... That baking powder and baking soda are not the same?
Yes, they are both leavening agents. They are both added to baking goods BEFORE cooking to produce carbon dioxide for the goods to rise. But they play their roles in two different ways.
Baking soda is sodium bicarbonate. When using baking soda in baking, it is combined with moisture and an acidic ingredient (buttermilk or honey) to create a chemical reaction that produces carbon dioxide for the baking goods to rise. Another reason to combine baking soda with an acidic ingredient is because of its alkalinity, it will produce a metallic taste when the chemical change happens. Baking soda also needs to be used at that very moment. It is not to be added and placed aside for awhile before baking as the good will fall flat!
Baking powder has 3 ingredients. It has sodium bicarbonate, cream or tartar (an acidifying agent) and a drying agent (starch).
There are two types of baking powder. The single-acting (fast acting) and the double-acting (slow acting) baking powder. The single-acting baking powder is activated by moisture/room temperature. The baking good which requires this single-acting baking powder must be cooked immediately after mixing. The double-acting agent reacts in two phases. When the baking powder is added to the baking good, some gas is released at room temperature but the remaining of the gas is only released when in the hot oven while baking.
You cannot substitute baking powder with baking soda when the recipe requires baking powder. However, you can make your own baking powder by mixing one part of baking soda and two parts of cream of tartar.