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hi it's mr. Anderson this is chemistry essentials video 14 it's on gases when

Hi. It's Mr. Andersen and this is chemistry essentials video 14. It's on

you see a hot air balloon flying looks

gases. When you see a hot air balloon flying, it looks pretty stationary. But if you're

pretty stationary but if you were to look at the molecules inside it if we were to look at the heat inside it we'd

to look at the molecules inside it, if we were to look at the heat inside it we'd see

see there's going to be way more hot air at the top than at the bottom it's less

there's going to be way more hot air at the top then at the bottom. It's less dense. And

dense and that's why the thing is going to flow so when we're looking at gases basically a real gas is going to be made

that's why the thing is going to float. So when we're looking at gases, basically a real

up of all these independent particles

gas is going to be made up of all of these independent particles that are all just shooting

that are all just shooting around moving around really really quickly they're not connected together at all and so in

around, moving around really really quickly. They're not connected together at all. And

science what we can do is we can model that using what's called an ideal gas

so in science what we can do is we can model that using what's called an ideal gas. And

and lots of times we'll use the ideal gas law and this one PV equals NRT is

lots of times we'll use the ideal gas law. And this one, PV=nRT is one that you should

one that you should learn right away and learn how to apply it over and over and over again it's basically built on two

learn right away. And learn how to apply it over and over and over again. It's basically

things the kinetic molecular theory this idea that molecules are bouncing around

built on two things. The kinetic molecular theory. This idea that molecules are bouncing

and they have a huge amount of energy as we increase the temperature and then the

around and they have a huge amount of energy as we increase the temperature. And then the

Maxwell Boltzmann distribution which means that even though they might

Maxwell-Boltzmann distribution which means that even though they might collide every

collide every once in a while the energy that they have is going to remain the

once and awhile, the energy that they have is going to remain the same and their state

same in their state is going to remain the same we can use the ideal gas law to figure out Absolute Zero but there going

is going to remain the same. We can use the ideal gas law to figure out absolute zero.

to be some deviations in other words

But there are going to be some deviations. In other words times where this model just

times where this model just doesn't work and we have to start looking at real gases and this usually occurs as we get

doesn't work. And we have to start looking at real gases. And this usually occurs as

around condensation that point at which that gas turns back into a liquid again

we get around condensation. That point at which that gas turns back into a liquid again.

and so this is going to be a real gas air what's between me and the camera

And so this is going to be a real gas. Air, what's between me and the camera right now

right now is going to be a real gas and an ideal gas is built on these two theories first one is kinetic molecular

is going to be a real gas. And an ideal gas is built on these two theories. First one

theory it's that all of the molecules are bouncing around moving off of each

is kinetic molecular theory. It's that all of the molecules are bouncing around. Moving

other and as we increase temperature we're going to increase the molecular

off of each other. And as we increase temperature we're going to increase the molecular speed

speed of those molecules and so that's a gas remember they're not connected together at all they're just moving

of those molecules. And so that's a gas. Remember they're not connected together at all. They're

around randomly and then we have the Maxwell Boltzmann distribution that

just moving around randomly. And then we have the Maxwell-Boltzmann distribution. And that

means that even though they might bounce into each other they're not interacting

means that even though they might bounce into each other, they're not interacting with each

with each other they're all going to be independent so this graph what we're

other. They're all going to be independent. And so this graph, what we're looking at are

looking at are a bunch of noble gases and we're looking at their speed and and the probability of having found

a bunch of noble gases. And we're looking at their speed. And the probability of having

molecules at that specific speed and what we'll find is that real light noble

found molecules at that specific speed. And what we'll find is that real light noble gases,

gases like helium are have a higher speed than those for

like helium, are going to have a higher speed then those for example like argon. They're

example like argon we're going to have a lower speed but they're all independent of one another and so when we're looking

going to have lower speed, but they're all independent of one another. And so when we're

at an ideal gas we basically have these five properties volume temperature

looking at an ideal gas, we basically have these five properties. Volume, temperature,

pressure and which is the number of moles and then some kind of a gas

pressure, n which is the number of moles. And then some kind of a gas constant. And

constant so you're going to have to look at your your units to figure out what gas constant to use but if we use this

so you're going to have to look at your units to figure out what gas constant to use. But

model which we use it three times V is

if we use this model, which we use it three times, v is going to be the volume. So let's

going to be the volume so let's say these are a bunch of gas molecules volume is going to be the side of the

say these are a bunch of gas molecules. Volume is going to be the size of the container that

size of the container that they're in T is going to be the temperature how warm or cold it is and that remember is tied

they're in. T is going to be the temperature. How warm or cold it is. And that remember

to the molecular motion pressure is going to be how much it's pushing out

is tied to the molecular motion. Pressure is going to be how much it's pushing out.

