College Physics I – Introduction

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Entropy

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College Physics I – Introduction

Definition

Entropy is a measure of the disorder or randomness in a system. It also quantifies the unavailability of a system's energy to do work.

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5 Must Know Facts For Your Next Test

  1. Entropy always increases in an isolated system according to the Second Law of Thermodynamics.
  2. The change in entropy ($\Delta S$) can be calculated using $\Delta S = \frac{Q_{rev}}{T}$, where $Q_{rev}$ is the reversible heat transfer and $T$ is the temperature.
  3. In any real process, total entropy (system + surroundings) always increases.
  4. Entropy can be seen as a measure of energy dispersal within a system.
  5. At absolute zero temperature (0 K), a perfect crystal has zero entropy according to the Third Law of Thermodynamics.

Review Questions

  • What does an increase in entropy indicate about the disorder in a system?
  • How is the change in entropy ($\Delta S$) calculated for a reversible process?
  • Explain why total entropy always increases in real processes.

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