 All right, gas video number two, measuring gases. There are a number of very important ways that we measure gas, and all our gas laws deal with these measurements. You know, Boyle's law will be the relationship between pressure and volume. Charles law will be the relationship between volume and temperature. It's all about how we measure these gases and how when one of those measurements change, how the other one will behave, how it will respond to that. These measurements are a very important thing. We'll measure gases in four main ways, one of which will be volume. Volume is the amount of space a gas occupies. The amount of space a gas occupies. How much room it takes up? As far as gases are concerned, one of the things that we talked about when we reviewed those definitions from physical science is how gases are the only substance that can assume the volume of its container. So the volume of a gas is equal to the volume of the container. So you take a gas and put it in a two liter bottle as volume will be two liters. Take a gas, put it in a gallon jug, it'll be a gallon. It's the only state of matter that can assume both the volume and the shape of this container. Now how do we measure that? What kind of units will it be measured in? The most common units will be liters, abbreviated L, milliliters, abbreviated ML, cubic centimeters, abbreviated CC or CM cubed, and cubic meters, meters cubed. Those aren't the only units that we could use to measure the volume of a gas, but these are the ones that are most commonly used. One you use depends on the situation. If you are bubbling a gas into a flask and trying to measure how much gas is bubbled into it, it's probably going to be in liters or milliliters, depending on the size of the flask. Because that's what we usually mark those off in. If we're trying to talk about the volume of a gas in a classroom, for example, but you can't really do that with a flask, you would have to measure the length, width, and height of the classroom and calculate its volume. And those calculated volumes end up being in these cubed length units, like cubic meters for the classroom. Converting between these units is a matter of metric conversion. That's your King Henry died by drinking chocolate milk. If I wanted you to convert between these volume units, all you have to know is the prefixes, where you're starting and where you're going. So if you had to convert 1.7 liters to milliliters, all you'd have to know is it's kilo hectodeca base unit, desiccene mille. And again, the way we most often do that, King Henry died by drinking chocolate milk, kilo hectodeca base desiccene mille. Leader is a base unit. So we're starting here, we're going to mille, which is over here, one, two, three places over the right. Take the decimal point, move it, one, two, three places over the right. Fill those empty place values with zeros. And we can say 1.7 liters equals 1,700 milliliters. Again, just a basic metric conversion. If you need more on that, there's a whole video I've posted on it. And that's really all you'd have to do with these volume ones. Another big way that we measure gases is pressure. Part of what we said about the kinetic molecular theory is that the particles of a gas will run into each other in the walls of the container. When they run into the walls of their container, they exert a force on the walls of those containers. The cumulative effect of that, the effect of all those different particles running into the walls of the container is pressure. We define it as force per unit area. So again, we have this wall of this container here and we have these gas particles coming at it. And they're gonna run into it various different angles because again, their motions random. The combined effect of all that force over this area, that's pressure. We measure pressure in a number of different units. Atmospheres, abbreviated ATM. That's one very common unit that we use to measure the pressure of gas. At sea level, the pressure of the air is one atmosphere. That's what it's defined on, that's what it's based on. We have millimeters of mercury, abbreviated M-M-H-G. It's a very old unit. It goes all the way back to the inventions of the barometer. The way the barometer worked was with a tube full of mercury and they'd measure how high that column of mercury was. We have Tor, abbreviated Tor. There's no real abbreviation for it. It's very closely related to the millimeter of mercury thing. In fact, one millimeter mercury is one Tor. We have Pascals. Usually we measure it in kilo Pascals, which would be KPA, kilo and then the PA for Pascals. And there's others, but these are the most common ones that we use in gas laws and chemistry. Converting between these units is more difficult because it's not just plain old metric. You have to know equivalences to make these conversions to be able to go from one unit to the other. And I kind of base mine around one atmosphere a lot of them anyways. That pressure at sea level is 101.325 kilo Pascals. One atmosphere, that pressure at sea level is 760 millimeters of mercury. One atmosphere, that pressure at sea level is 760 Tor. Again, one millimeter mercury equals one Tor. That's why those numbers are the same. We wanna relate some of these to each other. One kilo Pascals is 7.5 millimeters of mercury and one millimeter mercury