Color Fun - Experiment #25

"Is green really green?

You will need:
strip of paper towel
green felt-tipped pen or 1 drop of green food coloring
jar or glass with 1 inch of water

What to do: Make a spot of color about 2 inches from one end of the strip of paper towel. Hang the strip in the jar so the spot is above the water and the end of the strip is in the water. Let it stand for 15 to 20 minutes.

What happens: The green spot is gone but above the original spot, the paper has turned blue, and above that the paper is yellow.

Why: Most dyes and inks are combinations of coloring substances which can be taken apart by adding water or alcohol. Water moves up the paper the same way as sap rises in trees. As the water moves up, it dissolves the green spot and gradually moves the color up the strip of paper. But since the colors that make up green - blue and yellow - do not move at the same rate, they separate."


What happened when CKS tried it? I tried ink and food coloring. The food coloring was opposite from the ink because the blue is at the top, the green is in the middle, and only a little yellow at the bottom. And on the ink, there is a lot of yellow on the top and there is a little green in the middle, and some blue on the bottom. Ink worked better. Advice from CKS for when you try this at home: don't forget to label your paper towel strips.

CKS rating: 5 stars - Wow, better than TV!

Invisible Ink - Experiment #28

"You can use a lemon to write a secret message.

You will need:
1/2 lemon
saucer
water
cotton swab (Q-tip)
white paper
lamp

What to do: Squeeze the lemon juice into the saucer. Add a few drops of water and mix well with a spoon. Dip the swab into the lemon juice. Then use the swab to write a message on ordinary white paper. When it dries, the writing will be invisible. When you want to read the message, heat the paper by holding it near a light bulb.

What happens: The words appear on the page.

Why: The juice of lemons and other fruits contain compounds of carbon. These compounds are nearly colorless when you dissolve them in water. But, when you heat them, the carbon compounds break down and produce carbon, which is black."


What happened when CKS tried it? My message didn't show up that much - it was clear and shiny and I could hardly see the letters. My mom used a lot of lime juice and it showed up well and it was a little yellow, but some other letters were clear. My advice when you try this is: Use a lot of lemon juice or lime juice to make this work.

CKS rating: 4 stars - Pretty fun!