ACT Science Reasoning Practice Test 2026: Comprehensive Exam
Prep — Data Interpretation, Scientific Investigation, Experimental
Design, Research Summaries & Conflicting Viewpoints — 190
Multiple-Choice Questions with Answers & Detailed Rationales
Section 1: Data Representation and Interpretation
Question 1
A student measures the mass of a sample of a mysterious, uniform metal. The volume is
measured by water displacement. The data is recorded as follows: Mass = 54.0 g, Initial
Water Volume = 20.0 mL, Final Water Volume = 26.0 mL. What is the density of the metal?
A. 2.08 g/mL
B. 9.00 g/mL
C. 2.70 g/mL
D. 10.8 g/mL
Correct Answer: B
Explanation: Density is mass divided by volume. The volume is the difference in water levels
(26.0 mL - 20.0 mL = 6.0 mL). Density = 54.0 g / 6.0 mL = 9.00 g/mL.
Question 2
A researcher studies the effect of fertilizer on plant growth. Group A receives no fertilizer,
Group B receives 5g, and Group C receives 10g. After four weeks, the average heights are 10
cm, 15 cm, and 18 cm, respectively. Based on this data, what is the independent variable?
A. The average height of the plants.
B. The amount of fertilizer given.
C. The duration of the experiment.
,D. The type of plant used.
Correct Answer: B
Explanation: The independent variable is the factor the researcher manipulates. The amount
of fertilizer is deliberately changed to observe its effect on growth.
Question 3
A geologist measures the temperature of rock samples at various depths in a borehole. The
data shows a linear increase in temperature with depth. This observed rate of temperature
increase is known as the geothermal gradient. If the temperature at the surface is 20°C and
at 1000m it is 50°C, what is the geothermal gradient?
A. 0.03 °C/m
B. 0.05 °C/m
C. 20 °C/m
D. 30 °C/m
Correct Answer: A
Explanation: The gradient is the change in temperature divided by the change in depth:
(50°C - 20°C) / 1000 m = 30°C / 1000 m = 0.03 °C/m.
Question 4
A chemist performs a titration and generates a pH curve. The curve shows a sharp, nearly
vertical drop in pH at the equivalence point. This shape is characteristic of which type of
titration?
A. Strong acid with a weak base.
B. Weak acid with a strong base.
,C. Strong acid with a strong base.
D. Weak acid with a weak base.
Correct Answer: C
Explanation: A strong acid-strong base titration produces the most dramatic pH change at
the equivalence point due to the complete neutralization of strong ions.
Question 5
An ecologist records the population of a predator and its primary prey over a 10-year period.
The data shows that the predator population peaks approximately one year after the prey
population peaks. This relationship is best described as a:
A. Symbiotic relationship.
B. Predator-prey cycle.
C. Competitive exclusion.
D. Succession event.
Correct Answer: B
Explanation: The lagging peak of the predator population behind the prey population is a
classic indicator of a predator-prey population cycle.
Question 6
A physicist plots the kinetic energy of ejected electrons versus the frequency of incident light
in a photoelectric effect experiment. The graph is a straight line that does not pass through
the origin. The x-intercept of this graph represents:
A. Planck's constant.
B. The work function of the metal.
, C. The threshold frequency.
D. The stopping potential.
Correct Answer: C
Explanation: The x-intercept is the frequency at which the kinetic energy is zero, meaning no
electrons are ejected. This is the minimum frequency, or threshold frequency.
Question 7
A medical researcher measures the blood glucose levels of patients every hour after they
consume a sugary drink. The data for a healthy individual would most likely show:
A. A constant, high level of glucose.
B. A rapid spike followed by a rapid decline to baseline.
C. A slow, steady increase over 6 hours.
D. A gradual decrease below the baseline level.
Correct Answer: B
Explanation: A healthy pancreas releases insulin in response to a glucose spike, causing a
rapid uptake by cells and a quick return to normal levels.
