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

The primary difference between baking powder and baking soda lies in their composition and how they function in baking. Baking powder is a mixture that includes an acid, typically cream of tartar, and a base, which is usually sodium bicarbonate. This combination allows baking powder to produce carbon dioxide gas when it comes into contact with moisture and heat, making it a leavening agent that effectively causes doughs and batters to rise.

Specifically, the term "double-acting" refers to the fact that baking powder works in two stages: it reacts with moisture at room temperature when wet, and it also reacts a second time when heated in the oven. This dual-action is beneficial for ensuring the leavening occurs both when the batter is being prepared and while it is being baked, providing additional lift.

In contrast, baking soda is purely sodium bicarbonate and requires an acid (like vinegar, lemon juice, or yogurt) to activate its leavening properties. This means that, without an accompanying acid, baking soda cannot effectively help baked goods rise.

Understanding these differences is essential for proper baking techniques, as using one ingredient in place of the other can lead to unsatisfactory results.