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The Kinetic Molecular Theory of Gas (part 2)

The Kinetic Molecular Theory of Gas (part 2)
let's think about these rules a little bit deeper to explain a few properties of gases on that are unique to gases we don't see these properties in solids or liquids here's the first one let's assume that I have a container of gas just like I had at the beginning of the lesson and I have some gas

part

icles in it this is we said before here the gas

part

icles now remember these gases of course are in constant random motion and they're balanced against each other they're
the kinetic molecular theory of gas part 2
bouncing against the sides of containers that's what these arrows are indicating obviously they're all moving but I'm only drawing a few arrows when we talked about this the very beginning of the lesson we drew a container that had a top on it let's imagine what happens when we open that top if we can lift it up well these gases are in random motion and they only really change directions when they hit against the side of the container and so what that's going to mean is
eventually these guys are are going to bounce their way out of the container and they're going to spread out I mean imagine that we had a tiny little room filled with hyper

kinetic

little kids and we open the door the kids wouldn't all stay in the room they'd eventually move on out bounce against the walls bounce against each other until they filled as a big of a space as we gave them this is what we call expandability expandability because gases will move around they'll expand to
fill any area that we give them so let's assume that this whole area here is a new container we open the old one these guys are going to move out they're going to be randomly moving until they fill this whole area it's what we call expandability because they expand to fill a new volume now the process of these gases moving out is what we call diffusion you're familiar with the concept of diffusion even if you don't necessarily know what causes it or if you're not familiar
the kinetic molecular theory of gas part 2
with the technical name diffusion is the reason why when you're at one end of the mall and the movie theaters on the other end you still smell popcorn you get hungry over at the movie theater they're making popcorn and the the gas odor or fragrance of popcorn those gas

part

icles are moving around they're moving around very fast and they diffuse out from their original location because of that they can reach you all the way down at the other end of the mall because those gas

part

icles
that make up the popcorn scent are going to spread out to fill as large of a volume as you give them so that's expandability a very important quality of gas you don't see if the solids you don't see the liquids let's look at another quality again here we have a container of gas let's put some gas

part

icles in there remember though we're worried these guys might get out they're going to expand if we don't close this container so what I'm going to put here is
I'm going to put a plunger or a piston here so we can think about this container as a like a barrel or a cylinder so this piston is something that I can grab on to and I can move it in this direction let's look at what happens when I do that up here is it before here's the after I've moved the piston all the way in here and what I've done is I've pressed all of these gas

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icles closer together so here they are now why can I do this I can do this because of the first
the kinetic molecular theory of gas part 2
rule that we talked about in our

kinetic

theory

of gases and that's the gas

part

icles are tiny and there's a tremendous amount of empty space around them because there's so much empty space I can really squeeze these guys into a much smaller volume here we call this compressing it and this quality of gasses is known as compressibility compressibility is

part

icularly important like if you're into scuba diving what we can do is we can take a very large quantity of air and we can
squeeze all the

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icles that make up that air into a tank which can allow you to breathe for a very long period of time the

part

icles are very very very very pressed together or compressed now compressibility is unique to gases uh if I took a big hunk of metal and I tried to press down on it with a whole bunch of pressure it wouldn't change its size sometimes people think that liquids are compressible but they're not I could take a piston and a cylinder like this and fill it with water
and try to jam down on that plunger nothing's going to happen I can't compress the

part

icles in liquid I can compress them a tiny bit but not very much gas is on the other hand I can really cram them in a tank or I can cram them in a cylinder like this because that because there's so much space in between them they can really pack together this compressibility and expandability are two unique characteristics that we only see in gases so we looked at

kinetic

energy today and different
states of matter and then we looked at the

molecular

kinetic

molecular

theory

of gases some rules that gases abide by finally looked at expandability and compressibility this is all the foundation that we need now on to delve further into gases and start looking at conceptual problems and mathematical calculations for gas