and if you push in on a balloon you can start to feel that pressure pushing out

And if you push in on a balloon you can start to feel that pressure pushing out on you.

on you and then n is going to be the number of moles how much stuff is going

And then n is going to be the number of moles. How much stuff is going to be found inside

to be found inside it and so if we rearrange this PV equals NRT that's the relationship now you can learn all the

it. And so if we rearrange this PV=nRT, that's the relationship. Now you could learn all

different gas laws but it's better to just learn the ideal gas law and then

of the different gas laws. But it's better to just learn the ideal gas law and then apply

apply it in different situations and so we're going to use this simulation at pH

it in different situations. And so we're going to use this simulation at phet. And we're

et and we're going to look at Boyle's law so that's the relationship between pressure and volume and so we're going

going to look at Boyle's law. And so that's the relationship between pressure and volume.

to keep all those other constant and R

And so we're going to keep all those other constants, n, R and T are all going to remain

and T are all going to remain constant what we're going to look at is how our volume and pressure related so I'm going

constant. What we're going to look at is how are volume and pressure related. So I'm going

to keep the temperature constant if we look at the pressure it's around point six nine atmospheres

to keep the temperature constant. And if we look at the pressure it's around 0.69 atmospheres.

now let me decrease the volume so I'm making the volume get smaller and so

Now let me decrease the volume. So I'm making the volume get smaller. And so what's going

what's going to happen to the pressure well we have to wait for a little bit we

to happen to the pressure? Well, we have to wait for a little bit. We have to wait for

have to wait for that temperature go back down to 300 Kelvin again but once

that temperature to go back down to 300 kelvin again. But once it gets to 300 kelvin now

it gets to Kelvin now look it was point six nine atmospheres before and now it's one point seven three and so as we decrease the volume pressure went up now

look, it was 0.69 atmospheres before, and now it's 1.73. And so as we decrease the volume,

let's increase the volume so we're making the volume go up and then let's

pressure went up. Now let's increase the the volume. So we're making the volume go up.

look at what's going to happen to the pressure and so we got to wait for that

And then let's look at what's going to happen to the pressure. And so we've got to wait

temperature to come back to 300 Kelvin again and so now we're going to see that

for that temperature to come back to 300 kelvin again. And so now we're going to see that

the pressure is decreased so by increasing the volume we decrease the

the pressure has decreased. So by increasing the volume, we decreased the pressure. And

pressure and so there's going to be an inverse relationship between pressure and volume and you could actually apply

so there's going to be an inverse relationship between pressure and volume. And you could

this in a problem let's say we had a balloon at one point three atmospheres

actually apply this in a problem. Let's say we had a balloon at 1.30 atmospheres. That's

that's going to be the pressure it has a volume of 3.2 liters what will the

going to be the pressure. It has a volume of 3.2 liters. What will the volume be if

volume be if the pressure is decreased to 0.62 atmosphere and the temperature remains the same

the pressure is decreased to 0.62 atmospheres. And the temperature remains the same? Well,

well we just have a before-and-after so we have our pressure volume before initial and after so we'd put in our

we just have a before and after. So we have our pressure volume before, initial, and after.

values before our after and then we're going to solve for this final volume and

So we'd put in our values before. Our after. And then we're going to solve for this final

so we can make sure our units are correct and so what's going to happen to

volume. And so we could make sure our units are correct. And so what's going to happen

the volume the volume is going to increase as the pressure decreases as

to the volume? The volume is going to increase as the pressure decreases as long as we keep

long as we keep the temperature the same and a weather balloon as you send a

the temperature the same. And a weather balloon. As you send a weather balloon up, the weather

weather balloon up the weather balloon is going to get bigger and bigger and bigger there may be changes in

balloon is going to get bigger and bigger and bigger. There maybe changes in temperature,

temperature but it's related to that relationship now let's look at what's

but it's related to that relationship. Now let's look at what's called Charles' Law.

