 Hi, I'm Zor. Welcome to a new Zor education. We continue talking about transformation of energy, generation of electric energy in particular. Now the previous lecture was about transformation of kinetic energy into electric energy. Now this lecture is about transformation of chemical energy into electric. This lecture is part of the course called Physics for Teens, presented on Unisor.com. The website contains prerequisite course which is called Mass for Teens, which is, well, mass is mandatory to learn physics seriously. So I do recommend you to know whatever is in the Mass for Teens course prior to you learning anything serious in physics. Now the course is presented on this website, but at the same time all lectures are on different carriers like YouTube, for instance. But I do recommend you to watch this lecture from the website, from theunisor.com. First of all, because every lecture has textual notes which basically like a textbook. One thing is what you are listening to whatever I'm saying, and another is when you are reading basically the same thing, but it brings you a little bit better into a good level of understanding. Plus in certain cases I might present something slightly differently in writing versus at the board, so it's always useful. Also the website contains problems for many topics. Everything is free by the way on this website, there are no advertisements, so you don't even have to sign in if you don't want to. So basically I do recommend you to watch this lecture from the website, from theunisor.com. Now back to chemical energy. So we are talking about transformation of chemical energy into electric energy. Well, first of all let's just think about how can we transform one form of energy into another and generate basically electric energy. If we are generating something we should really take it from somewhere else, because there is an energy conservation. Now it's quite practical and natural for people to be able to transfer one form of energy into another. Now in this particular case chemical energy into electrical energy. Well, first of all we are all familiar with transformation of chemical energy into heat for instance. Well a simple example is burning. When you are burning something it's a chemical reaction of oxidation. Like for instance if you have a methane which is CH4 plus oxygen from the air, that's burning basically. This is the gas and this is the gas they are burning. And what's the result? CO2 plus H2O. We have to balance this thing. So we probably need two of these and two of these, right? So H4 and O4 and H4 and C, right? That's the proper balance. So two molecules of oxygen plus molecule of methane gas gives you carbon dioxide and vapors basically. Because it's heating, it's burning, right? So it's a chemical reaction and why do we have the heat released during this burning? Well if you think about again this energy conservation, the total energy here should be greater than total energy of these molecules. And that's why we have extra energy released into heat. So the energy is basically an energy of interatomic bonds inside the molecule, here and here. So if you will summarize somehow the interatomic energy of this molecule into two of these molecules and then you will do exactly the same here, you will have this difference in energy level. So these two have more energy in interatomic bonds inside the molecules than these two. So that's basically why we have this axis of energy released as heat. Now, so it should be no wonder for you that we can actually generate electricity in practically the same way from chemical energy. As long as we have some chemical reaction which produces extra electrons in one hand and then we will have some kind of a result, so these two electrons will have to travel somewhere. And if on another hand we will produce another chemical reaction where we will have a deficiency of electrons, then by combining these two reactions we have here axis of electrons, here deficiency of electrons and if we will connect them together the electrons will go and that's what electricity actually is, that's what current actually happens. Now, how do people come up with solutions to this particular problem? How did they come up with the device which is called a battery? That's what basically the most important device which converts chemical energy into electrical is a battery. Now, we know about batteries, well, first of all we have a car battery, right? And then we have some batteries which we are putting into different devices like remote control and TV and something like this. These are all batteries, they are different, there are many different kinds of batteries but again the principle is exactly the same. There is a chemical reaction on one hand which produces extra electrons chemical reaction on another and which produces deficiency of electrons and then if we are connecting them the current will go. Now, I will explain this on one particular example, the car battery which is used not in electric cars, I'm talking about our more classical car batteries which is in many cases is so-called lead acid battery. Lead acid because there is lead and there is an acid in this battery and I will talk right now about how this particular battery is arranged and how these chemical reactions are going. It actually means that many, many other batteries are constructed in a similar fashion. They have different material, they have lithium ions battery, we have some kind of alkaline batteries but they are all based on the same principle. People just found different chemical reactions which are producing electrons and consuming electrons and different chemical reactions resulted in different batteries. There are better ones, there are worse ones, there are old ones, there are new ones but in any