Color Changing Flowers

Key Concepts: chemistry, plants

This experiment combines the science of chemistry with the beauty of flowers. We will alter that beauty by causing the flowers to change colors.

To try this, you will need:

a tall container with a large opening and a tight fitting lid. A clear container is more fun, but any will do.
ammonia
a variety of flowers
string
tape

After gathering the rest of the materials, you need to gather some flowers.

Important Note: ASK BEFORE YOU PICK THE FLOWERS! I know from experience that gardeners get very unhappy if you pick them without permission.

Try to get flowers of different colors. I have found that purple, blue, yellow and red flowers usually work the best, but try a variety. Some may surprise you by dramatic changes, and others may not change at all.

Arrange the flowers so you can see the different colors easily. Use some string or thread to tie them together. Pour about half in inch of ammonia into the tall container. Then use the string to suspend the flowers, so that they hang just above the surface of the ammonia. Tape the string in place and put the lid on the container.

Now, all you have to do is wait about 10 to 15 minutes, just enough time for a bowl of ice cream. Check the flowers periodically, and you should be able to see the change happening. After a few minutes, you should notice some dramatic changes in the color of the flowers.

Purple flowers often turn green. I have read descriptions of this experiment which claim that this shows that flowers contain chlorophyll, but actually, the green color is due to a chemical change in the pigment of the flower. The flowers change because their color is produced by chemicals called anthocyanins. These chemicals change color in the presence of acids and bases. Chemicals that do this are called pH indicators.

Red flowers often change blue. Yellow flowers sometimes change to orange or red. Experiment with several kinds of flowers, to see what color changes you get. This is a fun way to make unusual flower arrangements.

In some plants, the reaction of these pigments to acidity can actually tell you about the soil. Hydrangeas can tell you about your soil. Acid soil will give you blue flowers. Basic soil will give you pink flowers. Your local garden shop will have soil pH test kits to tell you about your soil, and by adding chemicals like lime and sulfur, you can adjust your soil to get the color hydrangeas that you want.

Make this Experiment Better!