Question

for any substance why does the temperature remain constant during the change of state

Answer 1

The temperature of any substance remain constant during the change of state because the heat energy supplied is used up in changing the state of matter  and also this heat is used for breaking of several bonds or attractive forces.This heat, which does not raise the temperature of the body, is called Laten heat.

Answer 2

✳✳✳✳✳✳✳✳✳✳✳✳✳ during a change in state , the temperature remains constant because the heat provided is used in changing state so the temperature does not increases
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