Iron exhibits polymorphism, the ability of a solid material to exist in more than one crystal form.At low to moderate temperatures, it adopts a bcc structure; at temperatures above 913$\degree$C, it adopts an fcc structure.Silicon carbide also has polymorphs, including the wurtzite form with abab packing and the sphalerite form with abcabc packing.Which of the following statements is NOT correct?

Question

Quizplus · Accepted Answer

EThe bcc (body-centered cubic) and fcc (face-centered cubic) forms of iron do not have the same densities because the packing efficiency in fcc structures is higher than in bcc structures, leading to a denser arrangement in the fcc form. The statement about both SiC polymorphs being based on hexagonal packing of atoms is incorrect because the wurtzite form is indeed based on hexagonal packing, but the sphalerite form is based on cubic packing, not hexagonal.

Iron Exhibits Polymorphism, the Ability of a Solid Material to Exist