case I will just exemplify it on one particular example. Now, I didn't mention it before, battery produces direct current. If you remember, kinetic energy can be converted into electric depending on what kind of device we are using. It can be either direct or alternate current but in case of batteries, in case of chemical reaction, it's a steady stream of electrons from one place to another which means it's a direct current. Okay, next. So, lead acid battery. Lead acid battery basically is a reservoir filled with sulfuric acid plus the water, it's diluted sulfuric acid. Now, there are two terminals plus and minus. Well, you basically saw probably, you saw how car batteries are arranged. There are two poles basically, plus and minus. What's inside you don't really see but inside in many cases there is this sulfuric acid. Now, one particular terminal or pole, whatever, is made of lead dioxide, another is made of lead. I'm using chemical formulas for all the elements as you see. So, this is sulfuric acid, this is lead, plumbum, and this is lead dioxide, plumbum O2, and this is H2SO4. So, these are initial components of lead acid battery. That's how lead acid battery is made of. Well, obviously we are counting on certain chemical reaction on these things. We call this minus because probably the electrons will be born here as a result of chemical reaction between lead and sulfuric acid. And electrons will have some kind of a deficiency here as a result of reaction between sulfuric acid and lead dioxide. So, let's just think about what exactly is happening. Okay, now, first of all, I would like to talk about the sulfuric acid inside. By the way, it's called whatever is in between two electrodes which is causing this particular reaction is called electrolyte. So, it's a general, not only about sulfuric acid, but it's also about general kind of a liquid usually which is not necessarily liquid, can be a hard substance as well. So, what exactly is a very important property of electrolyte which actually is causing the production of electrons in one case and deficiency of electrons in another case. Now, here is something which you will understand what I mean. Now, let's talk about the molecule of sulfuric acid. Basically, this is sulfur, this is oxygen, this is oxygen, this is oxygen and hydrogen, and this is oxygen and hydrogen. That's how it's structured. Now, these are valensile links, it's called. It's all kind of chemistry, physical chemistry, but in any case, it's all related to whatever we are talking about. So, that's why this is a structural formula, if you wish, or structural composition of the molecule. Now, what happens is H-hydrogen is a very light atom. That's basically the lightest, it has only one proton and one electron which is circulating around it. So, it's very light, it's very volatile. And in many cases, in as much as you remember we were talking about electrons on outer orbits of certain atoms. They are far from the nucleus and electrical links between electrons and protons is not as strong as for electrons which are on the inner orbits. So, the outer orbits are, they have electrons not as strongly related to protons inside the nucleus and that's why there are many electrons which are kind of floating between different atoms, changing hosts, changing their nucleus. And that's how we are talking about free electrons and especially metals, they have a lot of free electrons which are just circulating and waiting for voltage to be put on one side and another side, plus and minus and then they immediately go to the plus, right? So, in molecules, things also can happen in the same way. So, in atoms we have electrons which are kind of free which are on the outer orbits and in molecules certain components can actually break away from the molecule. So, in this particular case what happens, this is these two atoms of hydrogen can actually break away but with an interesting property. Now, each atom of hydrogen contains basically the one proton and one electrons. Now, the way how it breaks, it's not exactly like this. It's like this. And what's very important, the nucleus of hydrogen atom which is basically one proton goes away but the strength of the molecule is sufficient to keep the electrons close to oxygen. Oxygen is much more heavy molecule atom actually and it holds this electron which is in between them somewhere. It's a balance electron and it actually keeps it on the side of the oxygen. So, the proton of hydrogen floats away but the electron is kept around orbit of oxygen. So, that's why we have this only proton positively and this is two electrons which are still kept in this part. So, this is called cations and this is called cation, anion. So, cation and anion, cations are positive and anions are negative. So, the molecule which is neutral is broken in pieces. Why is it happening? Well, it's probably some kind of a natural occurrence. I don't know, quite frankly. But in the same way as electrons are sometimes breaking away from the nucleus in the atoms and making this like a cloud of free electrons, same thing with this. Now, this whole process is called ionization because these are called ions, ion positive which is cation and negative ion which is anion. So, this process of ionization is quite natural for sulfuric acid and that's the key to understand what chemical reaction actually is happening. So, let's just state this as given. Again, I don't know how to explain it but that's how it goes basically. The ionization is happening and that's the key to chemical reaction which is occurring inside the electrolyte which is sulfuric acid. Okay, so that's one thing. Now, this is happening everywhere. Here and here and here and everywhere. So, we have floating ions of hydrogen positively charged and negatively charged ions of