Q.An example of amorphous solid is
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Crystalline and Amorphous Solids
Imagine you are in a school assembly. All students stand in neat rows and columns — every person knows exactly where to stand, and the pattern repeats across the entire ground. That is a crystalline solid. Now imagine a crowded market: people are packed together, but there is no fixed arrangement; everyone is just wherever they happen to be. That is an amorphous solid.
The difference is not about how tightly packed the particles are — both types can be dense. It is about order.
Crystalline Solids: The Ordered World
In a crystalline solid, atoms, ions, or molecules are arranged in a regular, repeating three-dimensional pattern that extends throughout the entire material. This pattern is called a crystal lattice. Because of this long-range order, every unit cell is identical to its neighbour, and the arrangement repeats for millions of atomic distances.
This order has two immediate consequences you can observe:
- Sharp melting point. When you heat a crystal, every bond is identical to every other bond. So all bonds break at exactly the same temperature — the solid turns into a liquid at one precise temperature, not over a range.
- Cleavage into smooth planes. If you break a crystal, it tends to split along flat surfaces because the planes of atoms are neatly stacked. Think of how a diamond (crystalline carbon) can be cut into facets.
Examples: sodium chloride (table salt), diamond, quartz, ice, and most metals.
The defining feature of a crystalline solid is long-range order — the arrangement of particles repeats periodically in all three dimensions.
Amorphous Solids: The Disordered World
An amorphous solid has no long-range order. The particles are arranged randomly, much like in a liquid. In fact, you can think of an amorphous solid as a supercooled liquid — a liquid that was cooled so quickly that its molecules did not get a chance to arrange themselves into a crystal before they froze.
Because there is no repeating pattern, the bonds between particles are not all identical. Some are stronger, some weaker. This leads to:
- No sharp melting point. As you heat an amorphous solid, the weaker bonds break first, then the stronger ones later. So the material softens gradually over a range of temperatures — it does not melt at one specific temperature. This is why glass can be blown and shaped while hot; it becomes soft and pliable over a range, not suddenly liquid.
- Irregular fracture. When broken, amorphous solids do not split along flat planes. Instead, they produce curved, shell-like surfaces (conchoidal fracture). Think of how a glass bottle breaks — it shatters into curved, jagged pieces, not flat cubes.
Examples: glass, rubber, plastic, wax, and amorphous silica.
Do not confuse "amorphous" with "weak." Amorphous solids can be very strong — glass is harder than many crystals. The difference is only about arrangement, not strength.
The Precise Statement …
Amorphous solids lack the regular long-range arrangement that crystalline solids have, and only one of these four substances fits that description. …
Amorphous solids lack a regular long-range arrangement of particles; among the options, rubber is amorphous.
Solids are classified as crystalline (regular, long-range ordered arrangement, sharp melting point) or amorphous (irregular short-range order only, no sharp melting point — they soften over a range and are sometimes called pseudo-solids or supercooled liquids).
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- CBSE 2025Set D1 markMCQQ.Which of the following is not a crystalline solid?(a) KCl(b) CsCl(c) Glass(d) Rhombic sulphur
›Reveal solutionSolution
Crystalline solids have long-range ordered arrangement; glass is amorphous, so it is not crystalline.
Solids are crystalline or amorphous:
- Crystalline solids have a regular, long-range ordered arrangement of particles, sharp melting points and are anisotropic (e.g. KCl, CsCl, rhombic sulphur). …
- CBSE 2024Set D1 markMCQQ.Which of the following is an amorphous solid?(a) Diamond(b) Graphite(c) Common salt(d) Glass
›Reveal solutionSolution
Glass is an amorphous solid.
Amorphous solids lack long-range order; their particles are arranged irregularly, they have no sharp melting point (they soften over a range) and they are isotropic. Glass is the classic example of an amorphous solid (a supercooled liquid).
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- CBSE 2021Set A1 markMCQQ.An example of amorphous solid is(a) Diamond(b) Graphite(c) Salt(d) Rubber
›Reveal solutionSolution
Amorphous solids lack a regular long-range arrangement of particles; among the options, rubber is amorphous.
Solids are classified as crystalline (regular, long-range ordered arrangement, sharp melting point) or amorphous (irregular short-range order only, no sharp melting point — they soften over a range and are sometimes called pseudo-solids or supercooled liquids).
…
- CBSE 2021Set A1 markMCQQ.Which one of the following is an example of an amorphous solid?(a) NaCl(b) ZnS(c) Glass(d) SiC
›Reveal solutionSolution
Glass has no long-range order -> amorphous; the others are crystalline.
Amorphous solids lack a regular, long-range ordered arrangement of particles (short-range order only) and have no sharp melting point.
- (A) NaCl — crystalline ionic solid (rock-salt lattice).
- (B) ZnS — crystalline ionic solid (zinc-blende structure). …
- CBSE 2019Set ANNUAL1 markMCQQ.The material that soften on heating to finally flow like a liquid is(a) liquid(b) crystalline solid(c) amorphous solid(d) poly crystalline solid
›Reveal solutionSolution
Amorphous solids lack a regular long-range crystal structure and so have no sharp melting point — they soften gradually over a range of temperature and eventually flow like a liquid — option (c).
Unlike a crystalline solid (with an ordered, repeating 3-D arrangement of particles and a sharp, definite melting point), an amorphous solid has only short-range order in the arrangement of its constituent particles. Because there is no single, uniform lattice energy to overcome, an amorphous solid softens gradually as temperature rises and eventually begins to flow — behaving somewhat like a very viscous (super- …
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