Solidification Definition and Examples in Chemistry

Solidification, also known as freezing, is a phase change of matter that results in the production of a solid. Generally, this occurs when the temperature of a liquid is lowered below its freezing point. Although the freezing point and melting point of most materials are the same temperature, this is not the case for all substances, so freezing point and melting point are not necessarily interchangeable terms. For example, agar (a chemical used in food and the laboratory) melts at 85 C (185 F) yet solidifies from 31 C to 40 C (89.6 F to 104 F).

Solidification is nearly always an exothermic process, meaning heat is released when a liquid changes into a solid. The only known exception to this rule is the solidification of low-temperature helium. Energy (heat) must be added to helium-3 and helium-4 for freezing to take place.

Solidification and Supercooling

Under certain conditions, a liquid may be cooled below its freezing point, yet not transition into a solid. This is known as supercooling and it happens because most liquids crystallize to freeze. Supercooling may be readily observed by carefully freezing water. The phenomenon can occur when there is a lack of good nucleation sites from which solidification can proceed. Nucleation is when molecules from organized clusters. Once nucleation occurs, crystallization progresses until solidification happens.

Solidification Examples

Several examples of solidification may be found in everyday life, including:

• Freezing of water to form ice in an ice cube tray
• Formation of snow
• Congealing of bacon grease as it cools
• Solidification of melted candle wax
• Lava hardening into solid rock