 Hi, I'm Zor. Welcome to a new Zor education. I would like to continue talking about different kinds of energy. And this lecture is about chemical energy. Chemical reactions, atoms and chemical reactions. This is kind of introductory lecture to chemical energy. And to tell you the truth, I think it's more belongs to the chemistry course rather than the physics course. However, again, one or maybe two general lectures about what actually chemical energy is all about will be presented in this particular course. Now, this course is part of this lecture actually is part of the course physics for teens which is available on Unizor.com If you found this lecture by itself somewhere on YouTube or somewhere else I do suggest you to actually go to the Unizor.com website because this lecture actually is linked from this site. And also for each lecture there is a detailed textual explanation which you can use as a textbook basically. And then it's a course so which means it's logically connected one lecture after another. And there are problem solving lectures and there are exams etc. And the site is completely free. There are no advertisement, no strings attached. Now, talking about chemical energy, let me start from something which we have already covered. We have started with mechanical energy and it's all about moving objects. One relative to another. We have potential energy like for instance some kind of an object above the level of the ground. It has potential energy because there is a gravity. And we had kinetic energy when the object is moving. Now, our next type of energy which we considered was heat. Now here we go a little bit deeper into the object if mechanical energy is all about objects and their positions and moving. Heat energy is related to molecules inside the objects. So how they are moving and the heat actually is the intensity of the moving molecules. Now we are going into deeper even inside the molecules and that's where the chemical energy is located if I can say so. Because the chemical energy is related to how the molecules are structured. Now again without going into very important details of how actually the molecules and atoms are constructed, let me just say that the molecules contain atoms related to each other using some kind of a bonding. There are some bonds between the atoms. It's related to their electromagnetic qualities. Now there are many different molecules. I mean the whole world is filled with extremely large number of types of molecules. However the number of atoms these molecules are created from is significantly less. At the moment the science knows something about a hundred, a little bit more than a hundred, a hundred and one or a hundred and two whatever, different types of atoms. And by the way not all of them actually exist in nature. Some of them are created artificially by people. But in any case we have a relatively small, like a hundred plus number of atoms. But from these atoms all the multitude of different molecules and different substances and different objects are created. Why? Well because we can have different atoms in different quantities and even in different configuration how one is attached to another using some kind of atomic bonds and we will get a new type of molecule. So from about a hundred different atoms we have millions and billions whatever different kinds of molecules whatever we can basically create. Okay so molecules are basically constructed from atoms and there are certain relatively limited number of atoms. Now atoms are related to each other through some kind of a bonding and that's what makes up the molecule. So molecule is these atoms of specific type in a specific configuration in specific quantities which are connected somehow among themselves and that's what makes up the molecule. And the chemical energy is, and now I'm making a definition, chemical energy is a potential energy of this bonding which exists between these atoms. Again potential energy for instance of the object relative to the earth is dependent on the gravity and the distance and the masses. Now same thing between the atoms they are related through these forces, electromagnetic forces. So it's electromagnetic field somewhere is acting and relative to this field relative to their action to each other they have potential energy. Now if we break some bond between the atoms basically destroying the molecule as it was created then we can actually release certain amount of energy. This potential energy will become kinetic energy of something or heat or something some other type of energy obviously. So again the definition is that chemical energy is a potential energy of the atoms in the molecule which are somehow related to each other using the atomic bonds. So how can we basically release this energy? Well this is the mechanism of chemical reactions. So that's why this lecture is about atoms and chemical reactions. So what is a chemical reaction? It's a reaction which basically arranges atoms in certain molecules to create some other configuration of atoms which means some other molecules. So again we have this type of hierarchy if you wish. Mechanical energy is objects, heat is related to molecule movement, molecular movement inside the objects and the chemical energy is related to atoms within the molecules. And the chemical reaction is basically rearranging the atoms in as much as the heating heat transfer mechanism is basically transferring of the movements of different molecules or mechanical energy is basically related to movements of the objects. So this is all hierarchically object, molecule, atom. Now there is something deeper like electrons for instance within the atoms or protons or neutrons etc but that's not subject of this particular lecture we will address this issue some other way. But anyway there is a hierarchy we are going from the macro world to the micro world which exists on every level. So the chemical energy is the energy on the level of atoms as they are combined into the molecules. We don't go deeper into the atom yet right? Okay, so I covered this I covered this. By the way all the atoms I was talking about 100 plus different atoms they are arranged into some kind of a periodic table which Dmitry Mendeleev the Russian scientist was the first one who actually came up with this. He positioned these elements