The Kinetic Molecular Theory of Gas (part 1)

Summary

This lesson introduces the concepts of kinetic energy, phase changes, and the states of matter, emphasizing how gases differ from solids and liquids. It explains the kinetic molecular theory of gases, which outlines five key rules: gas particles are small and widely spaced, they move randomly in constant motion, collisions are elastic, there are no forces of attraction or repulsion between particles, and the average kinetic energy depends on temperature. The lesson highlights how these principles help us understand gas behavior, setting the foundation for future problem-solving.

Takeaways

• 🧪 The lesson begins with a review of kinetic energy, phase changes, and states of matter, which serve as foundational knowledge for understanding gases.
• 💨 Kinetic energy is energy possessed by an object due to its motion, with faster objects having more kinetic energy.
• 🔴 In solids, particles are tightly packed with minimal kinetic energy, while in liquids, particles have more freedom to move and more kinetic energy.
• 🏃 Gases have the most kinetic energy, with particles moving rapidly and not connected to their neighbors.
• 📏 The Kinetic Molecular Theory of Gases provides rules for understanding how gases behave, even though no real gas follows all the rules perfectly.
• 🔬 Rule 1: Gas particles are extremely small and far apart, leaving lots of empty space between them.
• 🔄 Rule 2: Gas particles are in constant random motion, colliding with each other and the walls of their container.
• ⚡ Rule 3: Collisions between gas particles and the container walls are elastic, meaning no kinetic energy is lost.
• 🔗 Rule 4: There are no forces of attraction or repulsion between gas particles, unlike some other types of particles.
• 🔥 Rule 5: The average kinetic energy of gas particles depends on the temperature – higher temperatures result in faster movement.

Q & A

What is kinetic energy?

Kinetic energy is a type of energy that an object possesses if it is in motion. The faster something moves, the more kinetic energy it has.

How does the kinetic energy of gas particles compare to that of solids and liquids?

Gas particles have the most kinetic energy because they move rapidly and freely, while particles in solids have the least kinetic energy as they are packed tightly and move very little. Liquids have intermediate kinetic energy.

What are the key differences between solids, liquids, and gases in terms of particle movement?

In solids, particles are tightly packed and have very little movement. In liquids, particles have more kinetic energy and can move around but remain close to each other. In gases, particles have the most kinetic energy, moving freely and colliding with each other and the container walls.

What is the Kinetic Molecular Theory of gases?

The Kinetic Molecular Theory of gases is a set of assumptions that describe how gas particles behave. It includes concepts like constant random motion, elastic collisions, and no forces of attraction or repulsion between particles.

What is meant by 'elastic collisions' in the context of gas particles?

Elastic collisions refer to interactions between gas particles or between gas particles and the container walls, where no kinetic energy is lost during the collision. The particles bounce off each other or the walls without losing speed.

How does temperature affect the movement of gas particles?

The average kinetic energy of gas particles depends on the temperature of the gas. As the temperature increases, gas particles move faster, resulting in more collisions and higher kinetic energy.

Why is it difficult to depict gas particles visually in diagrams?

Gas particles are extremely small and spread far apart relative to their size, making it hard to represent them accurately in visual diagrams. For instance, if gas particles were the size of marbles, their container would be as large as a football stadium.

What does the term 'ideal gas' refer to?

An ideal gas is a theoretical gas that follows all the rules of the Kinetic Molecular Theory perfectly. However, in reality, no gas behaves perfectly, but most gases only deviate slightly from these rules.

Do gas particles experience forces of attraction or repulsion?

No, according to the Kinetic Molecular Theory, gas particles do not experience forces of attraction or repulsion. They neither attract each other nor repel each other when passing by.

What happens when gas particles collide with each other or with the container walls?

When gas particles collide with each other or the container walls, they undergo elastic collisions, meaning they bounce off without losing kinetic energy.

Outlines

00:00

🌬️ Introduction to Gases and Kinetic Energy

The first lesson in the unit introduces gases, starting with a review of kinetic energy, phase changes, and the states of matter. Kinetic energy is defined as the energy of motion, with faster movement equating to more kinetic energy. This concept is applied to the states of matter: solids have particles tightly packed with minimal kinetic energy, liquids have particles with more freedom and movement, and gases have particles with the most kinetic energy, constantly moving at high speeds. The lesson sets the stage for understanding gases through the 'Kinetic Molecular Theory of Gases,' which provides rules for conceptualizing gas behavior.

