But what if the product B turned into another product C? If we wanted to calculate the overall Free Power-free energy for A going to C, we could instead calculate the individual delta G for each step of the reaction that is A going to the product B, and B going to the product C. So I just want to reiterate here that B and C are products in their own right. They’re not transition states. But what we’re seeing here is that in some cases we may not be able to measure the change in Free Power-free energy going from A to C directly. So instead, we can add together the individual change in Free Power-free energy for each step, because remember Free Power-free energy is Free Power state function. And if we do that, we ultimately get the change in Free Power-free energy for the overall reaction of A going to C. Now one fun way that I kind of remember the state function like quality of delta G, as well as some other variables in chemistry, is that my chemistry professor used to tell us that life is not Free Power state function. And this of course helps me remember the definition of the function does not take into the path of reaction, because of course in life, it’s all about the journey and not the destination. But in chemistry, sometimes it’s the opposite. Now, the third point that I want to make is that delta G unlike temperature, for example, which can be readily measured in Free Power lab for Free Power particular situation, delta G is something that can be calculated but not measured. And to understand this, we need to go back to what the purpose of delta G was in the first place. So remember delta G, the value of it, tells us whether or not the reaction will occur. And it turns out that when chemists were trying to answer this question, they found out that the answer to this question relies on multiple variables. There’s not just one thing that determines whether or not Free Power reaction will occur. So what they did was, for simplicity, they took into account all of the variables into this one parameter that they came up with called delta G. And the way they did this was by creating an equation. So they said, the change in Free Power-free energy is equal to the change in enthalpy, or heat content, of Free Power particular reaction minus the temperature of the reaction times the change in entropy, or broadly speaking randomness, between products and reactants in Free Power particular reaction. Therefore, as I mentioned before, we can go ahead and calculate one single value that takes into account all of the variables that affect the extent and degree to which Free Power reaction will occur. And it turns out that we can actually measure the change in enthalpy, the temperature, and the change in entropy for Free Power reaction, so that works out quite well. Now, at this point, you probably have Free Power question of OK, I see that I have an equation to calculate delta G for Free Power reaction, but what does this value that kind of pops out of this equation tell me about Free Power reaction? So let’s go ahead and go back to our hypothetical reaction of A going to B. Let’s draw Free Power diagram that will help us understand this reaction better. So I’m going to go ahead and draw Free Power y-axis and an x-axis. On the y-axis will be the quantity free energy in units of joules, let’s say. And on the x-axis will be the quantity of Free Power reaction coordinate. And this is kind of an abstract parameter that simply is Free Power way for us to kind of monitor the progress of Free Power reaction over time. So this will make more sense when I actually indicate we’re putting in this diagram. So let’s say that our reactants A have Free Power much higher free energy than the products of our reaction, which is B in this case. So what we can say about this, which hopefully is more clear by this visual diagram, is that the change in free energy , which remember is equal to products minus reactants, is negative. Or we say it’s less than 0. On the other Free Power, let’s say that we started off with reactant A that had Free Power much lower free energy than the product B. Now in this case, we would say that the change in free energy of products minus reactants would be positive. Now, the key takeaway here is that for any chemical reaction that has Free Power negative delta G value, we say that the reaction proceeds spontaneously. That is, it proceeds without an input of energy. So I’m just going to write spontaneous there. On the other Free Power, when Free Power delta G value is positive, that is when the conversion of reactants to products requires Free Power gain of energy , we say that it’s Free Power non-spontaneous reaction and cannot proceed unless there is an input of energy. And one kind of loose analogy that helps me kind of think of these things more intuitively is to think about yoga breathing. So imagine that you’re taking Free Power deep, deep breath in, and all of this breath that you have inside of your body makes you feel kind of unstable and wanting to burst. So I kind of think of that as starting off at Free Power high free energy state. So let’s say we’re starting off with A. And then as I breathe out, I kind of feel myself becoming more relaxed and releasing energy. And that brings me to B, which has Free Power lower free energy. And that of course, breathing out, is Free Power spontaneous process. The internal energy U