ACT Science Practice Test: Data Representation
- Data Representation
- 12 questions
- 12 minutes
ACT Science is optional on the enhanced ACT: 40 questions in 40 minutes, and its score is not part of the composite. Data representation sets give you tables and graphs and ask you to read values, describe trends, and interpolate or extrapolate. Check the units and axis labels before you start on the questions.
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Question 1
Passage I
The amount of oxygen gas (O2) that can dissolve in water depends on the water's temperature and on its salinity, the mass of dissolved salts in grams per kilogram of water (g/kg). Table 1 gives the maximum dissolved oxygen (DO) concentration, in milligrams per liter (mg/L), for water in contact with air at sea-level pressure. Fresh water has a salinity of 0 g/kg; typical ocean water has a salinity of about 35 g/kg.
Table 1: Maximum DO (mg/L) at three salinities Temp. (°C) 0 g/kg 18 g/kg 36 g/kg 0 14.6 12.9 11.4 10 11.3 10.1 9.0 20 9.1 8.2 7.4 30 7.6 6.8 6.2 According to Table 1, what is the maximum DO concentration of water with a salinity of 18 g/kg at 20°C?
Correct answer: B
Find the row for 20°C and the column for 18 g/kg: the value is 8.2 mg/L. The value 9.1 mg/L is for fresh water and 7.4 mg/L is for 36 g/kg in the same row.
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Question 2
Passage I (see above):
For water with a salinity of 36 g/kg, as the temperature increases from 0°C to 30°C, the maximum DO concentration:
Correct answer: D
In the 36 g/kg column, the values fall at every step: 11.4, 9.0, 7.4 and 6.2 mg/L. They never rise, so the maximum DO decreases only. Warmer water holds less dissolved gas.
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Question 3
Passage I (see above):
Based on Table 1, the maximum DO concentration of fresh water at 25°C is closest to:
Correct answer: C
25°C lies halfway between 20°C (9.1 mg/L) and 30°C (7.6 mg/L), so the value should be about halfway between them, near 8.3 mg/L. The value 7.6 mg/L is the reading for 30°C itself.
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Question 4
Passage I (see above):
According to Table 1, at which temperature is the difference between the maximum DO of fresh water and the maximum DO of water with a salinity of 36 g/kg the greatest?
Correct answer: A
The differences are 14.6 − 11.4 = 3.2 mg/L at 0°C, 2.3 mg/L at 10°C, 1.7 mg/L at 20°C and 1.4 mg/L at 30°C. The gap is greatest at 0°C and shrinks as the water warms.
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Question 5
Passage I (see above):
If the trend shown in Table 1 continues, the maximum DO concentration of fresh water at 40°C would be closest to:
Correct answer: A
For fresh water the maximum DO drops at every step (14.6, 11.3, 9.1, 7.6 mg/L), by a smaller amount each time. Continuing this trend, the value at 40°C should be somewhat below 7.6 mg/L, and 6.4 mg/L is the only choice that fits.
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Question 6
Passage I (see above):
A student claims that a warm lagoon (30°C, salinity 36 g/kg) can hold less than half as much dissolved oxygen as a cold freshwater stream (0°C). Do the data in Table 1 support this claim?
Correct answer: D
Water at 30°C and 36 g/kg can hold at most 6.2 mg/L, while fresh water at 0°C can hold 14.6 mg/L. Half of 14.6 is 7.3, so 6.2 mg/L is less than half and the claim is supported. The 7.6 mg/L value belongs to fresh water at 30°C, not to salty water.
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Question 7
Passage II
Students studied photosynthesis in an aquatic plant. They placed a cut sprig of the plant in a test tube of water containing dissolved sodium bicarbonate (a source of CO2), kept the water at a constant temperature, and lit the tube with a lamp. A light meter measured the light intensity at the tube in kilolux (klux). After 5 minutes at each light intensity, the students counted the oxygen bubbles released from the cut stem during 1 minute. Figure 1 shows the results at 15°C and at 25°C.
Figure 1 According to Figure 1, at a light intensity of 10 klux, the plant at 25°C released about how many bubbles per minute?
Correct answer: C
On the 25°C curve (dark line with round points), the point at 10 klux lies on the gridline for 20 bubbles per minute. The value 15 is the reading from the 15°C curve at the same light intensity.
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Question 8
Passage II (see above):
According to Figure 1, as the light intensity increased from 0 klux to 30 klux, the number of bubbles per minute at 15°C:
Correct answer: B
The 15°C curve rises from 0 to about 20 bubbles per minute between 0 klux and 20 klux, and then it stays flat at about 20 up to 30 klux. It never turns downward.
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Question 9
Passage II (see above):
Based on Figure 1, at 25°C the plant first released 30 bubbles per minute at a light intensity between:
Correct answer: C
The 25°C curve is a little below the 30-bubble gridline at 15 klux (about 27) and above it at 20 klux (about 31), so it crosses 30 between 15 klux and 20 klux.
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Question 10
Passage II (see above):
At which of the following light intensities was the difference between the number of bubbles per minute at 25°C and at 15°C the greatest?
Correct answer: D
The gap between the curves grows with light intensity: about 2 bubbles per minute at 5 klux, 5 at 10 klux, 9 at 15 klux and 13 at 25 klux (33 compared with 20). At low light, light limits photosynthesis at both temperatures, so the curves stay close.
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Question 11
Passage II (see above):
If the students had repeated the procedure at 20°C, the number of bubbles per minute at 30 klux would most likely have been:
Correct answer: B
At 30 klux the plant released about 20 bubbles per minute at 15°C and about 33 at 25°C, so the count rose with temperature. A temperature of 20°C lies between the two, so the count should most likely fall between 20 and 33.
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Question 12
Passage II (see above):
Which of the following statements is best supported by Figure 1?
Correct answer: A
From 20 klux to 30 klux, the 25°C curve rises only from about 31 to 33 and the 15°C curve stays at 20, so extra light made little difference. At 5 klux the counts were about 11 and 9, far from a 2-to-1 ratio, and the 15°C count was never higher than the 25°C count.
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