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State Functions

A state function is a relationship between thermodynamic quantities--what it means is that if you have $\bgroup\color{blue}$ N$\egroup$ thermodynamic variables that describe the system that you are interested in and you have a state function, then you can specify $\bgroup\color{blue}$ N-1$\egroup$ of the variables and the other is determined by the state function.

A state function is a model for a material or a system.

Note that the definition of a state function implies a dependence between some variable and the current value of the other thermodynamic values--in other words, it doesn't matter how the system arrived at a certain state. State functions cannot depend on the any of the prior processes--state functions are history-independent.

Question: Can you write an equation that describes how far the lecturer is located from the corner of the room?

Question: Is the distance of the lecturer from the corner of the room a state function? What are the variables?

Question: Can you write a differential expression for this distance in terms of its variables?

Question: What assumptions have been made in writing down the model for distance?

Question: Imagine that you have closed your eyes for a few seconds and the lecturer walks to a new location in the room, can you write an equation expressing how far he has walked?

Question: Is the `distance the lecturer has walked' a state function?

Question: If the `distance the lecturer has walked' is not a state function, is there any modification to the phrase that would make it a state function?

Next: Some Example State Functions Up: Lecture_04_web Previous: Lecture_04_web

W. Craig Carter 2002-09-10