Solids belong to three basic physical states, including liquids and gases. These ordered or chaotic arrangements led to the classification as amorphous and crystalline. This article focuses on the main differences between the two terms. They are characterised by a rigid structure composed of ordered or disorderly arranged molecules, ions, and atoms.
Amorphous and crystalline are two states that represent typical solids in chemistry.
So understanding the concepts of these two states are integral before learning crystalline solid and amorphous solid differences.
Crystalline: Definition
Crystalline solids (crystals) require extreme temperatures to destroy intramolecular forces. A crystalline solid is a solid in which the constituent particles are arranged uniformly in a three-dimensional crystal lattice pattern. The particles intersect at an angle peculiar to the crystal.
They have a constant heat of fusion and melting point because their components are evenly distributed. The local environment is also uniform. However, when cutting in any direction, this is called anisotropy because of the different physical properties. They differ in many ways, including their chemical and physical properties.
When rotating around an axis, the crystal structure remains the same, known as the symmetrical arrangement of molecules, atoms, or ions. The internal structure has a well-defined geometry, and if you cut it somewhere in the structure, you will see a clear rift.
The three-dimensional pattern seen on x-rays is used to identify solids. However, it is not easy to tell the difference between crystalline and amorphous solids by touch.
The good thing about anisotropic solids is that they represent a perfectly placed internal structure with uniform attraction within the crystalline lattice. It shows the true properties of solids with long-range order and rigid structure.
The refractive index, mechanical strength, thermal conductivity, and electrical conductivity of crystalline solids vary depending on the direction. This is a drawback of this solid compared to amorphous solids.
Quartz, for example, is a crystal with ordered silicon and oxygen atoms. However, if it cools rapidly, it can become amorphous structural glass. Due to their wide range of industrial applications, the crystallisation process is usually avoided by rapidly melting the material into an amorphous solid.
Some crystalline solids can become amorphous depending on the cooling process. Others may have their components misaligned due to the presence of contaminants. Rapid cooling of material can also result in amorphous structures with irregular geometry.
Rubbers, polymers, and glass are perfect examples of important amorphous solids and are mainly used due to their immeasurable advantages and unique isotropic properties.
Amorphous: Definition
The word amorphous comes from the Greek word “amorphous”. This means “formless”. This is an informal, chaotic, and irregular arrangement of solid components. Their intramolecular force is not the same as the distance between particles. When split, amorphous solids produce fragments or curved surfaces due to irregular geometric shapes.
Solids do not have a sharp melting point or a specific heat of fusion. Thermal conductivity, mechanical strength, electrical conductivity, and refractive index are the same in all directions of amorphous solids. This explains the origin of the name isotropic.
Due to the unordered placement of the components, a wide temperature range must be applied before the components melt. In addition, amorphous solids are characterised by short-range order. Examples of amorphous solids include polymers, rubber, plastics, and glass.
As mentioned above, quartz differs from quartz glass due to the crystallisation process. However, in general, many amorphous solids have a chaotic pattern. It is commonly referred to as a supercooled solid because its structure shares some properties with liquids. They also do not show the true properties of solids, but they are still predominantly used in many applications.
Some amorphous solids can have some of the regular patterns called microcrystals. Solid atoms, ions, or molecules depend on the cooling process.
If an amorphous solid remains below its melting point for an extended period, it can become a crystalline solid. It can exhibit the same properties that crystalline solids have.
Difference between Crystalline and Amorphous Solids
Here are some crystalline solid and amorphous solid differences:
| Crystalline Solids | Amorphous Solids |
| They are called ordered or true solids because they have a wide range of orders. | They are called chaotic or pseudo-solid because they have a short degree range. |
| Crystalline solids have constant heat of fusion. | Amorphous solids do not have clear heat of fusion. |
| When cut, the crystalline solid gives a clean, sharp cleavage | When cut, the amorphous solid is clean and does not give sharp crevices. |
| Crystalline solids have a certain regular geometric shape. | Amorphous solids are very irregular in shape. |
| They have a sharp melting point. | They do not have a sharp melting point. |
| They are very hard and completely incompressible. | Like crystalline solids, they are rigid but can be compressed. |
| They are anisotropic and symmetric. | They are isotropic and asymmetric. |
| Examples of crystalline solids are table salt, diamond, etc. | Examples of amorphous solids are cotton, glass, and thin-film lubricants. |
Conclusion
Hope you now have a clear idea regarding the Crystalline and Amorphous Solids and the difference between them.
