Matter primarily exists in three distinct classical states—solid, liquid, and gas—which are determined by how tightly their constituent particles are packed and how freely they can move.

The state of a given substance can change when energy, such as heat, is added or removed, altering the temperature and pressure acting upon its molecules.

https://knowledgezone.co.in/posts/States-of-Matter-626f8efec2cd5665b9ab713b

Topological conductors (insulators/superconductors) are quantum materials: insulating inside but with conductive, gapless surface/edge states.

Protected by spin-orbit coupling and time-reversal symmetry, electrons flow immune to scattering from impurities or defects.

https://knowledgezone.co.in/trends/browser?topic=Topoconductor