Answer: Both are Chemical changes.
Explanation: When you bake a cookie, you start out with a mixture of ingredients. These can include substances such as Baking Soda. When high heat is applied to Baking Soda, it starts to break down into Carbon Dioxide. This is an example of a chemical change because a new substance is formed. Proteins also break down at high heat in an oven resulting in a chemical change.
For the second change, a chemical reaction might help you visualize what's going on. 3 Ag2S(s) + 2 Al(s) ---> 6 Ag(s) + Al2S3(s) is the reaction that's occuring. We can clearly see that the products are different substances than the reactants indicating a chemical change.
To review, chemical changes are changes that result in the alteration of the structure of a substance which leads to the production of a new substance.
Hope this helps!