Have you ever heard the term pH? The letters pH stand for potential Hydrogen. The pH scale is used to measure whether substances are acidic or basic in reference to the amount of hydrogen ion activity in the substance. A pH of 7 is considered neutral and represents materials such as water. A substance with a pH less than 7 is considered acidic, while a substance with a pH higher than 7 is considered basic.
You may need to measure the pH of a substance if you are testing the water in a swimming pool or hot tub, are checking your soil before planting in the spring, or if you’re just curious! Scientists have many different ways of testing pH, but one of them can be created by you at home!
Testing pH At Home
Red cabbage contains anthocyanin, a pigment that changes colour when mixed with an acid or a base. When blended with water, red cabbage produces a purple liquid but it changes to red or pink when mixed with an acid, and blue or green when mixed with a base.
You’ll need some red cabbage leaves, water, a blender, and a strainer. You’ll also need some containers to perform the test. Paper cups work great! You’ll also need a parent to help you be safe!
Next, you need materials to test - we’re using vinegar and baking soda. Avoid using bleach, as it can cause a dangerous reaction if it’s accidentally mixed with other substances such as vinegar or ammonia.
Fill the blender about half full with water then add a few red cabbage leaves. Put the lid on the blender and have an adult blend the cabbage leaves thoroughly. Pour through a strainer and collect the cabbage water.
Take three test containers and add some of the cabbage water to each. Notice the colour of the liquid.
Leave the middle container alone - this is your control.
Add vinegar to one container - what happens to the liquid? What does this indicate?
Mix some baking soda and water, then add this mixture to the third container. What color does the cabbage juice change to? What does this indicate?
What else can you test?
Look for things to test around your home. What happens if you test your soil, shampoo, or orange juice?
You can also soak strips of paper cut from a coffee in filter in the cabbage juice and let them dry. You can now dip these strips of paper in substances to test their relative pH!
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