Two Types of Heat
When you heat a substance, the energy can do one of two things: raise the temperature or change the phase. Understanding this distinction is crucial for sublimation calculations.
Sensible Heat
Sensible heat is thermal energy that changes a substance's temperature without changing its phase. You can "sense" it with a thermometer. The formula is:
Q = m × c × ΔT
Where m is mass, c is specific heat capacity, and ΔT is the temperature change. For example, heating 1 kg of ice from −20°C to −1°C involves only sensible heat.
Latent Heat
Latent heat ("hidden heat") is energy absorbed or released during a phase change at constant temperature. The temperature stops changing even though you're still adding heat — all the energy goes into breaking intermolecular bonds. The formula is:
Q = m × L
Where L is the specific latent heat (J/kg). For sublimation, this is the latent heat of sublimation.
Why Sublimation Requires More Energy
The latent heat of sublimation equals the sum of the latent heat of fusion and the latent heat of vaporization:
- Water fusion: 334 kJ/kg
- Water vaporization: 2,260 kJ/kg
- Water sublimation: 2,594 kJ/kg (= 334 + 2,260)
This is why sublimation is the most energy-intensive common phase transition. Use our latent heat calculator to compute these values for any substance.
🎯 Key Takeaway
During sublimation, temperature remains constant while energy is absorbed. This "hidden" energy breaks molecular bonds rather than increasing kinetic energy.