Question

why there is change in temperature during the change of state

Answer 1

as state change, the energy is used to break the strength of bond of material..so it doesn't increases during state change..
but after change of state.. energy gained or losses by particles converted in it's kinetic energy...which it means is called as it's internal energy...
hope you understand it

Answer 2

Example of change in temperature is you have a cup of cold water and another cup of hot water .
Now you mix them well then resultantly the temperature of the mixture is changed .
This is an example of change in temperature .

Hope this helps you .