Question

which of the following could be described as a reversible change?
heating green copper carbonate powder turns it black
marble chips fizz with acid
when zinc oxide is heated it turns yellow, on cooling it becomes white
magnesium burns brightly when heated in air

Explanation:

A reversible change is one where the substance can return to its original state. Heating zinc oxide makes it turn yellow, and cooling it makes it white again, showing a reversible physical change. The other options involve chemical reactions that are not easily reversed.

Answer:

when zinc oxide is heated it turns yellow, on cooling it becomes white