might be thought of as the energy required to create Free Power system in the absence of changes in temperature or volume. But if the system is created in an environment of temperature T, then some of the energy can be obtained by spontaneous heat transfer from Free Energy to the system. The amount of this spontaneous energy transfer is TS where S is the final entropy of the system. In that case, you don’t have to put in as much energy. Note that if Free Power more disordered (higher entropy) final state is created, less work is required to create the system. The Helmholtz free energy is then Free Power measure of the amount of energy you have to put in to create Free Power system once the spontaneous energy transfer to the sytem from Free Energy is accounted for. The internal energy U might be thought of as the energy required to create Free Power system in the absence of changes in temperature or volume. But as discussed in defining enthalpy, an additional amount of work PV must be done if the system is created from Free Power very small volume in order to “create room” for the system. As discussed in defining the Helmholtz free energy , an environment at constant temperature T will contribute an amount TS to the system, reducing the overall investment necessary for creating the system. This net energy contribution for Free Power system created in environment temperature T from Free Power negligible initial volume is the Free Power free energy. Free energy is the measure of Free Power system’s ability to do work. If reactants in Free Power reaction have greater free energy than the products, energy is released from the reaction; which means the reaction is exergonic. Conversely, if the products from the reaction have more energy than the reactants, then energy is consumed; i. e. it is an endergonic reaction. Equilibrium constants can be ascertained thermodynamically by employing the Free Power free energy (G) change for the complete reaction. This is expressed as: In summary, the total energy in systems is known as enthalpy (H) and the usable energy is known as free energy (G). Living cells need G for all chemical reactions, especially cell growth, cell division, and cell metabolism and health (Discussion Box: Free energy in Cells). The unusable energy is entropy (S), which is an expression of disorder in the system. Disorder tends to increase as Free Power result of the many conversion steps outside and inside of Free Power system. Thermodynamics is key to air Free Energy science and engineering. Heat exchange, partitioning, and other thermodynamic concepts are employed to determine the amount of air Free Energy generated, how an air pollutant moves after being emitted and the dynamics and size of air pollutant plumes. Another key area in need of thermodynamic understanding is the cell, whether Free Power single-cell microbe or part of an organism, especially human cells. Since disorder tends to increase as Free Power result of the many conversion steps outside and inside of the cell, the cells have adapted ways of improving efficiencies. This is not only important to understanding how air pollutants disrupt cellular metabolism, but is key to finding biological treatment technologies for air pollutants, once the mainly province of water and soil treatment. Bioengineers seek ways to improve these efficiencies beyond natural acclimation. Thus, to understand both air Free Energy toxicity and air Free Energy control biotechnologies, the processes that underlie microbial metabolism must be characterized. All cells must carry out two very basic tasks in order to survive and grow. They must undergo biosynthesis, i. e. they must synthesize new biomolecules to construct cellular components. They must also harvest energy. Metabolism is comprised of the aggregate complement of the chemical reactions of these two processes. Thus, metabolism is the cellular process that derives energy from Free Power cell’s surroundings and uses this energy to operate and to construct even more cellular material. energy that does chemical work is exemplified by cellular processes (Figure Free Power. Free Power). Catabolism consists of reactions that react with molecules in the energy source, i. e. incoming food, such as carbohydrates. These reactions generate energy by breaking down these larger molecules. Anabolism consists of reactions that synthesize the parts of the cell, so they require energy ; that is, anabolic reactions use the energy gained from the catabolic reactions. Anabolism and catabolism are two sides of the same proverbial metabolic coin. Anabolism is synthesizing, whereas catabolism is destroying. But, the only way that anabolism can work to build the cellular components is by the energy it receives from catabolism’s destruction of organic compounds. So, as the cell grows, the food (organic matter, including contaminants) shrinks.
Free energy is that portion of any first-law energy that is available to perform thermodynamic work at constant temperature, i. e. , work mediated by thermal energy. Free energy is subject to irreversible loss in the course of such work. [Free Power] Since first-law energy is always conserved, it is evident that free energy is an expendable, second-law kind of energy. Several free energy functions may be formulated based on system criteria. Free energy functions are Legendre transforms of the internal energy.