Reading Comprehension

PT113 · S1 · P2 · Q10 Marie Curie

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Spurred by the discovery that a substance containing uranium emitted radiation, Marie Curie began studying radioactivity in 1897.

Topic

Marie Curie's early research on radioactivity and its historical context

Framework

Old / New

Main Point

Marie Curie made foundational discoveries in radioactivity based on the evidence and scientific understanding available to her at the time, and any modern criticisms for not reaching later conclusions are misplaced because her work paved the way for those later breakthroughs. (Most Valuable Sentence: — last paragraph)

P1: Curie’s Pioneering Experiments

Marie Curie started her work on radioactivity after discovering that uranium emitted radiation. She found pitchblende was even more radioactive than uranium and, hypothesizing that a new element was responsible, discovered polonium and radium. She also noted that the emission rate for a given element seemed constant and couldn’t explain the underlying mechanism for radiation.

P2: Modern Understanding and Limits of Curie’s Evidence

Today we know that radiation is due to the decay of isotopes and that emission rates slowly decrease over time. Some have criticized Curie for not reaching these modern conclusions, but given what was available to her scientifically (especially since most radioactive isotopes of lighter elements don’t exist naturally), such criticisms are unfair.

P3: Scientific Context of Curie’s Era

During Curie’s time, the structure and nature of atoms were still being debated: physicists saw matter as eventually being indivisible, while chemists conveniently used the concept of atoms without worrying about whether atoms truly existed.

10.

The passage implies which one of the following with regard to the time at which Curie began studying radioactivity?

  1. Correct

    Pitchblende was not known by

    Why this is right

    This can be inferred from the logic of the 4th sentence. Acting on the hypothesis that pitchblende must contain at least one other radioactive element, Anything that Curie is testing / hypothesizing / discovering can be inferred to be an unknown at that time period. It was known in Curie's time that pitchblende contained uranium, but she was the one who discovered that pitchblende was more radioactive than uranium. So this clued her in to the idea that there might be some extra radioactive ingredient within pitchblende. If people of her time already knew that pitchblende had additional radioactive elements, then they would have already known that it was more radioactive than uranium, and she wouldn't be hypothesizing (i.e. making a speculative guess) that pitchblende had some other radioactive ingredient. She would just be accessing already-available knowledge about that.

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

    59% picked this

  2. Radioactivity was suspected by scientists

    Opposite

    Pitchblende was "a mineral that was known to contain uranium", and the discovery that a substance containing uranium emitted radiation came before Curie began studying radioactivity (that discovery was the catalyst that started Curie's studying). So if scientists already knew that pitchblende had uranium in it and already knew that uranium emitted radiation, it makes sense that they would suspect that pitchblende's radioactivity was caused by the uranium element within it. This answer is saying the opposite, that scientists would have guessed that pitchblende's radioactivity came from its structure, not from some radioactive ingredient.

    7% picked this

  3. Physicists and chemists had developed

    Out of Scope

    Out of Scope: rival theories of radiation The third paragraph highlights that physicists and chemists had rival theories regarding the nature of the atom, but we never hear that they had different theories about the cause of radiation.

    12% picked this

  4. Research was not being conducted

    Too Strong: no research

    Given that we know in the 3rd paragraph that both chemists and physicists were debating the nature of the atom, it seems pretty unlikely that zero research was being conducted in connection with the question of whether or not matter is composed of atoms. The fact that there was no consensus on the atom shows that any research that was being conducted was not sufficient to fully settle the matter. But the fact that there was no consensus doesn't prove that there was no research at all attempting to settle the matter.

    17% picked this

  5. The majority of physicists believed

    Too Strong: majority / sole

    We have no text that could support the idea that more than 50% of physicists thought that all radioactivity in the universe comes from uranium.

    5% picked this

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