Sodium, hydrogen, oxygen and carbon are the elements found in baking soda. Baking soda is known chemically as sodium bicarbonate, which has the molecular formula NaHCO3.
Baking soda is a base, which means that it wants to accept a proton. When baking soda is combined with an acid, bubbles of carbon dioxide form. This is because acids, such as acetic acid found in vinegar, provide this extra proton to the base. The bubbles of carbon dioxide expand under heat, meaning that food products that contain baking soda rise. This reaction begins when the ingredients are mixed, so the dish needs to be placed under heat rapidly in order to take advantage of its ability to expand.