 So in this chapter we are going to again learn about properties of matter only, but properties of matter we have already learned in the earlier chapter, right? We have learned about mechanical properties of fluid, mechanical properties of solids and thermal properties of matter, okay? But we never went into what is the cause of the property, alright? This chapter tells you that the cause of is kinetic nature of the molecules or the atoms, okay? It is because of the movement of molecules of the atom, it shows a property of temperature. It is because of the movement of atoms and molecules, it shows a property of pressure. Because of that there is a property of heat capacity. Because of that conceptual foundation based on which you will understand actually what is happening at the molecules properties, alright? And the basic assumption over here is that all kinetic nature of the atoms of the molecules, kinetic nature is in. So now the first time this concept was getting developed People were more focused in understanding about the behavior of this were focusing on how the small particles behave. There are pioneers who have assumed that there exists a fundamental particle which is an atom, alright? And in our ancient literature have you heard of Anuri? Yes, much before some emotional story attached to it and then we will understand. So they will have heat punishment. You will be clean, so you will not get any disease. But they will have to attend if you don't take a bath before prayer and you have to do a prayer, alright? So like that, because of that a lot of scientific knowledge of ancient India never documented properly and even it was documented on leaves. So people have this habit of writing on leaves and of course it will decay, right? So have you heard of Trakshila, Nalanda and all that? Okay, a lot of knowledge was there but a lot of textbooks were destroyed by people who were attacking people from that part of the country, alright? But then yes, when it comes to credit, the western people, especially Greeks were much smarter. They used to write on the copper plate, that will not decay very fast, right? So they get all the credit, they get the credit of Patakura's theorem also, which was discovered much, much before, okay? But then yes, let us learn like that, you can't write it in exam that no, Dalton did not do the whole list. So Dalton was the first person who has observed that whenever two matters combine, they combine in a specific ratio and they are integer ratios. What does it mean? If hydrogen and water has to combine, they should combine in a ratio of 2 is to 1, okay? It cannot be less than that, it means that assume that there is something called titanium. Nobody had seen atom that point in time, okay? But just because of this observation, Dalton came up with the theory that there is atom that exists and that cannot be divided further. But of course, atom can be divided later on, people have found out that there are electrons, protons and even electron proton can be divided, okay? But having them, you can treat as if it is smallest unit which has all the property of the bulk matter, okay? So you can divide hydrogen has no difference, same. The difference comes when it becomes an atom. Hydrogen atom is different from chlorine atom. Hydrogen electron is same as chlorine electron, okay? So that is why it is better to study at the atomic level and not go down further because then it will become more generic, okay? So Dalton was there, Gaeluswag was there, then Eregard. Assume that atomic model is the correct model. But at the same time, there are many scientists and great scientists who were opposing the idea that the matter consists of these small atomic particles, all right? So it has taken a lot of opposition and slowly it got evolved and then experimentally it got proven much later, okay? So various people have contributed to it. Then in order to understand the atomic nature of any matter, how atom behaves, we are going to understand how gas behaves. I want to understand how atom behaves. Then why I am studying gas, why not liquid and solid? Any guesses? There will be attraction between the two atoms in the solid. There will be lattice structure in the solid. So it is not only about how one atom is behaving, all right? I can ignore the attraction or repulsion between the two molecules. The way the entire gas will behave is very similar or close to the behavior of an atom. So I can extrapolate or interpolate the behavior of entire gas. I can say that similarly one atom might be behaving and the way one atom is behaving similarly the entire gas will behave. So that is why the analysis of gas or the ideal gas equation is in this chapter. To understand how gas behaves. That is the way the atoms will also behave. But it is not just about how two, three atoms together will interact. So when the analysis of the gas started, people had no idea that ideal gas equation exists. But they have this idea that there is something called pressure. You can measure the volume and you can measure the temperature also. With David Shachar scale or Kelvin scale, whatever would be right. Now they started to do research on how these variables are connected, if there is a connection. Or these variables are independent of each other. Is pressure has to do with temperature or not? Or pressure is independent variable, independent variable. They are just not depending on each other, right? So there were great, this Charles law is there, Boyle's law is there. All these guys without knowing ideal gas equation, they have done research and found out a relation between volume and temperature, pressure and volume and pressure and temperature. Fine? So what is Boyle's law? You know that? Pressure into volume is constant at temperature. But Boyle's P into P is constant by doing a lot of experiments. So he has taken a gas and then plotted pressure and volume. And he found out that the curve is like this at a particular temperature. And if he increases the temperature, the curve shifts upwards like that. And this curve represents pressure into volume becoming constant. Do you know that they were hyperbolic? Have you done a basic course on plotting graphs? I think in the previous program it was there. So can you quickly plot a graph of x into y is equal to 5? Plot x into y is equal to 5 on a graph. Just roughly plot that. So if you plot x into y constant, I want to plot x into y is equal to 5. So when x is equal to 0, y should be what? An axis 0, y should also be 0. X cannot be exactly equal to 0. Then product will be equal to 0. But what if x is very less, tending towards 0? Y should be infinite. Similarly when y tending to 0, x should be infinite. So it will be starting from like this and it should be like this. This is the plot of x into y is a constant. There is an error here or it is incomplete. Tell me why it is incomplete. There will be a third quadrant graph also. Negative x into negative y can volume the fourth quadrant. So when you draw something, physically no meaning. So this curve is very similar to that curve if you look at the shape. And that is the reason why boils have approximated it and came with that expression that pressure to volume should be a constant, roughly. So this is the discovery between the relation between pressure and volume. Similarly there was a plot between pressure and temperature. So this kind of graph was seen. And if you roughly approximate it, you can approximate it to be a straight line. So you get curve like this or you get curve like that. So roughly it represents a straight line. So pressure is directly proportional to temperature. That was also found. So two relations of this constant and pressure is proportional to temperature. And similarly volume is constant. I am getting two variables and keeping third variable constant. When I am plotting pressure and temperature, which is constant? Volume is constant. And when I say volume is proportional to temperature, pressure has to be constant. Because you can keep everything inside the pressure cooker, keep volume fixed and increase the temperature. Sorry, the volume is constant. So volume will not increase because pressure is not kept constant. Getting it? All right. So three relations we have seen. PV is constant. Right now pressure is proportional to temperature. And volume is proportional to temperature. At constant volume, at constant pressure, at constant temperature. Okay, you might have done this already in chemistry. Boyle's law, Jars law and what others? Yes. Right, and then comes an ideal gas equation. Okay, so not only, right now we have got a connection between just two variables. There is a relation among all three variables. Pressure, volume and temperature. That is your ideal gas equation. So that was also found experimentally only. So what we are seeing is the direct or the most fruitful experiment. Of course, people might not have arrived directly. Right, they might have encountered a lot of failure and then they would have arrived directly. Okay.