Learning Activity: Teeth Discoloration Experiment


•5 paper cups with lids

•Paintbrushes – 1 for every student

•Brown and yellow food coloring

•Student Worksheet


  1. Prepare five “unknown solutions” of food coloring and water for each group of students as follows:

A. 20 mL of water and 2 drops of yellow food coloring

B. 20 mL of water and 2 drops of brown food coloring

C. 20 mL of water

D. 20 mL of water and 5 drops of brown food coloring

E. 20 mL of water and 5 drops of yellow food coloring

2. Label the cups with their corresponding letter as listed above in bold.

Note to Teacher: Test the solutions on paper before doing the experiment. Slight differences in food coloring may change the amounts needed to create an easy-to-see continuum of “stains.” See the Results Table for descriptions of what color each solution should be when applied to paper.


  1. Place the five solutions in five different locations or stations throughout the classroom.
  2. Divide the students into groups and have each group rotate to each of the stations to paint the teeth on their worksheet with each solution. The letter beside the teeth should match the letter on the cup of solution they use.
  3. When they have finished applying all of the solutions and they have dried, have students guess which solutions match the corresponding type of smoker according to the results table.
  4. Next, have the student fill out the reading worksheet using the results from the experiment.
  5. Reveal the results to the students and have the students cut out and correctly re-order their teeth. The order should depict the spectrum of smoking, beginning with the non-smoker and ending with the heavy smoker. Students may glue this order on a separate piece of paper, or you may wish to have them write numbers next to the teeth to order them


Discuss the following questions with the students. Which teeth are the most stained and why? How could someone avoid staining their teeth like this? If Ann only used tobacco for a short time, why are her teeth yellow? Explain to the students that Denisha’s teeth are the darkest and most stained from smoking cigarettes and that not smoking is the best defense against discolored teeth. Highlight that Ann’s teeth are slightly yellow because any tobacco use, no matter how little, can yellow teeth. Stains get worse over time, but the stains begin to form right after the start of tobacco use.

Results Table

Light yellow

Solution A


Light/Early tobacco use

Dark yellow

Solution E


Moderate tobacco use

Light brown

Solution B


Long, moderate tobacco use

Dark brown

Solution D


Heavy tobacco use


Solution C


No tobacco use

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