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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

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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Entropy within the Cell01:22

Entropy within the Cell

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A living cell's primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers in the universe are completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, heat energy is defined as the energy transferred from one system to another that...
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Entropy and the Second Law of Thermodynamics01:20

Entropy and the Second Law of Thermodynamics

4.0K
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...
4.0K
Entropy Change in Reversible Processes01:10

Entropy Change in Reversible Processes

3.0K
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.
3.0K
Third Law of Thermodynamics02:38

Third Law of Thermodynamics

21.0K
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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Rare Event Detection Using Error-corrected DNA and RNA Sequencing
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Where Was Past Low-Entropy?

Carlo Rovelli1

  • 1Centre de Physique Théorique (CPT), Aix-Marseille Université, Université de Toulon, CNRS, F-13288 Marseille, France.

Entropy (Basel, Switzerland)
|December 3, 2020
PubMed
Summary
This summary is machine-generated.

The early universe

Keywords:
arrow of timeentropy in cosmologypast hypothesis

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Area of Science:

  • Cosmology and fundamental physics.
  • Thermodynamics and statistical mechanics.

Background:

  • The origin of the universe's low-entropy state is a key question in cosmology.
  • Previous explanations often involve complex cosmological models or assumptions.

Purpose of the Study:

  • To identify the primary source of low-entropy in the early universe.
  • To explore the implications of this source for cosmological models.
  • To discuss the interpretation of the universe's initial low-entropy state.

Main Methods:

  • Theoretical analysis of early universe thermodynamics.
  • Examination of the role of the scale factor as a degree of freedom.
  • Discussion of equilibrium and non-equilibrium statistical mechanics.

Main Results:

  • The dominant source of early universe low-entropy is identified as the scale factor being out of equilibrium.
  • This contrasts with popular explanations attributing low-entropy to other factors.
  • The 'improbability' of this initial state is discussed through theoretical interpretations.

Conclusions:

  • The scale factor's non-equilibrium state is the principal driver of the early universe's low entropy.
  • This finding offers a simpler, more fundamental explanation for cosmic initial conditions.
  • Further research can explore the implications for fundamental physics and the arrow of time.