Earth Science (Sunscreen experiment)

Focus Question: Why do we wear sunscreen?

Prediction/ Hypothesis: I think the sunscreen with the higher SPF will show as more protective for our skin because the number on the bottle is higher.

Planning:

• 1 Sheet of 81/2” x 11 clear plastic acetate (at local office supply stores)
  Black permanent marker
  Three “protection levels” of sunscreen SPF 8, 15 and 45.
  Photoreactive paper
  Plain cookie sheet
  9x13 Pyrex dish of water

• 1.)   Explain to students that they will be looking at what is really happening when they smooth sunscreen onto their skin.
  2.)   Take the clear plastic sheet. Draw a straight line vertically and horizontally through the middle of the sheet making four different “panes”. Mark one SPF 0, another SPF 8, then SPF 15, and finally SPF 45.
  3.)   Measure about ¼ teaspoon of each kind of lotion and use your finger to smooth it carefully over its appropriate “pane” on your plastic. (Remember one pane will have no sunscreen at all).
  4.)   Quickly remove four pieces of photoreactive paper from their protective envelope, place them on the cookie sheet, and then cover them immediately with the plastic sheet you just prepared.
  5.)   Place the cookie sheet in full sun, with no parts shaded, and leave it there for 1-4 minutes, or until the SPF 0 pane looks nearly white.
  6.)   Bring sheets inside, and carefully take the plastic sheets off. Then rinse the papers in the water tray and remove to observe. 

Data: 

	Predictions	Results
SPF 0	There will be no protection because there is no sunscreen.	This one had the most exposure to the sun. It turned white as the sun hit it.
SPF 8	This one will be the least protective besides no sunscreen.	This one looked white, but it looked like water. It might not protect us for as long because it looks thin.
SPF 15	This will be the second best sunscreen to protect our skin.	This one was the whitest. It looked thicker than the others and had less blue coloring showing through the sunscreen.
SPF 45	This will be the best protection for our skin.	This one showed the color blue all over and less white.

Claims & Evidence: We claim that SPF 15 had the most protection from the UV rays because it had the most white left underneath on the photoreactive paper.

Conclusion: We learned that the higher the SPF does not mean the more protection from the sun.

Questions: Do clothes help to protect our skin from the sun? Do animals get sunburned as well?