05:01

📏 The Kinetic Molecular Theory of Gases: Rules and Assumptions

This section outlines the key rules of the Kinetic Molecular Theory of Gases. Gas particles are extremely small and far apart, with significant space between them compared to their size. They are in constant, random motion, colliding elastically with each other and container walls, meaning their kinetic energy is preserved during collisions. Furthermore, there are no forces of attraction or repulsion between gas particles, and their behavior is influenced by temperature, with higher temperatures increasing their speed. These assumptions help simplify the study of gases, though real gases may deviate from these idealized rules under certain conditions.

Keywords

💡Kinetic Energy

Kinetic energy refers to the energy possessed by an object due to its motion. In the video, it's emphasized that the faster something moves, the more kinetic energy it has. For instance, a Mac Truck moving down the highway has a large amount of kinetic energy, and even tiny atoms have kinetic energy when they are moving. This concept is crucial when discussing the behavior of particles in different states of matter, such as solids, liquids, and gases.

💡Phase Changes

Phase changes describe the transition between different states of matter—solid, liquid, and gas. In the video, the discussion starts with a review of how kinetic energy affects these changes. As kinetic energy increases, substances transition from solid to liquid to gas. The differences in particle movement and energy between these phases are key to understanding how matter behaves.

💡States of Matter

The states of matter refer to solid, liquid, and gas. Each state is characterized by the arrangement and kinetic energy of its particles. In the video, solids are described as having tightly packed particles with low kinetic energy, liquids have more freedom of movement, and gases have the highest kinetic energy, with particles moving freely and quickly.

💡Kinetic Molecular Theory

The kinetic molecular theory explains the behavior of gases based on the motion of their particles. In the video, it is described as a set of rules or assumptions that help us conceptualize gases. For example, gas particles are in constant random motion, and there are no forces of attraction or repulsion between them. This theory is foundational to understanding how gases behave under different conditions.

💡Ideal Gas

An ideal gas is a theoretical gas that perfectly follows all the rules of the kinetic molecular theory. The video explains that, in reality, no gas behaves as an ideal gas all the time, but the concept is useful for simplifying gas behavior in many situations. Most gases only deviate from ideal behavior under extreme conditions.

💡Elastic Collisions

Elastic collisions are collisions where no kinetic energy is lost. In the video, gas particles are said to experience elastic collisions when they bump into each other or the walls of their container. This means that after each collision, the particles retain their kinetic energy and continue moving at the same speed.

💡Random Motion

Random motion refers to the unpredictable and constant movement of gas particles. According to the video, gas particles are always moving in random directions, colliding with each other and the walls of the container. This random motion is a fundamental characteristic of gases as explained by the kinetic molecular theory.

💡Temperature

Temperature is a measure of the average kinetic energy of particles in a substance. In the video, it is noted that the hotter a gas is, the faster its particles move. This is crucial for understanding how temperature affects gas behavior, as higher temperatures result in more rapid particle movement and increased kinetic energy.

💡Attraction and Repulsion Forces

Attraction and repulsion forces refer to the interactions between particles based on their charges or properties. The video states that gas particles do not experience attraction or repulsion forces, meaning they don't stick together or push each other away. This contrasts with substances like water, where particles may attract each other due to their molecular structure.

💡Particle Size and Spacing

In the context of gases, particles are described as being very small and far apart relative to their size. The video emphasizes that gas particles are so tiny that, if we were to scale them up to the size of marbles, the container they are in would be as large as a football stadium. This vast space between particles is a key feature of gases, allowing them to compress and expand easily.

Highlights

Introduction to gases and kinetic energy review, emphasizing phase changes and states of matter.

Definition of kinetic energy as the energy possessed by any moving object, with examples like a truck and an atom.

Kinetic energy increases with speed; a faster object has more kinetic energy than a slower one.

Overview of the states of matter: solids, liquids, and gases, with a focus on particle arrangement and energy levels.

In solids, particles are packed tightly, with low kinetic energy and limited movement.

In liquids, particles have more kinetic energy and can move freely but still remain close to their neighbors.

