Chemical Thermodynamics 3.3 - State and Path Functions

Short physical chemistry lecture on state functions and path functions.
A state is the set of all variables necessary to completely specify the conditions of a system. A path is the set of states connecting an initial state to a final state. State functions depend only on the initial and final state, while path functions depending on the path connecting them.
Notes Slide: i.imgur.com/KhU...
-- About TMP Chem --
All TMP Chem content is free for everyone, everywhere, and created independently by Trent Parker.
Email: [e-mail]
-- Video Links --
Chapter Playlist: • First Law / Enthalpy
Course Playlist: • Chemical Thermodynamic...
Course Review: • Thermo / Kinetics Chap...
Other Courses: • PChem Course Intros
Channel Info: • About TMP Chem
-- Social Links --
Facebook: / tmpchem
Twitter: / tmpchem
LinkedIn: / tmpchem
Imgur: tmpchem.imgur.com
GitHub: www.github.com...
-- Equipment --
Microphone: Blue Yeti USB Microphone
Drawing Tablet: Wacom Intuos Pen and Touch Small
Drawing Program: Autodesk Sketchbook Express
Screen Capture: Corel Visual Studio Pro X8

[@ps-js5vs]

These videos have helped me so much in preparing for my first p chem exam! Thank you so much!!!!

[@TMPChem]

Thanks Paige. Good luck on the exam and beyond. We'll be here for the next one, too.

[@gaurangagarwal3243]

Dude . It was great finally I understood what do we mean by path variable

[@humor5211]

Indeed!

[@ininc5983]

never knew what it was................ thanks

[@TMPChem]

Glad to help. Unfortunately there are many cases in pchem where some formal, abstract, mathematical concept is mentioned briefly, and then never explained again, but used often. Often it isn't that complicated to explain, but is quite confusing when you aren't aware where it comes from and/or what it means.

[@user-in4sg1nt4t]

Shouldn't the equation at the end be ∆Q=∆U+∆W as some of the heat supplied to system increases internal energy and some goes to do work?

[@TMPChem]

Heat and work are path functions, and not state functions, thus for a macroscopic change we don't use a preceding delta as we do for state functions, such as energy. Energy has a well-defined value at the beginning and end of the process, thus the term delta_U makes sense. Heat and work are the result of process, and are not properties of a given system state, thus it doesn't make sense to refer to delta_Q or delta_W, as these quantities are just Q and W themselves. Heat and work are both ways to change the internal energy of the system, and add up together to be the change in internal energy, thus the overall equation delta_U = Q + W.

[@haithamabdelrahman6276]

Nice , thanks

[@TMPChem]

Thanks for watching.

[@nkyu3035]

I have a feeling I might have asked you the same question but I couldn't find it T_T.
in the equation du=dw+dq, why does path function plus path function equal state function?

[@TMPChem]

Because the manner in which those functions depend on the path are equal in magnitude and opposite in sign. Thus, when you add them together you end up with a state function.

[@nkyu3035]

It make sense if these two path functions work that way.
But I wonder why the manner in which these function depend on the path is like that.
How should I understand it in terms of math or intuition?

[@TMPChem]

Honestly I don't have a full intuitive understanding of several macroscopic top-down classical thermodynamic concepts like the work / heat path function pairing. I've always understood things much better from the microscopic bottom-up statistical mechanics approach. I don't think I have much more to say on the topic besides following where the math leads.