Tricks & Treats That Leaves Teach Us
Why do leaves change color? What causes seasons? Why are some leaves yellow and some leaves red? What makes the leaves crunch so much? The first step of the scientific method is to ask a question…so keep kids asking! Some questions are testable with an experiment. Other questions can be answered by going to reliable sources like books, experts, or reliable websites. Here are some ideas and information that can help you and your little scientists explore, test, and answer questions about leaves.
Leaf Basics
The main parts of a plant are the roots, stem, leaves, flower, fruit/seeds. Leaves are built out of many kinds of chemicals that do different jobs like hold moisture or add shape or strength. Chlorophyll is the chemical in green leaves. Chlorophyll in green leaves uses the sun’s energy to make food for the plant.
Hidden colors
Trees respond to changes in light. With less sunlight, the chlorophyll goes away then we get to see the colors that were hiding underneath. The reds, oranges, browns, and yellows were always there, just covered by the green.
TRY THIS! Act It Out…
Whether using the dramatic play center or the coat closet at home, kids can act out how leaves change. Start with a bright light shining when t-shirts, sweatshirts, and hats that of various reds, oranges, browns, and yellows are put on. Over the top of that layer have kids wear a large green coat, wrap in a green bath towel, or use a green sheet to represent chlorophyll summer wear. In nature as the amount of daylight fades, so does the green color as chlorophyll goes away. With the kids, next dim light and remove the green costume wear. The chlorophyll has gone away and the autumn colors are visible. These reds, oranges, browns, and yellows represent the chemicals (called xanthophylls, anthocyanins, and carotenoids) that have been there all along. Autumn has arrived! Leaves then fall from the trees, get buried in winter snow and regrow new green leaves in the spring as the daylight increases.
TRY THIS! Chop It Up Chromatography…
Separating out a mixture, in this case the chemical leaf colors, using liquids and filter paper is called chromatography. You will need a minimum about 3 coffee filters and about 3 jars or up to one jar and coffee filter per student. If labeling the filter paper, be sure to use permanent marker. Collect colorful leaves then sort them by colors. Include a pile of green leaves if possible. Fold coffee filter in half, then in half again to make a cone shape. Place this cone shape over a recycled jar. Using an old blender or food processor, puree each pile of leaves with water then strain through a coffee filter into a jar. Watch the chemical colors collect on the filter paper and travel towards the edges like a bullseye. Tape to the window to dry and observe.
Black markers mask other colors just like the green chlorophyll hides the other pigments in leaves. Since different marker brands and types are mixtures of different chemical pigments, each different kind of marker will create a different bullseye pattern on the filter paper. Please know that most chemicals will dissolve in water then travel through the filter paper, however, some chemicals will dissolve and travel better in isopropyl alcohol. If an adult is leading this experiment, you may want to try the same steps as above using isopropyl alcohol for even more visible effects.
Seasons
Seasons are caused by earth’s tilted axis. Just like a globe on the shelf is tilted 23.5 degrees, earth is also tilted 23.5 degrees as it orbits the sun. Each full spin (rotation) of earth takes about 24 hours and that’s what we call one day (about 24 hours to complete day and night- even through the day length and darkness length vary per season). Minnesota is about halfway between the equator and the north pole, which means the amount of light varies depending upon how earth’s axis is tilted- this is the cause of seasons. In the summer the northern hemisphere is tilted towards the sun so Minnesota has longer daylight days. In the winter time the northern hemisphere is tilted away from the sun for more hours of darkness per day. As summer’s extreme tilt towards the sun transitions towards winter’s extreme tilt away from the sun we call it autumn.
Play. Learn. Love.
October 2014
