* Formation of New Substances: When zinc reacts with water, it forms zinc oxide (ZnO) and hydrogen gas (H2). This is evidence of a chemical change because new substances are formed.

* Irreversible Reaction: The reaction between zinc and water is irreversible, meaning you can't easily separate the zinc oxide and hydrogen gas back into their original components.

* Energy Change: The reaction releases heat, indicating a chemical change.

In contrast, a physical change only alters the form or appearance of a substance, not its chemical composition. For example, melting ice is a physical change because the water molecules remain the same, only their arrangement changes.