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/sci/ - Science & Math

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File: 93 KB, 800x593, Phase_diagram_of_water_simplified.svg (1).png [View same] [iqdb] [saucenao] [google]
15463384 No.15463384 [Reply] [Original]

How do you know what the phase diagram will look like for a Vander Waals fluid, for example? My prof is using the fermi notes and Fermi just makes claims that seem obvious (to him) about convexity and concavity but desu I can't seem to extend my geometrical intuition to thermo.
I can't understand why entropy is a convex function out of the relationship it has to heat, for example.

>> No.15463394

Literally ask chatgpt

>> No.15463460

Why does the freezing temp go down for a lil bit starting at around 100 bars?

>> No.15463482

>Explain phase diagrams like I'm 15
Stop looking at nerd shit and go get some tail.

>> No.15463487

Water might have one of the most complicated phase diagrams of all substances

>> No.15463500

A phase diagram shows how a substance behaves at different temperatures and pressures. Vander Waals fluids are substances that have strong intermolecular forces, making them behave differently from ideal gases. At different temperatures and pressures, Vander Waals fluids can change from a gas to a liquid. The phase diagram shows the regions for solid, liquid, and gas phases, with lines separating these regions. Entropy is a measure of the disorder or randomness of a system, and for Vander Waals fluids, adding heat increases entropy more rapidly at higher temperatures than at lower temperatures. This convexity of the entropy curve is important for understanding the behavior of Vander Waals fluids and predicting phase transitions.

>> No.15464211

brought yout mum to 647 kelvin and 22.064 MPa last night

>> No.15464315

Terrible idea. Stop doing this

>> No.15464346


>> No.15465284
File: 212 KB, 1186x801, vanderwalls.png [View same] [iqdb] [saucenao] [google]

This is a great idea, keep doing this, and if GPT/Google/books doesnt satisfy you, THEN ask for extra help with a real person. People seldom want to help someone when that person hasnt even tried to figure it out themselves.

Pic is my notes, which involves the gibbs free energy and the critical point. I try not to write words for my notes, but for thermo there's a lot I'd tend to forget. I didnt use Fermi's notes, and i know very little, but this makes sense to me, and how i rationalize how the van der waals model basically works

>> No.15465290

oh I should say it should be a (V,P) graph as the xy axes, not (P,V)

>> No.15465306

... [intro too long for post]

The phase diagram represents the equilibrium conditions between different phases of a substance as a function of temperature and pressure. At low temperatures and high pressures, substances are generally in a condensed phase, such as a solid or liquid, due to the stronger intermolecular forces and reduced thermal energy.

As the temperature increases, the thermal energy of the molecules also increases, leading to a greater tendency for molecules to overcome the intermolecular forces and transition into a less condensed phase, such as a gas. This transition is often accompanied by an increase in volume and a decrease in density.

The concave downward shape of the phase diagram arises from the behavior of the intermolecular forces with changing temperature and pressure. At low temperatures and high pressures, the attractive forces dominate, resulting in a condensed phase. As the temperature increases, the thermal energy becomes more significant, and the attractive forces become less effective in holding the molecules together. This leads to a decrease in the range and strength of the intermolecular forces, allowing the substance to transition into a less condensed phase.

Since the strength of the van der Waals forces decreases with increasing temperature, the transition from the condensed phase to the less condensed phase occurs more rapidly at higher temperatures. This results in a concave downward shape in the phase diagram, reflecting the decrease in stability of the condensed phase with increasing temperature.

It's worth noting that the concavity of the phase diagram can vary depending on the specific properties of the substance and the types of intermolecular forces involved. However, for substances primarily influenced by van der Waals forces, the concave downward shape is a common feature.

>> No.15466668
File: 33 KB, 545x535, file.png [View same] [iqdb] [saucenao] [google]

Man I now remember studying all those diagrams in material science.
Pic rel is literally something you will never forget anymore.
Eutectics, peritectics, phase transformations, intermetallic phases and so on