The Kinetic Molecular Theory of Gas (part 2)

Let's think about these rules a little deeper to explain some properties of gases that are unique to gases. We do not see these properties in solids or liquids. Here is the first one. Suppose I have a gas container like the one I had. at the beginning of the lesson and I have some gas

part

icles, as we said before here the gas

part

icles now remember that these gases, of course, are in constant random motion and they bounce off each other, they bounce off the sides of containers, that's what indicate these arrows, obviously everyone is moving, but I'm just drawing some arrows when we talked about this at the beginning of the lesson, we drew a container that had a top, let's imagine what happens when you open that top if we can lift it up good, these gases are in random motion and really only change direction when they hit the side of the container and what that will mean is that eventually these guys will bounce their way out. from the container and they are going to spread, I mean, imagine we have a small room full of hyper

kinetic

toddlers and we open the door, the children would not all stay in the room and eventually they would move out bouncing off the walls they bounce off each other until They filled a space as big as the one we gave them.

This is what we call expandability because the gases will move and expand to fill any area that we give them, so let's assume this entire area here. It is a new container, we open the old one, these guys are going to move, they will move randomly until they fill this entire area, it is what we call expansion capacity because they expand to fill a new volume, now the process of movement of these gases is what we call diffusion, you are familiar with the concept of receptive diffusion even if you don't necessarily know what causes it or if you are not familiar with the technical name, diffusion is the reason why when you are at one end of the mall and the cinema are at the other end you still smell like popcorn and you get hungry in the cinema they are making popcorn and uh, uh, the smell of gas or the fragrance of popcorn, those gas particles are moving, They are moving very fast and they diffuse from their original location because of that, they can reach to the other end of the mall because those gas particles that make up the aroma of popcorn will spread out to fill such a large volume. as you give them, that is the capacity for expansion, a very important quality of gas, you don't see it in solids, you don't see it in liquids, let's look at another quality again here we have a container of gas, let's put some gas particles there, remember Although we're worried that these guys might come out, they're going to expand if we don't close this container, so what I'm going to put here is a plunger or a piston here so we can think of this container as a barrel or a cylinder, like this. that this piston is something that I can grab onto and I can move it in this direction.

Let's see what happens when I do that. Up here is a before, here is the after. I've moved the piston here and what I've done is put all these gas particles closer together, so here they are now. Why can I do this? I can do this because of the first rule we talked about. in our

kinetic

theory

of gases and that is that the gas particles are small and there is a tremendous amount of empty space around them because there is so much empty space that I can actually squeeze these guys into a much smaller volume, here we call it compress it and this quality of gases is known as compressibility.

Compressibility is particularly important. If you like to dive, what we can do is take in a large amount of air and we can squeeze all the particles that make up that air into a tank that can allow you. to breathe for a very long period of time, the particles are very, very, very pressured or compressed now, compressibility is unique to gases. If you took a big piece of metal and tried to press it with a lot of pressure, it wouldn't change its size. Sometimes people think liquids are compressible but they aren't. You could take a piston and a cylinder like this and fill it with water and try to squeeze that plunger.

Nothing is going to happen. I can't compress it. particles in liquid I can compress them a little bit but not much in gases, on the other hand, I can really put them in a tank or I can put them in a cylinder like this, because since there is so much space between them, they can really combine, this compressibility and capacity of expansion are two unique characteristics that we only see in gases, so we look at kinetic energy today and the different states of matter and then we look at the

molecular

kinetic

molecular

theory

of gases, some rules that gases ultimately follow.

We looked at expandability and compressibility, this is all the foundation we need now to delve deeper into gases and start looking at conceptual issues and mathematical calculations for gas.