ACT Past Papers with Answers

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The scientist predicted that the ACD for Bacteria X colonies would be greatest when the bacteria were incubated at a temperature of 37°C on a growth medium having a pH of 7 and an Nacl concentration of 5 glL. Are the results in the table consistent with this prediction? in Tiial 8. inTrial 11. in Trial 8. No; the ACD for Bacteria X colonies was greatest in Trial 11. Growth medium: Incubation temperature Nacl concentration ACD (mm) Tri al (°c) pH (glL) 25 37 42 25 37 42 10 10 10 25 37 42 10 25 37 42 10 10 10 12

According to Combinations 5-8, as T increascs, F: increases only. varies, but with no general trend. remains the same. ACT-70C 39 GO ON TO THE NEXT PAGE. 40000000004 Passage 111 Figures adapted frorn Peter Keusch. "Kinotics: Hydrolysis of Ter- tiary Bulyl Halides First Order Reaction.. (&2000 by Universitat Regensburg. When t-butyl chloride [(CH.I)3CCI] is dissolved in an acetone-H O solution, it reacts with H O completely to form t-butyl alcohol [{CH3)ICOH]: (CH,),CCI + H,0 acelone-H O (CH3)3COH + H" + Cl- Acetone is less polar than H O. Thus, increasing the con- centration of acetone in H O decreases the polarity of the reaction solution. Figures l and 2 show how the electrical conductivity of each of 5 acetone-H O solutions varied over time after I mg of (CH ) CCI was dissolved in 100 ML of each solu- tion. The conductivity (which increased as the solution's ion concentration increased) .stopped increa%ing when the reaction had run to completion (indicated by the point labclcd "RC").

Based on the table, F will be greatest for wbich of the following D, T, and V ?

If experimental trials were conducted in which Combi- nations 1-4 were tested, what would be the indepen- dent variable and what would be the dependent variable? independent dependent

The conduciivity of the reaction solution at the end of a reaction is K. Which of the following graphs best shows how K_ vaiied with acetone concentration? Iofo 20*0 30¥ 400/0 50G/o acetone concentration RC.; 20Q/o acetone E 1.0 RC IOYO acetone 10% 20% 30¢Yo 40C/o 50fo acetone concentration l(K) 200 300 400 500 600 time (sec) Figure I RC 30Yo acetone RC 40fo acetone 10% 20% 30% 40% 500/0 acetone concentration E 1.0 RC 50% acetone 101, 20% 30¥0 4010 5010 acetone concentration 400 800 1,200 tiine (sec) 1,600 2,000

Based on Fiuure 2, if a 45 % acetone solution had been tested, the reaction would most likely have reached completion at a time: reater than 1,800 sec. Note: In Fi crure8 l and 2, concentration is given as the percent by mass of acetone in the solution, and conductivity is oiven as millisiemens per centimeter, mslcm. Figui'e 2 ACT-70C 40 GO ON TO THE NEXT PAGE. 40000000004

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How did the behavior of a subject training for Seq X differ from the behavior of a subject training for Seq Y ? A subject tralning for Seq X finger-tapped: Seq Y finger-tapped for I min intervals. with the right hand, whereas a gubject training for Seq Y finger-tapped with the left hand. training for Seq Y finger-tapped for a total of 3 intervals. finger-tapped 2-3-1-4-2. ACT.7C 43 GO ON TO THE NEXT PAGE. 40000000004 Passage V Gas-giant planers have a solid core surrounded by a tn(Issive envelope of gases. Gas-giant planets form within stellar ilebulae-large, fiattened clouds of gas and dust that surround newly formed stars. Planet formation be(Fins when some of the solid n]aterial within a Stellar nebula clumps together to form a spherical body called a plaiiet Gore. Two scientists discuss how gas-giant planets like Jupiter form from planet cores in stellaL nebulae.

What are the 2 scientists, estimates of the mass of a planet core that later becomes the center of a gas-giant planet? Scientist I exactly 10 M exactly 6 M at least 6 M Scientist 2 exactly 6 M exactly l O M atmost6M. atmost 10 M

Based on Scientist I's discussion, which of the follow- ing statements gives the niost likely reason Earth is not a gas-giant planet? At the time the planets were form- ing in the Sun's stellar nebLila, the: enough to attiact and hold a sufficient amount of gases. to attract and hold a large quantity of gases. nebula did not contain enough tT1c se5 to form any gas-giant planets. nebula contained only enough gases to form 2 gas- giant planets.

