Latent heat is the energy absorbed or released by a substance during a phase change (such as melting, boiling, or sublimation) at constant temperature and pressure. It is a key concept in thermodynamics and physical chemistry.

Key Concepts:

• Latent Heat (L): Energy per unit mass required for a phase change
• Heat Energy (Q): Total energy absorbed or released during phase change
• Phase Change Types: Fusion (melting), Vaporization (boiling), Sublimation, Condensation, Freezing, Deposition
• Phase Change Temperature: Temperature at which phase change occurs (e.g., melting point, boiling point)

Key Formulas:

• Q = mL - Heat energy for phase change
• m = Q/L - Mass from heat and latent heat
• L = Q/m - Latent heat from heat and mass

Common Latent Heats:

• Water (fusion): 334,000 J/kg
• Water (vaporization): 2,260,000 J/kg
• Ice (sublimation): 2,834,000 J/kg
• Aluminum (fusion): 397,000 J/kg
• Iron (fusion): 247,000 J/kg
• Copper (fusion): 205,000 J/kg
• Gold (fusion): 65,000 J/kg
• Silver (fusion): 88,000 J/kg
• Lead (fusion): 24,500 J/kg
• Mercury (fusion): 11,400 J/kg
• Ethanol (vaporization): 841,000 J/kg
• Oxygen (fusion): 13,900 J/kg
• Nitrogen (fusion): 25,700 J/kg
• Ammonia (vaporization): 1,370,000 J/kg
• Carbon Dioxide (sublimation): 574,000 J/kg

Units:

• Latent Heat: J/kg, kJ/kg, cal/g
• Heat Energy: J, kJ, cal, kcal
• Mass: kg, g
• Temperature: °C, K, °F

Applications:

• Melting and freezing of ice
• Boiling and condensation of water
• Refrigeration and air conditioning
• Phase change materials for energy storage
• Industrial and chemical processes
• Weather and climate science

Types of Latent Heat:

• Latent Heat of Fusion: Solid ↔ Liquid
• Latent Heat of Vaporization: Liquid ↔ Gas
• Latent Heat of Sublimation: Solid ↔ Gas