List some examples of state functions. Check all that apply:
- internal energy
- work
- volume
- pressure
I know that a state function is independent of the path taken, so I think work and volume are state functions. Am I correct?
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6$\begingroup$ No. Work is not a state function. To be more precise about the definition of a state function, the change in a state function from thermodynamic equilibrium state A to thermodynamic equilibrium state B is unique and independent of any and all process paths that take the system from state A to state B. In the case of work, the amount of work required to get from state A to state B depends on the process path, and varies for example with the amount of heat added or removed during the process or if the process is reversible or not. $\endgroup$– Chet MillerCommented Oct 23, 2015 at 15:03
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1$\begingroup$ Work and heat are major examples that are not state functions. Major examples of state functions are internal energy, entropy, enthalpy, free energy, and Heimholtz energy. $\endgroup$– CapricaCommented Aug 21, 2016 at 10:01
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2 Answers
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Let's say you go to Stonehenge.
You see a big rock there.
You can observe the state of the rock.
But how much work was done to bring the rock there?
How far away did the rock come from? Was it a downhill or uphill journey? Was the stone dragged, moved with wheels, or pulled on a sled over snow?
So you can know the exact state of the rock, but not how much work was done to bring it to that state.
Therefore work is not a state function. The others given in the exercise, i.e. internal energy, pressure, volume, temperature are all state functions.
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Examples of state function include (1) internal energy, (3) volume, and (4) pressure.
This is because a state function is a value in which is dependent on the state of that particular system. The value of a change in a state function is always the difference between the final and initial values. It is important to note that the value depends only on the state of the system, not on how the system arrived at that state.
