Answer and Explanation
The process of baking cookies involves a set of chemical and physical changes.
Physical change
In a physical change, the composition of the material involved in the change is the same before and after it occurs.
• An example will be that after being baked, the cookies are hot, then after a few minutes, the temperature will change, and they will become cooler.
Chemical change
A chemical change occurs when the composition of a substance is changed, which requires the breaking and forming of chemical bonds during a chemical reaction.
An example is that heating sodium bicarbonate (an ingredient of the cookie dough) causes it to decompose into water and carbon dioxide:
2NaHCO₃ → Na₂CO₃ + H₂O + CO₂
Carbon dioxide gas and water vapor form the bubbles which make cookies rise. Rising makes cookies taller, and it also opens up space to keep the cookie from becoming too dense.