Question

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

Answer 1

the temperature remains constant due to the heat trapped in the molecules or particles of the matter or any substanceand due to this the particles moves constantly..the temp heat goes inside the particles we may call it as latent heat..

Answer 2

Hello buddy..
Harshi this side..

The temperature if any substance remains constant during change of state coz 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...

Hope it helps you ^_^