Are baking soda and baking powder interchangeable?

While both are leaveners used in baking (to help baked goods rise) and both have “baking” in their name, that doesn’t mean they’re interchangeable. Baking soda needs acidic ingredients, such as buttermilk, brown sugar, molasses, or cocoa powder to activate it and expand the air bubbles created while creaming. If recipes don’t include those ingredients, baking powder would be used because baking powder already contains an acidic ingredient (cream of tartar). Some recipes use both baking soda and baking powder. In those cases, baking soda is a tenderizing agent.