ACT Science Practice Test: Research Summaries and Conflicting Viewpoints
- Research Summaries and Conflicting Viewpoints
- 12 questions
- 12 minutes
These 12 questions practice two ACT Science passage types: a research summary with several related experiments and a conflicting viewpoints passage with competing explanations of one phenomenon. For experiments, find what was changed, what was measured and what was kept the same; for viewpoints, judge each explanation on its own terms, not by what you already believe.
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Question 1
Passage I
Effervescent antacid tablets contain citric acid and sodium bicarbonate. In water, these compounds dissolve and react, releasing carbon dioxide gas. Students measured the dissolving time, the time from when a tablet touched the water until no solid remained. All tablets came from the same package. Each trial was done 3 times, and the tables give the average times.
Experiment 1
A whole tablet was dropped into 200 mL of water at each of 5 temperatures.
Table 1 Water temperature (°C) Dissolving time (s) 10 88 20 57 30 39 40 28 50 21 Experiment 2
A tablet was left whole, broken into 2 pieces, broken into 8 pieces or crushed into a powder, and then dropped into 200 mL of water at 20°C.
Table 2 Tablet form Dissolving time (s) Whole 57 2 pieces 49 8 pieces 36 Powder 17 Experiment 3
A whole tablet was dropped into different volumes of water at 20°C.
Table 3 Volume of water (mL) Dissolving time (s) 100 58 200 57 300 57 400 56 In Experiment 2, which of the following were the independent variable and the dependent variable?
Correct answer: B
In Experiment 2 the students chose the tablet form (whole, 2 pieces, 8 pieces, powder) and measured how long each took to dissolve. Water temperature stayed at 20°C in this experiment, so it was a controlled variable, not the independent variable.
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Question 2
Passage I (see above):
Which of the following was kept the same in every trial of both Experiment 1 and Experiment 2?
Correct answer: C
Both experiments used 200 mL of water in every trial. The temperature was varied in Experiment 1, the tablet form was varied in Experiment 2, and the dissolving time was the measured result.
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Question 3
Passage I (see above):
Based on Experiment 1, if a whole tablet were dropped into 200 mL of water at 35°C, its dissolving time would most likely be:
Correct answer: B
In Experiment 1 the dissolving time decreased steadily as the temperature rose: 39 s at 30°C and 28 s at 40°C. Since 35°C lies between these temperatures, the time should lie between 28 s and 39 s.
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Question 4
Passage I (see above):
Which conclusion is best supported by the results of Experiment 2?
Correct answer: D
Breaking a tablet into more pieces, and finally into powder, exposes more surface to the water, and the dissolving time fell from 57 s to 17 s. Temperature was not varied in Experiment 2, so this experiment says nothing about it (and Experiment 1 shows that temperature does matter).
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Question 5
Passage I (see above):
Suppose Experiment 1 had been repeated with 100 mL of water instead of 200 mL. Based on Experiment 3, the dissolving times would most likely have been:
Correct answer: B
In Experiment 3, changing the volume from 100 mL to 400 mL changed the dissolving time by only about 2 s (from 58 s to 56 s). Over this range the volume of water had little effect, so using 100 mL should leave the times about the same.
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Question 6
Passage I (see above):
Based on Experiments 1 and 2, a tablet crushed into powder and dropped into 200 mL of water at 40°C would most likely dissolve in:
Correct answer: A
Powder dissolved in 17 s at 20°C (Experiment 2), and raising the temperature from 20°C to 40°C cut the time for whole tablets roughly in half, from 57 s to 28 s (Experiment 1). Both changes speed up dissolving, so powder at 40°C should take less than 17 s.
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Question 7
Passage II
Earth orbits the Sun once a year along a path that is nearly a circle; its distance from the Sun changes by only about 3% during the year. Earth's axis is tilted about 23.4° from a line perpendicular to the plane of its orbit, and the axis points in the same direction in space all year. Three students explain why most places on Earth have seasons.
Student 1
Earth's orbit is an ellipse, so Earth is closer to the Sun at some times of the year than at others. When Earth is closest to the Sun, the whole planet receives the most energy and has summer. When Earth is farthest from the Sun, the whole planet has winter.
Student 2
Because the axis is tilted, the hemisphere tilted toward the Sun receives sunlight at a steeper angle. Steeper sunlight is concentrated on a smaller area of ground, and that hemisphere also has longer days, so it has summer. At the same time, the hemisphere tilted away from the Sun has winter. The small changes in Earth's distance from the Sun are not the cause of the seasons.
Student 3
Because the axis is tilted, the hemisphere tilted toward the Sun is physically closer to the Sun than the other hemisphere. Being closer to the Sun makes that hemisphere warmer, so it has summer, while the hemisphere tilted away, which is farther from the Sun, has winter.
Students 1 and 3 would both most likely agree that a place has summer when:
Correct answer: D
Student 1 links summer to the whole Earth being closest to the Sun, and Student 3 links it to one hemisphere being tilted closer to the Sun, so both explain summer by a smaller distance to the Sun. Only Student 2 mentions the angle of sunlight and the length of the day.
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Question 8
Passage II (see above):
Which of the following findings, if true, would best support Student 2's claim that sunlight striking the ground at a steeper angle heats it more?
Correct answer: A
Student 2's claim is that the same light concentrated on a smaller area delivers more energy to each part of that area. A lamp that warms a board faster when it shines straight down tests exactly that idea; the other findings are about distance, the Sun's output or the direction of Earth's axis, not about the angle of the light.
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Question 9
Passage II (see above):
Earth's tilt changes the distance between a hemisphere and the Sun by at most a few thousand kilometers, while Earth's average distance from the Sun is about 150 million kilometers. This information most directly weakens the explanation of:
Correct answer: C
Student 3 says the tilted hemisphere is warmer because the tilt brings it closer to the Sun, but a few thousand kilometers out of 150 million is far too small a change to matter. Student 1's explanation does not depend on the tilt at all, and Student 2 already says that distance is not the cause.
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Question 10
Passage II (see above):
In June, the Northern Hemisphere is tilted toward the Sun. According to Student 2's explanation, compared with December, a city at 40° north latitude in June would have:
Correct answer: A
Student 2 says the hemisphere tilted toward the Sun gets sunlight at a steeper angle, which means the Sun stands higher in the sky, and also has longer days. In December the same city is tilted away from the Sun, so its noon Sun is lower and its days are shorter.
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Question 11
Passage II (see above):
Suppose Earth's axis were tilted 35° instead of 23.4°, with no other changes. Based on Student 2's explanation, compared with today, places far from the equator would most likely have:
Correct answer: D
A larger tilt would make the summer Sun higher and summer days longer, and the winter Sun lower and winter days shorter. By Student 2's reasoning, summers would become hotter and winters colder, so the seasons would be more extreme.
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Question 12
Passage II (see above):
In January, it is winter in Canada (Northern Hemisphere) and summer in Australia (Southern Hemisphere). This observation is consistent with the explanation(s) of which student(s)?
Correct answer: C
Students 2 and 3 both say that the hemisphere tilted toward the Sun has summer while the other hemisphere has winter, so opposite seasons in Canada and Australia fit both explanations. Student 1 says the whole planet has the same season at the same time, which this observation contradicts.
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