Why is entropy a state function?

Its change depends only on the initial and final states, not on the path between them.

How is entropy change calculated for a reversible process with changing temperature?

$\Delta S = \int_A^B \frac{dQ_{\text{rev}}}{T}$, with the changing temperature kept inside the integral.

Can a system lose entropy during an irreversible process?

Yes. Its surroundings can gain more entropy than the system loses, making the total entropy change positive.

What is the entropy change for a monatomic ideal gas during an isochoric temperature change?

$\Delta S = \frac{3}{2}nR\ln\left(\frac{T_2}{T_1}\right)$, with temperatures in kelvin.

What does a regenerator do in an ideal Stirling engine?

It stores heat from the gas during one part of the cycle and returns it during another.

ThermodynamicsLesson 6 of 7 in the course The Second Law of Thermodynamics

Entropy, the Second Law, and Stirling-Cycle Applications

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson introduces entropy and explains how to calculate its change during reversible heat transfer. Entropy is central to the second law of thermodynamics and, like internal energy, is a property determined by a system’s state.

Entropy, represented by $S$ , is a thermodynamic state function. For a reversible process at a constant absolute temperature $T$ , the entropy change is

All flashcards

Why is entropy a state function?: Its change depends only on the initial and final states, not on the path between them.
How is entropy change calculated for a reversible process with changing temperature?: $\Delta S = \int_A^B \frac{dQ_{\text{rev}}}{T}$ , with the changing temperature kept inside the integral.
Can a system lose entropy during an irreversible process?: Yes. Its surroundings can gain more entropy than the system loses, making the total entropy change positive.
What is the entropy change for a monatomic ideal gas during an isochoric temperature change?: $\Delta S = \frac{3}{2}nR\ln\left(\frac{T_2}{T_1}\right)$ , with temperatures in kelvin.
What does a regenerator do in an ideal Stirling engine?: It stores heat from the gas during one part of the cycle and returns it during another.

Quiz questions

For an irreversible process, what happens to the total entropy of the system and its surroundings?Answer: It increases.
What is the net work during an isochoric step?Answer: Zero, because the volume does not change.
Which sequence describes the four steps of an ideal Stirling cycle?Answer: Isothermal expansion, isochoric cooling, isothermal compression, isochoric heating.
How is the efficiency of a heat engine defined?Answer: Net work output divided by heat absorbed from the hot reservoir.
How can a perfect regenerator affect the ideal Stirling engine's efficiency?Answer: It can allow the engine to reach the Carnot efficiency between the same reservoirs.

Based on University Physics Volume 2 by Samuel J. Ling, William Moebs, Jeff Sanny (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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