Question

when a piece of ice flating in water melts the level of water remain same

Answer 1

a floating object displaces an amount of water equals to its own weight. since water expands when it freezes,one ounce of frozen water has a larger volume than one ounce of liquid water.

Answer 2

Any object when placed inside another larger object it displaces the place in the larger one.
In this case after melting the ice flasje will displaces the volume of it in the water thus causing the level to rise depending on the volume of the flake but increase is confirmed