Lab: The Most Effective Sunscreen FOR THE TEACHER Summary In this lab, students will research and compare the effectiveness of various SPF levels in sunscreen lotions. The lotion’s ability to block UV (ultraviolet) radiation from the sun will be tested using a UV bead detector.
Submitted by Katie Wirsing Freeland Elementary School Freeland, Michigan Thanks to Dow Chemistry Teacher Summit
Grade Level Middle/High school Objectives By the end of this lesson, students should be able to • determine the effectiveness of sunscreen lotions in blocking the sun's UV radiation. • evaluate the amount of UV-A penetration when using sunscreens with different SPF. Chemistry Topics • Radiation • Electromagnetic Spectrum • Energy Time Teacher Preparation: 20 minutes Lesson: 60 minutes Materials • UV light detector beads (many online purchase options) • Multiple types of sunscreen, with various SPF ratings • 1 box of clear, quart-sized sealable bags Safety • Do not look directly at the sun while using the UV detector as it may cause permanent eye damage, nor stay exposed to the sun's ray for a prolonged time period. • Remind the students NOT to consume any of the materials. • Students should wash their hands thoroughly before leaving the lab. • When students complete the experiment, instruct them how to clean up their materials and dispose of any chemicals. Teacher Notes • For best results, plan to conduct this experiment on a bright sunny day. • During preparation you should put the sunscreen into smaller, labeled containers for each group, rather than having to distribute all of it at the time of experiment. • Have students complete the Research Questions prior to starting the investigation. It could be on the same day, or a day prior to this, depending on available time. • Additional Science Background/Resources: Everyday Mysteries: How does sunscreen work?
About Education: How does sunscreen work?
Cross-Disciplinary Extensions Connect to Math Students will be recording the data they’ve collected in multiple ways of expression—tables, graphs, etc. Connect to Reading Students will be reading research information on the effects of sunscreen on your skin and how the UV radiation is blocked through various levels of SPF. Connect to Writing Students will be answering multiple focus questions in written form throughout this investigation. They will also be recording data in multiple mediums. Connect to Social Studies Students will be able to apply their findings to real-world applications in their daily lives, as well as the lives of others around the world.
FOR THE STUDENT LESSON The Most Effective Sunscreen Background: Sunscreen works by combining organic and inorganic active ingredients. Inorganic ingredients reflect or scatter ultraviolet (UV) radiation. Organic ingredients absorb UV radiation, dissipating it as heat. Some sunscreens protect us from the two types of damaging UV radiation: UV-A and UV-B. Both UV-A and UV-B cause sunburns and damaging effects, such as skin cancer. Purpose: To research and compare the effectiveness of various SPF levels in sunscreen lotions for blocking UV (ultraviolet) radiation from the Sun using a UV Bead Detector. Materials: • UV light detector beads • Multiple types of sunscreen, with various SPF ratings • 1 box of clear, quart-sized sealable bags Procedure: 1. Complete the Research Questions prior to starting the investigation. 2. Create an appropriate data table similar to the one shown to collect your data. Use the terms "White", "Light blue", "Medium blue", and "Intense/dark blue" when recording the UV-bead color intensity.
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Place the UV light detector beads inside of a clear plastic bag and seal. Make sure that only the plastic is between the sun and the beads. In the data table, record the color intensity reading shown on the scale. This is the control reading, and will be a baseline to compare the other readings to see if they increase or decrease. Apply a uniform layer of the first sunscreen sample over the bag. Make sure the bag is thoroughly covered. Allow the lotion to dry. Place the bag in direct sunlight. Wait 10 minutes to allow the UV light detector beads to change color. Record the SPF value of the sunscreen and any color change in the data table. Remove the UV light detector beads from the bag. Place the UV light detector beads in area where it will not receive sunlight until the beads turn back to white. Place the UV light detector beads inside of another clear plastic bag and seal. Repeat steps 3-9 for each different sunscreen sample. For a scientifically accurate investigation the entire processed should be conducted at least 3 times. Calculate the average UV reduction (if any) for each sunscreen.
Sunscreen SPF Value
UV Light Bead Detector Color Intensity
UV Level
Using the data in the table, plot a bar graph with SPF Value along the x-axis and the UV Penetrating Intensity Level along the y-axis. Research Questions • What is the difference between UV-A and UV-B radiation? • Why is prolonged exposure to ultraviolet radiation harmful to the eyes and skin? • What protection from UV radiation should an effective sunscreen offer? • What does a sunscreen's "SPF" rating mean?
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Does SPF tell how well a product blocks UV-A or UV-B? How does sunscreen differ from sunblock? Which sunscreen is most effective at blocking UV light? Are the experimental results consistent with the SPF rating for each sunscreen tested? What safety features are designed into the UV Light Detector Beads? Does SPF 30 have twice as much protection as SPF 15? What reduces the effectiveness of sunscreen? What should one look for when buying sunscreen?
