Question

Which of the following is a crystalline solid?

• A. plastic
• B. rubber
• C. glass
• D. quartz

Hint:

Quartz is crystalline, while glass (its amorphous form) is not. Pay close attention to structure: regular pattern = crystalline, random pattern = amorphous.

Answer 1

The Correct Option is D

Step 1: Know the types of solids.
Solids can be divided into:
Crystalline solids: They have a long-range orderly arrangement of particles. These solids have a definite melting point and sharp cleavage planes.
Amorphous solids: They lack long-range order and do not have a sharp melting point. Step 2: Examine each option.

(A) Plastic: It is an amorphous solid. Its molecular chains are entangled and disordered.
(B) Rubber: It is also an amorphous solid. It has elasticity but lacks a regular structure.
(C) Glass: Although hard and transparent, glass is amorphous — its atomic arrangement is disordered like a supercooled liquid.
(D) Quartz: Quartz (SiO\textsubscript{2}) is a well-known example of a crystalline solid. Its atoms are arranged in a regular, repeating 3D pattern. Step 3: Final Answer.
Only quartz fits the definition of a crystalline solid.