Definition: Baking powder is a leavening agent used in cookies, quick breads and other baked goods to produce expansion of a batter. It is made of baking soda and cream of tartar or another acid powder. It is almost always double action. This means it releases carbon dioxide when mixed with liquid, and releases it again when exposed to heat. Make sure, when following a recipe, that you don't confuse it with baking SODA, because your recipe will be ruined. You can make your own baking powder, which will be single action, by combining baking soda with cream of tartar.
Examples:
The baking powder provides the leavening that makes the banana bread rise.
