Baking Powder & Baking Soda

Use your powers of deduction and a little chemistry to tell apart two common ingredients.

Materials Checklist

Baking Powder
Baking Soda
2 Containers
Distilled Vinegar (Other vinegars, lemon juice, etc. work well too)
A Marker
Paper
A Spoon
Water

Questions and Things to Notice

In this quick and easy experiment we're going to take a closer look at two common ingredients used for baking cakes, cookies, muffins, and other yummy foods: baking powder and baking soda. If you've always wondered what the difference was between these two ingredients, don't fret! That's what we're about to find out in a minute, and to help us figure out, we're going to use and learn some chemistry in the process. Specifically, we're going to learn how we can tell two unknown substances apart from each other, using their differences in chemical properties as a guide.

Even though baking powder and baking soda look pretty similar and are even used for similar purposes (making our baked goods fluffy, or leavened), the two are quite different. As it turns out, baking soda is only a single substance: the chemical compound sodium bicarbonate (NaHCO₃), a base. When sodium bicarbonate and an acid, such as vinegar, are mixed together, the two undergo an acid-base reaction to form several products, including water (H₂O) and the gas carbon dioxide (CO₂). Baking powder on the other hand, is actually already mixture of an acid and a base, and that base is sodium bicarbonate! So, why isn't your container of baking powder fizzing all over the place like a baking soda and vinegar volcano? The answer is pretty clever. The acid in baking powder is cream of tartar, the chemical compound potassium bitartrate (KC₄H₅O₆), and it only starts to react with the baking soda when it gets wet!

Procedure

Step 1

Using the spoon, place a spoonful of baking powder into one container and a spoonful of baking soda into the other.
Step 2

Close your eyes and and ask a labmate to shuffle the two containers until you don't know which contains baking soda and which contains baking powder. It's a good idea to label each dish, so you don't get the mixed up.
Step 3

Using the spoon, scoop a small amount of water into each container. Wait a few seconds and then observe each container. You should be able to see that one mixture is reacting and the other isn't.
Step 4

Now, repeat step 3, but this time with vinegar instead of water. You should now see both mixtures reacting. Can you figure out which container holds the baking powder and which container holds the baking soda?