7.33-1.png

Figure 7-20 The level of molecular disorder (entropy) of a substance increases as it melts or evaporates.

Boltzmann relation $S = k \ln W$

W the total number of possible relevant microstates of the system

Gibbs’ formulation $S = - k \sum p_{i} \log p_{i}$ p_i sum of all microstates’ uncertainties, i.e., probabilities

$k = 1.3806 \times 10^{- 23} J / K$ Boltzmann constant

A pure crystalline substance at absolute zero temperature is in perfect order, and its entropy is zero (the third law of thermodynamics).

7.34.png

Figure 7-22 Disorganized energy does not create much useful effect, no matter how large it is.

Figure 7-23 In the absence of friction, raising a weight by a rotating shaft does not create any disorder (entropy), and thus energy is not degraded during this process.

Figure 7-24 The paddle-wheel work done on a gas increases the level of disorder (entropy) of the gas, and thus energy is degraded during this process.

Figure 7-25 During a heat transfer process, the net entropy increases. (The increase in the entropy of the cold body more than offsets the decrease in the entropy of the hot body.)

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