In fact, there are liquid and gas-like states in supercritical materials, and the tipping point between them is surprisingly the same throughout matter. This could mean that there are universal rules governing these situations for different types of materials.

The declared universality of supercritical matter paves the way for a new physically transparent picture of matter under extreme conditions. This is an exciting possibility in terms of fundamental physics and for understanding and predicting supercritical properties in environmental applications, astronomy and other fields.
— Kostya Trachenko, a physicist at Queen Mary University of London, co-author of the study, explains in a statement.

Use of supercritical fluids

Supercritical fluids are currently used in a variety of ways in many industries. Because they combine the properties of liquids and gases, they can be used in a range of chemical reactions and processes, such as hazardous waste treatment, oil production, and industrial refrigeration. They are also found naturally in the atmospheres of gas giants such as Jupiter and Saturn.

However, understanding the properties of matter in the supercritical condition was not easy. What properties can explain the most important properties of matter when the boundaries between solid, liquid, and gas are blurred?

Researchers focused on two specific parameters:

• heat capacity, or how well the material absorbs heat,
• and the length at which the wave will propagate through the material.

universal rules

When these two parameters were compared with each other, the researchers found that there was a specific inversion point where the properties of the supercritical material changed from more liquid to more gas.

What’s more, this reversal point was very similar across all the supercritical systems the researchers studied. These include supercritical water, carbon dioxide, nitrogen, lead and argon – a wide variety of substances from metallic elements to noble gases.

Scientists say this is exciting from a basic science perspective because it raises new questions about whether the reversal point can be explained by existing theories about transitions between different phases of matter, or whether a new explanation is needed.