Why Do Leaves Change Color? Science Experiment

One of the most beautiful sights to see in nature is the epic color transformation that trees undergo when the seasons turn cooler. There’s some really incredible science behind why leaves change color. Explore the science with this fun, hands-on leaf science experiment and the kids will be ready to answer this classic question!

Answer the question Why Do Leaves Change Color with this fun science experiment for kids. It's a perfect fall STEM activity!
Answer the question Why Do Leaves Change Color with this fun science experiment for kids. It's a perfect fall STEM activity!

Why Do Leaves Change Color in the Fall? The Science!

Plants use a process called photosynthesis to get the energy they need to survive. Photosynthesis converts sunlight, carbon dioxide, and water into glucose which the plant consumes to grow. The trees use a bright green pigment called chlorophyll to absorb the sunlight they need through their leaves. This is why many leaves are green!

But why do the leaves on deciduous trees (trees that lose their leaves each year) change colors when the weather gets colder? In colder months with less sunlight, it would take a lot of energy for trees to grow. So instead, they drop their leaves, stop making chlorophyll, and take a big nap until the sunshine gets stronger again. As the chlorophyll goes away, other pigments that were hidden by the green begin to show. The other pigments are yellow xanthopyhll, orange carotenoids, and red anthocyanins.

fall forest with yellow red orange and green leaves

How the Leaf Science Experiment Works: Chromatography!

To find all these hidden pigments in your leaves, you’ll use chromatography. Chromatography separates a mixture by moving them across a different substance that is standing still. In this experiment, we’re moving the plant pigments that have been dissolved in alcohol across the solid coffee filter. The different pigments stick to the coffee filter for different amounts of time (this is called adsorption) and cause them to stain the filter in bands as the liquid wicks through the paper.

Why Do Leaves Change Color Science Experiment Supplies Needed

This science experiment uses supplies you can find in the kitchen plus it’s a great chance to head outside for an adventure! We love moving our science learning activities outside for a change of pace.

We’ve also pulled together a helpful lab worksheet for this leaf science experiment. The kids will record what colors they think they’ll find and clip on their chromatography strips and leaves. It’s a great addition to their science workbook this year. To download it, simply fill out the form below.

Here are the supplies you’ll need for the experiment. Please note, as an Amazon Associate I earn from qualifying purchases. This is at no cost to you.

How to Prepare the Leaves for the Experiment

  1. Gather a few leaves of four different kinds of deciduous trees. Save one of each kind to attach to your lab worksheet or journal.
  1. Chop one type of leaf with scissors and place in a bowl. Crush the leaves with a spoon and pour into a jar or test tube. It’s important that the leaves get throughly crushed up or the pigments inside won’t be released enough for the chromatography experiment. Having trouble getting them crushed? Use a blender or mortar and pestle. Repeat with the other three types of leaves.
  1. Pour isopropyl alcohol over the leaves in the test tubes just until covered. Cover with plastic wrap and let sit overnight.
  2. Short on time? You can speed up this process by placing the test tubes in a hot water bath for 30 minutes (adult supervision required). Make sure no water goes into your leaf solutions while they are heating in the water bath.
  3. Once you’re done with the above steps, you can move on to the chromatography phase of this experiment.

How to Conduct Leaf Chromatography to See Why Leaves Change Color

  1. Record your guesses for the colors that exist in each type of leaf on the lab worksheet on the next page.
  2. Cut 4 strips of coffee filter that are 1” x 5”.
  3. Insert a piece of coffee filter into each test tube until the coffee filter just touches the surface of the liquid. Roll the other end of the strip around a straw until it can rest on the edge of the test tube. Tape to secure.
  1. Wait 30 minutes or until liquid has traveled all the way up the coffee filter and you can see separate color bands.
  2. Analyze the chromatography strips. What colors do you see? Do all the leaves have the same colors? Record your results on the lab worksheet.

This is a future sneak peek into how our oak tree’s leaves will change color.

More Fall Fun for Kids

Explore another fun science question, Why Makes the Wind Blow? with one of these activities.

Learn about wind with 25 activities for kids: arts & crafts, science, motor skills, books, & more! Plus all the science behind what makes the wind blow.

This project is a sneak peek into the STEAM Explorers Fall unit study!

Join us as we explore all things FALL with STEAM Explorers. Kids will love learning physics with football, doing a leaf color-changing experiment, snacking on apple chips, exploring the beauty of sunflowers, and more! You'll love the helpful standards-based learning, printables, and tools that make STEAM (science, technology, engineering, art, & math) exploration easy!

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