Today at the Greensboro Science Center, we are making leaf skeletons!
What you need:
- Leaves (You will want to choose fresh, large, green leaves. For this project, we used oak and Kalmia L., a shrub in the Mountain Laurel family.)
- Sodium carbonate (aka washing soda – this can be found at most grocery stores in the laundry aisle)
- Metal pot – do NOT use aluminum
- Soft-bristled toothbrush
- Long-handled spoon
- Rubber gloves
- Shallow dish (again, do NOT use aluminum)
- Measuring spoons
- Coated paper plates
- Adult supervision
- Sodium carbonate is a strong base with a pH of 11 and can irritate your skin. Always use gloves when pouring, stirring, or touching the sodium carbonate mixture or bleach.
- Avoid getting the sodium carbonate or the bleach in your eyes or inhaling the powder. Follow the safety precautions on the containers.
- Use caution around the stove and hot water.
Begin your experiment by putting half a liter (a little over two cups) of water into your pot. Then add 4 ¼ teaspoons of sodium carbonate to the water.
Place the pot on the stove burner and stir to dissolve the sodium carbonate.
Next, turn on your burner and heat the mixture until it begins to boil. Add your leaves to the pot, and reduce the stove heat to a simmer. Let the leaves simmer in the mixture for about 30 to 45 minutes. Depending on the type of leaf you choose, you may need to simmer for a longer amount of time and add more water to the pot as it evaporates. This process can take up to three hours with some leaves!
After a half hour or so has passed, remove the pot from the heat and turn off your burner. When you begin brushing your leaves, you may find that getting the pulp off of the skeleton is extremely difficult, in this case we suggest placing the leaves back into the pot, and simmering them for another half an hour or so. Continue this step as needed.
Using tweezers, gently take the boiled leaves and place them in a shallow dish filled with water.
With rubber gloves on, use your finger to gently swirl the leaves in fresh water. It is important to use gloves for this part, since washing soda can irritate your skin.
Take your tweezers and carefully transfer your leaves from the water dish to a coated paper plate. Begin to gently brush your leaves in an outward motion from their stems using small brush strokes.
Continue brushing your leaves until you have removed as much of the leaf tissue as possible. This process can take time, so be patient!
Gently move your leaf skeletons into a cup of bleach, and let the skeleton rest for 20 minutes before moving it to a paper plate to dry. This will turn your leaf skeleton from brown to white.
The boiling water and the sodium carbonate (which has a pH of 11) worked together to break down the flesh of the leaf. The intricate lacy pattern you are left with is actually a pattern of hollow veins, which make up the skeleton. A leaf’s skeleton is not like an animal’s skeleton, which is made of bone or cartilage. The veins in a leaf skeleton contain lignin that make them harder to degrade or dissolve. The veining system in a leaf provides nutrients and water to the rest of its cells. There are many different shapes and sizes of leaves. Some are long and narrow like the leaves of a willow tree and some have lobes like the oak leaf. Some leaves are thick like magnolia leaves and others are thin like a beech tree’s leaves. See if you can identify your leaves using a tree I.D. guide such as this one by NC State extension:
To Make This an Experiment:
Remember, an experiment uses a variable (something that changes) to answer a question. To turn this demonstration into an experiment, you have to change something! See what happens if you use different kinds of leaves or boil the leaves for a different amount of time. Will all the leaves have the same skeleton?
Try it and let us know how your experiment turned out on our Facebook, Instagram, or Twitter page using the hashtag #gscscience