This is a great science project and results in beautifully colored paper that can be dried and used for art projects like collages.
All you’ll need is a head of red cabbage and some paper towels or white coffee filters. Alternately, you can just use the juice from canned red cabbage. I’d recommend wearing an old tee shirt or a home-made lab coat for this project, since I’m guessing that cabbage juice stains. To make a lab coat, just have kids write their name in permanent marker on the pocket of an old button-down shirt.
Chop half a head of red cabbage into small pieces and add it to a pan with about a cup of water. Boil the cabbage uncovered for about 15 minutes, stirring occasionally, let it cool, and strain the juice into a jar or bowl. (Save the cooked cabbage for your favorite recipe and make cole slaw with the other half!)
If you want to avoid the stove, chop half a head of red cabbage and blend it with about 3 cups of water. Strain the liquid through a colander and then through a coffee filter in a plastic bag with one corner cut off. Blended cabbage juice makes longer-lasting bubbles and turns a slightly brighter shade of blue!
Cut the paper towels or coffee filters into strips about an inch wide and a few inches long and soak them in the cabbage juice for about a minute. Remove them and let them dry on something that won’t stain. I blotted them a little to speed up the drying process. You might even try using a blow dryer!
When dry, your litmus paper will be ready to use for testing acidity. Your can dip the paper into orange juice, soapy water, lemon juice, baking soda in water, baking powder in water, vinegar, and anything else they want to test. The paper will turn red-pink in acids and blue or green in bases.
Everything in our world is made of very tiny pieces called atoms. Atoms are so small that if you blow up a balloon, it will contain about a hundred billion billion atoms of the gases that make up air. Atoms are often bonded to other atoms to form a group of linked atoms called a molecule. A water molecule, for example, has two hydrogen atoms and one oxygen atom, bonded together.
Acids usually dissolve in water to form free-floating hydrogen atoms. Bases are the opposite and take up free hydrogen atoms. The molecules in the cabbage juice litmus paper change when exposed to an acid or base, making the paper change color.