The discovery that some stellar nebulae remain in eKis- tence for more than 10 rnillion years would contradict a statement made by.. neither Scientist I nor Scientist 2. Scieiitist I A planet corc continuously attracts additional solid particles from the stellar nebula, gradually increasing its mass. If a planet core reaches a minimum mass of 10 times the mass of Earth (10 MF.), its gravity is then strong enough to attract and hold gascs from the surroundino stellar nebula. The formation of a l O ME planet core takes approx- imately I million years. The time required for a 10 M planet core to then attract a minimum 300 ME of gases and thus become a gas-giant planet like Jupiter is 10 million to 100 rnillion years more. Because it takes so long to fom gas-giant planets like Jupiter, they are very rare in our galaxy. Scientist 2 Gas-giant planets form in a stellar nebula if gravity variations cause the nebula to suddenly fragment into 2 or more massive spherical clumps of oas and du.st called gas- gia12r pi'ofoplanets (GGPP), each having a planet core at the center that is no larger than 6 M A GGPP forms in less than 1,000 years. After formation, the GGPP contracts to form a gas-giant planet. The entire process from the start of GGPP formation to a new ga8-oiant planet takes only about I million years.

Suppose a planet core in a stellar nebula has, over time, attracted and held 200 ME of gases from the nebula. Would Scientist I be likcly to claim that this planet core surrounded by 200 ME of gases is a (yas_ giant planet like Jupiterg 200 ME of gases must be attracted and held by a planet core lo form such a gas-oiant planet. Yes, because Scientist I claim% that no less than 200 ME of gases must be attracted and held by a planet core to form such a gas-giant planet. 200 ME of gases must be attracted and held by a planet core to form such a gas-giant planet. 200 ME of gases must be attracted and held by a planet core to form sucb a 17as-giant planet. Gas-giant planets like Jupiter would not haNe time to form as described by Scientist l. Ob8ervations indicate that stellar nebulae around newly formed stars do not remain in existence longer than 7 rnillion years after the stars are formed. Also, planet cores thai are not part of a GGPP do not have enough momentum to keep them from spiral- ino into the star at the center of the nebula within 100,000 years. Gas-giant planets like Jupiter are not rare. At least 130 gas-giant planets as large as or larger than Jupiter have been identified in our galaxy. ACT-70C 44 GO ON TO THE NEXT PAGE. 40000000004

The discovery of which of ihe following objects would provide the strongest support for Scientist 2's viewpoint? ing gas-giant planets ing gas-giant planets orbiting gas-giant planets Several 100-million-year-old stars, each with 2 orbiting gas-giant planets

Assume that the gas-giant planets and the non-gas- giant planets (terrestrial planets) in another solar system in our galaxy have spatial and size relation- ships the same as those of the gas-giant planets and the terrestrial planets in our solar system. Given this assumption, in the other solar system, an existing oas- giant planet would most likely bc: would any of the terrestrial planets. would any of the terrestrial planets. the same diameter as the largest terrestrial planet. a lesser diameter than any of the terrestrial planets.

Based on Scientist 2,8 discussion, in a stellar nebula, a 10 ME planet core that was NOT part of a GGPP would most likely: years. escape from the central star's gravity and travel out into space. continue to revolve around the central star at a constant distance and speed. move in toward the central star and eventually be destroyed. ACT-70C 45 GO ON TO THE NEXT PAGE. 40000000004 Passage Vl In a hydrothermal vent, anaerobic oxidation of methane (AOM) occurs in the top 20 cm of ocean-floor sediment (see Figure l). This reaction begins when hot fluid containing methane (CH4) rises from a source deep beneath the ocean-floor surface and mixes with seawater containing sulfate (S04 -). Key so,'- CN seawater 10 seawater containing Ca~, and SO moves down into sediment ocean-floor surface > 14 16 £ 18 20cm , ocean-floor sediment , A0￿1 occurs k Q;. ..7 f .,_l_ ..], 0 10 20 30 40 50 60 70 80 average concentration (mmoVL) . hot fliiid containing CH4 rises. Figure 2 Figure I Study 2 The sediment in the other core from each of the 10 locations was sampled at the top of the core (O cm depth), then every 0.5 cm along the core's length. The 10 samples from the same depth in each cole were com- bined and then analyzed to determine the average percent by mass of calcite and the average percent by mass of ara- gonite in tbe sediment from O cm to 20 cm depth (see Figure 3). AOM is represented by the following equation: ->HCO3 +HS-+HO One of the 3 direct pioducts of this reaction, HCO3 , can then combine with calcium (Ca") in the seawater in a second reaction to produce solid calcium carbonate (CaCO3). This Caco exists as calcite crystals andlor aragonite crystals. Over time, the crystals fill in the pores in the sediment. CH4 + SO, Key calcite aragonite At each of 10 locations in a hydrothermal vent, 2 ver- tica) cylindrical cores of the top 20 cm of ocean-floor sedi- ment were collected. 10 12 14 16 18 Study I One of the 2 cores from each of the 10 locations was cut every 0.5 cm along its length. Each piece of core was squeezed to extract all of the pore walep. (water present in the sediment's pores). The l O pore water samples from the pieces at the same depth interval in each core were com- bined and then analyzed for SO and CH,. The average SO,'- and CH4 concentrations, in millimoles per liter (mmollL), from O cm to 20 cm depth are shown in Figure 2. 0 5 10 15 20 25 30 average percent by mass in sediment Figure 3 Figures 2 and 3 adapt8d from Roger Luff et al., 'Simulation of Long-Term Feedbacks from Authigenic Carbonate Crust Formation at Cold Vent Sites., @2004 by Elsevier B.V. ACT-71 46 GO ON TO THE NEXT PAGE. 40000000004

