of heat, whereas a mole of solid copper requires over 3000 calories. Some solids dissolve in water to form conducting solutions (as does sodium chloride), others dissolve in water but no conductivity results (as with sugar). Some solids dissolve in ethyl alcohol but not in water (iodine, for example). Solids also range in appearance. There is little resemblance between a transparent piece of glass and a lustrous piece of aluminum foil, nor between a lump of coal and a clear crystal of sodium chloride. 

C mean specific heat including heat of melting over the range 80-Te, BTU/lb F r = throughput, lb/hr... 

Vesala, A. (1974) Thermodynamics of transfer nonelectrolytes from light and heavy water. I. Linear free energy correlations of free energy of transfer with solubility and heat of melting of nonelectrolyte. Acta Chem. Scand. 28A(8), 839-845. 

The difference Tm - Tmr is given by the Clapeyron-Clausius equation. Neglecting the variation of the latent heat of melting X (erg/g) and of the derivative dp /dT in the narrow temperature range of interest,... 

Heat of fusion This value, normally reported inkcal/mol, is also referred to as the heat of melting. For solids, the heat of fusion is required to estimate the solubility of the solute to account for crystal lattice interactions. The theoretical basis for introducing this value into the estimation of aqueous solubility of organic solids is explained by Irmann(1965) and Yalkowsky and Valvani (1979). Heat of fusion data is available in many texts including Dean (1987), Weast (1986), and CHRIS (1984). Experimentally determined data were reported by Plato and Glasgow (1969) and Hickley et al. (1990). 

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