Have you ever mixed together different paint colors and gotten a new color, like mixing red and blue to get purple, or mixing yellow and red to get orange? It’s fun chemistry to see how new color combinations can be created with just a few to start, but what happens in nature? How do flowers have so many different colors?
Were reds and yellows mixed together to make carrots orange? These natural colors we see in different plants are called pigments, and most often they are the result of different pigments mixing together to make cabbage purple, roses red, and spinach green.
The video above shows a cool way to see these different pigments through a process called chromatography, or filtering the pigments through paper. Here’s what you’ll need:
Plants (grass, spinach, cabbage, flowers, carrots, beets, strawberries, plums, etc.)- try to use some that are colorful all the way through (apples and cucumbers are not colorful all the way through)
Plastic cups- one for each plant you are testing
Skewers or chopsticks- one for each plant
Ethanol- 50 milliliters or about ¼ cup for each plant
Plastic bowls- one per plant
Safety gloves and goggles- safety is always important, especially when working with chemicals like ethanol
Adult supervision (Adult supervision at all times please)
- First, be sure to put on your safety goggles and gloves to protect your skin and eyes.
- Cut your plants into small pieces and store them each in their own bowl.
- Pour 50 milliliters (about ¼ cup) of ethanol into each of the bowls, stir and allow the plant pieces to soak for 30 minutes undisturbed.
- When the time is up, strain the plant pieces out of the liquid that should now be colorful. Put this colorful ethanol liquid into the plastic cups. Be sure to keep each plant’s pigments in separate cups.
- Cut the filter paper into strips that are each the same size. You will need one strip per cup.
- Attach the paper strips to the skewers or chopsticks, one strip of paper per stick. This can be done by rolling one end around the middle of the stick and taping it into place.
- Now lay one stick across each cup of pigment-laced ethanol. This should be done so the filter paper hangs down into the cup and in the ethanol. Make sure the paper does not touch the side of the cup though.
- Leave the cups undisturbed for another 30 minutes. You will see the colorful liquid “crawling” up the filter paper.
- After the time is up, pull the paper strips out of the cups and observe what happened with the different colors in each plant.
Some pigments are bigger and move slowly through the filter paper, while others are smaller and move more quickly. As time passes these pigments will be filtered through paper and become separated. Chromatography is one method to separate these different colors.