Using Ultraviolet Beads to Show the Scientific Method

Purpose: To investigate the parts of the scientific method by creating an experiment using ultraviolet beads, their reaction to sunlight, and sunscreen or suntan lotion with different sun protection factors (spf).

Background Information

Your skin is an excellent detector of ultraviolet (UV) radiation. When you expose bare skin to sunlight, your skin will either turn brown (a suntan) or red (a sunburn). These responses by your skin are a signal that the cells under your skin are being assaulted by Ultra Violet (UV) radiation. UV radiation wavelengths are short enough to break chemical bonds in your skin tissue and with prolonged exposure, your skin may wrinkle or skin cancer may appear. Therefore, a sunscreen lotion which blocks the sun’s UV radiation wavelengths is used to protect the skin from these harmful rays.

There is a safe way to detect UV wavelengths and how well a sunscreen lotion works by using UV Beads. These plastic beads contain a harmless chemical (or pigment) which changes color when exposed to UV radiation. The colors that develop depend on the wavelength of the UV radiation. If a sunscreen with a different spf is used, the intensity of the color will change based on how well the sunscreen lotion blocks the UV wavelength.

Question: What spf of sunscreen lotion will block UV waves most efficiently? Least efficiently?

Hypothesis: If a higher / lower spf of sunscreen lotion is used, it will block the UV waves causing the UV Beads to raise / lower in intensity of color. (Please select your choices of the underlined and italicized words.)

Materials:

4 UV Beads in container Sunlight

Choices of Sunscreen Lotion Soap to wash off Sunscreen Lotion

Procedures:

1. Obtain all materials. Set a baseline by placing a selection of UV beads near a fluorescent light for 3 minutes. Record the results of any change in color on a data table.

2. Take the UV Beads in the container outside, but not in the direct sunlight, for 3 minutes. Record the results of any change in color on a data table.

3. Place the UV Beads in the container outside, in direct sunlight for 3 minutes. Record the results o any change in color on a data table.

4. Return to the classroom and be sure the UV Beads have returned to the all-white color. Place your choice of sunscreen lotion in a thin coat surrounding each bead.

5. Repeat the procedure of #3. Record the results. (Note: The beads will always change color outside in sunlight regardless of how good the sunscreen blocks UC – the beads are very sensitive! The key is to rate the color of the beads on a scale of 1-5, with the 5 showing the most color or “burning” and the 1 showing the least color. The baseline will be the dish of beads without any sunscreen and is an automatic “5.”)

Results and Interpretations:

Record the results of the class. Create a graph of your data chart. Be sure to explain your results.

Conclusion Questions

1. What colors do the various beads turn when they are exposed to UV radiation?

2. Which of these colors are most intense? Which ones are the least?

3. Which sunscreen (spf) worked best and protected against UV radiation?

4. What was the control in th experiment? Independent variables? Dependent variable? Wad your hypothesis supported? Why or why not? What was the experimental error in the investigation?

5. You could also test the difference between new and old sunscreen. Sunscreen manufacturers suggest that you throw away old sunscreen because it does not block out harmful UV light. How could you test this suggestion and support this manufacturer’s claim?

6. Write a paragraph to describe another experiment you could do with the beads (Hint: types of materials like paper, sandwich bags, types of sunglasses, etc.) to see what blocks UV radiation and what does not.