Problem 16 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

A liquid which is permanently supercooled is frequently called a

Step-by-Step Solution

Answer

Permanently supercooled liquid is called a 'supercooled liquid'.

Step 1: Understanding the Question

The question asks for a term used to describe a liquid that remains in a supercooled state permanently. This means the liquid remains liquid below its normal freezing point.

Step 2: Recognizing the Term

A liquid that can stay in a supercooled state without freezing is often called a 'supercooled liquid'. Such liquids can maintain their liquid form below their freezing point and require a disturbance or a nucleating event to finally crystallize.

Key Concepts

Phase Transition

Phase transition refers to the process where a substance changes from one state of matter to another, such as from a liquid to a solid. This is commonly observed in everyday life, such as when water freezes into ice.
During a phase transition, energy is absorbed or released, but the temperature of the substance remains constant until the transition is complete. This energy change occurs due to the breaking or forming of intermolecular bonds.

• Energy absorption causes the substance to move to a higher energy phase, like from solid to liquid (melting) or liquid to gas (evaporation).
• Energy release moves the substance to a lower energy phase, like from gas to liquid (condensation) or liquid to solid (freezing).

Understanding phase transitions is crucial for grasping the concepts of supercooling and nucleation, as these phenomena involve delays and disruptions in normal phase changes.

Supercooling Phenomenon

Supercooling is a fascinating phenomenon where a liquid can be cooled below its normal freezing point and still remain in its liquid state. This can happen if the liquid is undisturbed and no impurities are present to trigger freezing's typical crystallization process.
This state is delicate because any minor disturbance, like shaking or introducing a seed crystal, can cause the liquid to freeze almost instantly.

• Examples of supercooled liquids include water in a carefully controlled environment or certain chemical solutions.
• Supercooling is widely used in scientific research and has applications in areas like meteorology, where it helps in studying cloud formation.

Because supercooled liquids are in a metastable state, they illustrate unique chemical and physical properties, which are essential for understanding how materials behave under different conditions.

Nucleation

Nucleation is the process that initiates the formation of a new phase or structure within a supercooled liquid, causing it to crystallize or solidify. It marks the point where the supercooling state is disrupted, leading to phase transition.
Nucleation can occur spontaneously or be induced by external factors, such as adding a small crystal or impurity to the liquid.

• This process can be homogeneous, occurring uniformly throughout the liquid without any preference for location.
• Or, it can be heterogeneous, where the presence of surfaces or impurities significantly encourages nucleation.

Understanding nucleation helps explain why some materials remain supercooled indefinitely while others crystallize quickly, and it is an essential factor in industries that require control over crystallization, like food processing and material science.