While staying at my grandparents’ house last weekend, I was craving pancakes—until I opened the baking cupboard and found a jar of baking soda with a label from the early 2000s. Could it still work?

If your favorite baking recipes suddenly stop turning out well, don’t panic! There may be a simple answer—your leavener may be expired. (By the way, this is the difference between baking soda and ...