In school, students are taught that matter is either solid, liquid, or gas. Now, physicists discover that atoms can actually exist as solid and liquid simultaneously.

It turns out, when certain elements are treated to extreme conditions, they can exhibit properties of both solids and liquids.

If the concept is difficult to imagine, the researchers describe the state as something similar to a sponge.

"It would be like holding a sponge filled with water that starts dripping out, except the sponge is also made of water," Andreas Hermann, study co-author and a condensed matter physicist at the University of Edinburgh, says in National Geographic.

Potassium Turns Solid, Liquid Under Extreme Conditions

In a study published in the journal Proceedings of the National Academy of Sciences, the scientists unveil this new state of matter using artificial intelligence on the simple metal potassium.

With powerful computer simulations, the team tested 20,000 potassium atoms to see how they'll behave under extreme conditions.

Findings reveal that exposing potassium to extremely high pressures and temperatures creates a state in which most of the atoms form a solid lattice structure, but another set of atoms form a fluid arrangement.

According to the researchers, pressure on the atoms results in two interlinked solid lattice structures with a very strong chemical link. This means that these structures remain solid even when high temperatures cause the other atoms to melt into a liquid state.

A Brand-New State Of Matter

Dubbed as the "chain-melted state," scientists used to wonder whether this is a new, distinct state of matter or a transitory stage before an element goes on to a distinct state. Now, they've confirmed that it is indeed a stable and distinct state.

"Potassium is one of the simplest metals we know, yet if you squeeze it, it forms very complicated structures," Hermann explains in a statement. "We have shown that this unusual but stable state is part solid and part liquid. Recreating this unusual state in other materials could have all kinds of applications."

More than half a dozen other elements, such as sodium and bismuth, are believed to exist in this simultaneous state as solid and liquid. Future simulations could confirm whether other minerals react to extreme conditions in the same way.

Potassium in this state of both solid and liquid could potentially exist in the conditions of the Earth's mantle, but it typically doesn't show up naturally unless it is linked with other materials.