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Gases - Concept

Teacher/Instructor Kendal Orenstein
Kendal Orenstein

Rutger's University
M.Ed., Columbia Teachers College

Kendal founded an academic coaching company in Washington D.C. and teaches in local area schools. In her spare time she loves to explore new places.

The gaseous state is one of the three phases of matte. Gases are obtained through vaporization from liquid and sublimation from solid. When a liquid vaporizes, it is often called boiling. Gases are the least dense state of matter because they contain high kinetic energy.

Alright. So we're going to talk about gases and the kinetic molecular theory. The kinetic molecular theory describes the behavior of gases in terms of motion. This theory is divided into five postulates. It's also describe how we can derive the laws to create the gas laws okay, and how they behave.

Alright. So there's five postulates, lets go through each one. The first one says the gases do not repel, attract each other. Actually, that we know is not the case. Intermolecular forces actually do exist within gas particles, the hydrogen bonding, the interactions and the dispersion forces actually do take place within gases. But they're so weak and so negligible that we're actually going to say we're going to ignore them. And the reason we're going to actually now call these, all these four postulates come from and make up what we call ideal cases. Ideal scenarios. Okay? So ideally, we're going to say we're ignoring the fact that they have IMF.

The second postulate we're going to talk about is that gas particles have no volume. Again we know that this is not true. I'm going to put an 'nt' by these two, not true. Gas particles do have volume but it's extremely negligible compared to the volume of the actual thing that holds it. So, again we're going to completely ignore it then the gas particles have no volume. It just makes calculations easier. We're going to put this under an ideal situation. An ideal gas.

The third one states the gas particles are in constant random motion. That's true. They're always moving around, they're always bouncing off things. They're always going in straight lines until they're dry, until they actually veer off. But that is true. Gas particles are constantly in motion. They never stop moving.

The fourth one is that no kinetic energy, we're going to call kinetic energy 'ke', you might see that in class, is lost when particles collide with each other with the wall of the container. That's true. When particles when they're going, when they're moving and they hit something, they actually have got what we call elastic collisions. Meaning that they do not lose any kinetic energy and kinetic energy is saved within that collision whether it's within another gas particle or at the walls of the container. They are elastic collisions.

The last one we say it's all gas particles have the same kinetic energy at a given temperature. Temperature is a measurement of kinetic energy and we when we measure the temperature, we're measuring that kinetic energy of these particles. So that's actually very true.

So when we're talking about the kinetic molecular theory, the first two are assumptions that we're talking about an ideal situation because these other things are very small. The IMFs and the volume. But everything else is true no matter what gas you're talking about in all scenarios.

So the behavior of gases are based on four main factors. They're based on the volume of the container that they're in, the pressure that is on the container within those gas particles, the amount of gas particles that we're talking about and the last one is the temperature. Temperature. And we want to make sure when we're dealing with gas particles that have temperature we're talking about calculations is always in Kelvin. Why would we want to, why do we care about that? Because kelvin is never ever negative and we don't have, we don't want to deal with negative values, when working with gases. Okay?

So those four, those five postulates make up the kinetic molecular theory.