Specific Latent Heat of FUSION (Lf):
- Energy to change between solid ↔ liquid (melting/freezing)
- For water: Lf = 334,000 J/kg
- "Fusion" = fusing/joining (particles come together when freezing)
Specific Latent Heat of VAPORISATION (Lv):
- Energy to change between liquid ↔ gas (boiling/condensing)
- For water: Lv = 2,260,000 J/kg
- MUCH bigger than fusion — particles must completely separate
Why Lv is much greater than Lf: Going solid → liquid only loosens bonds. Going liquid → gas completely breaks them. More bond-breaking = more energy needed.
Quick Check: Calculate the energy needed to melt 2 kg of ice at 0°C. (Lf of water = 334,000 J/kg)
E = m × L = 2 × 334,000 = 668,000 J (668 kJ). This is the energy needed to break the bonds in ice — temperature stays at 0°C throughout.
This key facts covers Two Types of Latent Heat within Specific Latent Heat for GCSE Physics. Revise Specific Latent Heat in Particle Model for GCSE Physics with 13 exam-style questions and 30 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 4 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Specific Latent Heat
What is specific latent heat?
During a state change, energy is being supplied to a substance but the temperature does not change. Explain where this energy goes.