 I have called it basic ideas and definitions for the simple reason that thermodynamics fortunately or unfortunately uses a number of terms which are common to not only thermodynamics but to many other subjects. Thermodynamics is a part of science and part of engineering so does not you know divorce from other branches of science and engineering and soon we will see that thermodynamics works with those branches of science and engineering. So in fluid mechanics we talk of pressure, velocity we use those ideas in thermodynamics but there are many ideas which are common to thermodynamics, many terminologies which are used by thermodynamics and also by other sciences which have slightly different meanings. For example we talk about he is running a temperature when somebody is feverish. So in a household language temperature runs. In thermodynamics temperature is a property it simply exists it can be measured but it cannot run. It is a school kidish question which moves faster heat or cold and the answer from a school kid's point of view is heat because you can catch a cold you cannot catch heat. So ideas of temperature particularly the idea of work, the work interaction or work which we talk of thermodynamics and it is one of the first topics which is discussed is common between thermodynamics fluid mechanics many branches of physics there is mechanical work there is electrical work in chemistry there is chemical work, electrochemical work, photochemical work and all that. So the ideas of work there and ideas of work in thermodynamics are they the same they may they may not be but we need to be very precise in our definition of work. Similarly some ideas from other branches of science we will simply adopt saying this is the idea this is the definition these are the characteristics or properties of that idea we will use it. So it is necessary for students to say that look we will redefine everything whatever you have learnt is true but may not be the whole truth may not be nothing but the truth. So we will straighten that out so ask them to be patient and then we first come to these things primitives, premises and derivations. So we should be clear about these ideas what are primitive what is a primitive how many of you are interested in or enjoyed school geometry Euclidean geometry nobody only one hand, two hand I still enjoy you know after every March, April I look at the ten standard books the geometry problems are the most enjoyable. Now all of you know those who have take interest in Euclidean geometry know that Euclidean geometry is based on Euclid's five postulates okay those postulates are something which are to be true those are the primitives the idea of a point is not defined in geometry it is a primitive. We know what its characteristic are it has a position but it has no extent otherwise except the position. So something an idea which is inherited is a primitive. So in thermodynamics ideas, concepts, definitions from other branches of science, engineering these are known as primitives we will adopt them as they are for example all ideas from mechanics so volume, stress, position these are primitives. So example it is good always whenever you talk of something to one or two sentences of thermodynamic talk possibly followed by an example keep them always illustrated with illustrations for example you take a position displacement from mechanics you can take volume from geometry you take pressure velocity from fluid mechanics you take mass force from mechanics the list is endless you take charge current from electricity magnetism magnetic induction magnetic flux from magnetism thermodynamics does not isolate itself from any other branch of physics if there is a good idea has something to do with energy directly or indirectly we will use it in thermodynamics that is a primitive. Primitive means we will not tell much about it velocity talk to a mechanics person or a fluid mechanics person the ideas which are useful there are simply adopted here. So everything from geometry everything from electricity magnetism everything from mechanics is adopted in thermodynamics and all those ideas are primitive we build on them. So somebody ask you to define pressure in thermodynamics they say nothing whatever you have learnt in fluid dynamics as pressure is applicable in thermodynamics of pressure. Now for example non-primitives non-primitives are proper thermodynamic which we will formally define in thermodynamics if you really go to the bottom of it there are only two things which we will define very formally and very properly in thermodynamics no other branch of science has any claim on these two properties and these two properties are the temperature T and the entropy S I am sure you will immediately take objection of few of you and before you raise your hand how many of you now want me to ask this question what about energy what about work I have not talked of them as primitives I have not talked of them as basic thermodynamic entities where do they lie they are derived no energy we had energy we have potential energy kinetic energy fluid kinetic energy and all that in fluid dynamics and mechanics we have work in mechanics we have work in fluid dynamics we have charge moving to a potential difference we have work in electromagnetic they are neither premises nor purely thermodynamics work and energy are special in the sense that they have some characteristics of premises but we will put them on proper thermodynamic basis because even before thermodynamics ideas of work existed idea of energy existed these two are on the borderline of thermodynamics and other branches of physics if they were not there thermodynamics would have been an isolated science it is not an isolated science we will adopt definitions of work but we will have a proper definition of work in thermodynamic which is slightly different but very proper consistent definition of work in thermodynamics and hence quite a few authors and quite a few people tend to call our work as thermodynamic work then we come to the definition we will realize the way work is defined in mechanics and work in defining thermodynamics work is defined in mechanics as force into displacement Fds whereas work is defined in thermodynamics as an interaction two