Material Classification — Identifying a Mesomorphous Material Which one of the following is commonly cited as a mesomorphous (intermediate-order) material?

Introduction / Context:
Materials can be broadly classified as crystalline (long-range order), amorphous (no long-range order), or mesomorphous, which show order intermediate between crystalline and amorphous. Recognising examples helps link microstructure to anisotropic properties and engineering applications.

Given Data / Assumptions:

• Mesomorphous refers to materials exhibiting partial or layered order.
• We consider classical teaching examples from materials science curricula.
• Metals listed are generally crystalline under ordinary conditions.

Concept / Approach:
Mica is a layered silicate exhibiting strong anisotropy, excellent basal cleavage, and a stacked-sheet structure that gives it characteristics sometimes grouped under mesomorphic behavior in traditional classifications used in some curricula. In contrast, silver, lead, and brass (a Cu–Zn alloy) crystallise into well-defined metallic lattices with long-range order (typically FCC for Ag and many brasses; Pb is close-packed with its own structure) and are not cited as mesomorphous examples.

Step-by-Step Solution:
Define mesomorphous as intermediate/partial order (often layered).Identify mica’s sheet-like structure and pronounced cleavage as non-isotropic, layered ordering.Recognise that Ag, Pb, and brass are conventional crystalline metals without such layered meso-order.Select mica as the representative mesomorphous material.

Verification / Alternative check:
Handbooks often discuss mica for layered structures with exceptional cleavage and anisotropic properties (thermal/electrical insulation), matching mesomorphic descriptions in classical notes.

Why Other Options Are Wrong:
Silver, lead, brass are fully crystalline metallic solids at room temperature, not mesomorphous.

Common Pitfalls:
Assuming any anisotropic metal texture qualifies as mesomorphous; texture is processing-induced in metals, whereas mica’s layered order is intrinsic.

Final Answer:
Mica