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Related Concept Videos

Entropy and the Second Law of Thermodynamics01:20

Entropy and the Second Law of Thermodynamics

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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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Entropy01:18

Entropy

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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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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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Entropy Change in Reversible Processes01:10

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In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
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The Second Law of Thermodynamics01:14

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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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Second Law of Thermodynamics02:49

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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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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
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Entropy Derived from Causality.

Roland Riek1

  • 1Laboratory of Physical Chemistry, ETH Zuerich, Wolfgang-Pauli-Strasse 10, HCI F 225, CH-8093 Zurich, Switzerland.

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

This study connects causality and entropy to define time as a measure of cause-effect relationships. It demonstrates that time must be discrete, not continuous, challenging fundamental physics theories.

Keywords:
causalitydiscrete timeentropy

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Area of Science:

  • Thermodynamics
  • Causality
  • Foundations of Physics

Background:

  • The second law of thermodynamics establishes an arrow of time through entropy increase.
  • Causality, the link between cause and effect, inherently implies a direction of time.
  • Standard physical theories lack an intrinsic temporal directionality.

Purpose of the Study:

  • To establish a connection between causality and entropy.
  • To propose time as the metric of causality.
  • To investigate the fundamental nature of time in physics.

Main Methods:

  • Defining time as the metric of causality, measured by clocks.
  • Analyzing the requirements of mechanical causality (antecedence).
  • Examining the mathematical distinction between cause and effect using time intervals.

Main Results:

  • Time emerges solely through cause-effect relationships.
  • Time is demonstrated to be discrete, not continuous.
  • An infinitely small time step (dt) is insufficient to distinguish cause and effect.

Conclusions:

  • Causality necessitates a discrete time interval greater than zero.
  • A discrete nature of time is a consequence of the relationship between causality and entropy.
  • This framework challenges the continuous time assumption in classical and relativistic physics.