Why does baking powder make dough rise?

All baking powders contain starch, baking soda, and either cream of tarter or phosphate. When flour is mixed with baking soda and a small amount of water, the cream of tarter or phosphate in the baking powder reacts with the baking soda to set free carbon dioxide gas bubbles. After it is covered and set aside for a couple of hours, the dough rises to almost twice its size because of this released gas of carbon dioxide.