According to the results of Study 2, there was NO cal- cite found at which of the following depths? 2cm 5cm 8cm

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The procedures of Studies l and 2 differed in which of the following ways? In Study I, samples were.. analyzed for the reactants of AOM, whereas in Study 2. samples were not analyzed for the reac- tants of AOM. not analyzed for the reactants of AOM, whereas in Study 2, samples were analyzed for the reactants ofAOM. analyzed for the direct products of AOM, whereas in Study 2, sarnples were not analyzed for the direct products of AOM. not analyzed for the direct products of AOM, whereas in Study 2, samples were analyzed for the direct products of AOM. ACT-70C 47 GO ON TO THE NEXT PAGE. 40000000004 Passage Vll A physicist tested various sheets for their ability to stop gamma rays (y-rays) that had different energies. Any y-ray that was not stopped by a sheet struck a detector (see Figure l), which then registered a detection, or count. Experiment 2 The physicist repeated the procedures from Experi- ment I with other sources of y-rays having diffeient ener- gies. For each combination of sheet material and y-ray energy, she produced a graph of I versus x. These graphs are not shown. From the graphs of I versus x, she found the half- value thickness, Xhalf, for each combination of sheet mate- rial and y-ray energy. A sheet of thickness Xhalf Stopped half of the y-rays striking the sheet. that is, l equaled (For example, based on Figure 2, for 4 Mev y-rays striking sheets of Material I, Xhalf equaled 1.0 cm.) Finally, the physicist plotted a graph of Xhalf versus y-ray energy for each material (se& Figure 3). sheet detector y-ray source Material 3 Figure I Each sheet was made of either Material I, Material 2, or Materia13. The thickness, x, of each sheet was uniform, but sheet8 of the same material had different thicknesses. Material 2 Jo represented the number of counts per minute (cpm) with no sheet between the y-ray source and the detector, and I represented the cpm with I sheet between the source and the detector. Material I Experiment I First, the physicist measured Jo for a source of y-ray8 having an energy of 4 million electron volts (Mev). Next, with Ihis same y-ray source. she measured I for various sheets of Material I, each having a different thickness x. Then, she plotted a graph of I versus x (in cm) for Material l. Similarly, she produced graphs of I versus x for Material 2 and Material 3 (see Figure 2). y-ray energy (Mev) Figure 3 10,000 9,000 8,000 7,000 6,000

Based on the results of Experiment 2, for a given mate- rial, as y-ray energy increased, Xhalf. increased only. varied, but with no general trend. remained the same. 4,000 Material 3 2,000 1,000 Material 2 ..Material l .

Based on the results of Experiment I, Xhalf for Mate- rial 3 and a y-ray energy of 4 Mev was closest to which of the following values?

Based on the description of the experiments, for y-rays of a given energy, as the.ability of material& to stop y-rays increased, did I decrease or increase, and why. the detector per minute increased. the detector per minute decreased. the detector per minute increased. Increase, because the number of y-rays reaching the detector per minute decreased.

In Experiment I, what was the value of l ? Ocpm Icpm . J. 8,000 cpm END OF TEST 4 STOP! DO NOT RETURN TO ANY OTHER TEST. ACT-70C 49 Form 17K ACT Writing Test Prompt (June 2012) Many school districts have banned students from wearing articles of clothing, such as T-shirts, that have statements about social or political issues printed on them. Some school administrators support such a ban because they think students should be restricted from wearing clothes with statements that might offend other students and disrupt the educational process. Other school administrators do not support such a ban because they think students have a right to express their opinions on social and political issues in school. In your opinion, should school districts ban students from wearing articles of clothing with statements about social or political issues printed on them? In your essay, take a position on this question. You may write about either one of the two points of view given, or you may present a different point of view on this question. Use specific reasons and examples to support your position. 52 Forni 70C (June 2012) Too Norn]al Math Readin Science l) D