 When you look outside, you see different states of matter, right? You can see solids with all these leaves, tree bark and buildings. You can see liquids that is water over here. And you can feel the air present around you, right? Matter can occupy three states, solids, liquids and gases. And I want to think about what is similar among these states of matter and what is different. In this video, we will answer that question and in doing so, we will realize how changes in the arrangement of particles can give rise to these three states of matter. Alright, so let's begin with solids. Take a book or an iron nail or a pen or a pencil and you will see that these objects have a very clear boundary to them. You can see where they end and where they start. A solid also cannot start flowing, right? So we can say that solids, they have a fixed shape and volume. They have a fixed shape and volume. So try compressing a solid and you will find that you can't. That shows that solids also, they are incompressible. The fact that solids have a definite shape, they have a fixed shape and volume and that it cannot be compressed is what makes them rigid. That's why we call solids as rigid. Now why do solids have these properties? How are the particles arranged which give rise to these properties for solids? Let's have a look at this image. So you can think of it as a jar and there is something kept inside this jar, maybe like an ice cube or any solid block. So the particles in a solid, they are arranged in a fixed pattern. Strong forces hold them together. So they cannot really leave their positions, they are not free to move. That is what gives solids its fixed shape and volume. The only movements that they do make are tiny vibrations. Finally, there are no spaces between the particles in a solid. So that's why we cannot compress it and that's what makes it incompressible. Now I have some more examples for you. I want you to take a look at these two images. You have a pair of rubber bands and this is a sponge. Let's look at the rubber band first. So here we have the rubber band and we can change the shape of a rubber band, right? When we apply a force in these directions, we can change the shape of a rubber band or if we take a sponge, we can easily compress it. The definition of solids is really breaking here, right? So does that mean that these two materials are not solids? Well, let's think about it. So if you look at the rubber band, the fact that we have to apply a force to change its shape shows that the rubber band resists or doesn't want its shape to be changed. Just like any other piece of solid, just like any pen, if you apply a force, it will resist. It does not want its shape to be changed and the rubber band is doing the same. Just that the amount of force that you are applying to a rubber band is much less and the amount of force to change the shape of, let's say, a book will be huge. But both of them are resisting a change to their shape and that is what solids do, right? Also when we remove the force, it comes back to its original shape, a property that is called elasticity and you will learn more about that in physics. Rubber band, just like any other solid, also doesn't flow, right? So that's why we can say that even rubber band is a solid. Now for a sponge, we can compress it easily. Does that mean that it's not a solid? Well, if we look closely, if we look closely, we will realize that there are a lot of air spaces. There are a lot of air spaces in a sponge. Air occupies a lot of space in a sponge. So when we compress it, all the air is expelled out or thrown out and then we are able to compress it. It seems as if the volume of the sponge is decreasing. But the fact is that, let's say, there was some amount of volume to begin with, there was also a lot of air spaces to begin with, right? And then when you compress it, you just throw out all of that air outside. Now what you're left with is just solid sponge. So initially you had solid sponge plus some air spaces, finally you have only solid sponge. The volume of the solid sponge is not changing. It's just that you are thrown out all the air. So it seems that the volume of the sponge is changing. But it's not really changing, right? And that's why we can say that even a sponge is a solid. All right, let's take one more example which will challenge the definition of a solid. So here we have sugar or salt. You can take anything. Now, if you take, if you take like something like anything that has salt in it, and if you try and pour salt, this looks like a salt shaker, okay? So when salt is coming out, when salt is coming out from it, you will see that salt can flow like a liquid. It flows like a liquid, right? So can we call it a solid? Well, it turns out we can because if we zoom in and if we only look at one salt crystal or one sugar crystal, we will see that this has very much of fixed shape and volume. We cannot compress it as well. So it's just that you see a lot of salt and a lot of sugar over here, too many crystals. So it gives, it seems that they are flowing, but if we just look at one small crystal, then that has the properties of a solid, a fixed shape, volume and it's not compressible. So even a salt or sugar, even that is solid. All right, now let's move on to liquids. So when we look at liquids, we can see that they can easily flow, right? They can easily flow. So let me, let me write that. They can flow easily. And what does that mean? What does that tell us about the shape and volume? Well, you must have realized that even if you take any shape of container, it can be, it can be any random shape of container. You will realize that water really takes up the shape of that container. So it does not really have a fixed shape. It does not have a fixed shape, but is the volume changing? Think about it. Even if we pour water in different containers, the volume still remains the same, right? Only the shape is changing. So it does have a fixed volume, but it does not have a fixed shape. Also if you try and compress a liquid, think of, think of having like a