To fizz, or not to fizz

To fizz, or not to fizz

Cowens, John

Baking powder and baking soda provide a lesson in acids and alkalis for grades 3-6

The Home Economics room is across the hallway from my sixth grade classroom. One day, I heard a Home Ec. student ask, “What’s the difference between baking soda and baking powder? Aren’t they the same?” The student was asking a very good question!

What is the difference between these two white baking substances? Here are three experiments that will give you an explanation.

1 Baking Soda Baking soda is sodium bicarbonate – sometimes called bicarbonate of soda. Not only is it used for baking cakes and cookies (it puffs them up), but some people use it for brushing their teeth, absorbing refrigerator odors or as an antacid for indigestion.

Materials: two clear drinking glasses, stirring rod or spoon, two teaspoons of baking soda, glass of orange, grapefruit, apple or lemon juice and glass of water.

Instructions: Fill one glass 2/3 full of water. Add one teaspoon of baking soda to the glass of water and observe the reaction. Fill the other glass 2/3 full of any juice. Add one teaspoon of baking soda and observe the reaction.

As your students will observe, nothing happens in the glass of water. However, in the juice, you get bubbles. You have made soda! The baking soda releases carbon dioxide in the form of bubbles.

Try adding baking soda to the other juices. If you have buttermilk, sour cream, yogurt and molasses, add a teaspoon of baking soda to each of them. They are all acidic and will bubble.

If you’re baking a certain kind of cake or baking cookies, be sure to add baking soda. When baking soda is added to dough made with any of these or other acidic liquids, bubbles form and cause the dough to rise.

2 Baking Powder Whenever it rains, I get the urge to make peanut butter/chocolate chip cookies. During one storm, I gathered all of the ingredients but couldn’t find any baking soda. However, I found a can of baking powder in a cabinet and decided to substitute it for the baking soda. Is there any difference between baking soda and baking powder? Definitely! (I ate the cookies despite the difference.)

Materials: two drinking glasses, water, 1/2 teaspoon baking powder and 1/2 teaspoon baking soda

Instructions: Add 1/2 teaspoon baking powder to one glass of water. Add 1/2 teaspoon of baking soda to the other.

The water that contains the baking powder bubbles up. The water that contains baking soda doesn’t bubble because it is an alkali, the chemical opposite of an acid. When an alkali combines with an acid, it forms carbon dioxide.

Baking powder, on the other hand, is a combination of baking soda and an acid. When you add baking powder to water or milk, the alkali and the acid react with one another and produce carbon dioxide – the bubbles.

There are three types of baking powder, all of which contain baking soda and an acid: (1) Cream of tartar (tartrate baking powder), (2) Monocalcium phosphate (phosphate baking powder) or (3) a combination of calcium acid phosphate and sodium aluminum sulfate (double– acting baking powder).

3 Baking Powder vs. Baking Soda What would happen if we added baking powder (which contains an acid) to another acid?

Materials: two glasses, apple, orange, lemon or grapefruit juice, buttermilk or sour milk, 1/2 teaspoon baking powder, 1/2 teaspoon baking soda

Instructions: Fill both glasses 2/3 full with one of the juices. Add 1/2 teaspoon baking powder to one of the glasses of juice and baking soda to the other glass with the same juice.

The juice with the baking powder doesn’t bubble as much as the one with the baking soda. When you add baking powder to an acid, you’re offsetting the balance of acid and alkali. In addition, you are adding more acid than alkali. As a result, less carbon dioxide is produced. Try experimenting with the other juices, buttermilk or sour milk. Do the same results occur?

More than meets the eye

Baking powder and baking soda look similar, but they’re two different substances that need different circumstances in order to “do their stuff.” Kids are the same way – they may all wear jeans and sport the latest haircuts, but what’s inside each of them is unique. Each child learns differently.

The Learning Champs by Colin Rose and Anne Civardi (Sterling Publishing Co., ISBN 0-8069-9032-5) is based on fascinating discoveries about the brain and how people learn. These discoveries have led to the recognition that each student has a way of learning that best suits him or her – a preferred learning style. If students can be helped to recognize those preferences – and acquire the techniques that best match their own learning style they can become better and more confident learners.

The book offers tips and techniques on motivation, goal-setting, concentration, note-taking, writing, revising and more. If we, as teachers, can help kids understand how they learn, we can help them to be better students.

John Cowens teaches science at Fleming Middle School, Grants Pass, OR, and is a Teaching Editor of Teaching K-8. E-mail:

Copyright Early Years, Inc. Oct 2002

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