The ability of a substance to assume two or more crystalline structure is called

ANS:B - polymorphism

The ability of a substance to assume two or more crystalline structures is called polymorphism. Polymorphism refers to the phenomenon where a substance can exist in multiple crystal structures, each with different arrangements of atoms or molecules in the solid state. These different crystal structures may exhibit distinct physical properties, such as density, hardness, and thermal conductivity, even though they are composed of the same chemical compound. Polymorphism is commonly observed in various materials, including minerals, metals, ceramics, and organic compounds. The existence of different polymorphs can significantly impact the behavior and properties of a substance, making polymorphism an important consideration in materials science, crystallography, and pharmaceuticals, among other fields. Polymorphism is a phenomenon observed in materials science and crystallography where a substance can exist in multiple crystalline structures or forms, known as polymorphs. Each polymorph has a distinct arrangement of atoms or molecules in the solid state, resulting in different crystal structures and physical properties. Here's a more detailed explanation of polymorphism:

1. Multiple Crystal Structures: Polymorphism occurs when a substance can crystallize into two or more different arrangements of atoms or molecules while maintaining the same chemical composition. These different arrangements lead to the formation of distinct crystal structures, each with its own unique arrangement of atoms in the lattice.
2. Distinct Properties: Each polymorph exhibits unique physical properties, such as density, hardness, thermal conductivity, and optical properties, despite being composed of the same chemical compound. These differences arise from variations in the arrangement of atoms or molecules within the crystal lattice, which affect the interactions between particles and the overall structure of the material.
3. Factors Influencing Polymorphism: Polymorphism can be influenced by various factors, including temperature, pressure, and the rate of crystallization during solidification. Changes in these factors can lead to different polymorphs being favored or stabilized, resulting in the formation of different crystal structures under different conditions.
4. Examples of Polymorphism: Polymorphism is commonly observed in a wide range of materials, including minerals, metals, ceramics, and organic compounds. For example, carbon can exist in several polymorphic forms, including graphite, diamond, and fullerenes, each with its own unique crystal structure and properties. Similarly, sulfur exhibits polymorphism with different allotropes, such as rhombic sulfur and monoclinic sulfur, depending on the temperature and pressure conditions during crystallization.
5. Importance and Applications: Understanding polymorphism is crucial in various fields, including materials science, pharmaceuticals, and crystallography. Polymorphs can have different solubilities, stabilities, and bioavailabilities, making them important considerations in drug development and formulation. Additionally, polymorphism can influence the properties and behavior of materials in technological applications, such as in the design of new materials with tailored properties or in the optimization of industrial processes.