systems must be involved we link it with some energy interaction two systems will involve similarly in thermodynamics we claim that we have we define the global energy or the total thermodynamic energy E and then we find that other branches of physics have already defined their components of energy so we say okay this energy will have all those components so long as we do not do anything inconsistent we are on firm ground so remember that primitives are something which are purely defined and adopted by thermodynamics adopt defined in other branches of science and adopted in thermodynamics thermodynamic entities are those which are very properly defined in thermodynamics and only in thermodynamics and there are only two basic thermodynamic entities temperature and entropy and there are two special entities the work interaction and energy which are persona grata in thermodynamics as well as other branches of physics so we will redefine work in a rather restrictive way because of that what will happen is some situation where a physicist will say so much work is done we will say where is the work interaction but something which is work in thermodynamics is definitely work in physics so we will have a restrictive thermodynamic definition of work similarly energy our energy definition will be a superset of all other energy definition and it is we claim it to be a superset because we have not come across any illustration or example of that being a superset any other branches have an energy that becomes just a component of this energy from that way thermodynamics turns out to be a overriding science does not go into detail just takes care of the energy interaction so this is about primitives and non-primitives now what are premises what is a premise it is another word for an assumption is not it if you look up a dictionary you will find a premise it is something which is assumed to be true why do not we call it an assumption just because premise is a rather uncommon word assumption is something which is a common a premise in thermodynamics it is something which is demonstrated to be a true characteristic of nature for example Einstein's fifth postulates about the parallel line is a premise the postulates of say about angles about a straight line for example one of the postulates of Euclid is that between on a plane geometry if you have two points you can draw one straight line and only one straight line between those two points that is a premise there is no proof in Euclidean geometry for it but we know it is true from our experience on a plane surface we have never been able to find two points through which we can draw two independent distinct straight lines so there are a certain number of ideas which we know as premises in thermodynamics so some of these you already know which are those laws of thermodynamics are they premises there is no proof they are assumed to be true and they are demonstrated they are not really demonstrated they are never derived we only have faith in them because we have not come across any contradictory situation somebody says demonstrate the first law of thermodynamics is it demonstrate anything I am moving from here to here that is first law of thermodynamics anything happens has to be consistent with the first law of thermodynamics it is not like demonstrate the boiling of water or demonstrate that soil to some extent is soluble in water we have not come across any situation which seems to violate those premises so how many premises do we have we are going to remain in the domain of classical thermodynamics so zeroth law first law second law but are they sufficient apparently not because it turns out that there are certain additional premises which are known as state postulates will come to those those are also premises in thermodynamics they for some reason and I do not know why they have never been given the status of a law of thermodynamics but without them we cannot proceed in thermodynamics and those generally go by the name state postulates and there is one of them which is demonstrated to be a proper premise the other one under certain assumptions of differentiability can be derived we will come to that so premises are laws and premises are always true again remember that something which is a premise in one branch of science may not be a premise in some other branch of science we are going to restrict ourselves to the classical thermodynamics so one of the premises of ours will be that all the entities that we come across pressure temperature volume energy entropy anything all our systems are continuous system they are continuous and all these properties and all these interactions anything which we are going to talk about are continuous variables there is no quantization that is one of our premises in classical thermodynamics but this would not remain a premise when you go to molecular or statistical thermodynamics so remember that one branch of science will consider something to be a premise that premise may not remain a premise when you come to some other even related branch of science this happens not only in physics it happens even in geometry for example you have Euclidean geometry remove the fixed postulate you have a whole set of non Euclidean geometry something which is a premise here will not be a premise so premises are laws which will always be true we will not derive them but we will have faith in them because there are no contradictions involved and beyond that there are only derivations in definition for example the second law of thermodynamics we will be using the Kelvin Planck statement as the basic statement that will be our premise but then the Carnot theorem will be a derivation okay the Clausius inequality will be a derivation the Clausius statement of the second law of thermodynamics will be a derivation we will use something as a premise everything else will be derivation it is possible for example in many textbooks show that a second law primary statement of the second law can either be the Kelvin Planck statement or the Clausius statement when we come to that we will decide to select one of them as a premise why not the other that we will comment that but it is in principle possible to accept Clausius statement as the premise and derive Kelvin