State functions

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pamcoronel1H
Posts: 45
Joined: Fri Sep 28, 2018 12:25 am

State functions

Postby pamcoronel1H » Sun Jan 27, 2019 9:49 pm

Hi!

Could someone explain why the work function is not a state function. I understand it is because you need to know the "pathway", but what is this pathway and why cant' it be added or subtracted to see the change in work?

Thanks!

Nathaniel 2E
Posts: 27
Joined: Mon Jun 25, 2018 3:00 am

Re: State functions

Postby Nathaniel 2E » Sun Jan 27, 2019 9:52 pm

Work can't be a state function because it is proportional to the distance an object is moved, which depends on the path used to go from the initial to the final state. Like Prof. Lavelle showed us in class with the mountain example, the hikers taking the different paths arrived at the same end point and started at the same initial point, but some hikers did more work than others because their route was longer.

1K Kevin
Posts: 47
Joined: Fri Sep 28, 2018 12:24 am

Re: State functions

Postby 1K Kevin » Sun Jan 27, 2019 10:01 pm

Work is not a state function because its current state depends on things preceding it. The example in the book is two experiments, one where a gas expands pushing a piston which pushes against water; work is done here because there is an external force. The second has a gas push a piston into a vacuum, because there is no external opposing force there is no work. The value of work depends on what it did to get to its position (like the hiker example). This is also why you can't add or subtract it because it depends on the pathway.


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