ACT Past Papers with Answers

Paper 75 · ACT January 2006 · Form 61C · Science Test

Based on the model presented by Student 3, if all 6 genes are replicated and the first gene replicated is Gene G, the third gene replicated would be: GeneA GeneG G e n e F G e n e X G e n e S G e n e R

Paper 75 · ACT January 2006 · Form 61C · Science Test

Which students believe that any of the 6 genes on the plasmid can be the first gene transferred to a recipient bacterium?

Paper 75 · ACT January 2006 · Form 61C · Science Test

Suppose that the model presented by Student 1 is cor- rect and that the transfer of genes between 2 bacteria was interrupted after 45 min. Based on the information provided, which of the following genes would NOT have been transferred from the donor bacterium to the recipient bacterium?

Paper 75 · ACT January 2006 · Form 61C · Science Test

Suppose that Student 2’s model is correct and that the transfer of genes between 2 bacteria was interrupted after 30 min. Under these conditions, which of the fol- lowing genes would definitely NOT be transferred from the donor bacterium to the recipient bacterium?

Paper 75 · ACT January 2006 · Form 61C · Science Test

Suppose that all 6 genes are transferred from a donor bacterium to a recipient bacterium. Under this condi- tion, which student(s) would argue that Gene A could be the last gene transferred?

Paper 75 · ACT January 2006 · Form 61C · Science Test

Suppose that the transfer of genes between 2 bacteria was interrupted, that the last gene transferred was Gene A, and that no incomplete copies of a gene were transferred. Based on this information, Student 1 would say that transfer was most likely interrupted how many minutes after the transfer began? GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 43 Passage II Color images of the surface of Io, one of Jupiter’s moons, show plumes of gas that resemble Earth’s geysers and active volcanoes that emit flows of molten material. The materials ejected from Io’s volcanoes and plumes rapidly solidify at Io’s cold surface temperatures. Scientists believe that these materials may be one of several allotropes (forms) of sulfur (S), or a sulfur compound. The following studies were performed to determine the compo- sition of these materials. Study 1 In a laboratory, scientists measured the reflectances (the fraction of light striking a surface that is reflected by that surface) of 4 allotropes of S (red, white, orange, and brown) and of a sulfur compound (sulfur dioxide [SO2]). Reflectances were measured at visible-light wavelengths between 0.35 µm (micrometers) and 0.60 µm. Figure 1 shows the data for the various S allotropes and for SO2. Figure 1 Io’s whole-disk reflectance (the reflectance of Io’s entire visible surface measured all at once) was measured at 2 different times. Figure 2 shows these data along with reflectance data calculated using a computer model. This model shows what combination of materials from Figure 1 would produce the closest match to the measured reflectance data. According to the model, the overall com- position of Io’s surface is 15% SO2, 50% orange S, 20% red S, and 15% white S. Figure 2 Study 2 At 2 different times, reflectances were measured of the crater floors of 2 volcanoes on Io: Pele and Surt. Figure 3 shows the reflectance data. Figure 3 reflectance Pele crater floor data 0

Paper 75 · ACT January 2006 · Form 61C · Science Test

At the wavelengths used in Study 1, as the wavelength of the light increases, the reflectances of the S allotropes and of SO2 do which of the following? S allotropes SO2

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Study 3, compared with the correspond- ing average reflectance for small plumes, large plumes on Io have an average reflectance at a given wave- length that is:

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Study 1, the reflectance of white S at a wavelength of 0.40 µm is closest to which of the fol- lowing?

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Study 1 and Study 2, the crater floor of the volcano Pele has reflectances most similar to which of the following S allotropes?

Paper 75 · ACT January 2006 · Form 61C · Science Test

If the averaged reflectances for large plumes and for small plumes had been measured at a wavelength of

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Study 1, white S has a reflectance of 0.98 at a wavelength of 0.60 µm. This means that white S reflects: surface. its surface. plume data 0 average reflectance

Paper 75 · ACT January 2006 · Form 61C · Science Test

In Experiment 1, the time constant of the circuit was the time required for the voltage across the capacitor to reach approximately 7.6 V. The time constant of the circuit used in Experiment 1 was:

Paper 75 · ACT January 2006 · Form 61C · Science Test

If, in Experiment 2, a 1.5 × 10–6 F capacitor had been used, the time required for the voltage across the capacitor to reach 6 V would have been closest to: switch capacitor voltmeter 12 V battery resistor V V GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 46

Paper 75 · ACT January 2006 · Form 61C · Science Test

The main purpose of Experiment 3 was to determine how varying the: at a given time. for the voltage across the capacitor to reach a set value. the battery at a given time. the voltage across the capacitor to reach a set value.

