Baking cookies is primarily a chemical change. A chemical change occurs when substances combine or break apart to form new substances with different properties. In the case of baking cookies, several key processes demonstrate this transformation:
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Ingredient Transformation: When the dough is baked, ingredients like flour, sugar, and eggs undergo chemical reactions. For example, the heat causes the proteins in the eggs to denature and coagulate, changing the texture and structure of the cookie.
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Maillard Reaction and Caramelization: As cookies bake, the sugars undergo caramelization, while the Maillard reaction (a reaction between amino acids and reducing sugars) contributes to the browning and flavor development. These processes create new compounds that were not present in the raw dough.
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Gas Production: The baking soda or baking powder in the dough releases gases (like carbon dioxide) when heated, causing the cookies to rise. This gas release is another indicator of a chemical change.
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Irreversibility: The changes that occur during baking are largely irreversible; once the cookie is baked, you cannot return it to its original dough form.
Overall, the transformation of ingredients, formation of new substances, and physical properties all reflect that baking cookies is a chemical change.