Entropy

[clarissa_ram 2L]

What is the difference between residual entropy, positional entropy, and thermal entropy?

[Ananya_2L]

Hello!

So a brief understanding of what each term you listed above means:

(1) Residual Entropy: Generally, Residual entropy is specific to looking at a system in the limit of temperature going to 0K, and seeing if there is residual (positional) entropy. Residual entropy arises due to the possibility of different orientations of the particles when we approach 0 Kelvin, therefore the position (orientation of particles) results in the residual entropy that we encounter.

(2) Positional Entropy: Positional and Residual Entropy is technically the same things! The only 2 types of entropy we’ve covered in class are residual (positional) entropy and thermal entropy.

(3) Thermal Entropy: Thermal Entropy is the entropy due to the uncertainty in motion and molecules, and vanishes at absolute 0. Thermal entropy is the motion/movement of particles, which is influenced by temperature.

Difference between Residual and Thermal Entropy?

The main difference between these two entropies is that Residual entropy is temperature independent (and remains present at absolute 0) while Thermal entropy is temperature dependent (and is absent at absolute 0).

[clarissa_ram 2L]

Thank you so much!! This really cleared things up :D

[Kylie Cheng 1G]

To add on to this discussion, what are instances in our calculations where we would have to do something differently depending on what type of entropy is asked for?

[SanthoshNandakumar3L]

Hi, I know in the lecture we discussed how the entropy increases from solids to liquids to gases. There were some questions that I came across where we have to compare the entropy of the of the same substance at different phases at absolute zero temperature. However, I was curious as to we are able to produce the same substance at three different phases at zero temperature. Like how are we able to produce a gas, liquid, and solid of water at zero temperature if water only exists at a certain phase at certain temperatures?