AUTUMN LEAF CHROMATOGRAPHY
Autumn is definitely upon us as the leaves begin their beautiful transition to red and gold. On a sunny day like today, why not get out with your family or class for some fun in the fresh air and a good helping of science thrown in!
Begin by collecting a wide selection of fallen leaves of different colours. Younger children can benefit by sorting these in different ways back at home or in the classroom. Make block graphs with them, mix the colours, draw the shapes…
This is also an ideal time to look at the different shapes of trees and leaves and to begin naming them. In 2007 the Oxford Junior Dictionary made the decision not to include many words associated with the natural world, including autumnal favourites such as acorn, bramble and conker, a sad indication that many children will not come across them if we do not make an effort to introduce them.
One of our FabLab favourites is M&Ms chromatography, where we carefully remove the colour from the coating of sweets. At this time of year, Autumn leaves can be collected and used in a similar way.
You will need:
Leaves of different colours, freshly collected
Solvent – we used nail varnish remover
Tear the leaves into small pieces and put them into the cup.
Tape a small piece of leaf onto the cup to remember what colour was used.
Cover with the solvent.
Place a piece of filter paper into the cup so that the solvent starts to absorb.
We left the cups overnight before taking out the filters to observe the colours.
Take care with nail varnish remover – keep away from eyes and heat sources.
What is chromatography?
Chromatography is the separation of a mixture by passing it through a medium – we use filter paper. Different parts of the mixture travel at different rates, depending on their solubility (how much of a substance can dissolve in a solvent). The most soluble pigments travel the furthest.
Why do leaves change colour in Autumn?
Green leaves are producing chlorophyll, in order to turn sunlight into food (photosynthesis). As the days get shorter, the leaves get less light. They stop making food to prepare for winter, the chlorophyll in the leaves breaks down and the green pigment fades, revealing reds, oranges, yellows and browns. The stems of the leaves weaken without food and this causes the leaves to fall from the trees, helping the tree conserve water and energy.
To accompany an outdoor collecting and naming session, we recommend the children’s book ‘The Lost Words’, written by Robert Macfarlane and beautifully illustrated by Jackie Morris.