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Crystalline and Amorphous Solids - Classification and Key Features
IMPORTANT LINKS
The Solid State
Classifying Solids: A Basic Overview
Solids are differentiated based on the unique characteristics of their atomic layers. When two solids are in close contact, the atomic layers separating them showcase properties that are significantly different from those of the bulk material.
Table of Contents
Solids can be broadly categorized based on their crystal structures into two main types: Crystalline solids and Amorphous solids. However, crystalline solids can be further divided into molecular, ionic, metallic, and covalent solids. This article will provide a detailed overview of these classifications.
Classification of Solids – Crystalline and Amorphous Solids
The image below offers a detailed illustration of how solids are classified.
What are Crystalline Solids?
Crystalline solids are those in which the particles, be it atoms, ions, or molecules, are arranged in an orderly and repeated pattern. This pattern forms a crystal lattice that extends in all directions. Examples of crystalline solids include quartz, iron, and sugar.
What are Amorphous Solids?
Amorphous solids, on the other hand, are those in which the particles are arranged randomly and do not form a crystal lattice. The term ‘amorphous’ is derived from Greek roots meaning “without form”. Common examples of amorphous solids include rubber, plastic, and wax.
While an ideal crystal is defined by an atomic arrangement with infinite translational symmetry in all three dimensions, an ideal amorphous solid does not have a specific definition.
Key Features of Crystalline and Amorphous Solids
- Nature: Crystalline Solids are True Solids, while Amorphous Solids are Pseudo-Solids or super-cooled liquids.
- Geometry: Crystalline Solids have a regular and ordered arrangement resulting in a definite shape, while Amorphous Solids have a random arrangement, resulting in irregular shapes.
- Melting Points: Crystalline Solids have a sharp melting point, whereas Amorphous Solids do not have sharp melting points and tend to soften gradually over a range of temperature.
- Heat of Fusion: Crystalline Solids have a definite heat of fusion, while Amorphous Solids do not.
- Isotropism: Crystalline Solids are anisotropic, meaning their physical properties vary along different directions of the crystal. Amorphous Solids are isotropic, with their physical properties being the same in all directions.
- Cleavage Property: When cut, Crystalline Solids form two new halves with smooth surfaces, while Amorphous Solids form two halves with irregular surfaces.
- Rigidity: Crystalline Solids are rigid and retain their shape even when mild forces are applied. In contrast, Amorphous Solids are not rigid and can have their shape changed by mild forces.
Frequently Asked Questions
What is meant by crystalline solids?
Crystalline solids consist of atoms, ions, and molecules arranged in a strongly ordered microscopic arrangement in consistent and repeated three-dimensional structures, forming a crystal lattice that stretches in any direction.
What are the 7 types of crystals?
Seven crystal structures are available in total: triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. A family of crystals is determined by groupings of lattices and lines.
Is coal crystalline or amorphous?
Graphite is one of three types of carbon which is crystalline, or crystal-forming. In compounds like coal and charcoal, carbon also occurs as an amorphous, or “shapeless,” form. Allotropes are called varying variants of the same substance. Some allotropes of crystalline carbon are, aside from graphite, diamond, and fullerenes.
Is a diamond a crystal?
Diamond is the solid shape of the carbon molecule with its atoms arranged in a crystal arrangement called a cubic diamond. Diamond also has relatively high optical dispersion (capacity to scatter various wavelengths of light). Many natural diamonds have ages ranging from 1 to 3.5 billion years.
Is wood amorphous or crystalline?
Crystalline solids are made of stone, wood, paper and cloth. Such solids consist of atoms arranged in a particular fashion. The transition to liquid, called melting, is sharp and transparent as crystalline solids are heated. Amorphous solids are made of rubber, glass, and sulphur.