Here's why:

Physical Changes:

* Changes in texture: When you cook meat, the proteins denature and change its texture from tough to tender. You're also changing the physical form of ingredients like chopping vegetables or melting butter.

* Changes in state: Water boils and evaporates during cooking, a physical change from liquid to gas. Freezing ingredients (like making ice cream) is another physical change.

Chemical Changes:

* Changes in flavor and color: Caramelizing onions involves a chemical reaction that creates new molecules responsible for their sweet flavor and brown color.

* Changes in composition: Baking bread involves chemical reactions like the Maillard reaction (browning), which creates new compounds. The starch in flour is also converted to sugars during cooking.

In summary:

Cooking often involves breaking down, rearranging, and creating new molecules, all of which are chemical changes. However, it also involves physical changes like altering the shape, size, and state of matter of the ingredients.