SO4. Okay, fine. So, what's happening next? Now, this is the key because it has actually a certain function. It actively goes against lead and chemical reaction actually is happening. So, what kind of chemical reaction is happening? We still have deficiency of two electrons here, okay? So, what happens here? What happens is... So, these extra electrons are not really needed for a steady molecule because this is a steady molecule. This is not because this is ions. So, it's very active. There are two balances which are actually missing. Remember this O, O, S, O, O, H, H and these guys are missing, right? That's ionization. So, we have two free links which really very actively seeking who to connect to. And very conveniently, here is lead and lead sometimes has two, sometimes it has four available links. It depends. But in any case, in this case, two links of lead actually goes into connection with the ion of SO4. And again, the connection is so strong that whatever is extra just released basically. It's just flowing. Well, not exactly flowing because this is a reaction between electrolyte and lead. So, where are these electrons? They are on the surface of this particular terminal of the battery, right? They are on the surface. Now, that surface is lead metal, right? And it's a metal which means it's very good for going electricity through it, right? It's a very good conductor. Now, what happens? It has a lot of free electrons. Now, why lead has a lot of free electrons? Just think about lead is a very heavy molecule or atoms actually. And which means there are many orbits around the nucleus. The first orbit contains, first level of energy contains two electrons. Next one is eight. Next one is 18. But we have a lot. So electrons are further and further from the nucleus and outer ones are really not very good as far as staying inside the atom. So that's why we have a lot of free electrons. So these electrons are basically going into this cloud of free electrons which are inside the negative terminal and increase its electric potential. Okay. So we are increasing electric potential as this reaction actually happens. Negative potential, okay? Okay, fine. So that's done. By the way, from the structural standpoint again, you remember that I will put it again. This is our initial sulfuric acid. Now these two broke away. And instead, these two connections come to lead. So this is the structural formula of this. And two electrons are just flying away. But within this negative terminal, within the lead which basically constitutes the terminal. Okay, that's done. Now pay attention to these two electrons. They're very, very important. Because this is basically where the source of electricity is. Okay? Meanwhile, what happens on the positive? So this is negative. By the way, called anode or anode. And this is cathode. Anode, cathode. Okay. So on the cathode, we have lead dioxide. Okay? And it also has chemical reaction with SO4. So what happens? We have plumbum O2. And we still have this SO4 with two negative extra electrons. And what happens? Well, what happens is, I shouldn't put equal sign. I shouldn't put the arrow here. So what happens here is, we still have the same plumbum SO4 as before. But now we have two molecules, two atoms of oxygen which are basically replaced. I'm not sure which two atoms of oxygen are here. These two or these two? I just don't know quite frankly. But it doesn't really matter. What matters is that these two electrons are still here. So it's still negatively charged. It still has two electrons. Now, this thing is part of the molecule of H2SO4, of sulfuric acid. So another part is this one, remember? So this is the main ionization formula. So this thing reacts with lead dioxide. That's how it does it. And how about this one? But that's not it. We still have 2H+, from reaction on this side because we didn't really use it here. It's still somewhere in the electrolyte. So this electrolyte after this reaction has two ions of hydrogen. And this reaction also takes only this part and there are two ions. So we have this plus this. And we have these guys, two of them. What is this? This is 2H2O water. Two molecules of water. So we have four atoms of hydrogen and two atoms of oxygen. However, that's very, very important. Let's count the electrons. This is, each atom has one missing electron. Two atoms have two missing electrons. And this guy has two missing electrons, right? So that's four. Two of them are provided. But two are still missing, which means two are still missing here. Well, actually, I should say, since I have two molecules, so one of them is. One of them has one electron missing and another has another electron missing. On this side, we have two electrons missing and on this side, it's on the surface somewhere, again. The concentration of these molecules of water with missing electrons somewhere is on the surface of this electrode. And these two are extra. So what happens now? If there is no connection between them, well, reaction goes and goes. This accumulates negative. This accumulates positive up until a certain extent when this thing doesn't really take anymore. Because the electrons which are already here prevent new electrons to come into this. So this reaction is probably somehow changing in a way that these extra electrons, after this is completely charged, these electrons are no longer goes into this. They are somehow probably neutralized whatever the reaction is. And reaction goes no more, basically. Just generally speaking. Again, the whole thing is actually much simpler than what's really happening. I'm pretty sure it's a much more complicated picture. However, as a good model, it really reflects what's going on. So the battery is charged up to a certain extent. What happens then? Well, what happens