Question

How could you show that the three states of matter are interchangeable

Answer 1

Take ice
melt it
it becomes liquid (water)
boil it
it becomes gas(water vapor)
hence States of matter are interchangeable

Answer 2

We can show it in this way:
We take a glass of water and freeze it at 0 degree then we will get ice and if we will boil the water at 100 degree we will get steam or vapour.
hope it helps you..