What happenes to the temperature during a phase change?
1 Answer
Dec 13, 2016
The compound temperature remains constant, the surrounding temperature changes.
Explanation:
Phase changes go both ways, so the thermal energy of the system may increase or decrease.
DURING a phase change, the temperature of the compound remains constant as the thermal energy is absorbed or released, where the magnitude is according to its unique heats of vaporization or fusion.
- Freezing (heat of fusion,
#DeltaH_"fus"# ) and condensation are exothermic (heat of vaporization,#DeltaH_"vap"# ), since they involve slowing down molecular motion, and thus energy is released and#DeltaH < 0# . - Melting (heat of fusion,
#DeltaH_"fus"# ) and vaporization (heat of vaporization,#DeltaH_"vap"# ) are endothermic, since they involve speeding up molecular motion, and thus energy is absorbed and#DeltaH > 0# .
