WRITE A SECRET MESSAGE
What You Need:
- liquid dishwashing detergent
- cup of water
- a few cotton swabs
- hand mirror or bathroom mirror
Place a few drops of dishwashing detergent into the cup of water. stir to mix well. This is your secret message “ink”.
Dip a cotton swab into the soapy solution. Write a short message on the mirror. When the liquid dries, the message will be invisible. (If not, use a little less of the solution.)
When you take a hot shower or bath, do not get the mirror wet, but get the mirror close enough to the steam from the water so that it gets fogged up. Close the door so the steam stays in the bathroom.
Observe what happens. Can you read the message?
More fun: Write a message and wait until someone else takes a shower or bath. See how quickly they discover your secret.
What’s Going On :
The steam on the mirror is made up of water molecules. These tiny drops of water stick together on the mirror because of a force called surface tension. The liquid dishwashing detergent breaks the surface tension of the water. Wherever there is detergent, the water molecules are unable to form into droplets. The words written with the soapy solution stand out clearly against the foggy background of the mirror.
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