then? If I connect these two things, let's say with a lamp or electric motor or something like this. Well, in case of car battery, we have, when this thing is actually working, when we start the engine, right? Because the car engine is in a standing still position. It's not really working. So we have to really start working to pump gas to start ignition and stuff like this. So that's what the battery actually is needed. In the very beginning, we turn on the car, which means we turn on this connection. And then it goes into some kind of an electric motor which rotates the whole car engine and ignites the gas. And that's how the car internal combustion engine starts working. Okay, so at that time, all these electrons, which are axes of electrons, are going into cathode from anode to cathode. And that's how electric current is. As soon as number of electrons here diminishes, the reactions start again. So it goes and goes and goes. Well, and you know that initially you have certain amount of sulfuric acid which reacts with these two things. And if you don't really do anything, it will basically completely exhaust the power of sulfuric acid. And there will be no more electricity, the car is dead, right? So that's why this particular battery has a property of not being discharged like this, but also being charged. Now, we are not talking about this in this particular lecture because it's not really... You see, the lecture is dedicated to generation of electricity. Now, when we are charging the battery, we are converting electric power into chemical, and that's kind of outside of this lecture. But basically, I'm just telling you that if instead of a lamp, you have really a source of electricity, like generator, and in the cars, in the internal combustion cars, you have alternator, which converts kinetic energy into electric, right? And then if you put the electric potential negative here and positive here, all reactions will go in reverse. And again, let's not talk about why it happens, but it happens. And we have sulfuric acid restored, basically, from these lead sulfite, I think it's called. So from lead sulfite and water, under the potential of electric energy applied to these terminals, reactions go in reverse. And in the textual part of this lecture, I actually have a nice picture, which basically kind of reflects what's going on in case when you're charging and discharging this lead acid battery. So the whole thing actually goes like this. You have plumbum. You have plumbum O2 plus S2SO4 plus plumbum. So this is plus, this is minus. That's in the beginning. And in the end, you have lead sulfite plus water plus lead sulfite again. So this is again, this is plus, this is minus. Now, when you are discharging battery, it goes this way. This is discharge, right? And when you're charging, it goes this way. So I have this nice picture more or less like this in the textual part in the notes for this lecture on Unizor.com. Okay. What did I miss? Well, actually, nothing. I think everything is fine. Let me just finish this lecture by saying that, well, whatever I was just talking about, I believe it's a simplified view on what's going on inside the battery. Batteries are complex, really, and chemical reactions are complex. Whatever I was just talking about is a simplified view. Now, there are many characteristics of the battery which are very, very important. Not only the amount of energy it can produce, but also how smooth the process is, how stable the voltage produced by these two terminals is. Because sometimes you see with diminishing amount of sulfuric acid here, you would expect that the voltage will go down. But don't we know that in the car battery we usually have 12 volts? So there is something which we have to really take care of, and I'm not sure myself how it's basically done, but it's complex how to make a battery which establishes the relatively steady voltage on its terminals, how to make the battery more capable of producing electricity. Because this thing is, well, I don't know if you know, but the car battery is heavy. Well, because of lead, here and here and sulfuric acid. So we probably can think about how to make our batteries lighter by producing the same kind of electricity. So the whole industry of producing batteries is really very, very intense, especially right now with electric cars. So I think in electric cars they're using clitium ions, which again is some kind of a way of producing electricity from the chemical energy. So there are better ways and there are different ways and there are more stable ways, etc. It's a very interesting part and definitely deserves a lot of research, which is being done obviously right now. Every year or something you have some kind of a new information, okay, we have a new way how to produce electricity in a battery, and the battery becomes lighter, the battery becomes more capable of producing electricity, so more productivity if you wish. So all that is very important, but my purpose was to exemplify creation of generation of electricity from the chemical energy. So from the energy of inter-atomic links within the molecule, we are producing electricity because the new chemical composition, which is a result of chemical reaction, has less inside energy, less inter-atomic energy inside the molecules than the original. So that's how this chemical reaction produces some energy, and in this case the energy which we are producing is electric energy. In some other it's heat, as I was explaining in the beginning, but in this case it's electrons basically. Okay, so I do recommend you to read the notes for this lecture on Unizor.com. There are some nice pictures, especially the very last one, which basically exemplifies the whole thing like this. So that's it, thank you very much and good luck.