called Charles law we're just going to look at volume and temperature and what happens to the volume as the temperature

We're just going to look at volume and temperature. And what happens to the volume as the temperature

changes let's use this simulation again we're going to try to keep the pressure

changes? Let's use this simulation again. We're going to try to keep the pressure constant.

constant and the same number of moles inside there as well and so now we're

And the same number of moles inside there as well. And so now we're going to increase

going to increase temperature so we're adding Heat and watch what happens to the volume as we increase the

temperature. So we're adding heat. And watch what happens to the volume. As we increase

temperature the volume got bigger as long as we kept the pressure the same

the temperature, the volume got bigger. As long as we kept the pressure the same? Why

why is that as we're increasing temperature there's more kinetic movement now let's lower the temperature

is that? As we're increasing temperature there's more kinetic movement. Now let's lower the

as we decrease the temperature those molecules aren't moving as quickly and

temperature. As we decrease the temperature, those molecules aren't moving as quickly.

what happens not pushing out as much and so the volume is going to go down so if

And what happens? Not pushing out as much. And so the volume is going to go down. So

we increase temperature volume goes up if we decrease temperature volume is

if we increase temperature volume goes up. If we decrease temperature, volume is going

going to go down and so there is a direct relationship between the two and

to go down. And so there is a direct relationship between the two. And so hopefully you're learning

so hopefully you're learning how to apply ideal gas law if they're both on the same side we had an inverse

how to apply ideal gas law. If they're both on the same side, we had an inverse relationship.

relationship but now since they're on opposite sides of the equal sign it's going to be a direct relationship

But now since they're on opposite sides of the equal sign it's going to be a direct relationship.

what's an application of this well you could find absolute zero in a basic

What's an application of this? Well you could find absolute zero in a basic chemistry class.

chemistry class and so what we could do is take a balloon and we could measure the volume of the balloon when the gas

So what we could do is take a balloon and we could measure the volume of the balloon

is around freezing and so let's say we do that by measuring the circumference

when the gas is around freezing. And so let's say we do that by measuring the circumference

around the balloon and then using a little geometry to figure out its volume

around the balloon and then using a little geometry to figure out its volume. If we increase

if we increase the temperature so let's say we bring it inside and we really increase the temperature the volume is

the temperature, so let's say we bring it inside, and we really increase the temperature,

going to increase and if we really lower

the volume is going to increase. And if we really lower the temperature, put it in a

the temperature put it in a freezer then we're going to decrease the temperature and what you'll find is a linear

freezer, then we're going to decrease the temperature. And what you'll find is a linear

relationship and so you could extrapolate that line and we could get to negative 273 which is going to be

relationship. And so you could extrapolate that line and we could get to negative 273.

absolute zero that's when there's no molecular motion and

Which is going to be absolute zero. That's when there's no molecular motion and everything

things can come to a stop now let's look at Avogadro's law now we're looking at

has kind of come to a stop. Now let's look at Avogadro's law. Now we're looking at volume

volume and N and remember is going to be the number of moles of the gas that we

and n. n remember is going to be the number of moles of the gas that we put in. So let's

put in so let's look at this simulation right here well there's no temperature and no pressure inside the container and

look at this simulation right here. Well there's no temperature and no pressure inside the

that's because there's no gas and so let me squirt a little bit of gas inside

container. And that's because there's no gas. And so let me squirt a little bit of gas inside

there as we increase that now those molecules are going to start bouncing

there. As we increase that, now those molecules are going to start bouncing around. And so

around and so we have a specific volume what do you think is going to happen as

we have a specific volume. What do you think is going to happen as I increase the number

