Secret messages and codes are as old as writing itself. However, the best secret messages are written in invisible ink. Follow the activity below to learn how to write and then reveal your own secret messages. This is a great activity for 4th - 6th grade students.
What you'll need: Medium-sized bowl; Tincture of iodine (this can be purchased at any drug store); Q-tip or small brush; lemon; notebook paper; and cup.
What to do: Squeeze the lemon into the cup. Using the Q-tip or the brush, write your secret message on the paper, and then let the paper dry. While the paper is drying, add 0.5 cup of water to the bowl and 10 drops of iodine. Stir the mixture well. When the paper is dry, you can dip it into the bowl. Voila! Your secret message is revealed. The paper will turn a dark purplish color, except where you wrote your message.
How does it work? The color change is due to a chemical reaction between the paper and the iodine. Paper is made of starch. When the iodine binds to starch, it makes the dark purple color, which is visible to the eye. Lemon juice contains vitamin C. When you write on the paper with lemon juice, you saturate part of the paper with vitamin C. When iodine binds with vitamin C, it is colorless. This difference in absorption and reflection of light (dark purple vs. clear) in the different areas of the paper reveals your message.
Thanks to Sabra Ramirez of U.T. Arlington for preparing and presenting this activity for DISCUS. Sabra obtained information about how to do this activity from Janice VanCleave's "Chemistry for Every Kid: 101 Easy Experiments that Really Work," published by John Wiley & Son's, Inc. We hope you enjoy this activity, as well as try many of the other activities we have posted in our Activity Corner. If you have your own suggestions for neat at-home activities, let us know about them.
No comments:
Post a Comment