The purpose for using a leavening agent such as baking soda or baking powder in cakes and cookies is to provide a source of ______________.

Using a leavening agent like baking soda or baking powder in cakes and cookies primarily serves the function of producing carbon dioxide. When these leavening agents are combined with moisture and heat, they undergo a chemical reaction that releases carbon dioxide gas. This gas forms bubbles in the batter, causing it to expand and rise during baking. As the carbon dioxide is produced, it creates light and airy textures in baked goods, contributing to their overall mouthfeel and structure.

Baking soda, a basic compound, typically reacts with acidic ingredients in the recipe to produce carbon dioxide, while baking powder contains both an acid and a base, allowing it to create carbon dioxide when it is moistened and heated, even without the presence of additional acidic ingredients. This leavening process is critical in achieving the desired volume and texture in cakes and cookies.