 Hello, my name is Arunabh Dutta and I am an assistant professor in chemistry department. And today we are going to discuss about thermodynamics, its basic concepts, fundamentals and applications. So let's begin with thermodynamics. So when we talk about thermodynamics and we look into this particular term, we found there are two important terms come together. One is thermo which means heat and one is dynamics that means movement. So this thermodynamics basically covers the study of flow of heat, a system and a surrounding and discuss how the system is actually exchanging heat around it and how a physical and chemical change can affect this particular system. So all together over here we are mostly following the physical and chemical change in the form of heat exchange between a system and a surrounding. And that is not only the heat, there are two important properties of the system and surrounding also come into the foray and they are energy and work. So now we have three different properties energy, heat, work they all come together and these properties are actually going to follow by certain quantifiable parameters that can give us an idea how these three parameters energy, work and heat are actually exchanging. And those parameters are actually going to change. And the change of the system we actually followed that with these quantifiable parameters and those are parameters like temperature, pressure, volume and even concentration of a system. So over here we are going to look into a change happening in a system when it is in a particular surrounding and those change are actually initiated by the physical and chemical change and those are actually changing the very basic properties of a system in the form of energy, work and heat and we can quantify them with this particular parameters. And all this study we are doing this that is known as the study of thermodynamics. So to give you an example what kind of system we are actually talking about. So how this thermodynamics is actually playing the role to give you an example we take the example of a system where the fuel is actually burning. So in this system we put some fuel we burn it and we create some heat and that heat is generated by the system. Now how much heat is generated? How much is actually the fuel is burning? So all this calculation we can quantify with the help of thermodynamics. Now say we have the heat and over there this heat is actually run through an engine which can transfer that heat into the form of a work. Now how much of this heat can we get transform into the work, how much it is getting lost into the mechanical force to run the engine that again we can calculate with the help of thermodynamics. Now imagine a second example of chemical reaction. During a chemical reaction it is a redox reaction or reduction oxidation reaction where an electron is actually getting exchanged. And this electron exchange can initiate a flow of the electron which is also known as electricity. Now how much electricity we are generating through this chemical reaction that also can come under the purview of thermodynamics. So thermodynamics can help us understand how a physical or chemical reaction is actually helping us to get in the different form of energy and how much we can actually transfer that into the form of a work. So that is the basic background of thermodynamics. Now to understand thermodynamics we need to understand some of the basic concepts of thermodynamics. So we will go through the basic concepts one by one. So let us start the first thing we actually think about and that is known as the thermodynamic system. So when we call about a thermodynamic system we are actually basically talk about two things a system and a surrounding. Now imagine that we are actually interested in one of the physical or chemical changes into a particular matter. And the region or space that we are interested in is actually known as the system. So for an example in this particular scenario we are actually very much interested what is happening in this particular region. So that will be the system. So whatever we are calculating whatever we are measuring all the parameters all the factors all the properties energy work or heat we are measuring with respect to this particularly confined region and that is known as the system. Now if we look into the system the rest of it the rest of the universe around it is known as the surrounding. So what is the basic difference between system and surrounding? System is the region or confined space that we are interested in where all the changes are happening. Now the changes are also getting exchanged with the other thing everything present around that system and that is known as the surrounding that is nothing but everything other than the system. Now how the system and surrounding are separated? They are separated by this particular boundary. So this is known as the boundary which actually separates the system and surrounding. So again if we want to recap there are 3 important factors one is the system one is the surrounding and the thing which is separating both system and surrounding it is known as boundary. Now depending how this system and surrounding are interacting through the boundary we can define system in 3 different factors let us take a look into them. So we can define system in 3 different ways the first one is known as a open system. Now what is an open system? An open system is such that we have a particular system present over here and that is the surrounding around it. So again this is the system and this is the surrounding. Now we have such a boundary that allows exchange of energy in between the system and surrounding and not only that it also allows the exchange of matter in the form of gas, liquid or solid if both of them are actually allowed then we call this particular system an open system. To give you an example say I have a glass of water and over there I put some hot water here. Over here the glass containing