Ask A Scientist
Why does baking soda mixed with vinegar fizz a lot?
Asked by: Alex Yurkiv
School: Glenwood Elementary, Vestal School District
Teacher: Mrs. Donahue
Career Interest: Soccer
Answer from Sree Naresh Koneru
Research Associate, CSERC (Clinical Science and Engineering Research Center) and PhD Candidate
Research area: Bio Electromagnetics
Interests/hobbies: Wellness, cricket, volleyball, tennis, cooking, video gaming and most outdoor activities
A curious, but great question Alex! Although fun to watch, the fizz you observed when baking soda and vinegar are put together, actually has some cool science behind it! In the world of chemistry, baking soda is called sodium bicarbonate and vinegar is known as acetic acid. Vinegar has a sour taste because it is an acid; remember putting a lemon in your mouth?
Combining two chemical substances (like baking soda and vinegar) to produce a new chemical substance (like the fizz!) is called a chemical reaction. Our reaction actually takes place in two steps: 1) The substances react to produce carbonic acid. 2) Carbonic acid is very unstable, so it decomposes into carbon dioxide, sodium acetate and water. The bubbles that you see in the fizz are just carbon dioxide molecules trying to escape the solution. Carbon dioxide is much heavier than air, so it flows out freely if the fizz overflows, creating a solution of sodium acetate and water. Baking soda and vinegar are important items that are found in almost every kitchen. Some of those tasty cakes and croissants that we all enjoy are so fluffy, because of the fizz-like reaction that occurs during baking. When added to raw dough, baking soda in the dough will react with any acidic substance including chocolate, yogurt, buttermilk, sour cream, fruits, honey, etc., to produce carbon dioxide, just like we discussed earlier. The carbon dioxide tries to escape from the dough and ends up giving fluffiness to the baked product. Sodium acetate is formed only when the acid is vinegar, but other acids may have other by-products. The best way to learn something is to do it yourself, so here is a fun activity for you to try under the supervision of an adult. All you will need is a balloon, an empty one-liter water bottle, some baking soda and vinegar. Add about 3-4 tablespoons of vinegar to the empty one-liter bottle, keeping the bottle upright. Next, place 1 tablespoon of baking soda into the balloon. Now carefully stretch out the balloon over the bottle's mouth so that the baking soda from inside the balloon will fall into the vinegar. What do you see happening? Try and compare the result with using only half the amount of baking soda and vinegar.