Let’s get this straight: as you recall from science class, that matter is any physical substance which occupies space and possesses mass as a distinct form of energy, and can be in three states, that is, solid, liquid, and/or gas, right? Sure, that’s right. But have you ever heard of a “phase of matter?” That’s another feature of matter; it seems that a state of matter, say a solid state, could change state into a liquid below the temperature of it’s freezing point in a process known as a reconstructive phase transition. Mind blown? Let’s explain!
Related media: Kinetic Theory and Phase Changes: Crash Course Physics #21
Phasing The Change
In 2017, scientists announced that they have successfully melted a solid below it’s freezing point. Like what? You’re probably familiar with the idea that a solid melts into a liquid and vaporizes into gas, and gas condenses back into liquid and freezes into a solid state again. These are some of the examples of a simple phase transition, that is, changing it states. These changes occur as a result of the chemical bonds of the substance morphing and rearranging itself while it stays intact, and you’re aware of this.
But as usual, science has quite a lot of mysteries, and that’s what nature does by pulling off stunts. There’s another kind of phase transition you probably didn’t learn about in school. That one is known as a reconstructive phase transition — that’s what we mentioned earlier — and it’s much more unpredictable, and way more bizarre as you’d expect. The reconstructive phase transition involves breaking down and rearranging molecules of a chemical bond into new molecular bonds. Surprisingly, these phase transitions are pretty common in nature.
Don’t Change, Phase Off
In a 2017 paper published in the journal Nature, scientists from the Carnegie Institution for Science announced that they had successfully melted the crystalline (or solid) form of the metal bismuth into a liquid without raising it’s temperature. Like how on Earth in the amazing world of science was such a stunt possible?
Here’s how: They placed the metal, that’s the bismuth, into a diamond anvil cell and subjected it to intense pressures and decompression while keeping it at a constant temperature of 489 degrees Kelvin (216 degrees Celsius, 420 degrees Fahrenheit) — that’s a few degrees colder than it’s actually melting point of 545.67 degrees Kelvin (272.52 degrees Celsius, 522.54 degrees Fahrenheit).
The pressures ranged from 32,000 times atmospheric pressure, or technically atmospheres, to 12,000 atmospheres. In the depressurization process of the metal, they got to the Holy Grail of molecular science: at a pressure of 23,000 atmospheres, the bismuth melted away into a liquid state, with no heat required. Once the metal was depressurized to 12,000 atmospheres, it recrystallized back into a solid. Like seriously!
That’s Phasing Into Liquid
When the bismuth melted, it transformed into a particular kind of substance known as a metastable liquid — technically that is, a liquid that is stable if you leave it alone. This particular liquid was able to stay as-it-is for hours, as long as the pressure remained constant, but immediately reverts back to it’s solid form if it’s disturbed.
Or, as Gizmodo puts it, “Metastable liquids have found a little nook in the laws of physics where they can stay liquid-like — but like a spinning plate balancing on a stick, any perturbation and the atoms zip back into a solid form.”
In a press release published by the study’s authors, “[its important] for developing new materials and for understanding the dynamics of planetary interiors, such as earthquakes, because a metastable liquid could act as a lubricant strongly affecting the dynamics of the Earth’s interior.”
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Written by: Nana Kwadwo, Wed, Mar 27, 2019.