Which of the following is an example of a reversible physical change?

• A. Water freezing to ice.
• B. Wood burning.
• C. Iron rusting.
• D. Tearing a sheet of paper.

Answer: (A)

A reversible physical change is when a substance changes form without becoming a new substance, and you can undo it to get back the original material by reversing the conditions. Freezing water to ice is a classic example: it’s a change of state, not a chemical reaction, so the water remains H2O; you can melt the ice and return to liquid water. This makes the change reversible. The other options involve forming new substances or more permanent alterations: burning wood creates ash and gases, which cannot be turned back into wood by simple means; rusting produces iron oxide, a new compound; tearing a sheet changes its shape and structure in a way that isn’t easily reversible to the exact original sheet. So freezing to ice best illustrates a reversible physical change.