Select the correct statements. (A) Crystalline solids have long range order. (B) Crystalline solids are isotropic. (C) Amorphous solids are sometimes called pseudo solids. (D) Amorphous solids soften over a range of temperatures. (E) Amorphous solids have a definite heat of fusion. Choose the most appropriate answer from the options given below :
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A key distinction between crystalline and amorphous solids is order. Crystalline solids are ordered (anisotropic, sharp melting point), while amorphous solids are disordered (isotropic, soften over a temperature range).
Let's analyze each statement:
(A) Crystalline solids have a regular, repeating arrangement of constituent particles that extends over a large distance. This is the definition of long-range order. So, statement (A) is correct.
(B) Crystalline solids exhibit anisotropy, meaning their physical properties (like refractive index, electrical conductivity) are different when measured along different directions. Isotropy is a property of amorphous solids. So, statement (B) is incorrect.
(C) Amorphous solids lack a regular structure and are considered supercooled liquids with very high viscosity. For this reason, they are often called pseudo solids or supercooled liquids. So, statement (C) is correct.
(D) Amorphous solids do not have a sharp melting point. Instead, they gradually soften over a range of temperatures as they transition from a solid-like to a liquid-like state. So, statement (D) is correct.
(E) Amorphous solids do not have a definite heat of fusion because they lack a sharp melting point. Crystalline solids have a definite and characteristic heat of fusion. So, statement (E) is incorrect.
The correct statements are (A), (C), and (D).
