 So, we will start with the solid state. So, normally there are three different states of matter we have that one reversible reaction. Show me the notes last one. This is one formula I will give you. Yes, yes, yes. This is a reversible reaction one formula. So, I will give you that formula. This is just one formula for reversible reaction what is the concentration of A B C A B reversible reaction at any time. So, that is one formula I will give you that because the derivation is so big. So, we are not doing that. Not that important also. So, I will give you that formula. Solid state will start. There are three different states of matter we have that we already know that is solid, liquid and gas. What is the basic difference among these three states of matter? The basic difference is what? Intermolecular force of interaction IMF. IMF in solid is maximum. So, here it is strong intermolecular force you see strong intermolecular force. The liquid is weak and the gas is state and very weak intermolecular force of interaction. So, because of weak intermolecular force liquid particles can move that is why the water and any in the liquid state can flow. Because the molecules the bonding between the molecules is not that strong. So, molecules can move that is the reason why the liquid and fluids all these particles close. Gas as particles we know there is random motion and gas as particles all the gas as particles move in random direction. And when it strikes to the wall it exerts pressure. So, random motion of gas as particles we have again because of weak interaction among the molecules. These two are interacting. So, it is motion will be hindered because of this interaction force. And solid particle what happens the molecules of solid particles are attached by a very strong bond or intermolecular force we can say. That is why if you want to break any solid particles you have to break this bond. And since it is strong. So, you have to apply some force. So, basic difference is intermolecular force. You keep on increasing intermolecular force and convert the states of matter into each other. Very weak to weak weak to strong it becomes solid. So, liquid particles gases particles will have certain range of intermolecular force. If you exceed that range the gas starts converting into liquid further you increase the intermolecular force liquid starts converting into solid. The best example we have of water converting into ice. S2L liquid. So, it converts into ice solid. What happens when this happens when you put this water into any low temperature this will make in freezer. If you put the water in freezer then it converts into ice solid after some time. So, what happens at low temperature the liquid particles has very less kinetic energy. As temperature decreases kinetic energy also decreases. However it is true for gaseous particles 3 by 2 kT kinetic energy of gases molecules. But it is true for solid and liquid also. As you increase the relation may be different. But as temperature decreases kinetic energy of liquid particles also decreases. So, when kinetic energy decreases the liquid particles moves with a lesser speed. And when the spirit is less they can interact. And when interaction possible it means intermolecular force is increasing. So, after some time what happens if this intermolecular force keeps on increasing this starts converting into solid. So, with liquidification of gas also we have discussed in gases state. Conversion of gas into liquid that is liquidification of gas. Then we have two different factors. One is pressure when you decrease the pressure and when we decrease the temperature sorry increase the pressure or decrease the temperature. When pressure increases what happens the average distance between the molecule also decreases. Because when pressure increases volume decreases volume decreases means gases particles are coming closer. So, if you want to increase the intermolecular force you have to decrease the distance or average distance between the particles or molecules or you have to decrease the temperature. So, that kinetic energy decreases speed decreases and interaction increases. That is why these are the factors we have these two factors we discussed in liquidification of gas. The objective is what? Objective is to increase the intermolecular force. So, that the change of state is possible. So, in this chapter we are going to deal with solid state. So, maximum intermolecular force of interaction we have. We will also see the packing of solids solid particles generally what we assume they have spherical shape. So, in the arrangement of solid particle you say it is not perfectly arranged means there will be some vacant space that we got it as void. Suppose you have particles like this and when you arrange like this side by side like this if you arrange. So, obviously you have some void present these are the voids. Why these voids are there? Because the shape is a square. If it is a square or something like this then the void won't be there. You can place a square like this perfectly you know efficiency is completely 1 or 100 percent you can say. So, because the shape of the molecules the efficiency is not 100 percent and we will have some void present in this. Now, this void can be of different types of the hydro voids of that triangle void, 2D, 3D void all these things are possible. So, we will discuss about voids how this void forms and we will also see ionic crystals. Ionic crystals if there are two types of crystal covalent and ionic metallic also we have non-structural material also. Important one is ionic one covalent. In covalent what happens the atoms will have the same size carbon-carbon atoms are in like in diamond correct. So, all carbon atoms so size of carbon