the water is my system and everything else is my surrounding and now what happens some of the water because if it is hot it can vaporized. So over there it is not only exchange energy in the form of heat but it is also exchanging some of the water molecules goes from the liquid state to the vapor state and escapes the glass or system. So over here the system is exchanging not only the heat but it is also exchanging the matter. So that is an example of an open system. The next one comes into the picture is known as a closed system. What is a closed system? A closed system is again a system we are considering which is surrounded by the again the surrounding. So this is my surrounding and this is my system. So over here system and surrounding are very much same as the open system we discussed earlier. Now what is the big difference over here? The boundary is such that it is still allowing the exchange of energy it is still allowed. However the matter exchange is now stopped. So the matter cannot come out of the system anymore. So that will be defined as a closed system where the energy can be exchanged but not the matter and that is known as a closed system. So what could be a good example of that? So example can be given with the help of a piston. So say this is actually a system where we have some gas and over there we put a piston on the top of that. Now if I decided to bring the piston down to do that I am actually doing some work and changing the energy. So the change there is a change in the energy between the system and surrounding. But the gas present in this system that cannot escape out that cannot escape. So over here this is a direct exchange of energy is possible between the system and the surrounding but not the matter. So that is actually known as a closed system. Now come to the next version. When we talk about a isolated system, what is an isolated system? Again we have a particular region that we are interested what is happening over there that means the system. And here is the surrounding and over here what is the difference is now even energy cannot come out of the system anymore. And the mass is also confined in the system it cannot come out of the system. So there is no direct exchange of neither energy nor mass between the system and surrounding and that is known as an isolated system. One of the good example would be again say I have a hot water but now I put that in a thermal flask. So thermal flask is such a way that it is closely system closely system which actually not allowing any of the water to escape the system compared to an open glass where the water evaporates out over here the water cannot evaporate. So this particular system is not allowing any mass transfer and also it has such a boundary that it is not even allowing the heat to pass out of the system. So there is no exchange of energy either. So thermal flask can be considered as an example of an isolated system which not allowing any transfer of energy or it is not allowing any transfer of the mass. So these are the three different system we can think about again to just put it together. So we have surrounding we have system we have boundary which is separating them and depending on the nature of them we can define their three different system possible open system close system and isolated system. And what is actually happening we define it whether it can exchange mass whether it can exchange energy or not. In an open system both of them are actually allowed. In a closed system energy exchange is allowed mass is not and in an isolated system neither mass nor energy is allowed to exchange. So that is the three different variants of system we can think about with the help of different qualities of the boundaries. Now we will go to the next section and we will discuss about three important thermodynamic properties. Those properties which will help us to understand the system properly. So what are those properties we are actually thinking about. So there are three different thermodynamic properties it comes to our mind. First is work. So what is the definition of a work? So if we go to the basic physics the definition of a work is the following. When an object can be moved against an opposing force we say that work is actually done. So that is the definition of a work when we actually doing or moving some object such a way that it is going against an opposing force. For an example very simple system is that we have a particular mass present on the ground floor and then we are lifting the mass up. Over here we are doing a work because over here we are working against the gravity because gravity wants to make sure that it stays on the ground level but when we are working it and moving it up we are working against the gravity. That is the opposing force over here and we can say a work has been done. Now to understand the thermodynamics we will take an example of a gas cylinder which is actually connected with a piston. So this gas cylinder is actually bound with a piston over here and here I have some gas. Now say I want to push this piston down, I am pushing this piston down and I am going to this particular state where I actually bringing it down. So I am working against the force because the gas molecules they are actually at a particular density. Now I am pushing them to bring it closer. So to do that I am acting as the natural force where the gas molecule wants to be as far as possible. So doing that I am doing an actually work. So over here I am doing this work on the system. So this is a definition of a work and we can explain that with the help of a gas cylinder bound with a piston. If we are moving it down I am actually doing a work. Now if I move that up so then I am actually making a work done by the system because the system wants to release it back. So the gas is actually going to again going back to the older condition where they are actually well separated and for that that will push the piston against. So now the gas