Amorphous solids, also known as non-crystalline solids, are a class of materials that lack a long-range ordered structure. Unlike crystalline solids, amorphous solids have a disordered arrangement of atoms, molecules, or ions, which results in a range of unique properties.
Amorphous solids are formed when a material is cooled rapidly, not allowing the atoms, ions, or molecules to arrange themselves into a crystal lattice. The atoms are left randomly arranged, with no long-range order.
Amorphous solids are ubiquitous in nature and have many practical applications in industries ranging from electronics to pharmaceuticals. Understanding the properties and behavior of amorphous solids is a fascinating area of research in materials science and physics.
Classification of Solids
On the basis of the arrangement of atoms, ions, or molecules, solids can be classified into two classes.
Crystalline Solids
The solids that have three dimensional regular and ordered arrangement of their constituents are called crystalline solids. Sodium chloride, diamond, sodium nitrate, etc are examples of crystalline solids.
Amorphous Solids
The solids that don’t have three dimensional regular and ordered arrangement of their constituents are called amorphous solids. In addition to the term amorphous solids, other terms in use include glasses, supercooled liquids, pseudo solids, non-crystalline solids, and vitreous solids.
Examples of Amorphous Solids
Glass, rubber, plastic, waxes, gels, fused silica, some lubricants, pitch tar, etc are very common examples of amorphous solids. The backbone of organic compounds, carbon, has some amorphous forms. Amorphous forms of carbon include coal, soot, charcoal, coke, lamp black, etc.
Properties of Amorphous Solids
- Amorphous solids don’t have a regular pattern of intermolecular forces that’s why they don’t have a regular and ordered arrangement of their constituents.
- They don’t have sharp and fixed melting points.
- Their physical properties are the same in all directions. This property is called isotropy. The coefficient of thermal expansion, refractive index, and electrical and thermal conductivity are some important isotropic properties.
- Their heat of fusion is not definite.
- They are usually less rigid as compared to crystalline solids.
- At some places in their structure, amorphous solids have small regions of ordered and regular arrangement of constituents called crystallites.
- They don’t have regular planes of cleavage.
- They don’t have sharp and fixed melting points.
Formation of Amorphous Solids
Amorphous solids are formed when a material is rapidly cooled from a liquid or gas state, preventing the atoms or molecules from arranging themselves into a crystal lattice. As a result, the atoms or molecules are left in random positions without any long-range order, leading to the formation of an amorphous solid. This process is also known as vitrification and can result in materials with unique properties and applications, such as glasses and certain types of plastics.
Many crystalline solids can be changed into amorphous solids by melting and then cooling this fused or molten mass rapidly. In this process, the constituent particles don’t find time to arrange themselves in three dimensions, and this results in the formation of amorphous solids. Due to this property amorphous solids can be molded and blown into different shapes.
Difference between crystalline and amorphous solids
Application of Amorphous Solids
Amorphous solids have a wide range of applications in various fields such as:
- Glass: Amorphous solids are used to make glass, which is used in windows, lenses, and optical fibers.
- Polymers: Amorphous solids are also used to make polymers such as plastics, which are used in a wide range of applications including packaging, textiles, and electronics.
- Pharmaceuticals: Amorphous solids are used as drug delivery systems in the pharmaceutical industry. They can increase the bioavailability of drugs and improve the stability of formulations.
- Coatings: Amorphous solids are used to make coatings for various surfaces, including anti-reflective coatings for solar panels and anti-fog coatings for eyeglasses.
- Solar Cell: Amorphous silicon is used in the production of thin-film solar cells.
- Food additives: Amorphous solids such as xanthan gum are widely used as food additives to improve the texture and stability of food products.
- Cosmetics: Amorphous solids such as silica are used as fillers in cosmetics to improve the texture and stability of the products.
Concepts Berg
How are amorphous solids formed?
Amorphous solids are formed when a material cools from a liquid or gas state too quickly for the atoms to arrange themselves into ordered structures. The atoms are left in random positions without any long–range order.
What does an amorphous solid mean?
An amorphous solid is a solid that has no definite shape or structure. It is a state of matter that is a neither liquid nor crystalline solid. Examples of amorphous solids include glass, plastic, rubber, and some polymers.
Do amorphous solids show cleavage properties?
No, amorphous solids do not show cleavage properties. Cleavage is the tendency of a crystalline solid to break along certain crystallographic planes. Amorphous solids lack the regular arrangement of atoms found in crystalline solids and therefore cannot show this property.
Is gold an amorphous solid?
No, gold is not an amorphous solid. Amorphous solids have a disordered atomic structure and are also known as non–crystalline solids. Gold is a crystalline solid with an ordered atomic structure.
Do amorphous solids conduct electricity?
No, amorphous solids do not conduct electricity. They are insulators.
What is an amorphous solid, and how do they form?
An amorphous solid is a material that does not have a regular crystalline structure and lacks a well–defined melting point. They form when a material cools quickly enough so that the atoms don‘t have time to arrange in an ordered pattern, resulting in a disordered structure. Examples of amorphous solids include glass and various polymers.
Reference Books
- Pharmaceutical Amorphous Solid Dispersions
