TEST WHETHER YOUR BAKING POWDER IS FRESH – Baking powder is a leavener that contains a combination of baking soda, an acid (such as cream of tartar), and a moisture absorber (such as cornstarch). Baking powder releases carbon dioxide gas bubbles when mixed with liquid, and this is what causes breads and cakes to rise. However, baking powder loses its potency over time, so if you’ve had the same supply for eons, be sure to test whether your baking powder is still good. Pour 1/4 cup of hot tap water over 1/2 tsp of baking powder and observe – the fresher the powder, the more actively it will bubble. If a weak reaction occurs, or none at all, your baked goods will end up flat!