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Current time:0:00Total duration:7:16

Video transcript

let's say that I have two different gases at two different temperatures that just got in contact with each other so this is my magenta gas right over here let me draw a bunch of the molecules of my magenta magenta gas right over here and it's just this system over here I guess what you whatever you want to call it has just come in contact with this blue gas then this blue gas right over here and let's say that right when we're starting our simulation or experiment that this magenta gas has a higher temperature higher higher temperature and our blue gas has a lower temperature lower lower temperature so let's just remind ourselves what temperature is especially if we think about it on on a molecular scale so higher temperature lower temperature temperature is proportional to average kinetic energy so these molecules they're going to be vibrating around they're going to be bumping around they're going to have their each of them are going to have kinetic energy and if you average them that's going to be proportional to temperature so let me let me depict each of these individual molecules kinetic energy maybe this one is doing that maybe this one is doing that maybe this one is going in this direction maybe that one is going in that direction that one is going in that direction this is going in that direction that is going to that direction so notice they're all have different directions and the magnitude of their velocity can be different they all have different speeds they or they all might have different speeds so they have different speeds right over here and they're all bumping into each other you transferring their kinetic energy transferring their momentum to from one particle to another but when we talk about temperature we talk about the average kinetic energy or what's proportional to the average kinetic energy of the system well this one each of these molecules are also going to have some kinetic energy but on average it's going to be lower maybe this one is doing something like this this one is doing something like this this is doing something like this this is doing something like this so they're different but on average they're going to be lower so hopefully you see that these Magette two arrows are bigger than these blue arrows that I'm doing and they don't all have to be for example this one might have a lot of kinetic energy but if you average it out the average here is going to be lower than the average here so just like that now if this is our initial state what do we think is going to start happening well before our different groups of gases we're colliding with kind of with itself or the magenta was colliding with the magenta the blue was colliding with the blue but now they're going to start colliding with each other and so you can imagine when this this molecule right over here collides with this molecule it's going to transfer some kinetic energy to it so after the collision after the collision this one might be going so after the collision so let's just say they just bounced into so this is right before and let's say they just finished bouncing into each other so right after they finish bouncing into each other this one might ricochet off so this one is going to go this way let me do this in a different color so it might hit this one bounced off and then transfer some of its kinetic energy and then it bounces off in this direction while this one after the collision after the collision is going to is maybe going to move much faster in this direction and so notice you have a transfer of energy just with that one collision you had a transfer of kinetic energy from this molecule to that molecule and this is going to happen throughout the system that the faster molecules the ones with more kinetic energy as they collide you're going to have transfer of energy so let's see you're going to have a transfer of energy from the higher temperature to lower temperature transfer transfer of energy and this transfer of energy and you could consider this transfer of thermal energy we're talking about temperature here so the word you know everything about things are related to temperature we would say thermal so these this is transfer of thermal energy transfer of thermal energy the amount so you're going to have if you start you're going to start with higher energy here you have higher average kinetic energy you had lower average kinetic energy here but this K this higher can this is going to transfer energy from the Magette to the blue it's going to go from higher temperature to the lower temperature and that energy that's being transferred that energy that's being transferred we call that' this is a word that you have probably heard many times in your life we call that energy that's being transferred we call that heat that literally these hotter this hotter gas over here is heating up is heating up this cooler gas and the way that this this transfer of thermal energy is happening where it's through the collision of the particles the cold the transfer of kinetic energy through the Colet the collision of particles it's a transfer of momentum we call this conduction we call this thermal conduction or I'll just call it conduction I'll call it let me write thermal conduction I'll do it in a new color so this that is being described it's thermal conduction which is a way that many times you've experienced heat being transferred for example you probably have had the experience of if you take a I don't know let's say you take a you take a pot let's say you take a pot like this and let's say it's a cold pot at first so it's particles the particles in the pot have a lower kinetic energy so I'm not going to be able to do all of them and then you put it over a fire you put it over a fire let me see if I can draw it you put it over a fire so this is the fire this is the fire we're talking about really just heating up the middle of the pot I'm not even concerned about what's in the pot right now so this fire is going to heat up is going to heat up the bottom of this pot first and it's actually going to do it primarily through thermal conduction because fire is nothing but superhot air particles and those super hot air particles are going to bump into the metal particles of your pot so these metal metal particles in this pot they're going to be their kinetic energy is going to start going up so this part of the plot is going to start heating up and right when you turn right when you turn your stove on the top of the pot but will still be cool but the bottom is going to get hot very fast but if you just wait a few minutes these these these metal particles are going to keep bound seeing and vibrating into each other and so eventually the top over here is going to get the top over here is going to get quite hot is going to get quite is going to get quite hot and the way that the top of this metal got hot it was through thermal conduction that these the the metal at the bottom got hot first and then they bounced into their neighbors or vibrated in to their neighbors and transferred some of that kinetic energy and so once again you see this transfer of heat from a higher temperature region higher temperature region to a cooler temperature or lower temperature region