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Mimi and Dean wondered which sunscreen product provides the best protection for their skin. Sunscreen products have a Sun Protection Factor (SPF) that shows how well each product absorbs the ultraviolet radiation component of sunlight. A high SPF sunscreen protects skin for longer than a low SPF sunscreen.
Mimi thought of a way to compare some different sunscreen products. She and Dean collected the following:
two sheets of clear plastic that do not absorb sunlight;
one sheet of light-sensitive paper;
mineral oil (M) and a cream containing zinc oxide (ZnO); and
four different sunscreens that they called S1, S2, S3, and S4.
Mimi and Dean included mineral oil because it lets most of the sunlight through, and zinc oxide because it almost completely blocks sunlight.
Dean placed a drop of each substance inside a circle marked on one sheet of plastic, then put the second plastic sheet over the top. He placed a large book on top of both sheets and pressed down.
Mimi then put the plastic sheets on top of the sheet of light-sensitive paper. Light-sensitive paper changes from dark grey to white (or very light grey), depending on how long it is exposed to sunlight. Finally, Dean placed the sheets in a sunny place.
Question 1
Which one of these statements is a scientific description of the role of the mineral oil and the zinc oxide in comparing the effectiveness of the sunscreens?
A. Mineral oil and zinc oxide are both factors being tested.
B. Mineral oil is a factor being tested and zinc oxide is a reference substance.
C. Mineral oil is a reference substance and zinc oxide is a factor being tested.
D. Mineral oil and zinc oxide are both reference substances.
Question 2
Which one of these questions were Mimi and Dean trying to answer?
A. How does the protection for each sunscreen compare with the others?
B. How do sunscreens protect your skin from ultraviolet radiation?
C. Is there any sunscreen that gives less protection than mineral oil?
D. Is there any sunscreen that gives more protection than zinc oxide?
Question 3
Why was the second sheet of plastic pressed down?
A. To stop the drops from drying out.
B. To spread the drops out as far as possible.
C. To keep the drops inside the marked circles.
D. To make the drops the same thickness.
The light-sensitive paper is a dark grey and fades to a lighter grey when it is exposed to some sunlight, and to white when exposed to a lot of sunlight.
Question 4
Which one of these diagrams shows a pattern that might occur? Explain why you chose it.
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