What is baking powder?

Baking powder is a chemical leavening agent composed of bicarbonate of soda (baking soda), an acid (usually cream of tartar or a phosphate), and a filler such as starch. The combination of these ingredients allows baking powder to produce carbon dioxide gas when it comes into contact with moisture and heat. This gas is what causes doughs and batters to rise, resulting in the light and airy texture desired in baked goods.

The presence of both the alkaline (bicarbonate) and acidic components in baking powder means that it can react immediately when moisture is added and again when heated. This dual action makes it a highly effective leavening agent, allowing bakers to achieve the desired rise without the need for yeast or fermentation processes.

Other options do not accurately describe baking powder. It isn't just a single ingredient used for flavor, nor is it a mixture of sugar and flour. While a leavening agent may require heat to activate fully, which somewhat describes baking powder, the most accurate definition encompasses the specific combination of bicarbonate soda, acid, and starch that creates its leavening properties.