Kitchen Science 01Little Helpers, ages 4 to 615 min

The Fizz Test

Big question: Why does baking soda need an acid like vinegar to fizz, when baking powder fizzes with plain water?

Mix baking soda and baking powder with water and vinegar, see which cups fizz, and meet the gas that lifts muffins.

The Fizz Test

What you need

  • 4 clear cups
  • 2 teaspoons baking soda
  • 2 teaspoons baking powder
  • 1/4 cup vinegar
  • 1/4 cup water
  • A tray to catch spills
  • Paper and a pencil

What to do

  1. Set up your labWash your hands first and check every ingredient with your grown-up. Put the cups on the tray. Add 1 teaspoon of baking soda to two cups and 1 teaspoon of baking powder to the other two, and ask your grown-up to help you label them.
  2. Water firstPour 2 tablespoons of water into one baking soda cup and one baking powder cup. Watch closely. Which one bubbles?
  3. Now vinegarStand back while your grown-up pours 2 tablespoons of vinegar into each of the last two cups. Listen for the fizz.
  4. Meet the gasKeep your face back and watch the bubbles in a fizzing cup. Each bubble is full of a gas called carbon dioxide. You cannot see the gas itself, and it is one of the gases you breathe out.
  5. Score itDraw the four cups on your paper and give each one a fizz score from 0 to 3. Which cup fizzed the most?

What is happening?

Vinegar is an acid. Acids taste sour, like lemon juice. Baking soda is a base, which is like the opposite of an acid. When they meet in water, they make bubbles of a gas called carbon dioxide. That is the fizz. Baking soda in plain water barely bubbles, because there is no acid. Baking powder is baking soda with a dry acid already mixed in, so plain water starts its fizz. In muffin batter, those bubbles get trapped and lift the muffin.

Stand back and keep your face away from the cups while your grown-up pours the vinegar, because vinegar and fizz sting eyes. If any splashes in your eyes, your grown-up helps you rinse them with cool water right away. Do not drink from the cups.

Try it

Check yourself

1. What two things meet to make the fizz?

Show answer

An acid, like vinegar, and a base, like baking soda.

2. Why does baking powder fizz in plain water?

Show answer

It already has a dry acid mixed in.

3. What gas is in the bubbles?

Show answer

Carbon dioxide.