atom will be what same right. In ionic crystal what happens here ions like n is here n is plus n c is minus. So, this size will be more than this. So, ionic crystal may have a size will be different of ions generally what happens cations are present in voids and ions occupy the lattice points. There are some exceptions also in which an ion occupy voids we will see that. Structures of various compounds like NaCl, ions of oxides of ions ZNS, borsi structures zinc grind structures all these things we will see. But before that we have to understand what is the different types of lattice. What is that is point? What is coordination number? What is rank of any unit cell? What is unit cell? All these things we have to understand coordination number covalent is different. So, we will see all these things and then we will discuss. So, basically in this chapter this is one part of the chapter. The second part is about it is all about theory like semiconductor you must have done in physics. So, we have that we have we will have extrinsic intrinsic semiconductor theoretical base question, three base question they ask them to that. Another thing is ferromagnetic substance, paramagnetic, diamagnetic, ferrimagnetic all these things are there. So, the last part of this chapter is theoretical. So, I will give you notes on to that. It is not very much I will dictate only because it is completely theory what is what are the important things I will let you know. So, here we will start with next right down. There are two types of solid. You have done this chapter in a school? No. No. No. No. No. No. No. It is not there. No. It is not there. No. It is not there. No. It is not there. No. It is not there. It is not there, but in j, you will have. No. No. Not in any other example. Okay. Right down. There are two types of solutes generally. One is amorphous it like this right down. Ameuphous and crystalline. See the difference of this two. Ameuphous and crystalline solid. Okay. Ameuphous, solid right down in this point was right down. It is irregular arrangement. Irregular arrangement. means irregular arrangement means there is no pattern in this, atoms are arranged in there is no ordered manner, randomly it is arranged, but this line is solid we have ordered arrangement, regular arrangement or ordered arrangement. Like all these examples write down, the moffers will have plastic rubber, you can also say coal, there is no regular pattern in life, but if you see crystalline diamond, graphite or any other, any CL structure there is a pattern, there is an ordered arrangement, this position of atoms will be fixed, there is a geometry fixed into this. Second point you write down in this, it has definite and sharp melting point in this, sorry in this one, in this one you are writing, it has no sharp melting point, am I first being no sharp melting point, here we have definite and sharp melting point, crystalline structure definite and sharp melting point, here am I first, no sharp melting point, no sharp melting point, you must have seen plastic means over a range of temperature, that is no sharp melting point, but in the case of solid the melting point of water is water, melting point, sharp melting point we have, am I first, we also called as pseudo solid, generally solids has sharp melting point, since it is, it does not have the sharp melting point that is why we call it as pseudo solid, crystalline is true solid, crystalline is true solid, am I first you write down, its properties are not direction dependent, am I first solid, properties are not direction dependent, this we call it as isotropy, isotropy means what, properties independent of direction, isotropy, crystalline you write down, anisotropy, this is important, anisotropy, its properties are, properties depends upon direction, diamond whatever you must have heard, you take direction, cut corner is easy with that, if you cut the diamond at a particular angle it is easier than the other, that is what its tensile strength depends upon the direction, that is why if you want to cut the diamond it is not easy to cut from every direction, because when you have atoms interact directly in one particular direction, it is difficult to cut from that direction, when the properties are direction dependent is anisotropy and am I first are isotropy, these are three four difference sometimes they ask this, this term you must remember isotropy and anisotropy, direction dependent it is independent of direction, next you write down, there are certain terms we use in this chapter, in this the first thing you write down the terms related to a crystal, the first term you write down, the first term is lattice point, these are the positions or points, these are the positions or points where the atoms position or points where the atoms are placed, atoms, ions, molecules anything you can say, atoms, ions in the case of what anisotropy is, when you have any crystals, atoms, ions, molecules are placed, all those points are lattice points, next term you write down, just one more line you write down, lattice points are joined together, lattice points are joined together to get the geometry of the lattice, join together to get the geometry of the lattice and generally we join this by a straight line, second point you write down, crystal lattice, it is the 3D arrangement of lattice points, 3D arrangement of lattice points, 3D arrangement of lattice points, third one, unit cell, unit cell write down, it is the smallest part of the crystal lattice, it is the smallest part of the crystal lattice, which smallest part of the crystal lattice, which when repeated, which when repeated in all direction, which when repeated in all direction generates the entire lattice, generates the entire lattice, okay.