Planck problem we will soon come to premises let us go in the order in which we have maybe I should keep this here so that I can flip back and forth so premises primitives premises derivations are all the derivations which come after our premises so first law open system will be a derivation similarly in fact even definition of entropy Clausius inequality will be a derivation because it is neither a primitive nor a premise now we are going to lay out our framework by some suitable definitions and when it comes to definitions we are going to have essentially two types of definitions the first type of definition we are going to use is short forms for example one of the famous short forms will be using is h is u plus p and when it comes to a short form definition I usually have a habit of showing with a triple lined equality meaning this is nothing but this anytime you see the left hand side you can replace it by right hand side or the right hand side by the left hand side vice versa so this could be a symbolic short form like this or it could be a verbal short form which we will soon come a large bundle of words will be reduced to two or three words for example the first law is a short form for a very big statement which we expect the students to know as the statement of the first law the second type of definition and which is going to be important for us is going to be what is known as operational definition now the question is what is operational definition the idea of operational definition was first proposed and expanded on by Paul Bridgeman the operational definition says something about the identity or the entity to be defined by providing a procedure or a sequence of operations for deciding whether that entity is something is true or false or how to measure it so operational definition of energy of a system would be a procedure as to how to measure the energy of a system operational definition of an open system would be a set of procedures to decide whether a system is open or not okay so this is a set of operations that means a procedure decide is yes or no for example open system it can be for major quantify an entity and we will come across these operational definitions throughout our course on thermodynamics everything which is measured unless it is a primitive in which case the other branch of science will tell us how to measure it even there operational definitions can be used but in thermodynamics we will be using operational definitions because of the strength of those definitions you have a procedure which anybody can follow or anybody interested enough and studios enough will be able to follow and decide whether that thing exists or not question of whether a system is an open system or not whether a process is reversible or not such things or in case of such things as temperature energy entropy things which we are going to define in thermodynamics it tells us a procedure by which these things are to be measured and one important thing for us is we are going to have no circular definitions what is a circular definition there is a book by one of the great people in computer science known as do not note he has a some book I think it is he has a set of books known as the art of computer programming go to the first volume go to the index try to find out what circular definition is now you look up under C circular definition it will say C definition circular and then you go under definition circular and it says C circular definition in fact he has given you the correct illustration of a circular definition this is neither a definition as a short form nor an operational definition but this is another type of useful definition which tells us what a circular definition is and by the way this is the perhaps the only exception where a definition can be we will understand by circular definition the circular definition but if you ask somebody where is Nagpur and you will say you know 65 kilometers northeast of Vardha where is Vardha 65 kilometers southwest of Nagpur you never know where Nagpur is in Vardha you know the relative positions this also is a circular definition now why am I saying no to circular definition and why did I spend 5 minutes signed upon slide on this I have collected your answer books today morning but I am going to return them to you soon I have not I have just browsed through but I am sure when it came to the last question on the first page and the first question on the last page what is heat and what is temperature okay and many many of you for these two together have provided a circular definition I have written the answer book to you you will find that that is true and if you think about it you will agree that many many of you have done that I do not really blame you because many many good books on thermodynamics traditionally renowned books on thermodynamics fall into the same trap defining heat in terms of temperature temperature in terms of heat in fact in 2000 and 1 or 2002 I gave a very small talk about teaching and learning in the 21st century and I gave this illustration but then when everybody started laughing about this I said this is what we learn in thermodynamics and from I will tell you which book from a book I extracted definition of temperature it says its degree of hotness without defining what it is such that heat can flow only from a higher temperature to a lower temperature then you go to heat because heat is one of the things used there oh heat is a type of energy which can flow from a system at a higher temperature to another at a lower temperature the same thing Golmal okay I have to straighten that out and we will do that because as a rule we do not want circular definition but that does not mean that we are not going to have forward references in thermodynamics unless you are a purist and want to teach it in an absolutely academic way so that half the students will simply run away even from mechanical engineering if you try only from backward to forward you cannot make much progress and illustration sooner or later we will talk about an ideal gas we will say ideal gas has two characteristics one is the equation of state is of the type PV equals RT and second one the thermal energy or thermal internal energy is a function only of temperature. Now