Victory for the ACT Student Text 15e

472 • C AMBRIDGE P RACTICE T EST R EINFORCEMENT

25. (C) (p. 413) Science/Evaluation of Models/Analysis . ‘’ƒ”‡ ”‹ƒŽ• ͳ ƒ† Ͷ ‘” ”‹ƒŽ• ʹ ƒ† ͵ –‘ •‡‡ ™Šƒ–…Šƒ‰‹‰ –Š‡ concentration of only one component has on rate. In this case, rate increases by the square root of the concentration of A . 26. (H) (p. 413) Science/Evaluation of Models/Analysis . Averaging or intermediate mechanisms do not work because one mechanism (Experiment 1) has no dependence on concentration of A with regard to rate. The likeliest explanation that reconciles Experiment 3 with Experiments 1 and 2 is that a different mechanism causes the reaction. 27. (B) (p. 413) Science/Evaluation of Models/A alysis . This is a subtle question. (C) and (D) are incorrect because they over-generalize from a single case. It cannot be said that mechanisms can always be changed, (C), or that in every case the mechanism depends on solvent effects, (D). (A) is a special case of (D), where the claim is made that all reactions are solvent dependent. (B) alone allows for the possibility that solvents need not have an effect (note the word “may”). 28. (G) (p. 414) Science/Interpretation of Data/Comprehension . ‹…‡ ‡˜‡”› ‘„Œ‡…– •–ƒ”–• ƒ– Ͳ ˆ–Ȁ•‡…ǡ…‘’ƒ”‡ –Š‡ instantaneous velocity of each object at a given time ( t v T T ). For example, at 2 seconds the instantaneous velocity of –Š‡ „ƒŽŽ ™ƒ• ͹ ˆ–Ȁ•‡…ǡ –Š‡ ‹•–ƒ–ƒ‡‘—• ˜‡Ž‘…‹–› ‘ˆ –Š‡ •Ž‡† ™ƒ• ͻǤͺͲ ˆ–Ȁ•‡…ǡ ƒ† –Š‡ ‹•–ƒ–ƒ‡‘—• velocity of the box ™ƒ• ͳǤ͵ʹ ˆ–Ȁ•‡…Ǥ Š‡ •Ž‡† Šƒ• –Š‡ Š‹‰Š‡•– ‹•–ƒ–ƒ‡‘—• ˜‡Ž‘…‹–› ƒ– ʹ •‡…‘†•ǡ ‡ƒ‹‰ –Šƒ– the t v T T is highest for the sled, and the sled has the greatest acceleration. 29. (A) (p. 414) Science/Evaluation of Models/Analysis . To know if friction is playing a major role, the acceleration in the oiled board experiment should be calculated. Acceleration can be calculated by using the equation . . d at 0 5 2 Each ‘„Œ‡…– –”ƒ˜‡Ž• –Š‡ Ž‡‰–Š ‘ˆ –Š‡ „‘ƒ”†ǡ ͳͲ ˆ‡‡–Ǥ Š‡”‡ˆ‘”‡ǡ ˆ‘” –Š‡ •Ž‡†ǣ d at 1 2

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. 3 5 ft/sec The acceleration (look at the 1s acceleration in the non-oil experiments) is the same in the normal and the frictionless environments so friction is not a major factor in either case. The difference is the rolling of the ball. 2