In gases, particles have the highest kinetic energy, move rapidly, and are not connected to their neighbors.

Introduction to the kinetic molecular theory of gases, a set of rules for conceptualizing gas behavior.

Definition of an ideal gas, which perfectly follows all the rules of the kinetic molecular theory.

Real gases rarely follow all the rules, but we assume ideal gas behavior for most problems.

First rule of the kinetic molecular theory: Gas particles are very small and far apart relative to their size.

Second rule: Gas particles are in constant random motion and frequently collide with each other and container walls.

Gas particle collisions are elastic, meaning kinetic energy is conserved in the collisions.

There are no forces of attraction or repulsion between gas particles, unlike particles in liquids.

The average kinetic energy of gas particles depends on the temperature—the hotter the gas, the faster the particles move.

Transcripts

this is the first lesson in our unit

about gases we're going to start off

this unit with a quick review about

kinetic energy phase changes and states

of matter um that's information may be

familiar to you but uh even if it is I

think it'll still be a useful review

then we're going to talk about a theory

with a really scary name the kinetic

molecular theory of gases which is a lot

scarier than it sounds and it gives us

some rules for how we can think about

gases and finally we'll look at a few

unique properties of gases uh that are

very different from those of solids or

liquids so let's take a look at uh

kinetic energy first of all kinetic

energy is a type of energy that anything

has if it's moving so a Mac Truck if

it's barreling down the highway it has

kinetic energy and even a tiny little

atom moving around has kinetic energy

thing about kinetic energy is the faster

something's moving the more kinetic

energy it has so kid sprinting down the

street has more kinetic energy than that

same kid just walking down the street

likewise an atom that's moving really

fast has more kinetic energy than that

same atom that's moving very

slowly the idea of kinetic energy is

particularly important when we start

talking about phases of matter let's

take a quick review um brushing up on

what we probably already know about

phases of matter I have here indicated

um some certain representations of

phases of matter I have a container and

some particles in it I've I've got a

representation of a solid a liquid and a

gas let's start with a solid a solid

here like all the other phases of matter

is made up of particles that's what

these little red circles represent

particles can be either atoms or they

can be molecules that are formed by the

atoms coming together either way all

things are all matter and all things are

made up of particles so in a solid the

particles as you can see are packed

together really tightly they have very

little kinetic energy they're moving

around a little bit but for the most

part they're locked in place and they're

locked to their

neighbors the particles in liquid have

more kinetic energy they're moving

around and they're Freer to move they're

still locked in with their neighbors to

some degree but they're swimming around

they're swimming in close proximity to

the particles

nearby gases on the other hand have a

ton of kinetic energy in fact to make

this picture even more accurate what I'm

going to do is I'm going to add a few

arrows these arrows are going to

represent the fact that these gas

particles are in constant motion they're

moving mov around all over the place

they're banging against each other and

they're banging against the sides of the

container that they're in in fact these

gas particles are moving so quickly that

a room temperature they have about an

average speed of a th000 miles an hour

that's just how fast they're zipping

around here in this

container so solid liquid and gas have

increasing amounts of kinetic energy

gases have the most kinetic energy

they're flying around in there and

they're not connected at all to their

neighbors now this is a very superficial

representation of what a gas looks like

but often we're going to want to look at

problems and think about gas

conceptually in a way that'll make it

necessary um to have some some deeper

understanding about what a gas is and

how these gas particles behave we

obviously can't see gas so in the

problems that we're going to do later on

we have to have a way to think about it

a way to conceptualize it so it's useful

to set up a series of rules for how we

expect gases to behave we'll make these

rules or assumptions and then we can

keep them in mind when we have to solve

problems or do

calculations now this list of rules is

What's called the kinetic molecular

theory of gases often times it's just

referred to as the kinetic theory of

gases and as I said it's a list of rules

expectations assumptions of how we

expect gases to behave now if a gas

follows every single one of these rules

we call it an ideal gas but in the real

world world it's very hard to come up

with an example of anything that always

follows all the rules we might want to

think that there exists something like a

perfect student an ideal student or an

ideal kid but rarely that's the case

almost always we find a few exceptions

to the rules and so because of that it's

helpful to think of an ideal gas but in

the real world none of these gases that

we're going to talk about ever follow

all the rules all the time at the end of

