Which baking ingredient is known to have acidic properties?

Baking powder is known to have acidic properties because it typically contains a combination of an acid (like cream of tartar or monocalcium phosphate) and a base (sodium bicarbonate). When baking powder is mixed with a liquid and heated, the acid-base reaction produces carbon dioxide gas, which helps baked goods rise. This reaction is essential in baking, as it creates the texture commonly associated with cakes and other leavened products.

In contrast, flour is generally neutral and provides structure, while sugar primarily adds sweetness and does not have acidic properties. Sodium bicarbonate, although it behaves like a baking soda base, does not contain an acid on its own and requires an acidic component to activate its leavening properties. Therefore, baking powder is the correct choice due to its nature of containing both an acid and a base, making it a key leavening agent in baking.