Scenario
Your group is a Consumer Watchdog agency that
independently tests commercial products to verify their
stated effectiveness. Your group has been asked to test
the Sun Protection Factor (SPF) ratings with which all
sunscreen products are labeled. You must check the validity
of 3 (three) SPF categories and verify that they are accurately
labeled for sun protection.
Test Parameters
1. No humans or animals can be used for this test.
2. Your methodology must be clearly stated with standard units of measurements to express your
results.
3. You must have one control subject and three additional subjects to manipulate.
4. You must test all three products.
5. The entire test should be run again for verification of accuracy with another independent test
group within the agency.
Results
1. Results should be compared with the other test group within the agency.
2. A formal report should be prepared and submitted.
Materials
One index card with four attached UV beads.
Three half-cards, to be labeled as SPF “_____,” “_____,” and “_____.”
Three Q-tips to apply sun blocks to the UV beads.
Lab Report
Seconds Timer – you may use a timer on your smart phone if you have one.
Procedure
1. Within your group, choose one person as the Reader/Technician (applies the sunscreen and
reads the procedure steps), one person as the Timer (times the UV beads reactions to sunlight)
and one person as the Recorder (records the data as directed by the Timer.
2. Check to make sure all your UV beads change color from pale whites to bright colors when
exposed to sunlight. How long does this take? Repeat this at least twice to verify your original
time. Come back into the classroom.
3. Now it is your time to think about your OBSERVATIONS of what your UV Beads did, and then
come up with your QUESTION – the first step of the Scientific Method. Record these
observations and your question in the appropriate sections of your lab report.
4. As a group, decide upon your HYPOTHESIS – a possible explanation for your question.
Remember the hypothesis must be (1) testable; (2) measurable by a standard unit and (3)
repeatable by someone else. Enter the hypothesis in the appropriate section of your lab report.
5. Assign one UV bead to be your Control bead, and therefore left uncovered by sunscreen.
Record which bead is your Control bead on your lab report.
6. Add about a teaspoon of each sunscreen – one sunscreen per card to each of your labeled cards.
7. Assign sunscreens to beads – one sunscreen strength per bead. Enter each bead’s sunscreen in
the appropriate chart on your Lab Report.
8. Now it is time to perform your EXPERIMENT. Carefully dip an unused Q-tip in one of the
sunscreens and smear the sunscreen onto its assigned UV bead. Try to smear it so thinly there’s
no visible build-up on the bead, but the entire bead is covered with its sunscreen.
9. Repeat the above for the other two beads. At the end you should have one “naked” bead and
three beads each covered in one of the sunscreens. Double-check to make sure you have
accurately recorded the beads’ numbers with their sunscreen strengths!
10. Cover the beads with your hand or a notebook, but don’t touch the beads with them!
11. Bring the bead card – still covered – into the sunlight. Uncover and begin timing how long it
takes your UV beads to go from pale to bright. RECORD the different times in the appropriate
places in your chart.
12. Now it is time for you to ANALYZE your data. Create a line graph in which the X (horizontal) axis
records your four beads and the Y (axis) records the time it took each bead to change color.
13. What CONCLUSION can you draw from your analysis? Does your conclusion prove your
hypothesis? Write your Conclusion in the appropriate section of your lab report.
14. Discuss as a team what outside factors could have affected your findings, and write down your
thoughts in the appropriate section of your lab report.
Finally, compare your findings with another team in the classroom. How are they similar? How are they
different? What factors could explain the differences? Write down your conclusions in the appropriate
section of your lab report.
Group Lab Report
Names: Technician/Reader ________________________
Consumer Watchdogs: Sunscreen
Timer: ________________________
Recorder: ________________________
Period: ________________________
Experiment: SPF analysis of sunscreens
Date: ________________________
Pre-Test: Amount of Time it takes for uncoated UV Beads to darken in bright sunlight:
First Trial
Second Trial
Observations: How did your UV Beads change during your Pre-Test Trials?
Question:
Hypothesis:
Results Chart:
Bead Number
1
2
3
4
Analysis:
Conclusion and Discussion:
SPF Rank of Coating
Seconds from Pale to Bright