molecules are actually doing a work against the force of the piston. So that is we can also define as a work actually being done. Now going to the next part. The second parameter we are going to discuss is going to be known as energy. Now what is energy? Energy of a system is defined by the capacity of doing a work. That means if we just imagine that we say that there is some energy present in a system what we mean that energy can be utilized to do some work by that particular system. How to explain it properly? So let us come to this particular picture again. Say I have again this particular gas cylinder, we have some gas and here is the piston present there and that is in situation A. Now from there I am going to a different situation where I am actually pushing the piston down. So I am actually doing some work against that gas. But what happens over there? Previously in the system A the gas molecules are present over here. They can push the piston up but if I compare that system with the new system say it is system B which has more tendency to push the piston back. Previously it was A now it is B. So which one has more propensity to push the piston back? It will be B because now the gas molecules are much more closer and they want to relax back where they can easily move the piston out. So over there if we compare A and B because of the molecular properties of the gas molecules it has more tendency to push the piston out and that we can explain in the following way that B has more tendency or more capacity to do and work. So we can say B has higher capacity now compared to A and that we define that B has now more energy again compared to A. Now say different scenario where with the same gas cylinder we are still playing with but now we are moving the piston up and go to a system C. So over here previously the piston was somewhere around here and now we have moved that up with respect to B we actually move it down in the beginning the piston now we are moving the piston up. So now in the case of C the gas has more volume to play with. Now if we compare A and C where we have more tendency to move the piston out because C already is getting more space that has less tendency to move the piston out. So we can say it has less capacity to do work compared to A. So we can say it has again less energy to system again in comparison to A. So over here you can see that work and energy are actually correlated. One system it can do more work we can say it has more energy and if we say a system which has less capacity to do a work we can say it has less energy. So that is the definition of an energy which can define in the form of a work. Now we go to the third important property of a system and that is known as heat. If we look into a heat, heat is such an energetic system which can also not only change the energy but also affect the capacity of doing a work in a system. So how we can explain? So heat we can also explain with the same gas cylinder system which is connected to a piston. So now see this is actually the system A I am talking about and over here I am not doing any work or not moving the piston at this moment. But what I am actually doing over here I am adding some heat to the system. So I am heating the molecules together. So over here what happens the same piston is in the same place. I am going to a condition B where I have now heated the system and the heat where it is going from it is going from the surrounding to the system. So there is a direct heat exchange from the surrounding and it is going towards the system and this particular system how it is affected. So now imagine over here in system A the gas molecules have a tendency to move the piston out. What happens now if I added some heat over there. Now gas molecules are more energetic because with the heat it directly affects its movement. Now it is moving way too faster than it is doing compared to its position in A. So over there in step B the molecules are going to have more energy and that will reflect with respect to their propensity or capacity to move the piston out. So over here they will have more capacity for work and that can be reflected we can say it has more energy compared to A. Now say I am doing that in a different way and I am moving the heat out of the system. What happens if I move the heat out of the system. So where I am taking the heat out I am taking the heat out from the system to the surrounding. Now the surrounding is accepting heat from the system and by that it is cooling down say in this system C. So when it cools down what happens the gas molecules the movement is going to slow down because I am extracting the energy out of it in the form of heat. And if that is happening what will be the propensity of it to move the piston up it will be comparatively very low with respect to A. So we can say actually when the heat is actually move out of the system to surrounding it is actually have less capacity to do a work and that means the overall energy of it it actually goes down in compare in form C with respect to A. So now you can see the heat is also connected directly in work and energy and if we want to put all these things together with respect to energy system or propensity to do a work we can say C has the highest propensity or energy to do work then it is the A then it is the B and you can see it is directly correlated with respect to how much heat it has. So all together so far in this first segment we discussed about the three important properties the heat work and the energy and at the same time we also talk about how a system can be defined how it is interacting with the surrounding with the respect to the boundary and they are the open system, the closed system and the isolated system. Over here we will conclude the first segment where we actually now got to know about the heat, energy and work how they are correlated and how it bring ups to the first law of thermodynamics we will look into that in the next segment thank you.