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Chromatography of Schoolyard Vegetation

Katherine Merckel merckelk@stclair.k12.il.us

Description: The purpose of this experiment is to determine the types of pigments found in schoolyard vegetation. The students will gather plants from the schoolyard, soak them in acetone and use coffee filter strips to separate the pigments. Then the students will determine the pigments found in each type of leaf.

Grade Levels: 4-8(Note: This experiment can be simplified or made more challenging depending on the developmental levels of your students. See Teacher Information.)

Approximate Time Involved: One or two 30-minute classroom planning sessions, 30 minutes to conduct the experiment, 20 minutes to study pigments, one or two 30-minute classroom sessions to examine results, state conclusions, draw inferences and make recommendations. Note: Paper should be allowed to set for at least 60 minutes.

Teacher Information:

The pigments found in spinach leaves, lettuce leaves and marigold leaves are all different. Paper Chromatography is a technique that enables us to separate plant pigments. The pigments found in plants vary and the process of chromatography is important in the detection of the types of pigments found in each.

Here is an opportunity for your students, especially those at late high school, to present and defend their pitfall trap results to a professional in the field:

Dr. Elaine AbuSharbain, Science Educator at Southern Illinois University at Edwardsville, has agreed to review any student designed experiments and their results, conclusions, inferences, and recommendations. Elaine's Email Address is: eabusha@siue.edu

Challenging Your Students to Be Problem Solvers:

To make this experiment more challenging to your students, you might just want to pose a question such as: How does the type of pigment present in a leaf affect its color in the natural habitat? What leaves will have the most variation in pigments? What location in the schoolyard will produce plants with the greatest amount of pigments? Design and conduct an experiment to measure how amount of sunlight a plant receives affects its pigmentation.

Student Instructions Available to download as a PDF file.

Needed Materials: Acetone fingernail polish remover, test tubes or other empty containers (enough for 5 containers per group), felt tip markers, coffee filters, pigment guide, masking tape, scissors, spinach leaves, mum leaves, iceberg lettuce and leaves of various plants found in your schoolyard.

Safety Rule: Avoid inhaling the vapors from the acetone and spilling it on your clothing.

Procedure:

Student Information: The following information will provide you with the steps for conducting your plant chromatography experiment. It is important to hold all of the variables constant except for those that are being manipulated. Constant (or controlled variables) would be such things as: the length of the filter paper strip, the amount of time the paper is left in the solution, the amount of acetone in the container, the size of the container being used, etc. Manipulated (or independent) variables would be those things that we change to see if the response will be different, such as: type of plant being studied. The responding (or dependent) variable for this experiment will be the different pigments found in each of the different types of vegetation.

The reporting form for this experiment is set up so that you can determine how many different kinds of vegetation you would like to use, the kind of container you would like to use and how long your strips of filter paper will be. Also remember that a good scientific experiment is repeated a minimum of three times. Therefore, your data will be more accurate if you conduct several experiments that are exactly the same and then compile an average of your data before submitting it.

Procedural Steps for Conducting the Investigation

  • 1. Collect two different plants from your schoolyard. You are going to test these two plants along with the spinage, mum leaves, and iceburg lettuce.
  • 2. Label each container with the kind of plant you are testing.
  • 3. Place a different leaf in the bottom of each test tube and crush it.
  • 4. Pour about 2 cm. of acetone (fingernail polish remover) into each of your test tubes.
  • 5. Let this sit twenty-four hours.
  • 6. Cut five strips out of the middle of a coffee filter.
  • 7. Place the end of one coffee filter strip in each of the test tubes. The solvent will travel up the paper, and as it does, it will dissolve and deposit the separate pigments.
  • 8. After twenty-four hours, check your results.
  • 9. Remove the strips of paper from the test tubes and lay them on dry paper towels that are labeled with the type of plant extract found on that strip.
  • 10. Use a magnifying glass and a pigmentation guide to determine the types of pigments in each extract.
  • 11. After group and classroom discussions have occurred, login to enter your data.

Below is a list of questions that can be used to stimulate student discussions. If your students are at a developmental level where you are able to challenge their higher level thinking skills, then only present them with the first set of questions from each group below. Use the second list of questions as a way to stimulate thinking when your students seem unable to expand their knowledge on their own.

Examining Local Results

Discussion Questions that Require More Critical Thinking Skills:

  • What were your conclusions for this experiment?
  • What could you infer based on your conclusions?
  • How would you design this experiment differently the next time?

Discussion Questions that Require Less Critical Thinking Skills

  • What types of pigments were found in each type of plant?
  • Did the color of the leaf affect the pigments found it them?
  • If the answer to the above question is "yes", which leaves had the most variation in the kinds of pigments found in them?
  • Did certain leaves have the exact same pigments?
  • If the answer to the above question was "yes", were the leaves similar in other ways?
  • Do you think the amount of sunlight a plant receives affects the pigments found in the plants? How could you test your predictions experimentally?
  • Would you expect to find the same results year round? How could you test your predictions experimentally?

Examining Local and Online Results

Discussion Questions That Will Require Critical Thinking Skills to Compare Local Data to the Online Data of Others

  • How did your results compare with the results of others?
  • What conclusions can you make when you compare your results with the results of others?
  • What inferences can you draw from your additional conclusions?
  • What changes would you now make in this experiment based on the information you now have?

General Discussion Questions that May Occur as a Result of Comparing Local Data to the Online Data of Others

  • Where is the geographic location of the schools who have provided online data?
  • How did the types of pigments you found in your plants differ from the types of pigments found in the plants of other people who reported their information?
  • What factors might contribute to differences in results among classes?
  • What similarities existed among those schools that used the same types of plants for this experiment?
  • Did others discover the same pigments in their plants? What might have made the difference?

Performance and Multiple Choice Assessment Options

Links

Chromotography In Search of Yellow Dye #5

Kitchen Chemistry, Candy Chromotography This page offers other experiments to try including Candy Chromotography. The purpose of the candy chromotography experiment is to identify the FD&C dyes from M&M's or Skittles using paper chromatography.

Unearthing The Secret Life of Plants This website provides some activities that you can do with plants.

What is Chromatography? This site explains what chromatography is as well as provides a look at the history of chromatography.

Gas Chromatography This website will give you and your students a look at gas chromatography.

More links to Schoolyard Habitat Information

Schoolyard Habitat Links Learn more about developing and maintaining schoolyard and backyard habitats by visiting these links.

Copyright, 2005

by Prism Press

ALL RIGHTS RESERVED
The text of this publication or any part thereof, may not be reproduced or transmitted in any means, electronic or mechanical, including photocopying, recording, storage in an information retrieval system, or otherwise, without the prior written permission of the authors.


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