The main ingredient in baking soda is sodium bicarbonate, a chemical compound often used in baking as a leavening agent. When it is combined with an acid, such as vinegar or lemon juice, it undergoes a chemical reaction that produces carbon dioxide gas. This gas forms bubbles, causing dough or batter to rise and become light and airy. Besides baking, sodium bicarbonate has various uses, including as an antacid to relieve heartburn, a cleaning agent, and in personal care products. Its versatility and effectiveness make it a staple in many households.