Paper 75 · ACT January 2006 · Form 61C · Science Test

Based on Figure 1, to measure the voltage across the resistor only, which of the following circuits should one use?

Paper 75 · ACT January 2006 · Form 61C · Science Test

Consider a circuit like that shown in Figure 1. Based on Experiments 2 and 3, the voltage across the capaci- tor will reach a given value in the shortest amount of time if the circuit contains which of the following capacitances and resistances, respectively? F, 0.3 × 107 Ω F, 1.0 × 107 Ω F, 0.3 × 107 Ω F, 1.0 × 107 Ω

Paper 75 · ACT January 2006 · Form 61C · Science Test

Consider the following hypothesis: In a circuit arranged as in Figure 1 containing a battery, a capaci- tor, and a constant resistance, as capacitance increases, the time required to reach a given voltage across the capacitor increases. Do the experiments support this hypothesis? time required to reach a given voltage increased. time required to reach a given voltage increased. time required to reach a given voltage decreased. time required to reach a given voltage decreased. V V V V GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 47 Passage IV A bomb calorimeter is used to determine the amount of heat released when a substance is burned in oxygen (Figure 1). The heat, measured in kilojoules (kJ), is calcu- lated from the change in temperature of the water in the bomb calorimeter. Table 1 shows the amounts of heat released when different foods were burned in a bomb calorimeter. Table 2 shows the amounts of heat released when different amounts of sucrose (table sugar) were burned. Table 3 shows the amounts of heat released when various chemical compounds were burned. Figure 1 Figure 1 adapted from Antony C. Wilbraham, Dennis D. Staley, and Michael S. Matta, Chemistry. ©1995 by Addison-Wesley Publishing Company, Inc. Table 1 Change in water Mass temperature Heat released Food (g) (°C) (kJ) Bread 1.0 8.3 10.0 Cheese 1.0 14.1 17.0 Egg 1.0 5.6 6.7 Potato 1.0 2.7 3.2 Table 1 adapted from American Chemical Society, ChemCom: Chemistry in the Community. ©1993 by American Chemical Society. Table 2 Amount of sucrose Heat released (g) (kJ)

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Tables 1 and 2, as the mass of successive sucrose samples increased, the change in the water temperature produced when the sample was burned most likely: firing element sample stirrer thermometer insulated outer container steel bomb water GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 48

Paper 75 · ACT January 2006 · Form 61C · Science Test

Which of the following graphs best illustrates the rela- tionship between the heat released by the foods listed in Table 1 and the change in water temperature?

Paper 75 · ACT January 2006 · Form 61C · Science Test

Based on the data in Table 2, one can conclude that when the mass of sucrose is decreased by one-half, the amount of heat released when it is burned in a bomb calorimeter will:

Paper 75 · ACT January 2006 · Form 61C · Science Test

Which of the following lists the foods from Tables 1 and 2 in increasing order of the amount of heat released per gram of food?

Paper 75 · ACT January 2006 · Form 61C · Science Test

Based on the information in Tables 1 and 2, the heat released from the burning of 5.0 g of potato in a bomb calorimeter would be closest to which of the follow- ing? heat released (kJ) change in temperature (°C) heat released (kJ) change in temperature (°C) heat released (kJ) change in temperature (°C) heat released (kJ) change in temperature (°C) GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 49 Passage V Density is defined as the mass of a substance divided by its volume: density = Table 1 lists the phases and the densities, in grams per cubic centimeter (g/cm3 ), of various pure substances at 25°C and 1 atmosphere (atm) of pressure. Table 1 Density Substance Phase (g/cm3 ) Arsenic solid 5.73 Glucose solid 1.56 Iron solid 7.86 Lead solid 11.34 Zinc solid 7.14 Ethanol liquid 0.79 Ethyl ether liquid 0.71 Glycerol liquid 1.26 Mercury liquid 13.59 Freon-12 gas 0.00495 Krypton gas 0.00343 Methane gas 0.00065 Figure 1 shows how the density of liquid water changes with temperature. Figure 1 Figure 2 shows how the density of solid water changes with temperature. Figure 2 Figures adapted from John C. Kotz and Keith F. Purcell, Chemistry & Chemical Reactivity. ©1987 by CBS College Publishing.