as I mentioned is one Tor. There are others, there are more. We didn't even put PSI in there, pounds per square inch. There's others and you can look these equivalences up. Bottom line is these equivalences would be given to you anyways. I don't expect my students ever to memorize these types of equivalences. To do the conversions here, you would have to do some dimensional analysis. So if we wanna convert 2.5 atmospheres to millimeters of mercury, we would need the equivalence for atmospheres and millimeters of mercury. One atmosphere equals 760 millimeters of mercury. This is very much like stoichiometry. You start with your given, the 2.5 atmospheres times and then a conversion factor. The conversion factor's job is to cancel out that given unit, those atmospheres. It's made from the numbers and the equivalence. So it's either one atmosphere over 760 millimeters of mercury or 760 millimeters of mercury over one. The key is looking here at the atmospheres because we're given atmospheres, we have to put the atmospheres on the bottom so that they'll cancel. Again, the same kind of things you've heard all through the stoichiometry unit. We can ignore the ones because mathematically they don't really do anything. So now we're just trying to figure out if we're multiplying by 360 or dividing by, or 760 or dividing by 760. The key is its location because it's on top. We will multiply by it and we get 1,900 millimeters of mercury. So again, very much like the dimensional analysis we've been working on with stoichiometry, mole mass conversions, mole particle conversions, you name it. It's all the same. Third thing that we see often is temperature. Temperature is the relative measurement of average kinetic energy. We say relative measurement of average kinetic energy because it really does differ from one substance to the next. But it's an indication anyways of how fast or slow the particles are moving. Again, high temperature means fast load, temperature means slow. There's two units that we use with these gas laws that they actually say we see with these gas laws. If Celsius and we have Kelvin. Interesting setup here. Celsius was like the original metric measurement for the temperature of a substance. The thing about it was it was based on water. And because there are things that freeze and melt at much different temperatures than water does, we have this issue of negative temperatures, negative degrees Celsius. And that's really where the whole degree thing comes from. How many degrees away from zero have you gone? 100 degrees means you're 100 degrees away from zero. Negative 100 means you're the same distance away from zero but below it. And this whole negative thing, positive thing was a real issue to scientists because if it's supposed to be average kinetic energy, then why do we have negative numbers? The energy would always be positive. So they came up with this Kelvin scale which eliminated the negative temperatures, which in the end eliminated the degrees too. So there are no degrees Kelvin, it is just Kelvin because everything is over zero. You know, the freezing point of water is zero degrees Celsius. And the boiling point of water is 100 degrees Celsius. What they did is they just lowered the temperatures down so that zero is the absolute lowest temperature that you can have. And what it ended up doing was pushing this whole scale around this whole scale downward 273 degrees. So when we look at the Kelvin equivalents to these, 273 Kelvin is where water freezes because then we just pushed it around a bit and the boiling point is now 373. Still 100 degrees of separation between the both, 100 separation between the both. They didn't really change the markings on it. They didn't really change the scale of it any. What they did is they just moved where zero was. Instead of zero being the freezing point of water, zero was moved all the way down to the bottom of the scale. And what that did is it threw these off by 273. That's good because it makes converting in Kelvin much, much easier to do than in Fahrenheit. If you want to know the Kelvin temperature, it's going to be equal to the Celsius temperature plus 273. That's the boiling point thing here. If it was 100 Celsius, you want to get to Kelvin, it's 100 plus 273. That's where the 373 comes from. If you ever wanted to know what the Celsius equivalent was, you would just take the Kelvin temperature minus 273, and that would convert it out for you. So 373 minus 100 would get us or minus 273 would give us down to that 100 degree Celsius temperature we're all used to that we all know and love. We need Kelvin in our gas laws. For our gas laws to work the way they're supposed to work because the ratios most of the time, we will use Kelvin in the gas laws. That means if you have a temperature that's in Celsius, you're going to have to convert it first. Last way we measure a gas is by amount. That's the number of particles. That's measured in moles. There are no other units. We know one mole of a gas is 22.4 liters at STP. STP is standard temperature and pressure. The pressure would be one atmosphere. The temperature, 273 Kelvin. So that one atmosphere of 273 Kelvin, one mole of a gas of 22.4 liters. We've been doing that stoichiometry so long I don't think we need to talk about moles much more. So that's that for now. Have fun.