Question

what is baking powder? How does it make the cake soft and spongy

Answer 1

Mixture of sodium bicarbonate and cream of tartar used instead of yeast in baking. It makes the cake soft and spongy

Answer 2

Normal “baking powder” consists of sodium bicarbonate (“baking soda”) and potassium bitartrate (“cream of tartar”). These react together with heat and moisture to release carbon dioxide, which makes the cake rise. Baking soda alone will release gas during baking, if the temperature is high enough.

Commercial cake mixtures use a variety of other raising agents, like sodium aluminum sulfate and sodium pyrophosphate, which have a different effect on the flavor; but the carbon dioxide still comes from combining them with sodium bicarbonate.