Specific heat negative

As an example of a negative heat capacity we have the specific heat of saturated steam. If unit mass of steam in the condition of saturation is raised one degree in temperature, and at the same time compressed so as to keep it just saturated at each temperature, it is found that heat is evolved, not absorbed, because the work spent in the compression exceeds the increase of intrinsic energy. 

Hence at this temperature, we arrive at the somewhat surprising result that the specific heat of saturated steam is negative. 

The temperature change is iy—Tf = io.o°C - 25.o°C = -i5.o°C. To find the heat removed, multiply this negative temperature change by the water"s specific heat and mass ... 

In this way the study of spectra gives even more detailed information than the consideration of specific heats. It is found that infra-red rotation and vibration spectra are only given by those molecules, such as HC1, which are composed of a negative and a positive portion. Strictly homo-polar molecules do not absorb in the infra-red, although the theory of specific heats, and the analysis of the visible spectrum, leave no doubt about the existence of... 

For a random solid solution, o = 0. Perfect order corresponds to cr = 1. A negative value of a indicates clustering. The tail of excess specific heat above the Curie temperature in Figure 8.4 reflects the loss of remaining short-range order. 

DSC data are recorded on a thermogram delineated by ACp v vs AT or At. Inasmuch as it is the energy consumption that is recorded, the thermogram shows + AE proportional to the change in property. DSC is therefore a method of directly quantifying ACp v, AH, AS [Eq. (3.16)], and ACp v/g (the specific heat). Exothermic reactions are characterized by positive peaks on the thermogram, and endothermic reactions are characterized by negative peaks. 

The first theoretician of the vitrification process was Simon (1930), who pointed out that it can be interpreted as a "freezing-in" process. Simon measured specific heats and entropies of glycerol in the liquid, crystalline and glassy state below Tg the entropy of the supercooled liquid could, as a matter of fact, only be estimated. Linear extrapolation would lead to a negative entropy at zero temperature (paradox of Kauzmann, 1948) which would be in contradiction with Nernst s theorem. So one has to assume a sharp change in the slope of the entropy, which suggested a second order transition as defined by Ehrenfest. 

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