How can we measure entropy using experiments.

In summary, it is possible to determine the entropy change of a system by considering the equation ∫(dQ/T), using measurable physical quantities such as temperature and specific heat. However, there may be a more economical way to calculate this change. The Claussius entropy and Boltzmann definition may not be suitable for experiments. Additionally, when determining the entropy of a system such as a tank of CO2, it may be necessary to construct possible quasi-static processes from perfect crystals to the present compound. This can be found in the book "Thermodynamics for the unsatisfied" by Thess, specifically on page 85 in the section "determination of the entropy of simple systems".
  • #1
raopeng
86
0
A friend asks me this. If considering the equation: [itex]∫\frac{dQ}{T}[/itex], then it is technically feasible to work out some forms of expressions with measurable physical quantities like temperature and specific heat, therefore it is possible to work out a precise value for entropy change. But is there a more economic way? I think Claussius entropy is too phenomenological to be directly observed in experiments, and the Boltzmann definition is not suitable for experiments.

While above is about the entropy change, my friend also asks how to determine the entropy of a system, for example a tank of CO2. If a perfect crystal has zero entropy, does that meran in order to calculate the entropy we have to construct possible quasi-static processes from perfect crystals to the present compound and work out the entropy change, which seems to be very uneconomic?
 
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  • #2
There is a good description in a book by Thess - search for "Thermodynamics for the unsatisfied" at amazon.com, and check "search inside this book". In the table of contents, click on page 85, "determination of the entropy of simple systems".
 
  • #3
Thank you so much, this is really helpful.
 

1. What is entropy and why is it important to measure?

Entropy is a measure of the disorder or randomness in a system. It is important to measure because it can help us understand the behavior of physical and chemical systems, and can be used to make predictions about the direction of a process.

2. How can we measure entropy using experiments?

Entropy can be measured experimentally by using techniques such as calorimetry, which measures the heat transfer in a system, or by measuring changes in pressure and volume of a gas. The change in entropy can then be calculated using thermodynamic equations.

3. What are some examples of experiments that can measure entropy?

Some examples of experiments that can measure entropy include mixing different substances together, measuring changes in temperature or pressure during a chemical reaction, and observing changes in the organization of molecules in a system.

4. Are there any limitations to measuring entropy through experiments?

Yes, there are limitations to measuring entropy through experiments. The accuracy of the measurement depends on the precision of the experimental techniques used and the assumptions made in the calculations. Additionally, some systems may be too complex or difficult to measure accurately.

5. How can measuring entropy through experiments help us in real-world applications?

Measuring entropy through experiments can help us in real-world applications by allowing us to understand and predict the behavior of physical and chemical systems. This can be useful in fields such as engineering, chemistry, and materials science, where the properties of systems are important for practical applications.

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