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Ch.11 - Liquids & Phase Changes

Chapter 11, Problem 18

A phase diagram for a substance that exhibits the liquid crystalline state is shown. (b) If the substance is at a temperature and pressure repre- sented by point 1 and the temperature is increased until the phase changes, what is the phase transition? Describe how the ordering of molecules changes, and propose a reason for the change.

Phase diagram showing crystalline solid, smectic, nematic, and isotropic phases.

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Video transcript

Hello everyone in this video. We're given a portion of a phase diagram that's showing right here and this is of a substance that has a liquid crystalline state. So, we're being asked what is the first phase change when the temperature is increased? The second question being asked is how will the order of the molecules change? And lastly, we need to provide a reason for this change. So we're saying that this point A. Is going to this point B. Let's actually go ahead and highlight this transition. All right. So our phase change will do this in green. So the face change that we have that occurs. You can see that stable here is going to pneumatic. Alright. Second question being asked is are how will the order of the molecules change? So order change. So we know that we're going from this phase to this phase. This phase here is highly ordered versus this one here is highly disordered. So, we're going from something that's more ordered to something that's less ordered basically, because this phase here has well defined layers compared to this phase here. Right. So the last answer were being for the last question being asked is to provide a reason for this change. So the reason is because we have an increase in temperature, whatever we're increasing our temperature, we do also go ahead and make something less ordered or something more disordered. So the reason is being that we increase the temperature. So this does have an effect. So these here are going to be all my final answers for this problem. Thank you all so much for watching.