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State functions and path functions chem?
For some reason I can't seem to differentiate between these 2 terms.
My book defines state function as
'a property of a system that depends only on its present state, which is determined by variables such as temperature and pressure and which is independent of any previous history of the system.'
What does that even mean ?
Ive seen sources try to explain it using GPE as an analogy but what does that do to me when it comes to determining whether Pressure or volume are state functions are or not ?
For context, I'm a first year uni student and this is from my general chemistry course.
1 Answer
- hcbiochemLv 71 year ago
So, things like pressure and temperature are states or conditions. You will run into a lot of concepts like Enthalpy (H), Energy of the system (E or U), Entropy (S) and lots of others. These are state functions described by the definition you gave. Their magnitudes depend on lots of other things, like pressure, temperature, amount of substance and so on.
Very often, state functions and path functions describe changes in some kind of condition. You will encounter Delta H and many others. The delta represents "change in". The magnitudes of these changes are calculated by only considering their initial condition and their final one. HOW that change happened doesn't matter. The magnitude of the change depends only on the difference between the initial and final conditions. For path functions, the magnitude of the change depends completely on HOW that change happened.
As a simplistic example, suppose you have a book on the desk, and you slide it from one spot to another. One state function for that change would just be the distance from the first spot to the second.
Now, suppose that to move the book, you picked it up, carried it around the house a while, and later, you put it into the second spot. The state function describing the distance of that change is exactly the same as the first time--just the difference between the initial and final spots. The path function describing that distance is very different and would have a much greater magnitude.
As you deal with thermodynamics later in chemistry, you will work a lot with state functions.
