 Department of Mechanical Engineering, Vulture Institute of Technology, Solopur. We are going to study in this series thermodynamics fundamentals in detail. In the first video, which deals with concepts of thermodynamics, we are going to discuss and try to understand the thermodynamics fundamentals in detail. Now, before we start any say module, we must know what is the outcome of it. So, let us see. When you complete this video, you will be able to define the system and surroundings, identify thermodynamic properties and you will be able to explain quasi-static process. Now, the important thing is, these things appear to be trivial, but in thermodynamics, they play a very important role. Now, first of all, what is system and what is surroundings? So, if I ask you, what is system? Now, generally, anything that is under consideration or on which we put our focus is the system. Now, this is a very vague concept and if I ask you, suppose there is a one bottle, it is closed by a cap and say, suppose there is water inside and if I ask you what is the system, then a novice will be not in a position to tell in detail exactly what the system is. For that, we must know what is the system. You know that in water, if you take, I have to define it. If I take air here, I have to define it. If I take atmosphere, I have to define it means any quantity of matter or subject under focus must be explained with the help of certain parameters. Now, if I ask you, how will define this particular say water condition? So, some may say that it has got certain pressure. Some may say it has got some temperature. Some may say it has got number of moles. Some may say that it has got certain amount of enthalpy. Some say it may have energy. Some say it may have availability or some may say that it has got some Gibbs energy. Then, if you see, it has got definite volume also. So, these are the 1, 2, 3, 4, 5, 6, 7, 8. These are the parameters by which we can define a system. Now, the question is, if I am focusing on water itself, then water is my control volume. Means, any change in the water I am interested in. In that situation, I am not bothered about what is happening to the air. But if water is a system, then I have to confine my focus only on this part. If air is a system, I have to say that air has got some pressure, some temperature, some mole, some internal energy and so many parameters. Now, the first thing is, this is not sufficient to understand. The system must interact. Now, the system must interact with the surrounding. So, this system may give energy. This may get work heat. This may get some work or this may produce some amount of work. So, either it will be Q given in or out. W given in or out. So, by this, you will find that the concept of system is very flexible. If I say there is a block, that is a metal block and if it is to be defined, how I define? I give it the dimensions. Then by the dimensions, I mean length, volume, length, breadth and height and dimensions are fixed. It is a solid. I may give its density. I may give its temperature. The system is well defined. If I supply heat to it, then it will change the dimensions. There is some volume strain. There is some compressibility. If the some motion is constrained, suppose I am constraining this motion. So, I can define system in variety of ways. Say for example, if I say consider a piston and cylinder assembly, there is a gas inside and if gas is my focus, then if I heat it, the piston will move to the right side. If I compress it, gas will be heated. So, by this, it is clear to you that system is a well defined thermodynamic quantity, parameter or say entity. Now, it is interacting with the surrounding and surrounding is not a vague concept. Many students have a problem that they say that anything of say excluding the system is surrounding. It is not like that because if I say that surrounding is something vague, then I am not in a position to find out what changes have taken place in the surrounding because surrounding itself is a well defined system. So, the correct thermodynamic representation of a system is this is one my system and this is the surrounding. So, between system and surrounding, there is heat and work interaction. So, either Q or heat, sorry work will be transferred and you know that we are studying in detail also in say Q and W, the sign conventions. If heat is supplied, if Q is supplied to the system, we take it as positive. If it is rejected by the system, we consider it as negative and very important thing that is work done by the system is positive. This is very important and on the system is negative. Now, you may wonder in chemistry, it is exactly opposite. In chemistry, work done by the system is negative and work done on the system is positive because there are our criteria is different. In chemistry, we have to find out how fast the reaction will take place and in the reaction process exactly say which parameter will help the rate of reaction. Now, you know that if I supply heat to the particular chemical, heat rate of reaction will be more. Again, if I do some work on the chemical substances, there will be more amount of say completion chances and because of this, we say that work done on the system is positive in chemistry, but in physics and engineering, we have to be very particular about it. So, you have learned one thing, system and surrounding are two well defined systems. Surrounding is also a system, though it is not appearing like a system. Say for example, suppose this bottle, this bottle which I have kept here, if I kept in a small container. So, for this bottle, this itself container is a surrounding, but if I say that this container itself is kept in a big room, then for this container as a system, this entire room is a surrounding. So, everywhere surrounding and system are always defined in relation to each other. This is the first part. Second thing is work and heat transfers that we have talked about. So, these work and heat transfers are very important concepts in thermodynamics. In the sense, both are energy transfers. So, Q and W both are energy in transient. Now, what is the meaning of energy in transient? I will give a simple analogy. Suppose, there is a cloud, what is this? This is a cloud in which there are water droplets. So, these are water droplets and these water droplets are in the cloud and there is one observer here. He is looking at the sky and by visualization, he sees that this particular cloud contains water. Now, my question is do we say that cloud contains rain? No, because when the water droplet falls, when they get a liquid temperature, then only it becomes rain. Means rain is water in transit. It has caused the boundary of the cloud. So, Q and W are energy in transit. So, whenever they cross the boundary, it is called as work or heat. Take a simple example. Suppose, this is a container in which there are number of molecules. I isolate this particular container, say chamber and this molecule is striking, this molecule, this is striking, this molecule, this is striking, this multi molecule because of this and the molecule is going here. But these are the transfers taking place inside and there is no external force acting. So, because of this, what happens? The work is not crossing the boundary and when work is not crossing the boundary, that is, it is cannot be called as a thermodynamic work. That is, the first thing that you must know as a basic learner. Again, there is some confusion. Suppose, I take this as a insulator system and say there is water inside or gas. If I put electric heater here, if I put electric heater here and if I ask you what I am transferring work or heat. Many students know that they have seen the geyser. They say that we are transferring heat, but it is wrong. It is not heat transfer. It is wrong. It is a work transfer because we are flowing current through the resistance and whenever anything goes through the resistance, it performs certain work. So, whenever there is a resistance to something, there is scope for work. Another simple example, you know, suppose I have two chambers and some membrane here. Here is some gas and here is some vacuum and this is insulated. Now, what happens when I puncture this, then automatically I get the gas moving from this to this system. So, because of this, there is no work done because there is no resistance to it. Now, you know that we can define the systems in very briefly as open system, closed system and isolated system. In open system, mass and energy both are allowed to transfer. In closed system, only energy is allowed and isolated mass and energy both are not allowed. Isolated system, classic example is your thermos flask. Open systems are normal open systems that we have and closed systems are very typical systems. When we allow only the energy transfer, not the work transfers. So, by this, it is clear to you that how the systems are classified, what is the property, how we define energy and how we differentiate between heat and work, their energy is in transit. We are studying in that in detail in our next slide when we go for calculation of work done for various processes. But before that, it must be clear to you that work and energy we define as the phenomenon in transit and work transfer is because of the parameters other than heat and heat transfer is a parameter only because of temperature difference. So, for this, I ask a simple question. Say, if there is a balloon, what is the boundary and whether it is fixed or flexible, think over it. Now, if you want to refer, you can refer thermodynamics by Nog and Sengel, Nog and thermodynamics by Yunus Sengel. So, thank you for this particular session.