Cabbage Indicator (6/1/16)
This is a really fun, but REALLY SMELLY science experiment! Be sure to ask for assistance from an adult before beginning this lab!
- ½ Head of Red Cabbage
- Metal Strainer (coffee filters work as well)
- Clear drinking glasses
- Measuring spoons ( 1 teaspoon and 1 Tablespoon)
- White paper for a colorless background
- Apron or Lab Coat (red cabbage juice can stain your clothes!)
- Test substances: vinegar, window cleaner (with ammonia), distilled water, baking soda, apple juice, lemon juice, Alka-Seltzer tablets, milk, dish soap, bleach***, or any other liquids you’d like to test!
- Ask an adult to assist you in performing this colorful science experiment! Be sure to put on a lab coat or apron to protect your clothes from getting stained by the red cabbage.
- Peel off four or five leaves from the head of Red Cabbage and add them to a blender filled one-half full of water. Blend the mixture until it is smooth.
- Pour the purplish cabbage liquid through a metal strainer to filter out all of the chunks of cabbage. Be sure to save the strained liquid for the experiment! You will want to add some extra water to your cabbage juice to lighten the color to a light blue or periwinkle.
- Place several clear glasses side by side, using a piece of white paper as a tablecloth. Fill each of the glasses half-full with the light purple cabbage liquid.
- To the first glass, add a Tablespoon of White Vinegar. Notice the color change!
- To the second glass, spray a few squirts of Window Cleaner. Notice another color change!
- To the third glass, add a Tablespoon of Distilled Water. Do you notice a color change this time?
- Set aside these three colorful glasses as a reference while you continue to test some other substances in your remaining glasses of cabbage juice. You could try adding a teaspoon of Apple Juice, Baking Soda, or Bleach*** to each glass. Notice the change in color (if any).
HOW DOES IT WORK:
All around us, liquids have either acidic or basic (alkaline) properties. Typically, acidic liquids taste very sour while alkaline liquids taste bitter and can feel slippery. Strong acids and bases can be dangerous to handle, and can even burn your skin! For this reason, it is very important to ask for assistance from an adult before performing this experiment!!!
Acids and bases can be thought of as opposites placed on either end of a range called the pH scale. The placement of a substance along the pH scale is determined by the concentration of extra Hydrogen ions (H+) in the solution. A high concentration of Hydrogen ions actually indicates a low pH (and high acidity); while low a low concentration of Hydrogen ions indicates a high pH (and high alkalinity).
Scientists have several tools and techniques to determine the acidity or alkalinity of a substance…including color-changing indicators, which actually change colors when introduced to acids or bases! Red cabbage contains a special pigment (or dye) called anthocyanin, which is a naturally-produced indicator of acids and bases!
Anthocyanin turns pink and then red in increasingly acidic solutions (like Vinegar). But it turns blue, then green, and then yellow in increasingly alkaline solutions (like the ammonia in Window Cleaner).
You can compare the color of your red cabbage mixtures to the colors on the chart below to determine the pH and acidity of each of the substances you have tested
YOU CAN ALSO TRY:
- First add a splash of Vinegar to your red cabbage juice. It turns red because Vinegar is an acid. But what happens when you now add a few sprays of Window Cleaner to the mixture? It changes to blue/green because you’re making the solution alkaline! Can you keep changing the color of the solution?
- Some liquids are more dense (they are heavier) than other liquids. By slowly pouring Apple Juice or Bleach into your red cabbage mixture, can you carefully make a layered, multi-colored glass?
- Let’s have some more fun. Acids nd bases react very energetically when mixed with each other. What happens when you add both Vinegar and Baking Soda to the red cabbage juice? (Caution: you may want to perform this experiment outdoors, or in a large bowl!)
DID YOU KNOW?
In addition to red cabbage, anthocyanin pigment can be found in a variety of garden produce like blueberries, raspberries, grapes, eggplants, cherries, and most types of flowers! As these plants mature, the anthocyanin in the fruit or flower will cause them to change color depending on the acidity of the plant. Amazingly, the anthocyanin helps the plant by absorbing harmfully strong sunlight, camouflaging young leaf growth from potential grazers, and may even act as antioxidants to remove toxins. Anthocyanin pigments in flowers can also attract bees, which assist in the pollination and reproduction of plants!
With a bit of flair and scientific know how…you can turn this colorful chemistry experiment into a magical summer display!!!
***PLEASE be sure to ask for assistance from a grown-up before you attempt this experiment! It can be fun and educational for both of you…but it can also be dangerous to handle strong chemicals without adult supervision!!!