Which of the following statements regarding metallurgy is false?

Metals in a molten state do not maintain an orderly arrangement of atoms; in fact, they exist in a disordered state. When a metal is molten, its atoms move freely and are not arranged in any specific pattern, which is a critical distinction from the crystalline structure that metals exhibit when they are solidified. This unordered arrangement in the liquid phase allows for the movement and mixing of atoms, which can also enable alloying processes.

Conversely, the other statements are accurate representations of metallurgical principles. Metals can indeed show different crystal structures depending on temperature and composition, often manifesting as face-centered cubic, body-centered cubic, or hexagonal close-packed structures. Heat treatment is utilized to change the microstructure and hence the physical properties—influencing hardness, strength, and ductility—through processes like annealing, quenching, and tempering. Lastly, metals can have various alloying elements, which are intentionally added to modify properties, enhancing mechanical performance and corrosion resistance based on specific requirements. Thus, the false statement is the one regarding the arrangement of atoms in a molten state.