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Two Path Functions to State Function


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#1 Infinity

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Posted 27 March 2005 - 04:59 PM

How is it possible that two path functions (heat and work, for example) add up to a state function (change in internal energy)? Why is energy a state function? Why is heat a path function? Why is work a path function?

Many thanks.
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#2 akcapr

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Posted 27 March 2005 - 07:10 PM

thats more of a physics question
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#3 Infinity

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Posted 27 March 2005 - 07:32 PM

thats more of a physics question


No, it's not. It's more of a thermochemistry question.
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#4 akcapr

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Posted 27 March 2005 - 07:40 PM

well i went through this stuff in physics
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#5 Infinity

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Posted 27 March 2005 - 07:46 PM

well i went through this stuff in physics


I'm going through this stuff in Thermochemistry.
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#6 collector

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Posted 29 March 2005 - 09:43 AM

Why is energy a state function?



It is another way of formulating the energy principle: energy cannot be created or destroyed.

Therefore, the difference in energy between 2 states cannot be dependent of the path.

If that was the case, the total energy (that is final energy - start energy) would give different results depending on the chosen local path.
Then energy would be created or destroyed somewhere along the path.

In theoretical physics they talk about conservative force fields, and potential functions. The same stuff, different terms.
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#7 Infinity

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Posted 29 March 2005 - 11:07 AM

So why is heat a path function ? Is it because when you use different method of changing temperature, the heat will be different? The same concept applies for work?

Now comes the ultimate question again: How is it possible that two path functions (heat and work, for example) add up to a state function (change in internal energy)? The formula is: (delta)E = q + w.

I've looked at it for several times but couldn't understand how it is possible for two path functions to become one state function.
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#8 chemistry

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Posted 3 April 2005 - 03:14 AM

Why is energy a state function? Why is heat a path function? Why is work a path function?


Energy itself is a state function if it the situation is conservative, such as with gravity and electric fields. Enthalpy itself relates to the chemical energy released/absorbed in an open system. The q relates to the temperature change (internal energy) while w relates to the work in expanding against the surroundings. It is simply a statement relating to the conservation of energy. I don't know why you're so confused with this. By the way q is a state function, it relates to the initial and final temperature, the w is a general expression for the energy lost in expansion.
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#9 Infinity

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Posted 3 April 2005 - 03:51 AM

Energy itself is a state function if it the situation is conservative, such as with gravity and electric fields. Enthalpy itself relates to the chemical energy released/absorbed in an open system. The q relates to the temperature change (internal energy) while w relates to the work in expanding against the surroundings. It is simply a statement relating to the conservation of energy. I don't know why you're so confused with this. By the way q is a state function, it relates to the initial and final temperature, the w is a general expression for the energy lost in expansion.


Thanks a lot. This is the kind of answer I've been expecting to see.
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