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Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
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Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
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Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

A gas is seen as a collection of molecules or individual atoms that are in constant motion. The Kinetic-Molecular Theory tries to use data of real gases to predict how an ideal gas would behave if they existed.  

Examining the Kinetic-Molecular Theory

Concept #1: Understanding the Kinetic-Molecular Theory

Transcript

Welcome back guys, in this new video, we’re going to take a look at the Kinetic Molecular Theory for gases.
Now, to better understand the behavior of gases, that’s why we use the Kinetic Molecular Theory. It’s a way of explaining what happens to gas particles as external pressures and temperatures influence them. We’re going to say a gas is not just simply a single thing, it’s a collection of particles that move together and are influenced by these pressures and temperatures on the outside of the container.
We’ve been talking about ideal gases this whole time, but what exactly is an ideal gas? Well, to be an ideal gas, you have to follow certain criteria or characteristics.
If we look, we’re going to say we have this vessel right here. Inside of this vessel, we have little black dots. Those little black dots represent individual gas particles. We have arrows pointing away from them because they’re moving in straight lines. They’re going to be bouncing off one another and bouncing off the walls on their containers. 

Ideal gases are imaginary and don’t actually exist. However, if they did exist then there would be certain characteristics that a gas would need to possess in order to be an ideal gas. 

Concept #2: The Characteristics of an Ideal Gas

Transcript

The first criteria to be an ideal gas is, we’re going to say the size of the particle is significantly small when compared to the volume of the container.
What does this mean? That means if you look, look at all this volume inside this container. If you compare the size that’s free to the size of each gas particle, you’re going to say that gases really don’t take up that much room. That’s what it takes to be an ideal gas.
So the first criteria is the gases have to be very small and there has to be tons of room around because an ideal gas assumes that it’s alone. It acts as though it’s the only person there. That’s what an ideal gas is. An ideal gas is kind of like a diva, it only thinks that it’s by there by itself, no other gases are around, no other gases matter. The only thing that is important is that particle by itself.
So if we think of this, usually an ideal gas will take up about less than 1%, usually about 0.0% of the total volume. So, an ideal gas, an individual gas particle would take up usually less than this percentage of the total available space.
The next thing to be an ideal gas, we’re going to say the average kinetic energy of a particle is directly proportional to the temperature of the container in Kelvins. What the heck that does mean? Well that means, an ideal gas, when we increase the temperature that increases the average kinetic energy of that gas. We’ve said this before, we increase the temperature to a container, the gases absorb that thermal energy and convert it to kinetic energy. So, they have greater kinetic energy.
Now, this is going to be different from velocity. Velocity and kinetic energy are different. If we increase the temperature, we don’t increase the speed of those gas particles. All we’re doing is increasing their kinetic energy. We’re making them vibrate at a higher frequency, a higher level, so they’re shaking more. Velocity comes from weight not from temperature so remember that. Increasing the temperature increases the kinetic energy, not the velocity or speed. To increase the velocity or speed, you need to reduce the weight of the gases. The less you weigh, the faster you move.
Now, we’re going to say the collision of a particle with another gas particle or with the walls of a container are completely elastic. That means that when the gas particles are hitting one another or hitting the walls of the container, they bounce off, kind of like ping-pong balls inside of a container. They’re all bouncing around but none of them are sticking together. So to be an ideal gas, when you hit another ball, another gas particle, you’re not suppose to stick to it.
We are also going to say because they’re completely elastic, once they bounce off each other there’s a transferring of energy. So Gas A hits Gas B. Gas A is going to transfer its energy to Gas B. B is going to transfer its energy to Gas A. There’s a transfer of energies. So no energy is lost. This is what we mean by the third criteria to being a gas law.
And so what we are going to finally say is these are the three criteria you need to follow in order to be an ideal gas. Your professor more likely will give this to you as a theory question. So, you just have to remember, to be an ideal gas you have to be very smaller compared to the total volume. To be an ideal gas, your average kinetic energy is influenced by the temperature, not your speed or velocity. To be an ideal gas, you’re bouncing off the walls, you’re bouncing off other gases but you don’t stick. You are just bouncing around.

Example #1: Two identical 10.0 L flasks each containing equal masses of O2 and N2 gas are heated to the same temperature. Which of the following statements is/are true?  

a) The flask with the oxygen gas will have a greater overall pressure.

b) The nitrogen and oxygen gases will have the same average speed or velocity.

c) The nitrogen and oxygen gases will have the same average kinetic energy.