are these two linked to each other yes they are after deriving property relations we can show that these two are consistent with each other that means if the equation of state of an of a fluid is PV equals RT its thermal internal energy should not be a function of any variable other than temperature that means if temperature is fixed it cannot vary with pressure temperature is fixed it cannot vary with volume this you have to tell the student because sir why is it independent of temperature we have to say that we derive it when we do property relation that is a forward link but this does not lead to circular definition because this is some information which we are going to demonstrate later being used in advance as an illustration or as a convenience. We are not going to derive any thermodynamic principle out of the ideal gas law so that way we do not fall into the trap of a circular definition. So now let us come to the first definition we have said thermodynamics at something to do with energy in particular we are going to look at the way how energy is transferred and in what form the forms of or modes of transfer the moment you talk of transfer there is going to be a recipient there is going to be a donor there is going to be something from something to it is a transaction it is a given take consequently we have to be very clear about what gives and what takes and that brings us to the first definition of a system or a thermodynamic system at this stage we should tell our student that the word system is a very general word you have social systems, you have systems of equations, you have economic systems, you have managerial systems, you have system thermodynamic systems what not planetary systems okay the system is a very common word and hence in thermodynamics what we define is a thermodynamic system however if we start using this thermodynamic system all our thermodynamics books will be 2, 3 millimeters thicker instead of 2 hours to write an exam we will need 2 hours 10 minutes. So in thermodynamic the word or the adjective thermodynamic is often dropped so in this course in this subject when we say system unless I say anything else it will be assumed to be thermodynamic system so when I define a system I will be defining a thermodynamic system you tell them that because in thermodynamics there are many, many adjectives even in heat transfer you talk of emissivity now by default we say when you say emissivity it is total hemispherical emissivity but we know that if we do not talk of total it is total unless we talk something else similarly unless we talk of angular it is hemispherical integrated over the hemisphere similarly when we talk of system it is going to be a thermodynamic system. If you are a purist you should not try system you should always write thermodynamic system that will unnecessarily heat up ink paper and time and our patients so thermodynamics whatever I have shown there in square bracket will be the default prefix. Now what is a thermodynamic system I think many of you have one of the questions was the first question right what is a thermodynamic system well thermodynamic system many of you I suppose have done more or less this is nothing but our reference point it is a region of space of our interest and something that we are going to study that is not the complete definition we are going to study energy transfer from that system to some other system. So for us defined boundaries are important any region of space with properly defined boundaries of course in which we are interested only then we will define all those boundaries. Make the students understand that unless the boundaries are defined we have not defined the thermodynamics. So sometimes we will say let us consider one thermodynamic system what are the boundaries with these defined boundaries. At this stage the student usually has a habit of a boundary means boundary of a polygon boundary of a sphere surface of a sphere all these things are real boundaries which you can draw we can show we can sometimes touch but in thermodynamics those boundaries can be imaginary. A good illustration is well this is a room all internal surfaces are room are the boundaries yes that is a thermodynamic system I myself as a human being my skin wherever it is that is a boundary I am a thermodynamic system this bottle of water I can say only the water inside with wherever its boundaries are that is a thermodynamic system then somebody will say sir the boundary is flexible it is moving you said so what but at any instant of time the boundary is defined that is good enough for us it may change shape it may even break into two if I pour it from one bottle to another but at every instant of time I know where the boundaries are you could even have defined but unphysical boundary for example assume there is nothing on top of this but I want to study the movement of air I say consider a rectangular parallel prepared type of a box whose bottom surface is the roof of this outer surface of this roof say flat then extend the four sides by three meters and imagine a top surface four side extended are also imaginary you can show it in a drawing with dotted lines but no surface exist is that a thermodynamic system yes it is a thermodynamic system we have defined the boundaries the boundaries may be physical I can touch it if it is safe to touch them the boundaries may be purely defined you can have all imaginary boundaries for example I can say here consider a sphere of diameter 20 centimeters with this as the center you do not see anything but you can imagine that as a thermodynamic system in solid mechanics fluid mechanics heat transfer quite often to derive the governing equation we take a small system data x data y data z rectangular parallel that is imaginary boundary those boundaries is something we have drawn there is do not exist in the fluid but we derive continuity equation momentum equation and all equations such illustrations you should give to the student so one thing you should emphasize is this and that also means that any thermodynamic system at any time will have its volume defined will come to this characteristic again the moment we define a thermodynamic system whether we want it or not its volume is defined that is something