There are three basic states of matter: solid, liquid, and gas. They are classified based on the structure of molecules, ions, and atoms arranged in proper order or scattered.
Based on their crystal structure, solids can be classified into crystalline and amorphous. These solids can be differentiated based on their chemical and physical properties.
Key Takeaways
- Structure: Crystalline substances have a definite, ordered structure, while amorphous materials lack this ordered arrangement.
- Properties: Crystalline substances have sharp melting points and unique properties that can be used to identify them, while amorphous materials have more variable properties.
- Formation: Crystalline materials are formed by the slow cooling of molten substances or through natural crystallization. Amorphous materials are formed by rapidly cooling molten substances or by adding impurities.
Crystalline vs. Amorphous
Crystalline solids have a highly ordered and repetitive arrangement of atoms arranged in a specific pattern or lattice structure. Amorphous solids have a disordered and irregular arrangement of atoms and lack well-defined surfaces and shapes, making them isotropic.
Comparison Table
| Parameter of Comparison | Crystalline | Amorphous |
|---|---|---|
| Structure | Regularly patterned ions | Randomly patterned ions |
| Melting Point | Fixed melting temperature | Not fixed melting temperature |
| Physical Properties | Anisotropic | Isotropic |
| Symmetry | Symmetrical | Unsymmetrical |
| Example | Quartz | Glass |
What is Crystalline?
A crystalline solid, also denoted as a crystal, is a solid material made up of atoms or ions arranged in an ordered microscopic structure that further forms the crystal lattice, which spreads in all directions.
All crystalline solids have a fixed melting point. The arrangement of atoms within a crystal is known as crystal structure. The atoms form a periodic arrangement. However, not all solids are crystals.
The crystal structure is featured by its unit cells. The unit cells are then stacked into a three-dimensional format to create a crystal.
Crystals are recognized by their distinct shape, consisting of a flat surface and sharp angles. It isn’t easy to differentiate between a crystalline and a non-crystalline by just feeling or looking at them.
They can be differentiated based on their chemical and physical properties.
The crystalline solid requires the extreme temperature to break down its intermolecular force. They have a fixed boiling and melting point as they have a uniform arrangement of molecules.
Although when they are cut in any particular direction, the physical properties change; hence, it is known as anisotropic.
On certain occasion’crystalline solid results in an amorphous based on its cooling process. For example, quartz is a crystal with oxygen and silicon atoms in an arranged form, but when cooled it can result in an A-structured glass.
Often the crystalline process is avoided to receive an amorphous solid as the final product for industrial purposes.
Crystals can be grouped into 7 different types based on lattices and lines: tetragonal, hexagonal, orthorhombic, trigonal, triclinic, cubic, and monoclinic.
Crystalline solid is also defined by the kind of particles they are made up of and their chemical bonding. Based on that, crystalline solids can b of 4 kinds ionic, covalent, metallic, and molecular.
What is Amorphous?
Amorphous has been derived from a Greek term meaning “shapeless.” They have irregular arrangements of constituent particles of solid.
These blocks are similar to the basic structural unit found in the corresponding crystalline phase of a similar compound.
The amorphous solid lacks a proper three-dimensional long-range order of crystalline material. The substance can be either solid or liquid, depending upon the connectivity between the elementary building blocks.
The solids have a high level of connectivity, whereas the liquids have a low level of connectivity.
Amorphous solid has no fixed melting point and can transform from solid to liquid over various temperatures. Amorphous solids are generally isotropic (perform uniform properties in all directions).
Any crystalline solid can be made amorphous by the process of rapid cooling. They do not allow their particles to be arranged in crystalline format.
An amorphous solid can be transformed back into a crystalline solid if left for a longer period below its melting point.
The internal structure of the amorphous substance is created of interconnected structural blocks; they have a similar resemblance to crystalline material.
Amorphous solid consists of both natural and manmade substances. The most common example of Amorphous that is noticed is glass.
Other amorphous solids are film lubricants, metallic glasses, polymers, and gels. If the liquid phase is cooled quickly, any material can solidify into an amorphous solid.
Main Differences Between Crystalline and Amorphous
- Crystalline solids are extremely structured. The molecules within the solid are organized in an arranged pattern known as a crystal lattice. Amorphous solids, on the other hand, are not at all structured. The molecules within the solid are in an unorganized manner.
- The crystalline solid has a fixed melting point, but the amorphous solid has no fixed melting point. They melt over various temperatures.
- Crystalline solids are anisotropic, whereas amorphous solids are isotropic.
- Crystalline solid is symmetrical, whereas amorphous solid is unsymmetrical.
- Crystalline is quartz, and an example of amorphous is glass.
- https://www.sciencedirect.com/science/article/pii/S0169409X01000977
- https://books.google.com/books?hl=en&lr=&id=Pl1b_yhKH-YC&oi=fnd&pg=PP1&dq=crystalline&ots=d7r_cEFX-f&sig=yfunsduS0YhIFEujbVKyNyTgUKc
- https://www.tandfonline.com/doi/abs/10.1080/00018738600101911
- https://aip.scitation.org/doi/abs/10.1063/1.1659873
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
