Baking soda needs an acid such as buttermilk or lemon juice to produce carbon dioxide bubbles.

The longer version

Sodium bicarbonate is a base, and it only releases carbon dioxide when something acidic donates a proton to it. Mix it into a batter with buttermilk, yogurt, citrus juice, or brown sugar and the reaction begins immediately, forming bubbles that expand further in the oven heat.

Without enough acid, only partial decomposition occurs, and the leftover alkaline salt leaves a soapy taste and a yellowish tint. Baking powder sidesteps this by including a dry acid alongside the bicarbonate, so moisture alone is enough to start the reaction. Both leaveners work quickly, so batters are usually baked soon after they are mixed.

Where this entry sits

Everyday ingredients turn out to be full of quiet chemistry and long history. This collection gathers short, plain explanations of how bread rises, why onions sting, where common spices originate, and how coffee, tea, and chocolate reached the modern kitchen. The full list sits on the Food and Drink page, where every entry is listed in order.