Question

How will you justify that ice, water and steam are the three states of a substance and not different substances?

Answer 1

Ice, water and steam molecules are of the same chemical formula H2O => same substance
They just appear in different ''forms'' (states) -> solid , liquid and gas respectively

Answer 2

Ice, water and steam molecules contain the same chemical elements, HYDROGEN and OXYGEN. They only appear in different states due to temperature and pressure differences, and are classified as solid, liquid and gas (vapour) states, respectively.