I am not a baker, just an aspiring chef but I have always been confused by these two. You may have also seen many questions asked on cooking forums if baking soda could substitute for baking powder and vice versa.
Here’s a good read to explain the difference ….. it’s all about the Chemistry.
“Baking soda and baking powder are both leaveners used in baking, but they are chemically different. The easiest way to explain it is that baking soda is a base—it’s alkaline.
Baking powder is a mixture of baking soda and a dry acid, such as cream of tartar, and perhaps some cornstarch to help keep the two separate and dry.”
Baking soda, baking powder, what’s the difference? How to substitute, how to make baking powder, how to test baking powder