Equations of state = superfluous state variables?

In summary, the conversation discusses the purpose of equations of state and the possibility of simplifying the number of state variables. The question is raised about how to work with a system if certain state variables cannot be measured. The concept of constant temperature processes and phase changes is also mentioned.
  • #1
AcidRainLiTE
90
2
I don't get the point of equations of state since they seem to me to just indicate that we defined too many state variables. Why not just trim down our set of state variables and do away with the equations of state (i.e. for an ideal gas, just notice that P and V are sufficient to describe the system)?
 
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  • #2
But what if you can't measure P and V? What if you know the volume of a vessel and you have a thermometer, but no manometer. How are you to work with that if you don't have an equation of state?

And what about processes that take place at constant T, like phase changes? Do you really want to describe the liquid -> gas transition only in terms of P and V?
 

FAQ: Equations of state = superfluous state variables?

1. What is an equation of state?

An equation of state is a mathematical relationship that describes the physical properties of a substance, such as pressure, temperature, and volume. It is used to determine the state of a substance at a given set of conditions.

2. What are superfluous state variables?

Superfluous state variables are additional parameters that are not necessary to fully describe the state of a substance. They do not contribute to the equation of state and can be eliminated without affecting the accuracy of the equation.

3. Why are equations of state important in science?

Equations of state are important in science because they allow us to predict and understand the behavior of substances under different conditions. They are used in various fields of study, such as thermodynamics, fluid mechanics, and material science.

4. Can equations of state be derived from first principles?

Yes, equations of state can be derived from first principles using fundamental physical laws and principles, such as the ideal gas law, the van der Waals equation, and the Maxwell-Boltzmann distribution. However, in some cases, empirical equations are used due to the complexity of the underlying physics.

5. How do superfluous state variables affect the accuracy of equations of state?

Superfluous state variables do not affect the accuracy of equations of state because they are not used in the calculation. They can be eliminated without changing the predicted behavior of the substance. However, their inclusion may lead to unnecessarily complex equations that are difficult to solve or interpret.

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