Cool Chromatography Science Experiment
Test out this unbe-leaf-ably cool autumn foliage experiment!
Submitted by
Sonam Adinolf
Sonam Adinolf
Does your little nerdlet keep asking how green leaves turn red in the fall? Show him with this cool science experiment! Use chromatography (a fancy term for lab techniques used to separate and analyze things) separate the colors from a leaf. It'll blow your kid's mind to see all the hues hidden in there!
- Little scientist:Your kid
- Two or three green leaves
- Two or three autumn leaves:Leaves that have changed color
- Baby food jars and lid:One per leaf. When your baby rejects his whirled peas (again), at least you can recycle the jar for your older kid's science experiment. That way it isn't a total waste of money!
- Rubbing alcohol and a nice chardonnay:The rubbing alcohol is for the project, the wine is for you ... for later.
- Coffee filters:You should have some lying around even if you do have a hopeless Starbucks habit.
- Shallow pan
- Hot water:Tap will do.
- Masking tape
- Sticky labels or masking tape
- A piece of paper and pen:Nothing fancy, just to make notes on.
- A plastic knife or spoon
- Timer:A watch or clock
Head outside with your kid and have him collect two or three colorful autumn leaves and two or three green leaves.
Before he begins, have him label the jars with the name of the tree each leaf came from. If neither of you knows the name of the tree, just label it as the "Big tree on the corner." You just want to differentiate the leaves. Your kid must be very organized and meticulous (don't laugh!) so as not to mix up the leaves.
Have him rip the leaves into little, tiny pieces and put them into their appropriate jars.
Help him fill each jar with enough rubbing alcohol to cover the leaves.
Get him to carefully grind the leaves in the alcohol until they are totally pulverized.
Have him very loosely cover the jars with the lids, i.e., don't screw them on tight.
Help him fill a shallow pan with about an inch of hot water from the tap.
Have him carefully place the jars into the water. Let them sit for about 30 minutes until the alcohol begins to turn black. The darker it gets, the better.
Make sure he jiggles the jars every five minutes or so while they are stewing in the hot water. Give him a watch and have him time the intervals himself.
Have him top off the hot water if it begins to cool at any point.- Meanwhile, he has to cut the coffee filter into long, thin strips. One per jar.
- Help him label each strip with the same moniker the jar is sporting (whether that's "Acer Macrophyllum"—the scientific name for a big leaf maple or a decidedly less nerdy "little tree in our yard").
- When the alcohol is dark and murky, have him remove the jars from the water and take the lids off and place the coffee filters into each jar so that one end is in the alcohol and one end is sticking up.
- Help him fold the free end of the coffee filter over the end of the jar and tape it in place with the masking tape.
- Then sit back and watch the magic happen! The alcohol will slowly move up the paper, dragging the colors with it. After 30 minutes to two hours (magic takes time, people!) you will be able to see different colors on the paper; reds, greens, oranges, yellows depending on the leaf.
- Have him carefully take the colored papers off of the jar and help him tape them next to each other on a piece of paper to let them dry.
- Get him to do the experiment with leaves from all different types of trees and see the different colors each tree has.
- Then help him analyze the results. Did the colored leaves create different colors on the coffee filter than the green leaves? Did the oak leaf make different hues than the maple? Which leaf had the most hidden color?
- Wondering how that happened? Leaves contain certain chemicals that give them their pigment. All trees have chlorophyll—which makes them green, and carotenoid, which colors them yellow, brown and/or orange (in the summer the chlorophyll covers the carotenoid so the leaf looks green).Some trees (like maple trees) produce anthocyanins in the fall. Anthocyanins make the leaves red. In the experiment above, your kid used chromatography to separate the chemicals in the leaves. The chemicals then traveled at different distances up the paper as the alcohol evaporated, staining it with their hues.
- So why do leaves change color in the fall? Here's the answer in a nutshell:
- During summer, leaves turn carbon dioxide and water into sugar when light reacts with the chlorophyll in the leaf.
- As fall sets in, and the days are shorter, there is less light and therefore less sugar made by the leaves. The leaf goes through some changes (kinda like grandma did a few years back.) One change is that it creates a membrane between the tree branch and the stem. This membrane mucks up the flow of nutrients to the leaf. That then causes a decline in chlorophyll production and the green in the leaf begins to fade.
- But as we learned from the experiment above, there are other chemicals (or colors) hidden in the leaf. So when the chlorophyll disappears, the other chemical's color shines through. For example, birch trees turn bright yellow because they contain carotene.
- In some trees (like maples) the sugar reacts to form anthocyanins. These chemicals cause yellow leaves to turn red. Cold temperatures aid the formation of anthocyanins, thus the fabulous fall landscape in the northern parts of the USA. Learn something every day, don't ya?
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