Homeschool Science - Using Cabbage to Learn About Acids and Bases

What fun is a homeschool science project without a little kitchen sorcery from time to time? With this homeschool science project, you’ll use cabbage juice, vinegar, and a few other common kitchen products to learn more about acids and bases and how they interact.

Before you begin, make sure that you have all of the necessary ingredients gathered together. You’ll need:
    •    Red cabbage (particularly the juice from a red cabbage)
    •    A blender or food processor
    •    Water
    •    A sieve (or strainer)
    •    White vinegar
    •    Three drinking glasses
    •    Laundry ammonia
    •    Baking soda
    •    Pen and paper to record your results

Once you have these materials gathered together, you’re ready to get started. You’ll test three different materials in this experiment. During the testing, you’ll learn about how the pH scale helps chemists to learn what properties are contained within a mixture. One of the best determinants of the properties is the color of the materials when measured against a scale.

Before you move on, you’ll need to have plenty of cabbage abstract available for testing. The cabbage extract will be your acid-base indicator, which will let you know whether a material is an acid or a base based on its color.
To get the cabbage extract:
    •    Place about 2 cups of cabbage cubes into your blender or food processor.
    •    Add about a cup of water.
    •    Blend well.
    •    Strain the mixture of pulp so you are left with only the liquid. Now you’re ready to begin.

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Cabbage extract and vinegar:
Vinegar is an acid (you’ll notice that the label probably says “acetic acid.” To test the properties that red cabbage has on an acid, complete the following steps:
    •    Pour half a cup of vinegar into the drinking glass.
    •    Add one teaspoon of red cabbage extract.
    •    Stir the mixture.
    •    Record your observations about its color.

Cabbage extract and laundry ammonia:
Laundry ammonia is a base. Bases are also called alkalis.
    •    Pour about half a cup of laundry ammonia into a drinking glass.
    •    Add about one teaspoon of cabbage extract.
    •    Stir the mixture.
    •    Record your observations about its color.

Cabbage extract and baking soda:
Baking soda is also a base. However, you may find that it has a different color than ammonia.
    •    Place about one teaspoon of baking soda in a glass.
    •    Add about half a cup of water to the glass.
    •    After the solution has dissolved, add a teaspoon of red cabbage extract.
    •    Record your observations about its color.

Think about what you saw:
Now that you have tested three different substances, compare the colors of each substance. Why are the bases different colors? Why are acids and bases different colors?

Chemists use a pH scale to determine the pH level of s substance. Any substance that has a pH level below 7 is considered to be acidic. Anything with a pH level above 7 is considered to be a base. The larger the number, the more basic the substance is.

Colors correspond to the pH levels. In your homeschool science experiment, you created the same solution that scientists sometimes use when comparing colors: cabbage extract.

Here’s how color corresponds to the pH levels:
2 - red
4 – purple
6 – violet
8 – blue
10 – blue-green
12 – green

Now that you have your pH level scale and plenty of cabbage extract left, why not take some time to figure out the pH levels of other household items?