In order to check whether your baking powder is still fresh, you should mix ⅓ cup of hot water with a teaspoon of baking powder. If the baking powder bubbles, it is still fresh. u003cbr/u003eu003cbr/u003eIf you want to test baking soda, you should put 1 teaspoon of baking soda in a bowl and add 2 tablespoons of white vinegar. Again, if the mixture fizzes and bubbles, it is still fresh enough to be used. u003cbr/u003eu003cbr/u003eIt is important to make sure these are still fresh because if they are not, it will affect the baking and stop it from rising correctly.