balloon, let's say you have a balloon and there is water inside of it. You can still compress it to some extent, but you cannot compress it entirely, right? So they are somewhat compressible, not entirely compressible. So they lie somewhere in between, let's say between solids and we will see gases can be compressed. They really lie in between solids and gases in terms of their compressibility. So we can say that they are somewhat compressible, not entirely compressible. All right, one more interesting thing about liquids is that you see all these aquatic animals living in water, right? How are they getting oxygen? Like every living being requires oxygen to survive. So how are they really getting oxygen out of living in water? Well, it does all that gases can mix with liquids and that really is called diffusion. In this case, oxygen can mix with water and then aquatic animals can take use of that oxygen to survive and live. Even solids can mix with liquid and again that is still called diffusion. Diffusion is when two different types of atoms are mixed with each other. So the other two states of matter can mix with liquids, solids can mix with liquids. We can take an example of crystal of potassium per magnet and if we just let it be inside a beaker of water, very soon you will see that it starts spreading out throughout the body of the water. That is really diffusion because you have intermixing of two different types of particles, water and potassium per magnet. In this case, you can see solids diffusing with a liquid. In the case in the example of aquatic animals living in a body of water, you can see gases diffusing with water, in this case oxygen. So liquids can have that property. All right, but why do liquids really have these properties? So let's have a look at what's happening at the molecular level. Now when it comes to liquids, the particles are not arranged in a fixed pattern. The particles are moving around or sliding past each other. They're still not going outside the container. They're very much contained within this volume, but they're still moving around, right? So that tells us that they do not really have a fixed shape, but they only have a fixed volume, fixed volume and not a fixed shape. And finally, there is some space between these particles, so they are somewhat compressible. And finally, the fact that these particles, they have some spaces in between them. This gives room for atoms of any other type of element to take up this space. And that is how diffusion works, right? When we had potassium per magnet, the particles of potassium per magnet, they took up the spaces in between these water molecules, these water particles, which is how they diffused. And if gas is diffusing with water, oxygen can take up this space between the particles of water. That is how diffusion works. So we see how a regiment of particles in a liquid can give rise to these properties. Fixed volume, not a fixed shape, the ability to have other substances mixed with itself and also allowing it to compress to some extent. All right, now let's look at gases. So when it comes to gases, it's difficult to see them really unless a gas is colored. But different types of gases are part of your daily life. So when you see an LPG cylinder, there's an enormous amount of gases. That is compressed and then the cylinders can be used. So the first main property of gases, we can say that they are really compressible. Even if you take a balloon with just air in it, you can very easily compress it, right? It'll even burst after you apply a certain amount of force. And the other thing is, if you have a gas in a container, it will fill up the entire volume. If there is a container and there is some gas in it, let's say there is a lid on top. So it's closed from the top. And if you have some gas, any gas, it will fill up the entire container. So it does not have a fixed volume. It does not have a fixed shape. So let's write that neither a fixed shape nor a fixed volume. So it has these two main properties. And also you can have two different types of gases mixing with each other. So it also allows for diffusion. Now these two are the main properties for gases. Now let's see how the particles are arranged, which can give rise to these properties. So in gases, the particles, they are moving randomly in all the directions. So in this case, you see a molecule, a molecule made up of two atoms. They can move in any direction. They can move randomly in all the directions. They fill up the entire volume of the container. So that means they do not have any fixed shape or volume. And there is a lot of space in between these molecules, which makes a gas highly compressible in nature. And now there's one more interesting thing about gases. So I'm sure you must have experienced this. If then someone's cooking anything near you or let's say there's a perfume being sprayed in the corner of a room, immediately you can smell that, right? How is that possible? So think about it. There is already air present around you. There is oxygen present around you. And when something is cooking or if there is a perfume being sprayed in a corner of a room, the gas particles from those two things mix with the oxygen or the air around you, and then it reaches your nose. So this is also an example of diffusion. Again, mixing of two different types of atoms. Atoms of a perfume, whatever compound is used over there. And the atoms of food, whatever food is being prepared, right? So that is mixing with the oxygen present around you and is able to reach your nose. And this shows that even gases can allow for diffusion. Different gases can mix with it. All right, so these three were the states of matter. Now you can see how the enrichment of particles can give rise to different, different kind of properties with these states of matter. Just quickly summarizing, solids have a fixed shape volume. They are not compressible. Liquids have a fixed volume, not a fixed shape. And they are somewhat compressible. Gases are highly compressible and they neither have a fixed shape nor a fixed volume.