I increase the number of molecules inside there the number of moles inside there well we're going to try to keep

of molecules inside there? The number of moles inside there? Well, we're going to try to

the pressure constant try to keep the temperature constant and what's going to

keep the pressure constant, try to keep the temperature constant. And what's going to

happen is look the more molecules we put in there now we're increasing that

happen is look, the more molecules we put in there, now we're increasing that. We're

really increase in the volume so we've got a direct relationship more moles

really increasing that volume. And so we've got a direct relationship. More moles, more

more volume and so this is for anodite ideal gas remember PV equals NRT only works if we have an ideal gas what is an

volume. And so this is for an ideal gas remember. PV=nRT only works if we have an ideal gas.

ideal gas it's a gas where these things are randomly moving around and there

What is an ideal gas? It's a gas where these things are randomly moving around. And there

also is no attraction between those those molecules aren't pulling on each

also is no attraction between those. Those molecules aren't pulling on each other. If

other if they start to pull on each other then this is going to fall apart

they start to pull on each other then this is going to fall apart. And also an ideal

and also an ideal gas only works when we have an infinite number of an infinite

gas only works when we have an infinite number of, an infinite volume, which we're not always

volume which we're not always going to have but let's say we do have an ideal gas if I just solve for n this should

going to have. But let's say we do have an ideal gas. If I just solve for n, this should

always be equal to 1 in other words PV over RT should always be equal to 1 for any kind of a gas and

always be equal to 1. In other words, PV over RT should always be equal to 1 for any kind

so let me just plot that for a specific

of a gas. And so let me just plot that for a specific gas. Let's say we're looking at

gas let's say we're looking at nitrogen right here it's ideal gas at different pressures should stay exactly at 1.0 but

nitrogen right here. It's ideal gas at different pressures should stay exactly at 1.0. But

let me throw up some data this is what nitrogen looks like at a thousand Kelvin

let me throw up some data. This is what nitrogen looks like at 1000 kelvin. This is what it

this is what it looks like at 500 Kelvin this is what it looks like a 200 Kelvin

looks like at 500 kelvin. This is what it looks like at 200 kelvin. And so these are

and so these are real gases ones that have been measured and so what are we

real gases. One's that have been measured. And so what are we finding? Is that they don't

finding is that they don't fit the ideal gas law and why is that well as we slow everything down as we make it cooler we

fit the ideal gas law. And why is that? Well, as we slow everything down, as we make it

start to get attraction between those molecules and also we are going to have

cooler, we start to get attraction between those molecules. And also we are going to

a finite volume in other words it's in a container when we're measuring it and so

have a finite volume. In other words it's in a container when we're measuring it. And

what we have to do is we have to start to look at real gas interactions as we

so what we have to do is we have to start to look at real gas interactions as we get

get towards condensation and what's condensation remember that's point which the gas becomes a liquid and so

towards condensation. And what's condensation remember? That's the point at which the gas

this would be water that was in the air

becomes a liquid. And so this would be water that was in the air that's becoming liquid

that's becoming liquid water on this cool bottle right here and as we get closer and closer to condensation then

water on this cool bottle right here. And as we get closer and closer to condensation

we have to throw out some of those ideal gas laws and use real gas interactions

then we have to throw out some of those ideal gas laws and use real gas interactions. And

and so did you learn the following to use KMT that's collective kinetic

so did you learn the following? To use KMT, that's kinetic molecular theory and force

molecular theory and force concepts to make macroscopic predictions of what's going on remember those are the two

concepts to make macroscopic predictions of what's going on? Remember those are the two

things that guide ideal gas law KMT things are moving around and then this

things that guide ideal gas law. KMT, things are moving around. And then this Maxwell-Boltzmann

Maxwell Boltzmann distribution they interact with each other but they're not going to influencing each other

distribution. They interact with each other, but they're not going to influence each other.

even though they might bounce into each other and the idea that faster molecules

Even though they might bounce into each other. And the idea that faster molecules are generally

are generally going to be lighter in a gas also could you apply ideal gas law PV equals NRT we did that in a number of

going to be lighter in a gas. Also could you apply ideal gas law, PV=nRT. We did that in

different simulations and then finally could you use this to solve some

a number of different simulations. And then finally could you use this to solve some problems?

problems and we did this for a basic pressure volume kind of problem and so those are gases they're everywhere and I

And we did this for a basic pressure volume kind of a problem. And so those are gases.

hope that was helpful

They're everywhere. And I hope that was helpful.