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Figure 1, as the temperature of liquid water decreases from 10°C to 0°C, the density:

Paper 75 · ACT January 2006 · Form 61C · Science Test

A student claimed that “If the masses of 1 cm3 of any solid and 1 cm3 of any liquid are compared, the mass of the solid will be greater.” Do the data in Table 1 support his claim? uids listed. solids listed. uids listed. solids listed.

Paper 75 · ACT January 2006 · Form 61C · Science Test

Which of the following hypotheses about the relation- ship between the temperature and the density of a solid is best supported by the data in Figure 2 ? As the tem- perature of a solid increases, the density of the solid: density (g/cm 3 ) –8 –6 –4 –2 0 2 4 6 8 10 temperature (°C) density (g/cm 3 ) –8 –6 –4 –2 0 2 4 6 8 10 temperature (°C) mass ____ ___ volume GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 50

Paper 75 · ACT January 2006 · Form 61C · Science Test

Equal amounts of ethyl ether, mercury, and water (density = 0.9971 g/cm3 ) at 25°C are poured into a single beaker. Three distinct layers of liquid form in the beaker. Based on the data in Table 1, which of the following diagrams represents the order, from top to bottom, of the liquids in the beaker?

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Figure 1, 100 g of water at 4°C would exactly fill a container having which of the following volumes? Ethyl ether Water Mercury Ethyl ether Mercury Water Mercury Water Ethyl ether Water Ethyl ether Mercury GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 51 Passage VI The clearing of rain forests results in forest fragmen- tation (the breakup of large forest tracts into small patches). Researchers predicted that fragmentation would result in a decrease in animal populations and aboveground tree biomass (AGTB) in the resulting fragments. They did 4 studies to test this prediction. Study 1 The researchers monitored the AGTB of twenty-five 100 m × 100 m forest plots near areas that had recently been cleared of vegetation. The distance from the center of each plot to the nearest clearing was measured. Figure 1 shows the average change per plot in AGTB in metric tons per year (t/yr) over 17 yr. Figure 1 Study 2 Twenty-five 100 m × 100 m forest plots were moni- tored as in Study 1. The center of each of these plots was at least 500 m from the nearest clearing. The average change in AGTB over 17 yr for these 25 plots was 0 t/yr. Study 3 Researchers monitored sixteen 100 m × 100 m forest plots near areas that had recently been cleared of vegeta- tion. Each plot was bordered on 1 side by a clearing. Figure 2 shows the average cumulative percent change in AGTB at these plots following fragmentation. (Note: Year 0 represents results prior to fragmentation.) Figure 2 Study 4 Researchers trapped and released birds in 10 forest fragments adjacent to areas that had recently been cleared of vegetation. Three types of birds were monitored: insecti- vores, frugivores (fruit eaters), and hummingbirds. Figure 3 shows the number of captures per 1,000 hours (hr) of trapping. (Note: Year 0 represents results prior to frag- mentation.) Figure 3 Figures adapted from William F. Laurance et al., “Biomass Collapse in Amazonian Forest Fragments.” ©1998 by the American Associa- tion for the Advancement of Science. captures/1,000 hr 180 160 140 120 100 80 60 40 20 0 0 1 2 3 4 5 6 7 Year insectivores frugivores hummingbirds average cumulative percent change in AGTB 0 –2 –4 –6 –8 –10 –12 –14 –16 Year 1 2 3 4 5 6 7 8 9 0 average change in AGTB (t/yr) 0 –1 –2 –3 –4 –5 –6 40 50 60 70 80 90 100 distance from center of plot to nearest clearing (m) GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 52

Paper 75 · ACT January 2006 · Form 61C · Science Test

In Study 4, as time increased from Year 0 to Year 6, the captures/1,000 hr of frugivores:

Paper 75 · ACT January 2006 · Form 61C · Science Test

Based on the results of Study 4, how did fragmentation most likely affect the population sizes of insectivores and hummingbirds in the fragments studied? both insectivores and hummingbirds. both insectivores and hummingbirds. insectivores and decreased the population size of hummingbirds. insectivores and increased the population size of hummingbirds.