according to certain principles in this so called periodic table and it explains in some way certain qualities of certain elements of this table some of them behave more or less similarly because they are related to each other in some particular property of their characteristics whatever. Now the molecules are made of atoms. Now how they are made? Well, there are very simple molecules which contain only one atom. Example iron. The symbol is Fe iron. So the one atom of iron constitutes one molecule basically that's basically what it is. One molecule consists of one atom that's it. Now there are some other cases for instance oxygen the letter is O this is a symbol oxygen but we use this O2Y because the molecule of oxygen contains two atoms of oxygen. Same thing let's say hydrogen hydrogen is H2 hydrogen. Now in this case we have one molecule in this case in this case we have two similar atoms within one molecule. Now there are other chemical compounds for instance we can have carbon dioxide which is CO2C for carbon over oxygen and 2 for 2 oxygens. So it's one atom of carbon and two atoms of oxygen combined together make up the carbon dioxide. So we're not talking about why they are connected to each other but there are some bonds right now. Let's just stop here. There are bonds which are actually combining these atoms together of electromagnetic kind bonds and that's why we have chemical energy because these bonds have some potential energies like electromagnetic field inside the molecule and these are relatively simple molecules. There are more complicated molecules for instance well actually one of the most complicated molecules is molecule of protein I mean some protein there are different kinds of proteins but they are all very very complex and the number of proteins within one molecule of protein somewhere on the order of half a million so you mentioned one atom two atoms three atoms half a million atoms inside one molecule and they are all connected to each other inside this molecule all these half a million atoms alright. Okay next I think I would like to exemplify how exactly our chemical energy can be released from the molecule so we're talking about rare ranging chemical reaction is a rare ranging of atoms so there is one set of molecules let's call it original molecules somehow mix them together or whatever it is and as a result of this we have another set of molecules and that other set of molecules obviously has different total potential energy of the elements these molecules are created from so there is some kind of a difference between original set of molecules and the potential energy of the bonds inside them and there is a final after the chemical reaction set of molecules which are basically transformed atoms are rearranged and the total potential energy of the atomic bonds may be different from this one so if this one the final one is greater than this one it means we need extra energy to convert this into this if the other way around if my final molecules have all together have less energy than original then we will have certain amount of energy released and that's actually how we get the energy from certain sources for instance right so let's just consider a very simple case case of coal burning coal contains carbon that's the element of the periodic system periodic table of Mendeley and what happens if we will start heating it let's say put some kind of a flame under it now the carbon will start the coal will start burning actually right if it's a real coal or whatever it will start burning it's the carbon inside which is the most important component of the coal it will start burning now what is burning actually well here is what happens there is oxygen in the atmosphere and whenever we are heating the coal well putting some kind of flame underneath the chemical reaction starts and the chemical reaction is this one so if before this was a separate element and this was a separate element now these two one molecule of carbon and one molecule of oxygen are combined together and they form a new molecule now let's think about just logically speaking we can compare amount of energy here and here and what happens actually is the following this amount of energy here is less than some of these two chemical energy and that's why it's supposed to release energy and yes indeed whenever the coal burns it release the energy the heat, the light and all that the only thing is in the very beginning we have to apply certain amount of energy to start chemical reaction as soon as it starts it produces its own heat and light and whatever and subsequently it feeds itself so the amount of heat which is produced by initial reaction is sufficient to have the next step and the next step and the next step and obviously whenever we are for instance using some kind of a fireplace or whatever that's exactly what happens what happens in the fireplace alright now so this is one molecule of carbon and one molecule of oxygen combined together make this one now there is a terminology endothermic and exothermic reaction so endothermic is consuming heat exothermic is releasing the heat so in the beginning this reaction is endothermic just to start it but then as soon as we started it actually releases so much heat that it's enough to not only to continue the process of burning but also release into outside world heat and light now let's consider a different case now you all heard about the water being H2O what it means is that one atom of oxygen is connected to two atoms of hydrogen now what if we will mix hydrogen and oxygen well if we will put the plus here we will have a disbalance right because you have three atoms here and four atoms here because the molecule of hydrogen contains two atoms and the molecule of oxygen has two items how can I make this equation correct I have to put two here and two here and what happens now I have four atoms of oxygen of hydrogen and two atoms of oxygen and we have three times two six atoms four atoms of hydrogen and two atoms of oxygen now this is correct now how can we make it happen well again apply some initial heat you have to light it up and if you have a proper mixture like for every two molecules of hydrogen you have one molecule of oxygen you will mix them in some kind of a reservoir and light it up then it will be like a little explosion