Baking soda is sodium bicarbonate (NaHCO3).
When it is mixed with an acid liquid it releases the gas carbon dioxide (CO2):
NaHCO3 + H+ -----> Na+ + H20 + CO2
(soda) (acid) (sodium) (water) (gas)
Baking powder is a combination of baking soda plus a few other things, most importantly a dry acid.
When the baking powder is mixed in a batter with the wet ingredients, the dry acid and the baking soda can then react together and release carbon dioxide.
When it is mixed with an acid liquid it releases the gas carbon dioxide (CO2):
NaHCO3 + H+ -----> Na+ + H20 + CO2
(soda) (acid) (sodium) (water) (gas)
Baking powder is a combination of baking soda plus a few other things, most importantly a dry acid.
When the baking powder is mixed in a batter with the wet ingredients, the dry acid and the baking soda can then react together and release carbon dioxide.