Experimenting with the colours of fall

As I was driving home from work this week, I noticed that the leaves are changing on the trees. I often find this time of year a bit sad as everything begins to die and turn brown; trees are different though. You will see the leaves on the trees turn from a beautiful green colour to golden yellow, bright reds, oranges and even some purples. With that said, let’s do some investigating of fall colour before it is too late.

*An adult must help you do this experiment.

Materials

- leaves from a tree of your choice (try different trees to see the difference) - 1 green leaf - 1 yellow leaf - 1 orange leaf - white coffee filter (I like the flat/cone ones the best) - scissors - pen or marker - ruler - rubbing alcohol - 3 clear cups – preferably glass as the plastic one may melt - masking tape - 3 pencils -safety goggles

Procedure

NOTE: Remember science safety. It is important to remember that when you do science experiments you never eat, drink or smell anything you are working with. This is for your own safety. Always wash your hands when you are finished.

1. Put on your safety goggles.

2. Measure a strip on the coffee filter that is about 2 cm x 10 cm long. Cut this out of the coffee filter. Repeat two more times so you have three strips in total.

3. Place one pencil on a flat surface.

4. Take a piece of tape and put it on one of the short end of the filter. Now tape it to the pencil on the table. Repeat for the other two pencils. 5. Set aside for a minute. 6. Label one cup “green leaf and poison - rubbing alcohol POISON.”

7. Label the second cup “yellow leaf - rubbing alcohol POISON.”

8. Label the third cup: “red leaf - rubbing alcohol POISON.”

9. It is important to label the cups as you do not want anyone to drink the rubbing alcohol by accident. It is poisonous. 10. Take the green leaf and cut it up into very fine strips with the scissors. Rub the leaves around in your fingers

crunching them up a little bit.

11. Place in the appropriately labelled cup.

12. Do the same for the yellow and red leaves.

13. In the cup labelled green leaf, pour in some rubbing alcohol. Just enough to cover the leaf pieces.

14. Now place the piece of filter paper that you taped to the pencil over the top of the cup.

15. Make sure the tip of the coffee filter is just sitting in the rubbing alcohol. You may have to add a bit more. Allow the leaf mixture to run up the filter paper for at least ten minutes.

16. Take the filter paper off of the cup and set aside to dry.

17. Repeat steps 13-16 with the other two leaves.

18. Try the experiment with leaves from different trees.

19. What do you see?

Explanation

As the leaf mixture moved up the filter paper you should have seen many colours appear. The green pigments are from chlorophyll, the oranges from carotene, the yellows from xanthophylls and the reds from anthocyanin pigments. You begin to see these colours because as winter approaches, plants begin to photosynthesize much less. The plant realizes that it is wasting its valuable energy making chlorophyll as the cold winter months approach. As photosynthesis slows down, the other pigments in the leaves begin to appear.

Teachers please do not forget to book your Hands on Learning Kits, Scientists in the Classroom presentations and Science Fair 101 Program as soon as possible. Spots are filling up fast.

Patty Rooks is senior scientific consultant at PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook.