A metal that changes its crystal structure with temperature exhibits which phenomenon?

A metal that changes its crystal structure with temperature exhibits which phenomenon?

• A. Allotropy
• B. Polymorphism
• C. Martensitic transformation
• D. Diffusion

Answer: (A)

Allotropy is the phenomenon where an element exists in more than one crystalline form, with the structure changing as temperature (and sometimes pressure) changes. For metals, this means the atoms rearrange into a different lattice at different temperatures, so a metal can have distinct crystal structures depending on how hot or cold it is. A well-known example is iron, which adopts different lattices at different temperatures, illustrating allotropy. Polymorphism is a broader term used for many substances, including compounds, not just elements; martensitic transformation is a specific diffusionless change that can occur during rapid cooling and is not the general temperature-driven switch between crystal forms; diffusion is just atomic movement and doesn’t by itself imply a crystal-structure change.

Allotropy is the phenomenon where an element exists in more than one crystalline form, with the structure changing as temperature (and sometimes pressure) changes. For metals, this means the atoms rearrange into a different lattice at different temperatures, so a metal can have distinct crystal structures depending on how hot or cold it is. A well-known example is iron, which adopts different lattices at different temperatures, illustrating allotropy. Polymorphism is a broader term used for many substances, including compounds, not just elements; martensitic transformation is a specific diffusionless change that can occur during rapid cooling and is not the general temperature-driven switch between crystal forms; diffusion is just atomic movement and doesn’t by itself imply a crystal-structure change.