this unit we'll look look at some

particularly bad offenders gases which

break rules more more often than others

do and we'll look at certain situations

that cause gases to break the rules for

the most part though in all the gases

that we're going to look at now we're

going to assume that they're ideal gases

we're going to assume that they follow

all the rules all the time and for the

most part most of these gases only break

the rules in Little Bits once in a while

so we we can safely assume that all the

gases we're deal dealing with these

rules R of the kinetic molecular theory

so let's take a look at what some of the

rules of this are and once again

sometimes it's just referred to as a

kinetic theory going to write down here

kinetic

molecular

theory of

gases so in no particular order let's

take a look at uh some of the

assumptions that we make about gases

here's the first

one gas consist of very small particles

that are far apart relative to their

size this is something that's very

difficult to depict visually and I

certainly didn't do a good job of it in

the phase in the phase diagrams that I

just showed

you gas particles in the uh in the

picture that I drew you look like

they're the size of marbles in a glass

jar this isn't true at all gas particles

are so tiny that instead of think of

them as marbles in a glass jar if the

gas particles are the size of marbles

are contain container would be like the

size of a football stadium so these guys

are absolutely tiny and there's a ton of

empty space between them that's the

first thing that we want to keep in mind

when we're dealing with

gases here is a uh a second thing and

this is very important gas particles are

in constant random motion we hinted

about this earlier with those arrows

that I drew of the the gas is moving

around the moving particles constantly

collide with each other and with the

walls of the container so so all the

time whenever I have gas in any sort of

a container or even if it's just in a

room these guys are zipping around

they're bouncing against the walls and

they're bouncing against each

other now let's think about those

balances a little bit more there are a

variety of ways for things to to bounce

into each other and here we say that

collisions between gas particles and

container walls are elastic

collisions what's an elastic Collision

let's think about two balls of slime

these two balls of slime on either Sid

come together and what's going to happen

they're just going to hit each other and

they're

gr this is what we call an inelastic

collision that means that the kinetic

energy that both of these guys had got

wasted in the Collision these guys were

both moving they came together and they

just kind of went blah and all the

kinetic energy to speed the motion that

they had disappears in the Collision

this is like what happens if you Chuck

an egg against the side of a wall it

hits the wall and then it just drips

down but the motion that it had the

kinetic energy

disappears that's an inelastic collision

the collision between gas particles and

container walls on the other hand are

elastic

collisions a good way to think about an

elastic Collision is think about what

happens when two red or or pink round

rubber balls hit each other they hit and

they bounce right off or one of those

pink rubber balls hits the side of a

wall bam it bounces right back the

kinetic energy isn't wasted in the

Collision this ball hits here and it has

a same amount of kinetic energy

afterwards that it had when it started

that's the exact kind of collision that

gas particles get into they Bang into

each other and they just fly right apart

or they hit the side of a container wall

and they just bounce right off it so

whenever you think about gas particles

colliding you always want to keep in the

in in mind the idea of elastic

collisions additionally we can say that

there are no forces of attraction or

repulsion between gas particles some

particles like water molecules kind of

like each other and so almost like weak

little magnets they tend to attract

other particles two particles that have

the same charge don't like each other

they're sort of afraid of each other and

so they're going to repel they don't

want to get anywhere near each other

what this law is is saying when we say

there are no forces of attraction or

repulsion between gas particles what we

mean is that gases are flying around and

they're not going to start clumping

together because they're attracted to

each other that doesn't happen there's

not that attract ction likewise let's

assume that two gas particles are

passing each other they're just going to

fly right by if they repelled each other

Zoom they'd hit out that way when they

get close that doesn't happen they don't

repel each other and they don't attract

each other

either lastly here's what I think is

probably the most important thing to

keep in mind when we're talking about

the kinetic theory of gases and that's

that the average kinetic energy of gas

particles depends on the temperature of

the gas the hotter it is the faster they

move so remember that hotter for gas

movement equals faster this is

tremendously important the hotter it is

the faster these gas particles move

around so in this kinetic theory of

gases we've looked at a few of the rules

that we always want to keep in mind

whenever we're dealing with gases and

again we're going to assume that all the

gases we're dealing with follow uh

follow these five rules that we just

talked about