Is a bread toasted physical or chemical change?

* New substances are formed: The heat causes the carbohydrates in the bread to break down and form new compounds, like melanoidins (which give toast its brown color) and other volatile compounds that contribute to its flavor.

* Irreversible: You can't easily reverse the process of toasting. Once the bread is toasted, it won't magically become un-toasted.

* Chemical reactions: The browning process is a complex series of chemical reactions known as the Maillard reaction, which involves the interaction of sugars and amino acids.

In contrast, a physical change only alters the form or appearance of a substance, not its chemical composition. For example, cutting bread is a physical change because it's still bread, just in smaller pieces.