hello and welcome back this video we are going to talk about kinetic molecular theory and ideal gas behavior kinetic molecular theory abbreviating is just KMT is a theory that describes the behavior of gases under changing conditions and kinetic molecular theory states five points that are going to be very important or are helpful for us to understand what's happening at the macroscopic level based on what the molecules are doing and it talks about the the theory based on the molecular motion kinetic molecular theory in describing what guests gas symbols are doing or happening within okay so the first point is that gas molecules are in constant random motion and let's consider what that's really telling us and how we know that point to be we know that gas molecules are moving very very fast that's something that we learn early on in elementary school what happens if as they're moving along they get slower and slower well if that's the case then eventually they're going to stop moving and we know gas molecules like let's say our air rate is a gas we know it remains gas over time which is telling us that the gas molecules don't stop moving and it's just constant motion and their motion is random alright this next point is one of the points that describes what an ideal gas is the volume that the actual molecules themselves are taking up relative to the volume that they're occupying the space in which they're moving and occupying is virtually nothing for example if we take all the molecules in this room and we condense them down so that they are all together and we can measure the space that they themselves bulbs are taking up we would find that relative to this overall size of the room that they're moving around and bouncing around in they may take up maybe that much space can you see that that's almost nothing right alright so the molecules themselves are not taking up much space relative to the overall volume in which they're moving that's the second point in kinetic molecular theory now the third point that I have here also in conjunction with the second point identifies ideal gas behavior okay so for the third point and in conjunction with the volume of the molecules that I just described now as these molecules are moving around right relative to the amount of space they're in even when they come close to each other they're simply going to collide and bounce off this point is telling us that when they get close enough before the collision and then after the collision they're not going to interact with each other for example if you have a polar molecule like water right and you get another molecule of water and they're approaching each other there's going to be a polarity thing happening where they can start interacting with each other well if we're dealing with an ideal gas then these molecules are in under certain conditions of pressure and temperature and volume that I'm going to talk about after we get done with these points whereas they're colliding and coming together they don't have a chance to interact they're simply going to collide and come back off of that collision without any kind of interaction with each other now that's kind of an approximation but that's what an ideal gas means is that you have conditions for gas that allows them to not or keeps them from interacting with each other all right so these are the two points that identify what an ideal gas is or what it means to to have a gas behaving under ideal behavior okay the next point tells us that the average kinetic energy of the molecules in the gas each sample is constant over time all right so what does that mean let's let's explore the following let's say that a gas molecule is moving at whatever rate and it collides right and it bounces off of that collision well if it loses any energy in that collision and count comes off the next collision it makes it may lose some more energy and what's going to eventually happen well it's keeps slowing down it's going to stop and we know that's not the case so whatever collision it it has if it loses some of its energy that energy is transferred to the other particle in which that it collided that it collided with and now the other particle comes off with greater energy when this one loses some energy and overall as they collide again with each other and so on and then large collection of molecules obviously in a macroscopic sample of gas that the average of all the kinetic energy with the collisions and what have you overall remains constant which brings us to the last point and that is the average kinetic energy can be measured by temperature and temperature and we saw in a previous video the properties of gases we define temperature as the average kinetic energy of the molecules well that is actually the definition that we get from kinetic molecular theory so the average kinetic energy of molecules has to is a proportional to temperature but it has to be the absolute temperature because what if you are in Celsius and you have zero degrees Celsius does that mean that there's zero average kinetic energy absolutely not okay what if you have negative temperature does that mean that the molecules have negative kinetic energy what exactly does that mean it does it's meaningless so we that's the reason why we have to deal with temperature in Kelvin that's a very important point all right so now we've seen the points of kinetic molecular theory and I've described for your identified defined for you what it means to for something a gas sample to be under conditions where it's behaving as an ideal gas now what exactly are those conditions that give rise to ideal gas behavior alright so for ideal gas behavior the conditions that cause or have a molecule or gas sample that is more conducive to being behaving as an ideal gas are large volume the more space that the gas molecules are moving in the farther they are from each other the less likely they're going to be close enough to interact and stick together and now the volume of the molecules collectively starts impacting the overall volume okay so the larger the volume the more ideal the gas is going to behave well with with that then the lower the pressure of the gas that means the larger volume needs to remember are well we haven't yet talked about it but you will see it in a later video where we've talked about the relationship between pressure and volume and lastly temperature usually when I asked students what do you think the temperature has to be whether it's low temperature or high temperature that would cause the molecules to be more ideal in their behavior and more often than not the students will tell me low temperature and that's actually backward let's explore what happens temperature remember is average kinetic energy and the faster the molecules are moving the more energy more energy in their motion and as they approach each other they're moving so much faster that they are more like likely to have an elastic collision one that comes where they come off with no interactions and no net loss of energy than if they're moving more slowly so they're more slowly they're moving and they're approaching each other they're going to be able to align themselves with the polarities or whatever the interactions are going to be for that for those particular molecules so the faster they're moving the less likely they will interact with each other so high temperature would be more conducive to ideal gas behavior when we talk about an ideal gas that is under seas types of conditions and if we take the same gas sample and we lowered the same temper the same sample and we take it and we lower the temperature the lower the temperature goes the less ideal that same sample is going to behave if we decrease the volume if we're compressing the gas we're pushing them closer to each other the more likely they're going to interact with each other the less ideal and behavior so it's not that this gas is ideal and this gas is not it's this gas under these conditions is more ideal the same gas under these conditions is less ideal and a less ideal gas what we call that is a real gas okay and there is a specific equation or several equations that exist that describe real gas behavior for our course we're only going to deal with ideal gases okay and that wraps up our tutorial on kinetic molecular theory and ideal gas behavior