 Okay. A pure gaseous substance is cooled as indicated in the heating cooling curve shown on the board. Let's answer some questions associated with this. Okay. On which portion of the graph is only a liquid present? Okay. So, well, why don't we just label the portions of this graph? Okay. And what they're actually saying here. So, what did the problem say? It said that we had a gas that was being cooled. Something like that, right? So, we would expect it probably to go to a liquid then to a salt, right? Something like that. So, if we're starting out up here, that's effectively what it's saying, with a gas, then hopefully you would expect that this portion would be the gaseous portion. Okay. So, I guess the first question said, well, which place is the liquid associated with? Only. There's only liquid. It's from here to here, right? So, in this C region, only liquid. Okay. So, this is where the liquid is. Gas B, well, it would be here in A, right? Only gas, A. So, and then hopefully you guys would expect that only solid would be down here. Other questions. It says, where is a solid present? Okay. So, not only solid, but where else on the graph could you find a solid? Okay. Well, you have to understand what's going on in these portions of the graph B and D. Well, in this portion, right, you're going from a gas to a liquid. So, here is where you've got that gas-liquid equilibrium, okay? And here you're going from a liquid to a solid. So, in here, you've got the liquid-solid equilibrium. So, what it's saying here at D, what this curve is saying, is that you've got both a liquid and a solid in equilibrium at that point. So, if it's saying, if it asks like that question did, where is there a solid anywhere on the curve? So, solid, not only solid, but anywhere there's a solid, it's going to be, then, of course, if you wanted to say where is there a liquid, where is there a liquid, guys? B, C, and B, right? Because we've got, here we've got this gas-liquid equilibrium. So, gas-liquid, so there's a liquid there, a liquid there, and a liquid there. So, solid, if there's a liquid, it's going to be B, C, and D. And then gas, of course, A, and B. What is the name of this portion here? Yeah, this one's called, this is showing the enthalpy of vaporization here. And here, showing the enthalpy of fusion. What it's saying, what it really asks is which part of this gas is, I mean this graph is showing the melting point. Where's the melting point indicated on this graph? D, right? So the melting point is D, and the boiling point is B. So, in other words, we go from a gas-cooled to a gas-liquid equilibrium, which is further-cooled to a liquid, which is further-cooled to a equilibrium, which is further-cooled to a solid. Okay, so that's what this heating-cooling curve is showing. Are there any questions on this one? I think we kind of beat this one. Heating-cooling curve, yeah. Or a cooling curve, yeah. I mean this in particular would be a cooling curve, but I think they're, you know, in general called heating-cooling curves, yeah. Well, so you can call it that, but usually people will say vaporization put a negative. Yeah, just to standardize it, just like here, you know, you'll say fusion or melting, you know, but usually you'll just say fusion, you know, and put a negative sign, you know, if you're talking about going the opposite way. So vaporization is the more common way to say it, with a negative sign. Okay, any other questions about that? I'm sorry.