Baking soda and Baking powder are used for baking and fermentation purposes. Fluffiness and airy texture in baked goods, fermentation of batter can be achieved by using one or both of these ingredients.
They are called chemical leavening agents which means they are added to baked goods before cooking to produce carbon dioxide that cause them to rise. However, they are used under different conditions.
Pure Sodium bicarbonate.
When it is mixed with acidic ingredients like honey, buttermilk, yogurt the chemical reaction is pretty much fast which produces CO2.
The trapped CO2 gas makes the baked goods to expand/rise during oven temperature.
Since the chemical reaction takes place very fast, the recipes that call for baking soda has to be cooked immediately or they will fall flat.
Baking powder addresses this problem with its extended reaction.
It contain Sodium bicarbonate with two different acids.
Baking powder is called a "double acting agent" as it produces CO2 gas at different stages of the baking process.
The first reaction occurs when baking powder is added to wet dough or batter.
The second reaction occurs only in a hot environment i.e when the batter or dough is placed in the oven. The second reaction allows the batter to rise for a longer period of time making lots of air bubbles in a cake or muffin.
* Baking powder is used instead of yeast in bread recipes. The introduction was revolutionary in minimizing the time and labor required.
* Baking powder can be used as a substitute for baking soda but the reverse is not possible.