It is an example of a chemical change. When concentrated sulfuric acid is poured onto sugar, the acid strongly dehydrates the sugar molecules, stripping away water and leaving behind hot, porous black carbon, along with gases like steam and other vapors that make the tall, smoky column rise. This irreversible transformation produces new substances (carbon, water vapor, acidic fumes) and cannot be undone by simple physical means, which is why it is classified as a chemical change rather than a physical one.