Consider the phase diagram for iodine shown here. a. What is the normal boiling point

Consider the phase diagram for iodine shown here. ...

$\begin{array}{l}{\text { Consider the phase diagram for iodine shown here. }} \\ {\text { a. What is the normal boiling point for iodine? }} \\ {\text { b. What is the melting point for iodine at } 1 \text { atm? }} \\ {\text { c. What state is present at room temperature and normal atmo- }} \\ {\text { spheric pressure? }} \\ {\text { d. What state is present at } 186^{\circ} \mathrm{C} \text { and } 1.0 \text { atm? }}\end{array}$

Key Concepts

Phase Diagram

A phase diagram is a graphical representation that shows the conditions of temperature and pressure at which different phases (solid, liquid, and gas) of a substance exist. It illustrates the boundaries between the phases and indicates the conditions under which transitions such as melting, boiling, or sublimation occur.

Melting Point

The melting point is the temperature at which a substance transitions from a solid to a liquid at a given pressure, typically determined under standard atmospheric pressure. It is a critical property used to characterize the purity and identity of a substance.

Normal Boiling Point

The normal boiling point is defined as the temperature at which a liquid boils and converts to vapor at standard atmospheric pressure (1 atm). It is a key thermal property that helps in understanding the energy requirements for phase transitions in liquids.

Phase Transition Conditions

Understanding phase transition conditions involves analyzing how varying pressure and temperature affect the state of a substance. This concept explains why a substance may be found in different phases under different environmental conditions, as depicted in a phase diagram.

Transcript

00:09 Okay, all right.

00:14 Now we're going to work on problem 74 from chapter 11.

00:19 Okay, to do this one it asks consider the phase diagram for iodine shown here.

00:26 So first of all, i think it's going to be useful in the beginning to start out by labeling the phases.

00:34 So what do you have here when you have high pressure and low temperature? it's probably going to be a solid state.

00:41 So this area, here is going to probably be solid right and if i start from some high pressure low temperature and i know it's solid and then i increase my temperature and i cross a phase boundary what's the next one probably going to be i say it's going to be liquid and then the rest of this is going to this region here is going to be gas okay so this i thought probably be helpful before we start.

01:20 Okay, so part a asks, what is a normal boiling point for iodine? and when you hear normally, you should think one atmosphere.

01:30 Okay, so the line that they're talking about specifically is this line, the one atmosphere line.

01:41 So they're asking, what is the boiling point at one atmosphere, boiling temperature at one atmosphere? and that means you're going to find where the boundary between, liquid and gases because it's boiling.

01:55 So always keep in mind moiling liquid to gas transition, right? so that means you're going to look for the position, the place, the temperature at which the system crosses the liquid to gas boundary.

02:19 And it turns out that that is right along this line here.

02:25 So the point at which it goes from when at liquid to gas crosses this line that turns out to be this temperature very messy but so the temperature is 184 .4 degrees celsius b what is the melting point for iodine at one atmosphere so also at one atmosphere so what's the melting point in which it goes from solid point in which it goes from solid to liquid.

03:09 That's the melting point.

03:11 So what you're going to look for is the point at which this boundary is crossed.

03:18 And that happens right here.

03:19 You're crossing this boundary and you're crossing it at 113 .6 degrees celsius.

03:33 So i'm going to write this down anyway.

03:35 Just be clear.

03:37 Melting.

03:40 That's the crossing between the solid to liquid boundary.

03:48 Remember how we've labeled these.

03:51 We kind of clean this up, so it's a little bit more legible.

03:58 Let's remember what those phases are.

04:00 I put the back in here, solid, liquid gas.