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Related Concept Videos

Entropy02:39

Entropy

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Salt particles that have dissolved in water never spontaneously come back together in solution to reform solid particles. Moreover, a gas that has expanded in a vacuum remains dispersed and never spontaneously reassembles. The unidirectional nature of these phenomena is the result of a thermodynamic state function called entropy (S). Entropy is the measure of the extent to which the energy is dispersed throughout a system, or in other words, it is proportional to the degree of disorder of a...
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Entropy01:18

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The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
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The second law of thermodynamics can be stated quantitatively using the concept of entropy. Entropy is the measure of disorder of the system.
The relation  between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...
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In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Scientists refer to the measure of randomness or disorder within a system as entropy. High entropy means high disorder and low energy. To better understand entropy, think of a student’s bedroom. If no energy or work were put into it, the room would quickly become messy. It would exist in a very disordered state, one of high entropy. Energy must be...
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A pure, perfectly crystalline solid possessing no kinetic energy (that is, at a temperature of absolute zero, 0 K) may be described by a single microstate, as its purity, perfect crystallinity,and complete lack of motion means there is but one possible location for each identical atom or molecule comprising the crystal (W = 1). According to the Boltzmann equation, the entropy of this system is zero.
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In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
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Applications of EEG Neuroimaging Data: Event-related Potentials, Spectral Power, and Multiscale Entropy
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Entropy and Time.

Arieh Ben-Naim1

  • 1Department of Physical Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.

Entropy (Basel, Switzerland)
|December 8, 2020
PubMed
Summary
This summary is machine-generated.

Entropy is not linked to the arrow of time. This study examines entropy definitions and finds no connection, concluding entropy is timeless, despite historical scientific associations.

Keywords:
H-functionH-theoremShannon’s measure of informationarrow of timeentropysecond law of thermodynamics

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Area of Science:

  • Thermodynamics
  • Statistical Mechanics
  • Philosophy of Time

Background:

  • The Second Law of Thermodynamics, stated by Clausius, posits that the universe's entropy always increases.
  • Eddington explicitly linked the concept of entropy to the directionality of time, often termed 'time's arrow'.
  • This association has led to widespread belief in a fundamental connection between entropy and time's progression.

Purpose of the Study:

  • To review the historical association between entropy and the arrow of time.
  • To critically examine different definitions of entropy for any inherent link to temporal direction.
  • To clarify misconceptions regarding entropy's relationship with time.

Main Methods:

  • Review of historical scientific statements on entropy and time.
  • Analysis of three distinct, yet equivalent, definitions of entropy.
  • Examination of Boltzmann's H-Theorem and its interpretation.

Main Results:

  • No examined definition of entropy inherently demonstrates a relationship with the direction of time.
  • The study finds entropy to be a timeless quantity, independent of temporal direction.
  • Misinterpretations and historical context contributed to the erroneous association of entropy with time's arrow.

Conclusions:

  • Entropy is a timeless quantity and is not intrinsically linked to the arrow of time.
  • The perceived connection between entropy and time's direction stems from historical interpretations and potential misunderstandings.
  • Boltzmann's H-Theorem, while significant for thermodynamics, does not prove an intrinsic link between entropy and time's arrow.