Baking powder and baking soda are not the same. Baking soda is pure sodium bicarbonate, which needs an acidic ingredient and moisture to activate and produce carbon dioxide bubbles that help baked goods rise. Baking powder contains baking soda along with acidic salts (such as cream of tartar) and often cornstarch, making it a complete leavening agent that only needs moisture and heat to activate.

Key Differences

• Baking soda = pure sodium bicarbonate, requires acid + liquid to react.
• Baking powder = baking soda + acid + cornstarch, needs only liquid and heat to activate.
• Baking soda is about 3 to 4 times stronger than baking powder.
• Baking powder comes in single-acting and double-acting types, with double-acting most common, which reacts twice: once when moistened and again when heated.

Uses in Recipes

• Use baking soda when the recipe contains acidic ingredients like buttermilk, yogurt, cocoa, or vinegar.
• Use baking powder when the recipe lacks acidic ingredients since it contains its own acid.

Substitution Notes

• Baking powder can sometimes replace baking soda but requires triple the amount.
• Baking soda can replace baking powder but requires adding an acid for activation.

In summary, baking powder and baking soda serve similar purposes to lighten baked goods through leavening, but their chemical compositions and activation requirements differ significantly.