which should be clear to the students so it is not anything abstract and one of the words which is used in thermodynamics in a thermodynamic way but is used in other branches of science in an entirely different way is the world universe I think you would have come across determine the entropy change of the universe quite often in your exercises that is a thermodynamic universe the universe used by astronomers and cosmologists is the physical universe for astronomical universe now is the astronomical universe a thermodynamic system yes or no no there are some yeses some no no very emphatic no why I am not talking of earth I am talking of the astronomical universe is it defined I say my thermodynamic system is the astronomical universe which all these astronomers and cosmologists and Stephen Hawking have been talking about is it a thermodynamic system we are unable to define what the boundaries are because the moment you define a boundary the question arises what is on this side of the boundary what is on the other side of the boundary they have not yet decided whether the universe is bounded or unbounded so where is the question of a boundary so that means the cosmological universe of the astronomers universe is not a thermodynamic system we cannot consider it as take for example the astronomical universe as a thermodynamic system wrong not possible and because of this remember immediate consequence of this all the laws that we talk about of thermodynamics are not applicable directly to the astronomical universe so in our thermodynamic universe we will say the entropy of any thermodynamic universe can only increase or remain constant it can never decrease and generally because all processes in real life are reversible the entropy of any thermodynamic universe will always be increasing during a process you cannot apply this to cosmological universe in this entropy of the universe is increasing but only in thermodynamics not in cosmology it may be increasing it may not be increasing but we cannot say anything about it ok make this clear because students those who are interested in physics would have learnt about the cosmological universe big bang theory something and this question is likely to come up so our discussion on that should be that universe is not a thermodynamic system because the boundaries cannot be defined ok is that clear that is the first emphatic point you should make in thermodynamics in thermodynamics in cosmology if you say universe is our system what is the surrounding what is the boundary astronomers do not yet have an answer to that so the astronomers universe is not our thermodynamic you are right thermodynamic universe its system plus surrounding so long as both together form an adiabatic system since there is no boundary we do not know what is happening outside the boundary for the astronomers universe and hence we cannot determine whether it is adiabatic or not so that is a stalemate but we have to live with it ok so that bring brought me to thermodynamic systems so 2.3 then I have mentioned the importance of boundaries why are boundaries important because energy transfer will take place across a boundary and at this stage we should say the importance of boundaries we will always be looking at one system and some other system and we will be looking at what happens across the boundary this is system A and a system B and this is the boundary and as we proceed we will notice that everything of thermodynamics has to do with some such schema there will be a system A there will be a system B something will happen across the boundaries changing some something for system A changing something for system B and we will relate that to what happens across the boundaries that is why the boundary or boundaries of a system are important now just now I said that look there is a give and take so system A undergoes a change system B undergoes a change so this changes this also changes now the question is how and how much so we must notice the change and how do you notice the change here we formalize this idea by defining the state of a system that is the next topic actually the complete thing should be thermodynamic state of a thermodynamic system but I have already started deleting the objective thermodynamics by default it remains everywhere now when it comes to the state of a system we do the following the state of a system is crudely this is not a definition is the situation the system is in so what is the state of our mind when we are asleep the state of our mind is cool quiet crescent no thoughts happening that is the situation that is the state of our mind find itself in just before an examination what is the state of our mind thinking only thing about thermodynamics tensed high blood pressure may be high temperature that is the that the situation of our mind now how do we quantify what is the operational definition operational definition of the state of a system is like this we define the state of a system is defined by the following so this is the process number one a list of relevant characteristic of the system you think volume is important write it down you think mass is relevant write it down you think pressure is relevant write it down what is whatever list out now what is relevant and what is not relevant it is something which thermodynamics will not tell us that will come out of our experience for example if this water is our system water inside the bottle and maybe I am interacting it by holding it my in my warm hands it came out of the refrigerator so it was chilled my teeth do not agree with chilled water so I was warming it so called in a crude sense heating it up now when I am doing that you agree mass of the volume water is important volume of the water perhaps is important but do you think the shape of the water the surface area of the water is important it may not be relevant but suppose I am trying to make it Pradi then naturally the surface area of the water may be come important so depending on what we are going to study and in what detail the list of relevant characteristics may go up and down but remember thermodynamics does not by itself as a science tell us how many and which relevant now the second part of this is the state of a system will be completely