Instantly determine if a phase change absorbs energy (endothermic) or releases energy (exothermic) with detailed thermodynamic explanation
Watch how energy moves during different phase transitions
Select the initial and final states to determine energy direction and calculate heat involved
Choose initial and final states to determine if the transition is endothermic or exothermic.
Choose the starting phase: solid, liquid, or gas.
Choose the ending phase after the transition.
Enter mass to calculate total energy absorbed or released.
See if it's endothermic or exothermic with full explanation.
Endothermic transitions absorb heat from surroundings. The substance gains energy to overcome intermolecular forces. Examples: melting, vaporization, sublimation.
Because melting is endothermic — ice absorbs heat from your hand to break its crystal lattice, making your skin feel cold.
Exothermic transitions release heat to surroundings. Molecules lose kinetic energy and form stronger bonds. Examples: freezing, condensation, deposition.
Because condensation releases latent heat (2,260 kJ/kg for water) directly onto your skin — much more energy than liquid water at the same temperature.
If the substance gains freedom (solid→liquid, liquid→gas, solid→gas), it's endothermic — it absorbs energy. If it loses freedom (gas→liquid, liquid→solid, gas→solid), it's exothermic — it releases energy.
Sublimation is always endothermic. It requires the most energy of any single phase change because molecules must overcome all intermolecular forces to go from a rigid solid directly to free-moving gas.
No! During a pure phase change, temperature remains constant. All energy goes into breaking (endothermic) or forming (exothermic) intermolecular bonds. This is why it's called "latent" heat — hidden heat that doesn't change temperature.
The latent heat of sublimation equals the sum of fusion (melting) and vaporization. Since sublimation skips the liquid phase, all bond-breaking energy must be supplied in one step.
If the initial and final states are the same, no phase change occurs and no energy transfer happens. Every actual phase change must be either endothermic or exothermic.