Difference between Crystalline and Amorphous Solids

By Jaxson

Main Difference

There are 3 states of matter, solid is one of them. The other two are liquid and gases. Solid have a definite volume, mass and shape because molecules are arranged at a fixed positions. Solid is divided into two type: crystalline solids and amorphous solids. Crystalline solids totally differ from amorphous solid in every aspect, for example: crystalline solids have a fixed geometric pattern while amorphous solids have no definite pattern. Crystalline solids have a very sharp melting point and amorphous solids don’t have sharp melting point.

Crystalline Solid

Crystalline solid a type of solid which is made up of atoms or molecules that are arranged in a highly ordered manner which is termed as crystal lattice. Crystal lattice is basically a three-dimensional symmetrical arrangement of molecules or atoms inside a crystal. Crystalline solids have a definite internal structure which in turn lead to a definite flat faces or surfaces. The surfaces intersects at angle that are characteristic of the substance. These angle do not depend upon the size of the crystal, they only define the regular repeating arrangement of atoms or molecules inside the crystal. Crystalline solids have very sharp and well-defined melting points because all the atoms or molecules are arranged at the same distance from the same type of neighboring atoms and they tend to have uniform intermolecular force of attraction which creates a regular local environment. Thus a large amount of thermal energy is required to break down a crystal.  The structure of a crystal is defined by its unit cell, a tiny imaginary box that contains one or more atoms in a specific spatial arrangement. Unit cells when arranged in a three-dimensional space forms a crystal.  Crystalline solids are anisotropic which means that they show physical properties like electrical conductivity, mechanical strength, refractive index and thermal conductivity in different directions. The anisotropy signifies the orderly arrangement of the atoms in crystal.

Amorphous Solid

Amorphous solid is another type of solid which is made up of atoms or molecules that are not arranged in a fixed geometric pattern like crystal. Amorphous solids have two characteristics. When they are cleaved they produce fragments which have irregular or conchoidal surfaces and when exposed to x-ray they have very ill-defined patterns because the atoms in amorphous solid are not arranged in a regular array. Amorphous solid do not have very sharp melting point because of its atoms that are not arranged at the same distance from the same neighboring atoms. Because the local environment of amorphous solid which includes distance and number of the neighbor atoms varies throughout the material. Amorphous solids are isotropic which means that the physical properties like thermal conductivity, refractive index and mechanical strength are same in all directions. Glass, plastic and gel are types of amorphous solids. The isotropy signifies the irregular arrangement of the atoms or molecules in amorphous substance.

Key Differences

  • Crystalline solids have a definite shape because the atoms are arranged in a geometric pattern while amorphous solid lacks definite shape.
  • Crystalline solids have very sharp melting points while amorphous solid do not have sharp melting point.
  • Crystalline solids are anisotropic while amorphous solids are isotropic.
  • Crystalline solids cleaved in a definite plane while amorphous solid when cleaved they produce fragments that have irregular surfaces.
  • Examples of crystalline solids are table salt, diamond, sugar etc.
  • Examples of amorphous solids are glass, plastic, coal, rubber etc.

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