Step-by-step explanation:
A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity. Examples of chemical changes are burning, cooking, rusting, and rotting. Examples of physical changes are boiling, melting, freezing, and shredding.
To understand why cooking is a chemical change, you should first understand what is a chemical change. Basically, all changes in this world can be classified as either physical changes or chemical changes. The difference is that chemical changes bring about new substances while physical changes don’t. Take the example of baking: when you bake a cake, the most immediately observable change is that it expands. This is because the baking soda in it has undergone a chemical change under heat to release carbon dioxide. Notice there is no carbon dioxide in the cake before we bake it. That is what I mean by bringing about new substances.
So why is cooking a chemical change? Because almost all cooking methods involving the rise of temperature (which is basically to say, all cooking methods) involve chemical changes. Once under heat, the antioxidants omnipresent in vegetables will get oxidized and the proteins in meats will get denatured. Among other things, the former process will mostly result in the change of color of the vegetables, and the latter the stiffening of the meats