Specific latent heat
The energy per unit mass required to change a substance's physical state at constant temperature and pressure. Specific latent heat of fusion (solid to liquid) and specific latent heat of vaporisation (liquid to gas) are typically several hundred kJ/kg, much larger than sensible heat.
Formula
Q = mL
Real World
Ice packs used in sports injuries stay at 0°C for an extended time because the ice must absorb 334 kJ for every kilogram that melts before the temperature of the remaining ice begins to rise.
Exam Focus
Distinguish specific latent heat of fusion from vaporisation explicitly — using the wrong value (e.g. 334 kJ/kg vs 2260 kJ/kg for water) will lose all calculation marks.
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