maybe but it all depends how we do it but for instance it's a little explosion and as a result you will have just the water and obviously the sound maybe etc etc and maybe some light also by the way this is the principle on which there are some cars which are working on hydrogen on liquid hydrogen actually if I'm not mistaken but anyway that's the reason actually they supply oxygen from the air and they start this reaction they light it up and then the reaction starts and it will produce certain amount of heat and other types of energy which moves the car alright so these are two very very simple examples now let me just talk about very very complicated example of chemical reaction which also by the way this is also in the beginning it's endothermic and at the end I mean not at the end whenever we start the reaction it starts to be exothermic so first you have to consume certain amount of energy to start the reaction and then it produces enough energy to feed itself alright so the complicated much more complicated way of chemical reaction is photosynthesis now photosynthesis is basically the process to decide the plants how they grow why do they grow well they have a very complicated mechanism of basically extracting the needed material from whatever is available now what's available air is available and from the air they take CO2 why is it important because they need carbon to build their cells from water they are getting hydrogen because hydrogen is also very very important for organic objects like trees for instance a lot of C's a lot of H's a lot of connected between themselves carbon and hydrogen atoms participated in all the molecules which are inside the cells of the plants and oxygen as well so but these are major components plus there are some other obviously they take from the soil some other minerals or whatever but these are two very very important and they are using carbon and hydrogen to build their cells and what happens by the way in between actually they there are something some material which they are building and there is an extra oxygen which they basically release back into the atmosphere so that's exactly why we need the plants to replenish the oxygen which we are all consuming so the more plants we have the more CO2 which we are producing as a result of our functionality will be consumed by these plants and instead they will release the oxygen and meanwhile they will grow obviously so that's what this component is but this is again this is a very complicated process which I don't think we can actually reproduce just by ourselves in a laboratory I mean the plants are doing this but the way how these reactions are actually happening I don't think we can do it right now maybe I'm mistaken alright so what's next let me just check yes another example okay another example is the batteries now what is the battery it's also chemical reaction but actually it's even a little bit more than chemical it's also reaction inside the atoms now I was telling in the beginning that I'm not going to go inside the atoms but in this particular case for the case of a battery we do need it because it's not only chemical but it's also electromagnetic kind of reaction and here is what happens inside the battery the battery has something which is called a node something which is called cathode and something inside which is electrolyte electrolyte some substance now there are different kinds of batteries there are different kinds of material used for a node and cathode and electrolyte but the whole story is that there is a chemical reaction between a node and electrolyte as a result of which there are certain changes chemical changes in the a node and electrolyte and some electrons actually are going from the a node to electrodes to electrolytes then another chemical reaction between this and this and these electrons are going to here so there is a rearrangement so now there are chemical reaction as well because the original material can change whatever it's made of but in any case the result of this and again we are going a little bit deeper than atom inside the atom are electrons which are basically carrying the negative charge and these electrons are moving from here to here through the electrolyte using two chemical reactions which are happening here and then since this is done we have an excess of electrons here and less electrons than neutral here so this is negative this is positive becomes and basically the electricity can actually go if you will close the loop with a wire then electrons will go back here because there is a there is less electrons than neutral and this is more electrons than neutral so electrons will go this way now as a summary chemical reaction is a reaction which is rearranging atoms in the molecules now during this reaction we have certain original molecules and certain final result of reaction final molecules and their energy their chemical energy which is inside them which is a potential energy of the inter-atomic bonds can be different and depending on this different reaction should either consume more energy or release energy and in cases which we are more interested in we are releasing energy for instance for our existence now we humans we are consuming food and somehow the chemical reactions inside our body is changing the composition the atomic composition of the food converting into whatever it converts into but what's important is that during this chemical reaction we have energy produced and that's why we actually exist that's the source of life actually these chemical reactions are the source of life because they are allowing to basically to extract the energy the chemical energy from the food which we are eating which is a very very complicated process much more complicated than coal burning but somehow we still call it burning but that doesn't really reflect all the complexity of this mechanism ok so it was kind of an introductory lecture about what is exactly chemical energy and I'll probably do another lecture which will be about some kind of quantitative characteristics which chemical reactions are exothermic which endothermic etc for a couple of examples and probably that's it because again the more detailed study of the chemical reactions is definitely belongs to the course of chemistry ok that's it thanks very much and good luck