Science experiments for children – Why do leaves change color in autumn ?. To live plants take up water from the soil and carbon dioxide from the air, and use sunlight to transform water and carbon dioxide into glucose through a process called photosynthesis, which also happens thanks to a chemical substance called chlorophyll. Chlorophyll is what gives plants their green color.
During the winter the amount of light and water available to the plants decreases, and the trees come into a state of low activity: the green chlorophyll disappears from the leaves, and gradually we begin to see yellow and orange colors. Small amounts of these colors have always been present in the leaves, even when they were green. But we could not see them because they are covered by the green chlorophyll.
During the autumn days the light becomes smaller and smaller, and as the chlorophyll is produced by light, this also decreases, and the green color begins to fade from the leaves. At the same time, the concentrations of sugar on the rise causing an increase in the production of pigments of red color (anthocyanin pigments), orange-yellow (carotenoids) and browns (tannins), which does not need the light to form.
So in autumn we see the leaves yellow, brown and orange because the chlorophyll, which masks the other colors, it degrades.
________________________
Science experiments for children – Why do leaves change color in autumn?
Chromatography experiments
http://www.scuolamediacoletti.org/
The chromatography experiments allow you to separate all the colors hidden in what apparently looks like a single color. Before proceeding with the leaves, you can show the experiment with a marker, as shown in this video:
_________________________
Chromatography with spinach
Science experiments for children – Why do leaves change color in autumn?
What to do?
Place a leaf of spinach on a strip of absorbent paper and, running over, over and over, the edge of a coin, drawing a green line at about 2 cm from the edge. Repeat because the line must have a
intense color.
Pour the bottom of a transparent glass jar few ml of alcohol. Insert the strip into the beaker, with the green line downwards, making sure that the ends of the strip just touches alcohol, and fix the paper to the edge of the glass with a paper clip.
Be careful not to wet directly the colored line with alcohol. Wait a few minutes, until the alcohol has climbed along the strip almost to the rim of the glass and dry the paper strip on the radiator.
_____________________
Science experiments for children – Why do leaves change color in autumn?
What happens?
Alcohol goes back along the paper by capillary action.
The green color of the leaves is actually the result of the blending of different colors that correspond to different substances.
As members of a family, each substance has its own likes and dislikes.
Some love the most stand clinging to the paper and are not at all attracted by alcohol, other prefer to be dissolve and carry more or less easily, by alcohol.
It is precisely this different “liking” of each pigment in respect of alcohol to allow their separation.
Science experiments for children – Why do leaves change color in autumn?
To separate the colors of a green leaf with chromatography
What do you need?
leaves,
small jars,
lids for jars or aluminum foil or transparent film,
alcohol,
absorbent paper ,
pan,
hot water,
pen,
knife or a plastic spoon,
clock or timer.
What to do?
Collect 2 or 3 large leaves from different trees.
Cut the leaves into very small pieces and put them in jars labeled with the name or location of the tree.
Add the alcohol in each jar which serves to completely cover the pieces of leaf, and dicing further by using a knife or a teaspoon, until obtaining a kind of mash.
Carefully close the jars and place them on a tray containing a few centimeters of hot water. Wait at least half an hour, until the alcohol has not been well-colored (the darker the better).
Place the jars carefully in a tray containing 1 inch of hot water. Replace the hot water if it cools and occasionally shake the jars.
Cut a long thin strip of absorbent paper to each jar and label it.
Remove the jars from the hot water, open them and place a strip of paper in each jar, so that its end it is immersed in alcohol. Fold the other end on top of the jar and secure it with duct tape.
Alcohol will travel along the paper, bringing the colors with it.
After about two hours, the colors will trail different distances along the paper, and alcohol will gradually evaporated. You should now be able to see different shades of green, and perhaps some yellow, orange or red, depending on the type of leaf.
http://www.parentsconnect.com/
_________________________
Science experiments for children – Why do leaves change color in autumn?
Chromatography with green leaves and autumn leaves
What do you need?
two or three green leaves,
two or three autumn leaves that have changed color,
glass jars with lid (one for each leaf),
alcohol,
absorbent paper ,
baking sheet,
hot water,
Scotch tape,
spoons and knives,
a timer.
What to do?
Proceed as explained in the previous experiment.
Science experiments for children – Why do leaves change color in autumn?
Video:
__________________________
Science experiments for children – Why do leaves change color in autumn?
Other links
http://www.parentsconnect.com/
http://www.hometrainingtools.com/
http://www.sciencemadesimple.com/
http://www.miniscience.com/projects/
http://chemistry.about.com/cs/howtos/ht/
