You're absolutely right! Ice water, water vapor, and liquid water are not three different substances, but rather three different states of the same substance: water (H₂O).

Here's how we can justify this:

* Chemical Composition: All three states of water have the same chemical formula (H₂O), meaning they are composed of the same atoms (two hydrogen and one oxygen) in the same ratio.

* Physical Properties: The difference between ice, liquid water, and water vapor lies in the arrangement and movement of these water molecules, not their chemical composition.

* Interconversion: Ice can melt into liquid water, and liquid water can evaporate into water vapor. These transitions are reversible, meaning water can change back and forth between these states without changing its fundamental chemical nature.

In summary: While ice, liquid water, and water vapor exhibit different physical properties due to their molecular arrangement and energy levels, they are all different states of the same fundamental substance: water (H₂O).