E

Enthalpy of Fusion

Solid→Liquid at T_m; ΔH_fus > 0; e.g., H₂O: +6.01 kJ/mol
Quick Reference
Formula / NotationSolid→Liquid at T_m; ΔH_fus > 0; e.g., H₂O: +6.01 kJ/mol
Also Known AsHeat of fusion, latent heat of melting, molar enthalpy of fusion, ΔH_fus

What is Enthalpy of Fusion?

The heat energy required to convert one mole of a solid into a liquid at its melting point, at constant pressure. Also called latent heat of fusion. It reflects the energy needed to overcome the intermolecular forces holding the solid structure together.

Formula & Notation

Solid→Liquid at T_m; ΔH_fus > 0; e.g., H₂O: +6.01 kJ/mol

Other Names / Synonyms: Heat of fusion, latent heat of melting, molar enthalpy of fusion, ΔH_fus

Properties & Characteristics

The enthalpy (standard molar enthalpy) of fusion is the energy required to convert one mole of a solid into a liquid at its normal melting point under standard pressure. It is always endothermic (ΔH_fus > 0). It equals the enthalpy of solidification (ΔH_solid = −ΔH_fus). The entropy of fusion ΔS_fus = ΔH_fus / T_m. Substances with strong intermolecular forces have high enthalpies of fusion (H₂O: 6.01 kJ/mol; NaCl: 28.2 kJ/mol).

Uses & Applications

Enthalpy of fusion data is used in: phase diagram construction, calculating energy needs for industrial melting operations, designing thermal energy storage systems (phase change materials, PCMs), assessing purity by DSC (melting point depression from impurities), and in food science (chocolate tempering).

Safety Information

Industrial melting operations require energy input management to prevent accidental solidification blocking equipment or energy surges causing overheating. Handling molten materials at their fusion temperatures presents severe burn hazards.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Enthalpy of Fusion
Formula Solid→Liquid at T_m; ΔH_fus > 0; e.g., H₂O: +6.01 kJ/mol
Synonyms Heat of fusion, latent heat of melting, molar enthalpy of fusion, ΔH_fus

Frequently Asked Questions

The heat energy required to convert one mole of a solid into a liquid at its melting point, at constant pressure. Also called latent heat of fusion. It reflects the energy needed to overcome the intermolecular forces holding the solid structure together.

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