The Question is from neet-chemistry the-solid-state , and it was created by the author P SRAVAN KUMAR

Question

A novel crystalline solid exhibits anisotropic conductivity, high melting point, and is insoluble in common organic solvents. However, upon heating above a critical temperature, it transforms into another solid form that becomes isotropic in conductivity.  What can be inferred about the nature of the transition and the high-temperature phase?

P SRAVAN KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
	**Primary Concept**: Solid-state phase transitions
	**Related Topics**: Crystal structures, Anisotropy, Isotropy, Amorphous solids
	**Prerequisites**: Basic understanding of solid-state materials and their properties.
## SOLUTION PATHWAY
**Given Information**:
	- Initial phase: Crystalline, anisotropic conductivity, high melting point, insoluble in organic solvents.
	- Transition: Occurs upon heating above a critical temperature.
	- High-temperature phase: Solid, isotropic conductivity.
**Method & Steps**:
	1. Analyze the initial state:
		Reasoning: The anisotropic conductivity suggests a structured, ordered crystal lattice.
	2. Analyze the transition:
		Working: The transition occurs upon heating, which typically increases disorder in a system.  The fact that the high-temperature phase is still a solid rules out melting or sublimation.
		Key Point:  The change from anisotropic to isotropic conductivity indicates a change in the crystal structure to a more symmetric form.
	3. Infer the nature of the high-temperature phase:
		Result: The high-temperature phase is likely a solid with a more disordered structure.  The isotropic nature suggests a highly symmetric structure, potentially amorphous or cubic.
		Verification: The observation of a solid-state phase change aligns with the described properties.
## OPTION ANALYSIS
[A] :x:  'The transition is melting, and the high-temperature phase is a liquid.'
	Incorrect because the question explicitly states the high-temperature phase is another 'solid form'. Melting would produce a liquid.
[B] :x: 'The transition is sublimation, and the high-temperature phase is a gas.'
	Incorrect because the question explicitly states the high-temperature phase is another 'solid form'. Sublimation would produce a gas.
[C] ✓: 'The transition is a solid-state phase change to a more disordered structure, and the high-temperature phase is likely more isotropic and potentially amorphous or cubic.'
	Correct as it accurately describes a transition between two solid phases, explains the change in conductivity due to increased disorder and symmetry, and suggests plausible structures for the high-temperature phase.
[D] :x: 'The transition is a chemical decomposition, and the high-temperature phase consists of simpler molecular species.'
	Incorrect as there is no information given to suggest a chemical change. The question describes a change in physical properties (conductivity), not a change in chemical composition.
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing phase transitions: It's crucial to distinguish between melting, sublimation, and solid-state phase changes.
		2. Misinterpreting anisotropy and isotropy:  Anisotropy implies direction-dependent properties, while isotropy implies uniformity in all directions.
	**Quick Tips**:
		1.  Heating generally increases disorder in a system.
		2.  Cubic crystal structures and amorphous solids exhibit isotropic properties.

P SRAVAN KUMAR · Answer

The transition is melting, and the high-temperature phase is a liquid.

P SRAVAN KUMAR · Answer

The transition is sublimation, and the high-temperature phase is a gas.

P SRAVAN KUMAR · Answer

The correct Option is "The transition is a solid-state phase change to a more disordered structure, and the high-temperature phase is likely more isotropic and potentially amorphous or cubic."

P SRAVAN KUMAR · Answer

The transition is a chemical decomposition, and the high-temperature phase consists of simpler molecular species.

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