 Let's try this second phase change diagram question. So this is the phase diagram of carbon dioxide. And it says, for this phase diagram, answer the following question. So the first question says, what phases are present at point C? So I think the easiest way to do these problems is to write out the phases of the graph to begin with. So hopefully, we could do that this time. So what phase is present up here at very high pressures and low temperatures? Solid, right? So that's probably a good way to look at it. And what phase is present down here at very low temperatures and high pressures? Dacid. And then in the middle is a liquid. So we have that written down to start off, OK? Some things we know about carbon dioxide is atmospheric pressure does it, like just from what you know from dry ice, does it go to a liquid phase? No. So we want to keep that in mind, OK? So the first question is, what phases are present at point C? So notice point C is on that phase change boundary line, right? So this is actually the line you get. Does anybody know what equation will give you this line here? Is that equation that we learned in this chapter? The Clausius-Clapeyron equation, OK? If you do that Clausius-Clapeyron, it will give you that phase change line there, OK? That's what it's actually measuring. But what phases are present at point C? Liquid phase. And gas, OK? If since it's on the line, if it was up here, it would just be liquid, OK? So at point B, what phases are present? Solid. Just solid, OK? So let's turn our attention to point B and say, if we start at point B and we lowered the pressure to zero pressure, what phases would we go through, OK? So what would we start at here? Solid. And then when we go down, down, down, what do we change to? Gas. Gas. Do we ever see a liquid phase? No. No? So we just go from solid to gas. What's that phase change called? Solid to gas. Solid to gas is sublimation, right? Deposition would be the opposite of that, OK? And I'm sure you can understand why, OK? What if we started at point and increased the temperature? What would we do? What phases would we go through? Solid to gas. And gas again. So what is that called, phase change? Sublimation. Sublimation, like we just said, right? Solid to gas, OK? So what if we started at point C and decreased the temperature? What would we go through? Gas, liquid. Yeah, gas. Solid to solid, right? Like that, OK? Makes sense, right? OK, so now it'll ask us, well, what is the name of point D there? So point D, all phases are present at point D. So that kind of gives you a clue as to the name. So what is the name of that? That's your whole point, very good. So let's write that down so we don't forget it. There's one more point that wants us to identify. It's point E. What is that point called? The critical point. Above that point, what happens? Anybody know? No phases, liquid, gas, or water are present. This is the phase supercritical fluid, OK? That you won't know anything else about, except for supercritical fluid. Let's see what else we want to ask. What is the normal sublimation point of carbon dioxide? So remember, what does that mean? The normal, like if I said, what's the normal boiling point, or the normal freezing point? What would that mean? And the freezing point. The point at freezing at atmospheric pressure. So the normal sublimation point is going to be the point of sublimation at what? At atmospheric pressure, right? So what would be that temperature? Negative 78. Negative 78.5 degrees Celsius. OK, so that one there. And if I asked you, well, what's the pressure at the triple point? Could you tell me that? 5.11 ATM. Yeah, 5.11 ATM, OK? And then I guess the one last question we want to ask is, can we tell just by looking at this graph whether the solid is more dense or the liquid is more dense? And how will we do that? Well, part of the graph will we have to look at. Anybody know? So it's this portion here, the solid to liquid phase change line. We have to look at it, OK? If this is positive, OK? That means the solid is more dense than the liquid, OK? If it's negative like waters is, that means the liquid is more dense than the solid. So remember with water, the ice cubes float on top of the liquid, right? So the solid's less dense. And carbon dioxide is opposite, OK? So in this case, the solid is more dense than the liquid. So if you had both of those in the same container, the solid would be on the bottom of the liquid. Any questions about this phase diagram? OK, wonderful. Good job, guys.