AccelePrep for the ACT Test 2nd Edition Student Text

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

1. According to Theory 1, the compound XeF 4 : A. exists with an octet structure around the xenon. B. should not exist since more than eight electrons surround the xenon. C. will have similar chemical properties to CH 4 . D. exists with the xenon surrounded by twelve electrons. 2. The atom boron has three outer electrons, and in bonding to boron, ƒ ϐŽ—‘”‹‡ ƒ–‘ Šƒ• ƒ •‹‰Ž‡ǡ —’ƒ‹”‡† ‡Ž‡…–”‘ –‘ „‘† ™‹–Š ƒ „‘”‘ atom. The BF 3 molecule is known to exist. Which of the following is true? F. BF ͵ obeys Theory 1. G. The existence of BF 3 contradicts Theory 2. H. According to Theory 2, the structure of BF 3 is a pyramid: J. According to Theory 2, the structure of BF 3 is triangular and planar: Spotting the Assumptions items ask you to identify any assumptions regarding the data that were used to support either viewpoint. These ƒ••—’–‹‘• ƒ› ‘” ƒ› ‘– „‡ Œ—•–‹ϐ‹‡†Ȅ–Ї ‡› ’‘‹– ‹• –Šƒ– –Ї› ™‡”‡ not proven true. Sometimes an assumption is easy to spot because it includes a weak phrase such as “may be,” “it is likely that,” or “this could indicate.” Scientist 1 The atmosphere of Earth was at one time almost totally lacking in oxygen. One piece of evidence supporting this assertion is the very fact –Šƒ– Ž‹ˆ‡ ‰‘– •–ƒ”–‡† ƒ– ƒŽŽǤ Ї ϐ‹”•–…Ї‹…ƒŽ ”‡ƒ…–‹‘• –Šƒ– ƒ”‡ ‡…‡••ƒ”› for the origin of life, the formation of amino acids, require ultraviolet light. Most of the ultraviolet light coming from the Sun is now absorbed by oxygen in the atmosphere. If there were as much oxygen in the atmosphere then as there is now, there would have been too little ultraviolet light available to enable life to begin. In addition, the oldest bacteria, the ones that have the shortest DNA, are almost all anaerobes—either they do not need oxygen or they die if exposed to oxygen. Most of the oxygen that exists now entered the atmosphere later from volcanic fumes.

Explanations for the example questions are included later in the chapter. Circle your answers now. Later when you reach the explanations at the end of the section, come back and check to make sure you answered the questions correctly.

SPOTTING ASSUMPTIONS

Examples:

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