Red Cabbage Chemistry
Whether you love or hate your veggies, Red Cabbage is sure to become your favorite fun food. It certainly is the most entertaining vegetable to play with when discovering science at home. The molecule that turns this leafy vegetable a purple-red hue is an indicator that changes to different colors depending on the pH or acidity. Low pH acids like lemon juice or vinegar will turn the cabbage indicator red to pink, neutral solutions like water remain blue to purple, and basic solutions with a high pH, such as ammonia, make the cabbage indicator turn green to yellow.
The red cabbage indicator is a great home science project. It is fun for all ages and safe for the youngest science explorers. To make a solution of indicator, take two red cabbage leaves in a blender filled with water and process until the leaves are finely shredded and dispersed in the water. Pour the solution through a strainer to remove the solid cabbage from the solution and store the solution in a container with a lid. That’s it!
With the setup complete, the fun can begin. We recently let a group of grade-school scouts test foods and a variety of household items in order to classify them as acids or bases. The group’s favorite test was sour gum that was soaked in water. Not surprisingly, the gum was very acidic and turned our cabbage indicator pink. Dish soap turned our solution blue-green and ammonia, our strongest base, made the cabbage solution turn yellow-green. Adult supervision is necessary when testing ammonia.
Chemistry Inside the Cabbage – It is a molecule from the Anthocyanin family that makes the red cabbage indicator a rainbow of colors. Anthocyanins are found in other colorful foods that we eat and also in the leaves of trees that are red in the fall. This spring and summer the hydrangea flowers will tell you the acidity of the soil because of the anthocyanin in the flower. Our hydrangea plant blooms in pink and blue and sometimes green – just like our red cabbage indicator!
Notes: Adult participation/supervision is required when making the cabbage indicator solution and when working with younger children on this science project.
Test out drinks like fruit juices, soda, packaged drinks and milk. Solids like baking powder, baking soda and salt can be dissolved in water to test. Other items like hard candy and gum can be soaked in water to extract coatings. Hand and dish soaps are often neutral but some will test more basic.