Energy Transfer and Thermodynamics Essay Example | Topics and Well Written Essays - 2500 words

Energy Transfer and Thermodynamics - Essay Example rmodynamics  is an expression of the universal law of increasing  entropy, stating that the entropy of an  isolated system  which is not in  equilibrium  will tend to increase over time, approaching a maximum value at equilibrium. The second law expressed in terms of an entropy change is given as: ΔS ≠¥ 0 (universe). The Third Law of Thermodynamics states that: Every substance has a finite positive entropy, but at the absolute zero of temperature the entropy may become zero, and does so become in the case of a perfect crystalline substance. In a perfectly ordered crystal, every atom is in its proper place in the crystal lattice. At T= 0 Kelvin, all molecules are in their lowest energy state. Such a configuration would have perfect order; and since entropy is a measure of the disorder in a system, perfect order would result in an entropy of zero. Thus, the Third Law gives us an absolute reference point and enables us to assign values to S and not just to ΔS as we have been restricted to do with U, H, A, and G. The molecules of water that make up an ice crystal are held rigidly in place in the crystal lattice. When ice melts, the water molecules are free to move about with respect to one another and to tumble around. Thus, in liquid water the individual water molecules are more randomly distributed than in the solid. The well-ordered solid structure is replaced by the much more disordered liquid structure. 3) Calculate ΔS for the following reaction, using the information in a Table of Thermochemical Data, and state whether entropy increases (becomes more random) or decreases (becomes less random)? Based on entropy changes, do you predict a spontaneous reaction? A reaction that leads to a decrease in the number of gaseous molecules generally leads to a DECREASE in entropy. The entropy change of this reaction is NEGATIVE because the three molecules of gas react to form one molecule of gas. In a Carnot cycle a system, as cylinder of gas, is set  out of