Are phase changes physical or chemical changes? why?

Physical! Because they do not modify the nature of the substance (if you look at the chemical level) and it is reversible

Vapor is H20

Water is H20

Ice is H20

A chemical changes is not reversible

Burning wood for example! And the reactants interact together to form a new product.

Physical changes

Example:

You added enough energy to create a phase change from solid to liquid. Physical actions, such as changing temperature or pressure, can cause physical changes. No chemical changes took place when you melted the ice. The water molecules are still water molecules.