Anyway, it's a good question. You would think that two products whose names sound so similar, and look so similar, would also work similarly. And the fact is, they are similar — but not identical. (Yes, baking soda is a powder, but it's not baking powder.)
Another tip that can't be repeated too frequently is this: Both baking powder and baking soda go stale after about six months. So you should replace them at least that often, even if you haven't finished the whole container. Once it gets stale, it loses its potency, which means whatever you're baking won't rise properly.
Here's an in-depth explanation of the difference between baking powder and baking soda, how they work, and whether you can substitute one for the other: Baking Soda and Baking Powder. And also, here are a few more resources to do with baking:
- What is Baking Soda?
- Make Your Own Baking Powder
- How to Cut In Shortening
- What is All-Purpose Flour?
- What is Gluten?
- Measuring Ingredients in Baking
- Why Do Cookies Spread?
- Classic Cake Recipes
- How to Make Biscuits