Baking soda and baking powder look the same, smell the same, and sound the same, but trust us: They are not the same. 

Can you substitute baking soda for baking powder or vice versa? Kind of. To do so, you’ll need a solid understanding of the chemical reactions produced by each as well as other ingredients to supplement the swap. In other words, it’s possible, but not for beginners. So do yourself a favor and just keep both in the cupboard. 

BAKING SODA

Baking soda, also known as bicarbonate of soda, is a chemical compound made of tiny white crystals. If you think back to chemistry class, baking soda is basic (that is, the opposite of acidic; not the other thing, come on). When it comes into contact with acids like those in vinegar, lemon juice, yogurt, or buttermilk, it immediately starts foaming, creating carbon dioxide bubbles. Those bubbles help give lift, or leavening, to baked goods. Baking soda’s grit also makes it an astonishingly versatile cleaning product. 

Good for: Science fair projects, fancy Easter eggs, eliminating fridge odor, extra-scrubby toothpaste, house cleaning, pancakes, and muffins

Not great for: Recipes with no acidic ingredients

Watch out for: Using too much. A heavy hand with the baking soda could result in a violent volcanic eruption or a metallic taste in your baked goods.

When to throw it out: After three months, or when a half-teaspoon stirred into vinegar fails to produce bubbles.

BAKING POWDER

Baking powder is baking soda taken to the next level. It’s a blend of baking soda and two acids: monocalcium phosphate and either sodium acid pyrophosphate or sodium aluminum sulfate. The two acids lay dormant in the baking powder until two things happen: First, the powder is added to a wet mixture, which sets off a reaction between monocalcium phosphate and baking soda. Then, when the batter or whatever is put in the oven, the heat triggers a second reaction between the second acid and the baking soda. This two-step leavening is why baking powder is often labeled as double-acting. 

Good for: Many, many types of baked goods. It’s often used in combination with baking soda.

Not great for: Much else

Watch out for: Swapping it out for baking soda

When to throw it out: After three months, or when a half-teaspoon mixed into warm water fails to start fizzing.

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