Sulamise

Sulamise is the physical process by which a solid substance changes into a liquid when heat is added. In pure crystalline materials, melting occurs at a specific temperature called the melting point at a given pressure; impure materials melt over a range of temperatures, forming a liquid with varying composition as temperature increases.

During melting, the process is endothermic and involves latent heat of fusion. For a mole of material at its melting point, this is the energy required to overcome the forces holding the solid’s crystal lattice, allowing a transition to the liquid phase without a sudden rise in temperature.

Mechanism and structure: The supplied energy weakens the lattice, and once enough energy is absorbed, liquid nuclei form and grow, eventually converting the solid into a flowing liquid. The behavior depends on crystal structure, impurities, and defects, which can broaden or alter the melting region.

Factors and variations: Melting points are influenced by pressure and impurities. For most solids, increasing pressure raises the melting point, though some systems show nonintuitive behavior. Alloys typically melt over a range of temperatures rather than at a single point due to multiple constituent interactions.

Examples and applications: Ice melts at 0°C at standard pressure; iron melts near 1538°C; waxes and salts vary widely in melting temperatures. Melting is fundamental in metalworking, casting, soldering, glassmaking, and many food and chemical processes, where materials are heated to reach their liquid phase.

Related concepts: In many amorphous solids (such as glass), there is no sharp melting point; instead, they soften over a broad temperature range. In geology, partial melting of rocks produces magmas through the coexistence of solid and liquid phases.