In physics, supercooling refers to cooling a liquid to which temperature condition without it becoming solid?

Introduction / Context:

This question belongs to thermodynamics and the study of phase changes. Normally, when a liquid is cooled to its freezing point, it begins to solidify. However, under certain conditions, a liquid can be cooled below its normal freezing point and still remain in the liquid state. This phenomenon is known as supercooling. Understanding this concept helps in explaining real life behaviours of water droplets, clouds and industrial processes.

Given Data / Assumptions:

• Every pure substance has a defined freezing or melting point under standard pressure.
• Under ideal conditions, cooling to the freezing point should cause a phase change from liquid to solid.
• Supercooling occurs when the liquid is cooled further without crystallisation.
• The question asks at what temperature condition this happens for the liquid.

Concept / Approach:

Supercooling is a metastable state where a liquid is cooled below its normal freezing point but does not freeze because crystal nucleation has not occurred. This can happen when the liquid is very pure and undisturbed, with no suitable nucleation sites for crystals to form. The key idea is that the temperature is below the usual freezing point, yet the phase remains liquid. The approach is to distinguish between cooling at the freezing point and cooling below it, and to ignore options that mention unrelated temperatures such as boiling point or room temperature.

Step-by-Step Solution:

Verification / Alternative check:

Physics texts and laboratory demonstrations show that very pure water can be cooled a few degrees below zero degrees Celsius and still remain liquid in a supercooled state. A small disturbance or introduction of a seed crystal then triggers rapid freezing. This experimental behaviour directly matches the definition that the liquid temperature is below its freezing point, but the state is still liquid. No other standard definition suggests supercooling at exactly the freezing point or above it.

Why Other Options Are Wrong:

Cooling at exactly the freezing point describes the normal onset of solidification, not supercooling. At the melting point, solid and liquid phases coexist in equilibrium, but this is the reverse process and does not describe cooling a liquid beyond its freezing point. Temperatures above the boiling point or at room temperature are not related to the phenomenon at all. Therefore these options cannot be accepted as correct descriptions of supercooling.

Common Pitfalls:

Some learners confuse supercooling with reaching the freezing point, thinking that any temperature near that value qualifies. Others may mix up superheating and supercooling, where superheating refers to heating a liquid above its boiling point without it boiling. Remembering that supercooling specifically involves going below the freezing point without freezing, while superheating involves going above the boiling point without boiling, helps keep these concepts distinct.

Final Answer:

Supercooling refers to cooling a liquid Below its freezing point without solidification.