The physics of 'supercritical' matter may be surprising simple

It is remarkably simple when liquids and gases seem to disappear at this critical point.Under extreme heat and pressure, the matter becomes supercritical, and the distinction between liquid and gas disappears. According to new research, matter at this extreme supercritical state is less complicated than previously thought.

Supercritical materials have liquid-like and gas-like states, with the tipping point between the two being consistent across the matter. In other words, different types of materials may be governed by the same universal rules.

According to study co-author Kostya Trachenko, a physicist at Queen Mary University of London, 'the universality of supercritical matter opens up a new view of the matter under extreme conditions.'

The prospect of understanding and predicting supercritical properties in green environmental applications, astronomy, and other areas is exciting from the point of view of fundamental physics.

In many industries, supercritical fluids are already being used in a variety of ways. Due to their combination of liquid and gas properties, they can be used for a variety of chemical reactions and processes, such as hazardous waste purification, oil extraction, and industrial refrigeration. Also, gas giants such as Jupiter and Saturn naturally have them in their atmospheres. 

It is not easy, however, to understand the properties of matter in the supercritical state. As the lines between solid, liquid, and gas blur, what characteristics of matter explain its most important characteristics? 

During their study, Trachenko and postdoctoral researcher Cillian Cockrell focused on two particular parameters: the heat capacity of a material, which is the amount of heat it can absorb, and the wavelength at which a wave can propagate.

In plotting these two parameters against each other, the researchers found that there is a specific inversion point at which the properties of the supercritical material become gaseous.

The researchers found that the inversion point was very similar in all the supercritical systems they studied. Among these substances were supercritical water, carbon dioxide, nitrogen, lead, and argon - a diverse group of metallic and noble gases.

According to Trachenko, this raises new questions about whether existing theories about transitions between phases of matter can explain the inversion point or whether a new explanation must be found.

'The more we push the limits of what's known, the more innovative questions we'll uncover and answers we'll find.' Trachenko said.