Cabbage

Cabbage

Red Cabbage pH paper

Summary

      Some of the most important kinds of chemicals in science are acids and bases.   Although you may not realize it, you use acids and bases in your home everyday.   You can recognize an acid because it makes food and drinks taste sour.   If you have ever tasted something chalky or ever felt a liquid that feels slippery like soap, those substances are probably bases.
      One way to test if a substance is an acid or base is to test its pH.   pH is the scale used in science to rate acids and bases.   The scale is numbered from 1 – 12.   Acids have a pH between 1 and 6.   Bases have a pH between 8 and 12.   If your pH is at 7, that means the substance is neutral, and it is neither an acid nor a base.
      Just like we use a temperature scale on a thermometer to find out if something is hot or cold, we can use the pH scale to find out if something is an acid or a base. An easy way to do this is to use pH paper, which is a piece of paper with a chemical on it that will change colors if it is mixed with acids or bases.   Some fruits and vegetables contain this special type of chemical.   One example is red cabbage.   In this activity you will learn how to make your own pH paper using juice from red cabbage.
      Once you make your red cabbage juice, you will want to know how to use it.   If the color of your red cabbage juice is a purple color, then you know that the pH of your solution should be around 7, which means that your solution is neutral.   When you first make the red cabbage juice, the liquid should be this color.   When you begin to test the pH of other liquids, the juice will change different colors if it is mixed with an acid or a base.   Match the colors you get while you are testing liquids to the chart below to see what pH you have.

pH scale for Red Cabbage Juice
|pH                 |1-2       |3-4             | 5-6       |7-8                   |9-10               |11-12                         |
|Color             |Pink...