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Write brief answers to the following questions:
 
Why does the temperature of a substance remain constant during its melting point or boiling point?
 
The of a substance remains constant at its melting and boiling points until all the melts or boils because the supplied is continuously used to change the substance's state by overcoming the forces of attraction between the . This heat energy absorbed without showing any temperature rise is the latent heat of fusion/latent heat of .