Paper 75 · ACT January 2006 · Form 61C · Science Test

Based on the results of Study 1, if the distance from the center of a 100 m × 100 m plot were 75 m from the nearest clearing, the expected average change in AGTB at the plot over 17 yr would be closest to which of the following values?

Paper 75 · ACT January 2006 · Form 61C · Science Test

After examining the results of Study 2, a student con- cluded that the AGTB at each of the 25 plots remained constant. Which of the following alternative explana- tions is also consistent with the results? AGTB at some of the plots decreased. and the AGTB at plots bounded by clearings remained constant.

Paper 75 · ACT January 2006 · Form 61C · Science Test

Which of the following sets of results from the studies is least consistent with the prediction proposed by the researchers?

Paper 75 · ACT January 2006 · Form 61C · Science Test

In Study 4, the researchers trapped birds for 10,000 hr per year. Thus, how many insectivores were trapped in Year 2 ? GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 53 Passage VII Glaciers deposit till (a poorly sorted sediment). If glaciers repeatedly advance over an area and then melt back, thick till deposits may form. Figure 1 shows a verti- cal core taken through layers of till, non-glacial sediments, and bedrock at a site in Canada. The resistivity (an electri- cal property of a material) and CO2 measurements taken along the core are also shown. Resistivity is related to a sediment’s particle sizes, compaction, and mineral compo- sition. Table 1 shows the average percent sand, silt, and clay contents and descriptions of the various till layers. GO ON TO THE NEXT PAGE. 4 4 ACT-61C-PRACTICE 54 Figure 1 10 20 30 40 50 60 70 80 90 100 110 CO2 (mL/g) 0 10 20 30 40 cooler climate warmer climate Resistivity (ohms) Depth in core (m) 0 (surface) 0 50 100 150 No data surface sediments brown till gray tillA yellow till gray till B olive green and gray till gray till C gray till D sand and gravel bedrock No data No data Table 1 Average percent by volume of: Depth of larger particle → smaller particle till layer (m) Description of till sand silt clay 4−9 brown (oxidized*) 54.1 31.7 14.2 9−14 gray A 44.8 36.6 18.6 14−19 yellow (oxidized) 43.5 31.7 24.8 19−24 gray B 37.4 34.3 28.3 24−35 olive green and gray 25.5 34.3 40.2 35−55 gray C 31.7 33.6 34.7 55−85 gray D 37.5 31.7 30.8 *Oxidized sediments have at some time been exposed to the air. Sedi- ments that have been deprived of oxygen will be gray or green. Figure 1 and Table 1 adapted from E. A. Christiansen, “Pleistocene Stratigraphy of the Saskatoon Area, Saskatchewan, Canada: An Update.” ©1992 by the Geological Association of Canada.

Paper 75 · ACT January 2006 · Form 61C · Science Test

A sample of gray till was recovered from another core taken from a nearby area. The table below shows the results of an analysis of the sample. Percent by volume of: Resistivity CO2 content sand silt clay (ohms) (mL/g)

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Figure 1, the oldest glacial advance in this area deposited which of the following till layers?

Paper 75 · ACT January 2006 · Form 61C · Science Test

According to Figure 1, which of the following state- ments best describes how the resistivity of the sand and gravel layer compares to the resistivity of the till layers? The resistivity measured in the sand and gravel layer is: till layers. till layers. face sediments. rock.

Paper 75 · ACT January 2006 · Form 61C · Science Test

The average resistivity of the bedrock in the core is most similar to the average resistivity of which of the following till layers?

Paper 75 · ACT January 2006 · Form 61C · Science Test

The sediments being deposited at the present time at the site where the core was taken have a much higher CO2 content than any of the tills. Given this informa- tion and the information in Figure 1, the CO2 content of sediments recently deposited at the site would most likely be in which of the following ranges? [See Note on page 56.] 4 4 END OF TEST 4 STOP! DO NOT RETURN TO ANY OTHER TEST. ACT-61C-PRACTICE 55 56 Note: If you plan to take the ACT Plus Writing, take a 5-minute break and then continue with the Writing Test on page 57. If you do not plan to take the ACT Plus Writing, turn to page 59 for instructions on scoring your multiple-choice tests.