#phase diagram

[highlyentropicmind]

[er-cryptid]

Patreon | Ko-fi  

[noosphe-re]

Comparison of phase diagrams of carbon dioxide (red) and water (blue) showing the carbon dioxide sublimation point (middle-left) at 1 atmosphere. As dry ice is heated, it crosses this point along the bold horizontal line from the solid phase directly into the gaseous phase. Water, on the other hand, passes through a liquid phase at 1 atmosphere. (via Wikipedia)

[highlyentropicmind]

My phase diagram for the state density of magnetic chains on a superconducting substrate looks like the 80s

[a-h-87769877]

M11Q1: Features of Phase Diagrams – Chem 103/104 Resource Book

[subcritical-extraction]

What is subcritical extraction technology

A solvent exists in a liquefied state at a certain pressure in a temperature interval above its boiling point but below its critical point, which we define as the subcritical state of the solvent. The solvents used for extraction of biological components in this state are subcritical extraction solvents by utilizing their physical properties of similar solubility, and their extraction processes are called subcritical extraction processes. Suitable for extraction and desolvation solvents at room temperature and lower temperatures, we define as low-temperature subcritical solvents, currently there are five main low-temperature subcritical solvents suitable for industrial production: propane, butane, dimethyl enigma (DME), tetrafluoroethane(R134a), and liquid ammonia. Summarized in one sentence: Subcritical extraction process is a low-temperature, low-pressure and high-efficiency physical methods.

[whats-in-a-sentence]

The phase diagram for water, shown in figure 7.20, illustrates these features for a familiar substance. (...) The dashed lines on figure 7.20 show two paths that involve phase changes for water. (...) As shown in the magnified section of figure 7.20, if you start with solid H2O at a temperature just below the triple point and increase the pressure at constant temperature you will effect phase change from solid to liquid (dashed line).

"Chemistry" 2e - Blackman, A., Bottle, S., Schmid, S., Mocerino, M., Wille, U.

[whats-in-a-sentence]

An example is provided in figure 7.19. (...) Figure 7.19 illustrates many of the characteristic features of phase diagrams:

Boundary lines between phases separate the regions where each phase is thermodynamically stable. (Substances can exist as a metastable outside their metastable phase outside their thermodynamically determined boundaries, e.g. carbon can exist as diamonds, rather than graphite, under ambient conditions.)

Movement across a boundary line corresponds to a phase change. The blue arrows on the figure show six different phase changes: sublimation and its reverse, deposition; melting and its reverse, freezing; and vaporisation and its reverse, condensation.

On a boundary line, the two neighbouring phases coexist in a dynamic equilibrium. In addition, at a given pressure, for example, when heat is added or removed, the temperature of this two-phase system does not change until all of one phase has converted to the other. The normal boiling point of a substance (shown by red dots) are the points where the phase boundary lines intersect the horizontal line that represents p = 1.013 × 10⁵ Pa.

Three boundary lines meet at a single point (shown by another red dot), called a triple point. All three phases are present simultaneously at this unique combination of temperature and pressure. Notice that, although two phases are stable under any of the conditions specified by the boundary lines, three phases can be simultaneously stable only at a triple point.

Above the temperature specified by the critical point (again shown by a red dot), the gas cannot be liquefied under any pressure. Instead if the pressure is high enough a supercritical fluid forms. It has the viscosity typical of a liquid, but it is able to expand or contract like a gas.

What happens to a substance as temperature changes at constant pressure can be determined by drawing a horizontal line at the appropriate pressure on the phase diagram (shown as a horizontal red line).

What happens to a substance as pressure changes at constant temperature can be determined by drawing a vertical line at the appropriate temperature on the phase diagram (shown as a vertical red line).

The temperature for conversion between the gas phase and a condensed phase depends strongly on pressure. Qualitatively, this is because compressing a gas increases the collision rate and makes condensation more favourable.

The melting temperature is almost independent of pressure, making the boundary line between solid and liquid nearly vertical. Qualitatively, this is because moderate pressure has hardly any effect on the condensed liquid and solid phases.

The solid-gas boundary line extrapolates to p = 0 Pa and T = 0 K. This is a consequence of the direct link between temperature and energy. At 0 K, atoms, ions and molecules have minimum energy, so they cannot escape from the solid lattice. At 0 K, the vapour pressure of every solid substance would be 0 Pa.

"Chemistry" 2e - Blackman, A., Bottle, S., Schmid, S., Mocerino, M., Wille, U.