Testing baking soda/powder

Baking soda and baking powder are essentially chemical leaveners that react to temperature and other ingredients, so you are testing to see if the chemicals are still active. All you have to do is drop a little bit of the baking soda or baking powder into hot water (and vinegar if testing baking soda) and look for a bubbling reaction — if there's fizzing, it's still good to use!