(a) Which of the thermodynamic quantities T, E, q, w, and S are state functions? (b) Which depend on the path taken from one state to another?

Video transcript

Welcome back everyone. We need to consider the following thermodynamic quantities heat or sorry, entropy heat entropy free energy and work and classify each of them as a state function or as a path function. So let's begin by defining these terms. Beginning with state function. Recall that a state function does not depend on a path Taken from one state to another. Moving on to our second term which is a path function which we should recall is past dependent from initial two final state. So defining our thermodynamic quantities, recall that H is a term used to describe entropy which we should recall represents our heat content of a system under a given pressure. Next we have our term for Q which we should recall represents heat that can either be exchanged by our system or added to our system and also removed. So it's important that we understand that this is a lower case Q. Because we don't want to confuse it with the capitalized Q. Which is representative of our reaction quotient which compares our products to our reactant and a ratio. So recall that heat is typically expressed in units of jewels and moving on to our next quantity we have us which we recall represents entropy and this is going to be the energy of disorder nous of our system that's not available for work recall that our units for entropy I should have mentioned are killed jules Permal whereas our units for entropy are going to be jewels, per kelvin. Now we're going to define our next quantity which is G. Which we recall stands for gibbs, free energy or you can just say free energy for short and recall that this is defined as the energy that is associated with a chemical reaction that is available to do work. And that means it's going to determine whether or not a reaction will be favorable or not. And so we can think of the fact that when we have a free energy value that is less than zero. Where our free energy change is less than zero. Specifically, we would say that therefore our reaction is going to be spontaneous, meaning it won't need any extra energy. Whereas if we have a free energy change that is positive or greater than zero. Therefore our reaction would be non spontaneous and not favorable. Moving on to our last quantity, we have the term W which as you can guess means work, which we should recall can either be done to or by the system A. K. A. Our reaction so based on everything we've outlined, we're going to say that since we know n therapy is based on the heat exchange of a system which is not path dependent entropy is going to be considered a state function. Moving on to entropy, we defined it as the energy of disorder nous of our system, which does not depend on a particular path, especially because it's all random and disorder. And then lastly we have our free energy change which is also not past dependent because it's just based on the energy associated with our system A. K. Or chemical reaction. Whereas our terms heat and work are definitely path dependent. They're going to be affected by the process of our reaction. So how the reaction is going to begin and then how it will end in a certain state. And so we will define below for our final answers that are terms as we stated, entropy or sorry, entropy, entropy and free energy are all non past dependent state functions, whereas our terms heat and work are both path dependent path functions. And so these two grouped terms are going to be our final answers to complete this example. I hope that everything I explained was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video.