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                                                                                                                   Molecular Spectroscopy Project:

FLUORESCENT WHITENING AGENTS
IN LAUNDRY DETERGENT & PAPER

1: History        2:Importance and Usage        3: Spectroscopy        4: Current Studies        5: Future Expts.

6: HS Classroom Lesson:        A: Lesson Plan        B: Worksheets        C: Instructor Guide

    Because of their widespread use in real-life and the easy access students have to FWAs in laundry detergents and paper, this lesson provides students with a connection between concepts previously learned (quantum theory, light, molarity) and fun, interesting hands-on application.
prismHS CLASSROOM LESSON:   Fluorescent Whitening Agents

A: Lesson Plan
Objectives and Length (4-5 days total):
  • Part 1: How do we see color?  (POGIL PhET applet activity--1 class period activity + 0.5 class period discussion/ review)
  • Part 2: How does fluorescence/ phosphorescence happen/ work? (Lecture notes/ fluorescence wkst--1.5 class period)
  • Part 3: What is the qualitative spectral emission properties of various laundry detergents with and without FWAs?  How does the intensity of emission change with differing concentrations (Lab activity using blacklights--1.5 class periods lab + 0.5 class period for class discussion/ review)
Possible Supplement that can be added in the future? Using FWA detection to determine how polluted local waterways are from human wastewater (See Resource #3)--requires purchase of FWA-free cotton pad samples and construction of sampling traps to be placed in local waterways.
Intended Audience: High School Chemistry (any level--first year, Honors, or AP).  This particular lesson is written for my Honors level course, in terms of expected length and instruction detail.  This is a supplementary topic, so there is no special knowledge assumed except an introductory understanding of quantum theory and molarity.  Much depends on your perception of students' ability/ motivation.  I would feel comfortable giving this to all three levels of students, simply increasing or decreasing the amount of instructor guidance and review time based on students' mastery and aptitude.  Please note the resources at the bottom which have been borrowed from heavily and modified for my use--some of them are quite good.

Prerequisite Knowledge: Light & the electromagnetic spectrum, Quantum theory, Molarity

B. Worksheets
  • POGIL PhET applet activity (.doc /  .pdf)
  • Fluorescence notes/ worksheet  (.doc  /  .pdf)
  • LAB: Fluorescent Brightening Agents in Laundry Detergent (.doc / .pdf)
C. Instructor Guide (to Lab and Wksts)
Some notes of interest:
I think this unit would be particularly good to correlate the banded line atomic emission spectrums with the actual perceived color of spectral tubes.  (E.g. students often don't "get" why a Neon spectral tube looks oranigish-red if it emits so many different wavelengths.)
  • POGIL PhET applet activity ANSWER KEY (.doc/  .pdf)
  • Fluorescence ANSWER KEY (.doc / .pdf)
  • LAB: Fluorescent Brightening Agents in Laundry Detergent INSTRUCTOR GUIDE (.doc / .pdf)

Resources:
  1. Spectrofluorimetry. http://www.resonancepub.com/spectrofluor.htm (April 2, 2009).
  2. Moog, R.S., Spencer, J.N. & Farrell, J.J. (2004). ChemActivity 22: Electronic spectra of atoms and molecules. Physical Chemistry: A Guided Inquiry: Atoms, Molecules, and Spectroscopy, Houghton MIfflin Company, New York, p. 209, 212, 213.
  3. Glickstein, N. (2006). Optical brighteners in laundry detergents help us determine the source of bacterial contamination. The American Biology Teacher, 68(5), 296-298.
  4. PhET applet: Color Vision. http://phet.colorado.edu/simulations/sims.php?sim=Color_Vision (April 3, 2009).
  5. Moutoux, D. (Updated March 2008). Color Vision (or Seeing Colors) HS Lab.  http://phet.colorado.edu/teacher_ideas/view-contribution.php?contribution_id=386 (April 18, 2009).
  6. Perkins, K. (Updated November 2008). Color Vision Simulation HS Homework.  http://phet.colorado.edu/teacher_ideas/view-contribution.php?contribution_id=573 (April 18, 2009).
  7. Dallas, K. (Updated December 2007). Introduction to Light & Color. http://phet.colorado.edu/teacher_ideas/view-contribution.php?contribution_id=317 (April 18, 2009).
  8. Atomic absorption and emission spectra (applet). http://jersey.uoregon.edu/vlab/elements/Elements.html (Jan 4, 2009).