Full transcript of “Boyle's Law”. Click a timestamp to open the video at that moment. Need another video? Use the YouTube transcript generator.
0:00 let's take a look at the relationship between pressure and volume of a gas to do this we're going to imagine that we have a container similar to ones that we've looked at before where I've got a plunger on one end this container is filled with gas particles which I'll indicate as usual by these red circles here right now the pressure on this gas sample is relatively low P stands for pressure but as we've learned previously because gas is compressible I can put pressure on this piston and I can push it further into the container and what's eventually going to happen after I've increase the pressure there is that I'm going to have all these gas particles squeezed into a much smaller area so over here the
0:47 pressure is much higher let's look at what happens to the volume during this change volume right here relatively speaking is pretty high these gas particles have a good amount of room to move around in on the other hand the volume over here is pretty low we've squeezed them into a much smaller space so as pressure goes up from low to high volume goes down what this means is that the relationship between pressure and volume is an inverse relationship as pressure goes up volume goes down they move in different directions on the other hand if pressure were to go down the volume would be able to go up you're familiar with an inverse relationship uh
1:34 because you see this a lot with the cost of things you buy as something becomes more expensive fewer people want to buy it on the other hand as the price of something lowers more and more people want to buy it so that's an example of an inverse relationship too things moving in different directions pressure and volume also move in different directions because they have an inverse relationship let's look at how we can actually plug num into an equation and use this relationship to solve math problems the relationship between pressure and volume of a gas is described by Bo's law which is named after the scientist who figured out what the relationship between pressure and volume of a gas was Bo's law can be
2:20 stated that P1 * V1 equals P2 * V2 Bo's law assumes that we have a gas and it experiences some sort of a change maybe we increase or decrease the pressure change the volume in some sort of a way so P1 V1 means that the pressure and the volume before the change multiply together so here we have before equals the pressure and the volume after the change multipli together so let's move right into an example of a math problem that we might do to see how we can use this I think it'll make a lot more
3:07 sense here is a sample problem we say here at 1.70 ATM a sample of gas takes up 4.25 L if the pressure on the gas is increased to 2.4 ATM what will the new volume be so as we said before there's a change that takes place we increase the pressure we now want to look at the before of the gas and after of the gas figure out which of these variables we need to solve for okay at 1.7 ATM a sample of gas takes up 4.25 l so we have the before pressure 1.70 ATM and we have the before volume 4.5 L we now say if the pressure on the gas increased to 2.4 ATM what will the new volume be so we
3:53 have P2 we have the second pressure after the change we don't have the volume so it's going to V2 that we're going to be solving for we'll want to rearrange this by moving P2 under uh under this other thing so we're going to get P1 V1 / P2 equals V2 and now let's go ahead and plug in our numbers initial pressure is 170 ATM time initial volume which is 4 4.25 L divided by the second pressure which is
4:39 2.40 ATM now let's take a look at how we set this up ATM's up here ATMs down here which means that the atmospheres are going to cancel out we're left with liters and our final answer is going to be 3.01 l before we uh before we call it quits let's see if this makes sense well we started at 4.25 L and we increased the pressure on the gas which means that we squeezed it into a smaller space so 3.01 L is less than 4.25 L this makes sense that we'd have a smaller volume after increasing the pressure now if you need to learn more about Bo's law how Bole
5:24 figured out this relationship in the first place or uh want to look at graphs or something in your textbook that says P * V equal K go ahead and look at the uh the more complex boils law video otherwise you can just move on to the next gas law videos
