How are the Kelvin and Celsius temperature scales related? The absolute entropy of any substance can be calculated using equation 1 in the following way. Imagine cooling the substance to absolute zero and forming a perfect crystal no holes, all the atoms in their exact place in the crystal lattice. Since there is no disorder in this state, the entropy can be defined as zero. Search for:. Measuring Entropy and Entropy Changes Learning Objectives To gain an understanding of methods of measuring entropy and entropy change.
Key Takeaways At absolute zero 0 K , the entropy of a pure, perfect crystal is zero. The entropy of a substance can be obtained by measuring the heat required to raise the temperature a given amount, using a reversible process. The standard molar entropy, S o , is the entropy of 1 mole of a substance in its standard state, at 1 atm of pressure. Licenses and Attributions. Here a constant is applied that makes it so that the entropy at absolute zero is defined to be zero. Actively scan device characteristics for identification.
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Develop and improve products. List of Partners vendors. One would think that the act of opening and shutting the door would tip back the balance, but actually, most contra-demon arguments have been somewhat more subtle, focusing instead on the act of acquiring and storing the information relating to energy states of the individual gas molecules.
Acquiring information by the demon implies an expenditure of energy. Due to the interaction between the gas and the demon, it is the total entropy that is relevant. Entropy increase of the demon is sure to be greater than entropy lowering of the gas.
The discourse between pro- and anti-demon theorists reached a new level in the s when it was proposed that an act of measurement may not necessarily increase entropy in a closed system provided that the measuring process could be thermodynamically reversible. The thinking is that once the molecule is moved, the information concerning its pre-move status is no longer required. It is hard to believe, but in University of Stuttgart physicist Eric Lutz and others devised a real-world experiment that measured the minimum energy dissipated by deleting information.
They confirmed that to approach this limit, the system must come close to zero processing speed. They assert that it is questionable to assume the erasing of information requires significant energy consumption.
In any event, it is circular reasoning to defend the second law of thermodynamics solely on that basis. This argument addresses the consistency between the second law of thermodynamics and the demon strategem for challenging it, but a more recent interpretation reopens the question from a new perspective.
It is based on non-equilibrium thermodynamics for small fluctuating systems in which measurement is seen as a process where mutual information between the system and demon increases. Through a feedback loop, that correlation decreases, and once again the second law of thermodynamics is challenged. It has been theorized that if mirror matter exists, it may be feasible to vent entropy-encumbered particles into the mirror world and actually construct a heat engine that does not require fuel.
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