defined when you have the relevant characteristic listed and quantify each characteristic typically by measurement so suppose our volume is V you say 100 cc how did I do it I pulled it out in a measuring glass it said 100 cc so that is 100 cc pressure well this is not leak proof so it is one atmosphere why it is open so it will be atmospheric pressure I found out from a barometer that it is one atmosphere mass I measured the mass of this then pulled it out measure the mass of the empty bottle by difference I got the mass okay if you want temperature use the thermometer to determine what the temperature is so when you do do these two things we say we have defined the state of a system so let me again take an illustration let us take gas in the LPG cylinder in a word okay you will say look mass of the gas is an important thing we are paying for it volume may be important but it is a solid cylinder and let us forget it is expansion contraction so you may cross out volume temperature yes I do not want it to be too hot pressure yes I do not want it to be core burst and then you may say that look when I got it fresh 14.6 kg temperature it came in a shaded van pressure well I was told by the refinery that this is say 18 so what we have done is we have created a list of relevant property and then we have quantified that list provided a value to each and every relevant property and what we have done we have defined the state of a system and this is an operational definition because it provides us a procedure it says step one make a list of property step two or step one a strike out whichever are irrelevant list of characteristics strike out irrelevant one so you end up with only relevant one and then for every relevant ones provide a value or obtain a value by measurement reference whatever it is and you can take I took gas in a cylinder you can take water in a this thing you can even take water flowing through a pipe the rate at which flows the mean velocity these are all relevant characteristics and when you quantify that you are providing the state of that system you will notice that I have jumped from 4 to 6 there is a topic in between classification of systems closed open isolated I have not done it by inadvertence I have done it on purpose we will do that after say 15 or so remind me at that time because this is a revelation that being closed or being open is not the property of a system itself it is a property of the system while undergoing a process so unless we talk of a process we should not really talk of a closed and open system we will come to that ok now the next thing is our microscopic and macroscopic viewpoints now here notice mass temperature pressure volume the properties which we listed and which we considered where the so called macroscopic properties because we said that we will be considering everything to be a continuum so these macroscopic gross properties were relevant to us but if you are talking to a physicist or a chemist he will tend to look at this water as a collection of so many Avogadro numbers of the molecule H2O so he always talks in terms of molecules and atoms microscopic particles so the next thing we do is look at the viewpoint possible viewpoints the viewpoints are for description of a system one viewpoint is microscopic one viewpoint is macroscopic in microscopic we say that any system will consist of a large number N of molecules or particles or atoms or whatever what is the order of N 10 raise to 25 10 raise to 26 18 grams even smaller quantity of this 18 grams of water has 10 raise to 23 molecules of H2O each molecule assuming that each one is simply a particle point particle then typical each one will have three velocity components and three position components so minimal 6 N variables there and if it is an H2O molecule which is not a point molecule orientation which also may be changing with time so you have a huge number of variables huge number of variables but do physicists and chemists really talk about this 10 raise to 26 values never what they do is they go into the realm of kinetic theory of statistical mechanics so you end up with statistical stuff that means you talk about averages and variations about average and you end up with kinetic theory or stat or stat thermodynamics whatever you call when it comes to statistical thing the distinction between mechanics and thermodynamics sort of blurs what do we do when it comes to macroscopic we consider the system to be a continuum we also say no quantum effect we will say it is scale independent in the sense that our thermodynamics is not going to be restricted only to gram mass type of systems will be applicable to grams kilo grams even tons of systems so our systems will be made up of continuum all variables will be varying continuously there will be no quantum effects that gives us essentially scale independent what is the consequence the consequence is a few variables which can very easily be handled in the most complicated thermodynamic problems n will be here n is of the order of 10 raise to 26 here it will be of the order of 10 then also is too much for simple thermodynamic system but even if you take a very reasonably complex thermodynamic system maybe 10 20 interacting systems few dozens at most so ease of handling but of course since we say it is continuum since we say it is no quantum effect when you go to situations where these assumptions are not valid so called macroscopic thermodynamics will lose its validity when it comes to very rare flow of very rarefied gas we cannot use classical thermodynamics we will have to modify similarly when you have very significant quantum effect nano mechanical engineering thermodynamics as we know it will not be applicable we will have to modify in this course we are going to restrict ourselves to macroscopic thermodynamics and because the laws are derived by generalizing our understanding of natural phenomena this is also known as phenomenological thermodynamics here we will not worry about existence of a molecule so things like entropy being related to the randomness of movement of molecules etc we do not have to worry about we will derive entropy from Kelvin Planck statement of second law and its derivation I think I will stop here okay so break for lunch