Why do leaves change color?

Author: Maddie Van Beek

A trail in the fall. Notice the vibrant colors!

It’s officially fall! Thursday, September 22nd marked day one of a new season, and you may have already felt it in the weather. Fargo has been characteristically chilly this past weekend! With the fall season comes new colors in your surroundings. You’ll notice once-green, lush plants either dry out and turn brown, OR as they dry, they may transform into a vibrant yellow, red, or orange! How do you know what color the leaves will change? There’s actually a way to find out, and that’s what we will learn about today! Before we get going on our activity, let’s learn more about why leaves change color in the first place. 


Why are leaves green? Chlorophyll is a chemical in plants that helps photosynthesis occur. Photosynthesis is the process in which plants are able to absorb water and carbon dioxide and turn it into food. This could not happen without the help of sunlight! 


Here is a diagram of how photosynthesis occurs: ​

Take a look at the diagram and answer the following questions: 
What does a plant take in during photosynthesis? What does it give off? 


One component that’s not shown in the diagram above is the chemical chlorophyll. Chlorophyll is the pigment in the leaves that help them absorb sunlight. Chlorophyll is also what makes leaves so green. The colors to which leaves change in the fall isn’t just random. That color (red, yellow, orange, etc.) was in the leaf all year, but the green from the chlorophyll is so strong that it covers everything else up. As the season nears winter, days get shorter and drier; there isn’t nearly enough sunlight or water for photosynthesis to continue. Thus, chlorophyll begins to disappear. As the chlorophyll dissipates, the green fades with it and reveals the other colors underneath.

Why do leaves change color?

YOU SHOULD KNOW:

• What makes leaves green? 
• Describe what photosynthesis does? 
• What do leaves need for photosynthesis to occur? 
• What purpose does chlorophyll serve? 
• How do leaves change color? 

Now that you know the science behind the beautiful fall scenery, let’s move on to our activity! Your job is to determine the future colors of the leaves. Let’s get started! 
 
YOU WILL NEED:

• Fresh, green leaves (make sure they haven’t begun to change color and aren’t crunchy)
• Bowl
• Hot water
• Rubbing alcohol
• Coffee filter
• Scissors
• Clear glass or jar
• Plastic wrap
• Spoon or fork

Here’s what to do! 

1. Gather some fresh green leaves from your yard or somewhere outside. Make sure the leaves are all green. Your leaves should NOT be dry or crunchy. 
2. Bring your leaves inside and rip them into tiny pieces. 
3. Put the leaf pieces into the clear glass or jar. Pour rubbing alcohol over the leaf shreds until they are completely covered. 
4. Use a spoon or fork to mash the leaf bits up and stir them in with the rubbing alcohol. You may see the rubbing alcohol begin to turn green. 
5. Place plastic wrap over the mouth of the jar and secure it. 
6. Heat up a bowl of hot water. Carefully place the jar in the center of the bowl. The level of the hot water should be just above the level of the rubbing alcohol. 
7. Leave the jar in the bowl of hot water for at least 30 minutes. Swish the jar around every once in a while the stir up the leaves. You should notice the rubbing alcohol turning a very dark green. 
8. After 30-60min, you should be ready to move on! Cut a strip of coffee filter (or paper towel) so you have a long rectangle. 
9. Dangle the coffee filter strip into the jar of rubbing alcohol so one end of the strip is touching the surface of the rubbing alcohol and the other end rests over the edge of the jar. 
10. Now, just wait patiently. The rubbing alcohol will travel up the coffee filter strip and carry the green pigment with it. As the rubbing alcohol travels upwards, the once all-green pigment will separate into more than one color. You’ll see green (the chlorophyll) and another color such as yellow, orange, or red appear. 
11. Gather leaves from other types of trees and repeat the process to see if you can get other colors to appear! 

Image and video credits, in order of appearance:


Jongleur100, 2007. Country lane. File uploaded from Wikimedia Commons on 9/25/2016. https://upload.wikimedia.org/wikipedia/commons/thumb/1/18/Country_lane.jpg/800px-Country_lane.jpg File in the Public Domain. 

At09kg, 2011. Photosynthesis. Uploaded from Wikimedia Commons on 9/25/2016.
https://upload.wikimedia.org/wikipedia/commons/thumb/d/db/Photosynthesis.gif/800px-Photosynthesis.gif
File used in accordance with the Creative Commons Attribution-Share Alike 3.0 Unported license. No changes were made. 
​

References
https://en.wikipedia.org/wiki/Autumn_leaf_color
https://en.wikipedia.org/wiki/Chlorophyll
https://en.wikipedia.org/wiki/Photosynthesis
http://www.howweelearn.com/science-experiments-for-kids/