Freezing of water changes it's state from liquid to solid, i.e, ice. Melting of ice changes it's state of matter from solid to liquid, i.e, water. And when we
boil this water, it's state of matter changes from liquid to gas, i.e, steam. And when we condense this steam, it forms water.
Therefore,we conclude that, ice - water - steam are the three different states of a substance and not different substances.All these change of states are due to different temperatures applied.
ice on heating ---> (melts to) water on further heating ----> (by evaporation) gas
Gas by condensation ---->water on freezing ----> ice.