Answer: remains constant.
Justification:
1) The phase changes are:
i) Boiling: pass from liquid to gas (absorbs heat energy)
ii) Condensation: pass from gas to liquid (release heat energy)
iii) Melting: pass from solid to liquid (absorb heat energy)
iv) Freezing: pass from liquid to solid (release heat energy)
v) Sublimation: pass from solid to gas (absorbs heat energy)
vii) Deposition: pass from gas to solid (release heat energy)
2) When a phase change occurs, whichever it is, the heat energy related with the process, either absortion or release, is used, to overcome the intermolecular forces (in the case of heat energy absortion) or to create stronger intermolecular forces (in the case of heat energy release).
Because of that, the heat energy exchange does not change the temperature of the substance.