Question 8
A student is analyzing a chart showing the solubility of various salts at different
temperatures. The curve for Potassium Nitrate (KNO₃) slopes steeply upwards. This indicates
that KNO₃ is:
A. Less soluble in hot water.
B. More soluble in hot water.
Prep — Data Interpretation, Scientific Investigation, Experimental
Design, Research Summaries & Conflicting Viewpoints — 190
Multiple-Choice Questions with Answers & Detailed Rationales
Section 1: Data Representation and Interpretation
Question 1
A student measures the mass of a sample of a mysterious, uniform metal. The volume is
measured by water displacement. The data is recorded as follows: Mass = 54.0 g, Initial
Water Volume = 20.0 mL, Final Water Volume = 26.0 mL. What is the density of the metal?
A. 2.08 g/mL
B. 9.00 g/mL
C. 2.70 g/mL
D. 10.8 g/mL
Correct Answer: B
Explanation: Density is mass divided by volume. The volume is the difference in water levels
(26.0 mL - 20.0 mL = 6.0 mL). Density = 54.0 g / 6.0 mL = 9.00 g/mL.
Question 2
A researcher studies the effect of fertilizer on plant growth. Group A receives no fertilizer,
Group B receives 5g, and Group C receives 10g. After four weeks, the average heights are 10
cm, 15 cm, and 18 cm, respectively. Based on this data, what is the independent variable?
A. The average height of the plants.
B. The amount of fertilizer given.
C. The duration of the experiment.
,D. The type of plant used.
Correct Answer: B
Explanation: The independent variable is the factor the researcher manipulates. The amount
of fertilizer is deliberately changed to observe its effect on growth.
Question 3
A geologist measures the temperature of rock samples at various depths in a borehole. The
data shows a linear increase in temperature with depth. This observed rate of temperature
increase is known as the geothermal gradient. If the temperature at the surface is 20°C and
at 1000m it is 50°C, what is the geothermal gradient?
A. 0.03 °C/m
B. 0.05 °C/m
C. 20 °C/m
D. 30 °C/m
Correct Answer: A
Explanation: The gradient is the change in temperature divided by the change in depth:
(50°C - 20°C) / 1000 m = 30°C / 1000 m = 0.03 °C/m.
Question 4
A chemist performs a titration and generates a pH curve. The curve shows a sharp, nearly
vertical drop in pH at the equivalence point. This shape is characteristic of which type of
titration?
A. Strong acid with a weak base.
B. Weak acid with a strong base.
,C. Strong acid with a strong base.
D. Weak acid with a weak base.
Correct Answer: C
Explanation: A strong acid-strong base titration produces the most dramatic pH change at
the equivalence point due to the complete neutralization of strong ions.
Question 5
An ecologist records the population of a predator and its primary prey over a 10-year period.
The data shows that the predator population peaks approximately one year after the prey
population peaks. This relationship is best described as a:
A. Symbiotic relationship.
B. Predator-prey cycle.
C. Competitive exclusion.
D. Succession event.
Correct Answer: B
Explanation: The lagging peak of the predator population behind the prey population is a
classic indicator of a predator-prey population cycle.
Question 6
A physicist plots the kinetic energy of ejected electrons versus the frequency of incident light
in a photoelectric effect experiment. The graph is a straight line that does not pass through
the origin. The x-intercept of this graph represents:
A. Planck's constant.
B. The work function of the metal.
, C. The threshold frequency.
D. The stopping potential.
Correct Answer: C
Explanation: The x-intercept is the frequency at which the kinetic energy is zero, meaning no
electrons are ejected. This is the minimum frequency, or threshold frequency.
Question 7
A medical researcher measures the blood glucose levels of patients every hour after they
consume a sugary drink. The data for a healthy individual would most likely show:
A. A constant, high level of glucose.
B. A rapid spike followed by a rapid decline to baseline.
C. A slow, steady increase over 6 hours.
D. A gradual decrease below the baseline level.
Correct Answer: B
Explanation: A healthy pancreas releases insulin in response to a glucose spike, causing a
rapid uptake by cells and a quick return to normal levels.
Question 8
A student is analyzing a chart showing the solubility of various salts at different
temperatures. The curve for Potassium Nitrate (KNO₃) slopes steeply upwards. This indicates
that KNO₃ is:
A. Less soluble in hot water.
B. More soluble in hot water.
