Acids and bases can be found all over the kitchen. Lemon juice and vinegar are common acids, and baking soda is a base. But just what are acids and bases, and what do they do in the kitchen? Read on to find out how they work together to make tasty treats bake up fluffier! These kitchen experiments help to give kids some basic (no pun intended) knowledge of the building blocks of chemistry.
What Are Acids and Bases?
Acids and bases are substances measured by their pH. What is pH? Short for “hydrogen power” in German, a pH level is how acidic or basic something is on a scale of 1 (very acidic) to 14 (very basic). Low numbers have lots of “hydrogen power,” or hydrogen ions (H+). Water’s pH sits in the middle at 7 and is considered neutral. Using your sense of taste is one way to tell the difference between (edible!) acidic and basic ingredients in kitchen chemistry without having to test their pH with a meter or pH papers. Acids like lemon juice, vinegar, and buttermilk taste sharp and tangy, while bases like baking soda taste bitter and soapy.
Here are some approximate pH levels of common ingredients, from most acidic to least:1
Lemon juice: 2
Vinegar: 2
Buttermilk: 4
Bananas: 5
Milk: 7
Water: 7
Eggs: 8
Baking soda: 9
What happens when an acid “meets” a base in a bowl of batter? What we can’t see in a chemical reaction happens when the tiniest building blocks of matter, atoms, combine with each other like magnets. Acids have more protons, or positively charged hydrogen ions (H+), that they “give” to a base, which has fewer protons and a negative (-) charge in an acid-base reaction.
These atoms are very tiny, so tiny that even under a magnifying glass, you can’t see them, but you can observe what happens when you combine baking soda, a base (pH 9), and vinegar, an acid (pH 2). And if your baking soda has been sitting around for a while, this quick experiment is a great way to test its freshness before you bake and fun to do with kids!
Baking Soda and Vinegar Fizzy Freshness Test
To test baking soda, you can add a small amount to some vinegar. When the two substances react and the powder dissolves into the liquid, you get lots of bubbles and fizz!
1. Add 1 tablespoon of vinegar to a small bowl.
2. Add ½ teaspoon baking soda.
3. Watch what happens!
Did it fizz? That means your baking soda is reacting and is ready to use! If nothing happens, it might be time for a fresh box.2
Where Do the Bubbles Come From? When baking soda and vinegar mix, they react to create something new: water, carbon dioxide gas, and another substance called sodium acetate. The carbon dioxide gas escapes as bubbles. In baking, those tiny gas bubbles get trapped in the batter or dough, helping cakes, muffins, and other treats rise and become fluffy!
What About Baking Powder? Baking powder works in a similar way, but there’s one big difference. Baking soda needs an acid to react. Baking powder already has an acid mixed in! That means baking powder can start creating bubbles when you add liquid. Most baking powders are double-acting, meaning they work twice: once when mixed with liquid and again when heated in the oven.
Baking with Acids and Bases
Now that you know what baking soda and powder can do when they react, you can try almost any recipe to see it—and taste it—in action! Both pancakes and cupcakes will work well to show the leavening (rising) power of baking soda and powder, but just remember that the presence of sugar, the gluten in flour, and eggs (which are also a leavening agent and have a basic pH of 8!), affect the rise of baked goods.
Acid-Base Cupcake Experiment
For an easy “control” for your kitchen chemistry experiment, this kid-friendly chocolate cupcake recipe combines an acid (vinegar) and a base (baking soda) to create the rising action.
But any simple recipe that combines acids and bases with flour, sugar, and fat can be mixed and cooked up quickly on the stove or in the oven. Try any favorite from-scratch pancake or cake recipe as your control. If you’re planning to eat them right away, be sure to save some for taste testing against your acid-base ingredient swaps!
Acid-Base Chocolate Cupcakes (adapted from King Arthur Flour’s cake pan cake)
- Muffin tin and 12 cupcake liners
- Toothpicks
- Ruler
- 1 1/2 cups all-purpose flour (or replace with an equal amount of gluten-free flour)
- ¾ cup sugar
- 1/4 cup unsweetened cocoa powder
- ½ teaspoon sea salt
- 1 teaspoon baking soda
- 1 cup water
- 1/3 cup neutral vegetable oil (safflower, sunflower, or canola)
- 1 tablespoon apple cider vinegar or white vinegar
- 1 teaspoon vanilla extract
- Preheat the oven to 350 degrees, and place 12 cupcake liners in a muffin tin.
- Mix all the dry ingredients in a large bowl, and whisk to combine.
- Add the water, oil, vinegar, and vanilla extract to the dry ingredients and mix until just combined (try not to overmix).
- Fill each muffin liner about three-quarters high with batter.
- Bake for 20–24 minutes, until a toothpick or cake tester inserted in the oven comes out with a few crumbs. Start checking when you smell chocolate!
Acid-Base Ingredient Swaps
1. First, review the recipe you’re using with your kids, if not the cupcake one above. Ask them: Which ingredients might be the acids? Which are the bases? These are the ingredients you can swap in your experiment.
2. After mixing up the batter and placing it in the pan or muffin tin, ask kids to observe and measure the batter’s height before cooking. Stick a toothpick into the middle of the pancake or cake batter, then measure the wet area with a ruler and make a note. Cook or bake the batter according to your recipe’s directions.
3. When the cake has fully baked and is off the heat, use a new toothpick to measure the height, or cut into the center of the cupcake and measure with a ruler. How much did it rise?
4. Next, to avoid too much food waste, reduce your recipe by a half or a quarter (ask kids to help with the math!), and try one or more of these (less tasty) variations. Or experiment with the acids and bases you’ve identified in your own recipe.
- Omit the baking soda or replace it with an equal amount of baking powder.
- Replace water with buttermilk. In buttermilk pancake recipes, swap the buttermilk with regular milk.
- Omit the vinegar.
5. Bake according to your recipe’s directions, and once again measure the batter before baking, and then measure the finished product.
6. Once you have your controls and experimental samples, it’s time for a taste test! Ask kids to taste each one and describe the appearance and flavor of the first recipe. Next, ask kids to test the baked goods with acid-base tweaks. How do they look? Taste? What differences do they notice? Look at the recipe and discuss what removing or replacing one of the acids or bases may have done. Did it affect the taste or appearance? How?
For more science fun, enroll your child in one of STEMful’s afterschool programs or school break camps today!
Footnotes:
1. Water Science School, “pH Scale,” United States Geological Survey, accessed October 14, 2026, https://www.usgs.gov/media/images/ph-scale.
2. PJ Hamil, “How to Test Yeast, Baking Powder, and Baking Soda for Freshness,” King Arthur Baking, November 5, 2015, https://www.kingarthurbaking.com/blog/2015/11/05/test-yeast-baking-powder-baking-soda-freshness.