Science Experiments - How to Make Litmus Paper
Turn Red Cabbage
Into Litmus Paper
The litmus paper that is used in schools and in chemical labs is colored by lichens, plants that are combination's of algae and fungi. But here we are going to make an Acid Base Indicator From Cabbage Leaves, and this is a really easy and useful science experiment.
Indicators are substances whose color changes in acids and bases. Litmus is a common indicator that is removed from plants.
An acid is a substance that
has lost an electron. A substance that is capable of neutralizing an
acid is called a base or alkali. In an acid Litmus is pink in color. In a base, litmus is blue.
New Oxford American Dictionary Definition of:
a dye obtained from certain lichens that is red under acid conditions and blue under alkaline conditions.
ORIGIN Middle English : from Old Norse lit-mosi, from litr ‘dye’ + mosi ‘moss.’
paper stained with litmus, used to indicate the acidity or alkalinity of a substance.
Material You Will Need
To Make Litmus Paper
- 1/2 Head Red Cabbage
- Pot to Boil Cabbage
- a rectangle glass dish
- Paper Towels
- Rubber Gloves
Paper Towel Strips
How To Make Litmus Paper
- 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
- Cut strips from the paper towels about an inch wide and a couple inches long.
- Take the paper towels and soak them in the cabbage juice for about a minute. Remove
them and let them dry on something that won’t stain. (Its a good idea to wear rubber gloves while doing this)
- Let the paper strips dry and as soon as they are dry your Litmus paper is ready to start experimenting!
Colors from Experimenting with Litmus Paper
Interesting to Note
Next time when you see a "red" cabbage at the store, notice that it is actually purple. When you submerge it in tap water, it will appears blue. Yet when you add it to coleslaw, it will take on a red color. This is because the cabbage contains a pigment that functions as a natural pH indicator. Tap water is slightly basic, causing it to turn blue. Vinegar in coleslaw is a dilute form of acetic acid, which makes the cabbage turn red.
Ideas for Experiments
Try dipping the paper into orange juice, soapy water, lemon juice, baking soda
in water, baking powder in water, vinegar, and anything else you want to test. It is a good idea to keep notes on what changes you observed.
More Experiments for Kids
Acids and Bases
Solutions are often seperated into two classes, acids and bases. Strong acids and strong bases must always be handled with caution. Sulfuric acid is a strong acid that can "eat away" metals and other substances. Lye (sodium hydroxide) is a strongbase that may be used as a cleanser.
Weaker acids like lemon juice and weaker bases like soap are more stable and less dangerous.