MCQ Detailed View

Solids are broadly classified into crystalline and non-crystalline (amorphous) solids. Crystalline solids have a well-defined, orderly, and repeating arrangement of atoms, ions, or molecules. This long-range order gives them definite geometrical shapes, sharp melting points, and distinct physical properties. Examples include table salt (NaCl), sucrose, and diamond.

On the other hand, non-crystalline or amorphous solids lack this long-range order. Instead, their atoms or molecules are arranged irregularly, similar to the arrangement in liquids, but frozen in place. These solids do not exhibit a sharp melting point; instead, they soften gradually over a range of temperatures. Glass, wood, plastics, and rubber are classic examples of amorphous solids.

In the given options:

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  Diamond, wood → Diamond is crystalline (strong covalent network solid), while wood is non-crystalline. So, not both are amorphous.

  
  


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  Glass, table salt → Glass is amorphous, but table salt is a crystalline ionic solid.

  
  


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  Wood, glass → Both wood (an organic, non-crystalline biomaterial) and glass (an inorganic amorphous solid) are non-crystalline. ✅

  
  


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  Sucrose, glass → Sucrose is a crystalline sugar, while glass is non-crystalline.

  
  

Therefore, the correct pair of non-crystalline solids is wood and glass.

Understanding the distinction between crystalline and amorphous solids is important in physical chemistry and material science. Amorphous solids often exhibit isotropic properties (same in all directions), while crystalline solids are anisotropic due to their ordered structure. Glass is widely used in technology and construction because of its amorphous structure, and wood is a natural amorphous solid used in countless applications.