What is the main difference between baking powder and baking soda?

The distinction between baking powder and baking soda is fundamental in baking chemistry, and option C accurately captures this difference. Baking powder contains both an acid and a base, meaning it can create carbon dioxide gas when it is moistened and heated. This dual composition allows baking powder to work independently, as it does not require any additional acidic component in the recipe to activate its leavening properties.

On the other hand, baking soda, which is pure sodium bicarbonate, requires an acid (such as vinegar, buttermilk, or lemon juice) to activate its leavening capabilities. When combined with an acid, it produces carbon dioxide gas, which helps baked goods rise. Therefore, understanding that baking powder is self-contained with its acid component while baking soda relies on an external acid is crucial for effective baking.

This understanding helps prevent common baking mistakes, such as using baking soda in a recipe that does not contain an acid, leading to flat or dense baked goods. Knowing the roles and chemical interactions of these two ingredients ensures that bakers can achieve the desired texture and rise in their recipes.