Reading Comprehension

PT146 · S4 · P4 · Q26 Chlorofluorocarbons and the Ozone

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By 1970 it was well established that ultraviolet light from the sun contributes to skin cancer.

Topic

The effects of chlorofluorocarbons (CFCs) on ozone depletion and the resulting public policy response.

Framework

Problem / Solution

Main Point

Molina and Rowland discovered that CFCs deplete the ozone layer, which protects us from cancer-causing ultraviolet radiation, prompting international policy change to control these pollutants. (Paragraph 2) This is wrapped up in Paragraph 4, where it summarizes the outcome:

P1: Importance of the Ozone Layer

By 1970, it was understood that ultraviolet radiation from the sun can cause skin cancer, but thankfully Earth's ozone layer filters out much of this harmful radiation.

P2: Discovery of the Ozone Problem

Scientists Molina and Rowland revealed that man-made chemicals called CFCs, found in products like aerosols and refrigerants, break down in the upper atmosphere and release chlorine, which destroys ozone. A single chlorine atom can wipe out thousands of ozone molecules.

P3: The Lasting Threat and Call to Action

Their research showed that even if we stopped using CFCs immediately, the chemicals already present would keep damaging ozone for many years. Molina and Rowland pushed for urgent public policies to address this environmental danger, leading to political attention and involvement in research committees.

26.

Based on the passage, the information yielded by which one of the following experiments would be most useful in determining whether a particular chemical could replace CFCs without damaging the ozone layer?

  1. testing to see whether the

    Unrelated to Goal

    We want to test whether the chemical would react with ozone, not stuff other than ozone.

    2% picked this

  2. testing to see whether the

    Unrelated to Goal

    We want to test whether the chemical would react with ozone in the stratosphere (upper atmosphere), not whether it reacts with other stuff in the lower atmosphere.

    8% picked this

  3. testing the chemical to determine

    Unrelated to Goal

    We want to test whether the chemical would react with ozone, not whether it reacts with chlorine. The goal of this chemical is to replace chlorine, so chlorine wouldn't even be in the picture anymore.

    7% picked this

  4. Correct

    testing to see what chemical

    Why this is right

    We want to test whether the chemical would react with ozone the way chlorine reacted with ozone (by destroying the ozone). If we can see whether this potential replacement has chemical properties in common with chlorine that would cause it to react with ozone the same way, then we'll get the answer we're seeking. This answer is designed to be un-tempting by only talking about part of what we would want / need to know to make our assessment. We would not only need to know what chemical properties this potential replacement shares with chlorine, but we would also need to know which chemical properties of chlorine cause it to destroy ozone. But presumably the chemists doing chemical testing do know such stuff. Even though an answer to this question wouldn't give us the final verdict on its own, it's still a more valuable question to answer than any of the other answer choices.

    Skill tested: Evaluate · how this choice captures the passage's function is the move to repeat next time.

    60% picked this

  5. testing the chemical to see

    Not as Helpful as Correct Answer

    This is tempting. If we tested the chemical and found out that it didn't break down into its components, would that show that it's harmless in the ozone layer? Not necessarily. It might not need to break down into constituent elements in order to react adversely with ozone. If it does break down into constituent parts, does that mean it would be harmful in the ozone layer? Not necessarily. Its constituent parts might not have any adverse reactions with ozone. Even though answering this question would be somewhat useful, it leaves us farther from a final verdict than would answering the question in (D). Ultimately what we care about the most is whether this replacement would react adversely with ozone. The question posed by (D) potentially reveals that answer, whether the replacement chemical breaks down into constituent elements or not, because the language of (D) covers the reactive possibilities of the replacement molecule as well as the reactive possibilities of the constituent atoms in the replacement.

    23% picked this

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