Chlorophyll Chromatography


Source: Negativespace.co

Type: Investigation

Theme: Ratios

Grades: 5, 6, 7, 8, 9, 10, 11, 12

Learning Target: Students will analyze the Rf values for two species of plant material and analyze those values in a classroom spreadsheet.

Instructions

Chromatography of chlorophyll resultsThis is a group project (two or three). Submit as a Code.org Web Lab project.

Materials

  1. Mortar and pestle
  2. Test tubes and racks
  3. Pipettes
  4. Strips of chromatography paper (or coffee filter, fitting in test tubes)
  5. Isopropyl alcohol (70%)
  6. Toothpicks

Lab Procedure

  1. Finely cut up some leaves and fill a mortar to about 2 cm depth.Add a pinch of sand and about six drops of isopropyl alcohol (70%) from the pipette.
  2. Grind the mixture with a pestle for at least three minutes.
  3. On a strip of chromatography paper (or coffee filter strips), draw a pencil line 2 cm from the bottom.
  4. Use a toothpick to put liquid from the leaf extract onto the centre of the line. Keep the spot as small as possible.
  5. Allow the spot to dry, then add another spot on top. Add five more drops of solution, letting each one dry before putting on the next. The idea is to build up a very concentrated small spot on the paper.
  6. Attach the paper to a toothpick with tape so that when placed in the test tube, the paper is just clear of its base. Test fit it in test tube.
  7. Place 2 mL of isopropyl alcohol in the bottom of the test tube. Ensure the level is below where the spot is on the paper, but so the bottom of the paper will soak in the isopropyl alcohol.
  8. Allow the paper to sit in tube and dry over night. 

Analysis

  1. Record your data. Measure each color band from the original spot up to the center of the color band. Create Rf value (ratio), by dividing that measurement by the maximum distance the solvent traveled up the paper.
  2. Record your data in the class database.
  3. After all data is recorded make data observations. Write a minimum of one paragraph explaining what you observe.
  4. Obtain and provide a Peer Review for your presentation.
  5. Revise your work.
Pigment (examples)Rf value
β-carotene 0.98
Chlorophyll a 0.59
Chlorophyll b 0.42
Anthocyanins 0.32-0.62
Xanthophylls 0.15-0.35

 

Submission

  1. Code.org webpage.
  2. Answer the following questions:
    1. What species did you test (Latin name, habitat)?
    2. Why are chlorophyll a and b green?
    3. In the summer, how could you predict the color a tree’s leaves will turn in the fall?
    4. What is the main function of the green pigments (chlorophyll a & b)?
    5. What are some functions of the plant pigments that are NOT green?
  3. Include photographs from your lab.
  4. Include final data from group spreadsheet.
  5. Peer Review

 Resources

Exit Ticket
CCSS Math Practice
  • I can construct viable arguments and critique the reasoning of others.
  • I can model with mathematics.
NGSS Crosscutting Concepts
  • Patterns
  • Scale, Proportion, and Quantity
  • Structure and Function

Samples