Why temperature stays constant during boiling
While water boils at constant pressure, its temperature stays at 100 °C even though heat is still being added. Why?
Answer C: explanation for every choice
A
Heat is absorbed. That is why water keeps turning into vapor.
B
Specific heat applies within a phase. During a phase change, ΔT is zero by definition.
C
Correct. During a phase change, absorbed heat (the latent heat of vaporization) raises potential energy by separating molecules, not their average kinetic energy.
D
Liquid water stays at 100 °C throughout.
TakeawayPhase change at constant pressure: heat goes to the latent heat, not to temperature.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp71.