AccelePrep for the ACT Test 2nd Edition Student Text

222 • S URGE TO S UCCESS ! S CIENCE T EST P REP

6. Which of the following is the strongest argument Scientist 1 could use to counter Scientist 2’s suggested mechanism for the origin of life? F. There was not enough ultraviolet light available. G. Chemical reactions occurred differently then. H. The temperature at the surface of Earth at that time was always ƒ„‘˜‡ ͵ͷι „‡…ƒ—•‡ ‘ˆ ‰‡‘–Š‡”ƒŽ Š‡ƒ– ”‡Ž‡ƒ•‡Ǥ J. Most lakes would not have covered large enough areas to guarantee that all the essential building blocks were present. 1. Theory 1 is based on the octet rule: stable compounds form when the central atom is surrounded by eight valence electrons. However, as stated in Theory 2, xenon has eight electrons in its atomic state, so “that xenon could form compounds such as XeF 4 forced consideration of a new theory.” This implies that according to Theory 1 and the octet rule, XeF 4 should not exist as a stable compound since it would have more than eight shared electrons, (B): eight electrons from the central š‡‘ ƒ–‘ ƒ† ˆ‘—” ‘”‡ ‡Ž‡…–”‘• ˆ”‘ –Š‡ •—””‘—†‹‰ ϐŽ—‘”‹‡ atoms. 2. Since the BF 3 molecule has six electrons, it violates Theory 1— eliminate (F) and (G). According to Theory 2, “the shapes of compounds were such as to keep the pairs of electrons as far from each other as possible.” The compound’s structure in (J) has the ϐŽ—‘”‹‡ ƒ–‘•ǡ ƒ† –Š—• –Š‡ •Šƒ”‡† ‡Ž‡…–”‘•ǡ ˆƒ”–Š‡” ƒ’ƒ”– –Šƒ –Š‡ arrangement in (H). So, (J) must be correct. 3. Scientist 1 holds that the behavior of the anaerobic bacteria is based on the environment in which they developed, which lacked oxygen. Š‹• ‹• •‹‰‹ϐ‹…ƒ– ˆ‘” ‡ƒ”Ž› ƒ”–Š ‘Ž› ‹ˆ –Š‡ ƒƒ‡”‘„‡• ™‡”‡ ƒ‘‰ the oldest living things. Scientist 1 assumes that since the anaerobes have short DNA, they indeed must be among the oldest, (A). 4. It is inferable that Scientist 2 assumes a link between the oxygen in the rock and the oxygen in the air; otherwise, there is no point in bringing up the oxides at all; eliminate (F). Scientist 2’s argument is based on the idea that there was once oxygen in the atmosphere, though it does not require that all the oxygen in the rock be free, or that the reactions use the rock oxygen, (H) and (G). The oxygen in the rocks was related to that in the atmosphere, so (J) is correct. 5. The key point of Scientist 1’s argument is that life could begin only ‹ˆ —Ž–”ƒ˜‹‘Ž‡– Ž‹‰Š– ϐ‹Ž–‡”‡† –Š”‘—‰Š –Š‡ ƒ–‘•’Š‡”‡Ǥ Š‹• ƒ”‰—‡– is destroyed by eliminating the biological molecules’ need for ultraviolet light, (B). (A) could be used as an argument for either side—Scientist 1 could claim that the fact that the amount of oxide does not change demonstrates that it is not relevant to what is going on in the atmosphere; Scientist 2 could claim that it indicates that the atmosphere has also held a constant amount of oxygen. (C) is a weak retort to Scientist 1’s second point—Scientist 1 could respond that the complex anaerobe evolved later under special circumstances. (D) says nothing about composition since the pressure can remain unchanged while the relative amounts of the gases change.

Answers:

Return to the pages below to review each item:

1. p. 220 2. p. 220 3. p. 221 4. p. 221 5. p. 221 6. p. 222