Nice work!
Review your answers above to learn from any mistakes.
About This Drill
ACT Science: Research Summaries (Drill 2) is a Science practice drill covering Research Summaries. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
ACT Research Summaries questions assess understanding of experimental variables and results. This drill presents three experiments examining osmosis in potato tissue under varying sucrose concentration, time, and temperature, requiring data comparison and evaluation of the students' experimental controls.
Questions & Explanations
Experiments 1–3
Students investigated osmosis, the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. They placed standardized cylinders of raw potato (initial mass 5.0 g each) into sucrose solutions of varying concentration and measured the percent change in mass after soaking. A positive percent change indicates the cylinder gained mass (water entered the potato); a negative value indicates mass loss (water left the potato).
Experiment 1; Effect of Sucrose Concentration
Potato cylinders were soaked for 60 minutes at 25°C in sucrose solutions of six different molar concentrations.
Table 1. Sucrose Concentration vs. Mass Change
| Sucrose Concentration (M) | Mass Change (%) |
|---|
| 0.0 | +12.4 |
| 0.2 | +6.1 |
| 0.4 | 0.0 |
| 0.6 | −5.8 |
| 0.8 | −11.2 |
| 1.0 | −15.3 |
Experiment 2; Effect of Soaking Time
Potato cylinders were soaked in a 0.6 M sucrose solution at 25°C for varying lengths of time.
Table 2. Soaking Time vs. Mass Change
| Time (min) | Mass Change (%) |
|---|
| 0 | 0.0 |
| 15 | −2.1 |
| 30 | −4.0 |
| 60 | −5.8 |
| 90 | −6.3 |
| 120 | −6.4 |
Experiment 3; Effect of Temperature
Potato cylinders were soaked in a 0.6 M sucrose solution for 30 minutes at five different temperatures.
Table 3. Temperature vs. Mass Change
| Temperature (°C) | Mass Change (%) |
|---|
| 5 | −1.8 |
| 15 | −3.0 |
| 25 | −4.0 |
| 35 | −5.2 |
| 45 | −5.7 |
Question 1. According to Table 1, in which sucrose solution did the potato cylinders neither gain nor lose mass?
-
A) 0.0 M
-
B) 0.2 M
-
C) 0.4 M ✓
-
D) 0.6 M
Explanation: Table 1 shows a mass change of 0.0% at 0.4 M sucrose, the only concentration where the cylinder neither gained nor lost mass. This concentration is the isotonic point, meaning the solute concentration of the sucrose solution equals the solute concentration inside the potato cells. With no concentration gradient, there is no net movement of water in either direction. At lower concentrations (0.0 M and 0.2 M) the solution is hypotonic and water moves into the potato; at higher concentrations (0.6 M and above) the solution is hypertonic and water moves out.
Experiments 1–3
Students investigated osmosis, the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. They placed standardized cylinders of raw potato (initial mass 5.0 g each) into sucrose solutions of varying concentration and measured the percent change in mass after soaking. A positive percent change indicates the cylinder gained mass (water entered the potato); a negative value indicates mass loss (water left the potato).
Experiment 1; Effect of Sucrose Concentration
Potato cylinders were soaked for 60 minutes at 25°C in sucrose solutions of six different molar concentrations.
Experiment 2; Effect of Soaking Time
Potato cylinders were soaked in a 0.6 M sucrose solution at 25°C for varying lengths of time.
Experiment 3; Effect of Temperature
Potato cylinders were soaked in a 0.6 M sucrose solution for 30 minutes at five different temperatures.
Question 2. Experiment 2 was designed primarily to investigate how which of the following affects the rate of osmosis?
-
A) The concentration of the sucrose solution under the conditions described
-
B) The duration of exposure to the sucrose solution ✓
-
C) The temperature of the sucrose solution
-
D) The initial mass of the potato cylinders
Explanation: In Experiment 2, the sucrose concentration (0.6 M) and temperature (25°C) were held constant while soaking time was varied from 0 to 120 minutes. The independent variable, the one being deliberately changed, is therefore time. The experiment was designed to show how long it takes for osmosis to proceed at a given concentration and temperature, and whether mass change levels off over time as equilibrium is approached. Concentration was varied in Experiment 1, and temperature in Experiment 3.
Experiments 2 and 3
Students investigated osmosis, the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. They placed standardized cylinders of raw potato (initial mass 5.0 g each) into sucrose solutions of varying concentration and measured the percent change in mass after soaking. A positive percent change indicates the cylinder gained mass (water entered the potato); a negative value indicates mass loss (water left the potato).
Experiment 2; Effect of Soaking Time
Potato cylinders were soaked in a 0.6 M sucrose solution at 25°C for varying lengths of time.
Table 2. Soaking Time vs. Mass Change
| Time (min) | Mass Change (%) |
|---|
| 0 | 0.0 |
| 15 | −2.1 |
| 30 | −4.0 |
| 60 | −5.8 |
| 90 | −6.3 |
| 120 | −6.4 |
Experiment 3; Effect of Temperature
Potato cylinders were soaked in a 0.6 M sucrose solution for 30 minutes at five different temperatures.
Table 3. Temperature vs. Mass Change
| Temperature (°C) | Mass Change (%) |
|---|
| 5 | −1.8 |
| 15 | −3.0 |
| 25 | −4.0 |
| 35 | −5.2 |
| 45 | −5.7 |
Question 3. Based on Tables 2 and 3, which of the following statements best compares the results of Experiments 2 and 3?
-
A) In both experiments, mass loss increased steadily with no sign of leveling off
-
B) In Experiment 2, mass loss leveled off over time; in Experiment 3, mass loss increased steadily with temperature ✓
-
C) In both experiments, mass loss decreased as the independent variable increased
-
D) In Experiment 2, mass loss increased steadily; in Experiment 3, mass loss leveled off at higher temperatures, across the experiments described
Explanation: Table 2 shows mass loss increasing from 0% to −5.8% between 0 and 60 minutes, then barely changing from −6.3% to −6.4% between 90 and 120 minutes, a clear leveling off as osmotic equilibrium is approached. Table 3 shows mass loss increasing steadily from −1.8% at 5°C to −5.7% at 45°C with no sign of plateauing within the temperature range tested. Higher temperatures increase the kinetic energy of water molecules, speeding up diffusion across the membrane. The two patterns differ: Experiment 2 shows equilibrium being reached, while Experiment 3 shows a continuous increase.
Experiments 1 and 2
Students investigated osmosis, the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. They placed standardized cylinders of raw potato (initial mass 5.0 g each) into sucrose solutions of varying concentration and measured the percent change in mass after soaking. A positive percent change indicates the cylinder gained mass (water entered the potato); a negative value indicates mass loss (water left the potato).
Experiment 1; Effect of Sucrose Concentration
Potato cylinders were soaked for 60 minutes at 25°C.
Table 1. Sucrose Concentration vs. Mass Change
| Sucrose Concentration (M) | Mass Change (%) |
|---|
| 0.0 | +12.4 |
| 0.2 | +6.1 |
| 0.4 | 0.0 |
| 0.6 | −5.8 |
| 0.8 | −11.2 |
| 1.0 | −15.3 |
Experiment 2; Effect of Soaking Time
Potato cylinders were soaked in a 0.6 M sucrose solution at 25°C.
Table 2. Soaking Time vs. Mass Change
| Time (min) | Mass Change (%) |
|---|
| 0 | 0.0 |
| 15 | −2.1 |
| 30 | −4.0 |
| 60 | −5.8 |
| 90 | −6.3 |
| 120 | −6.4 |
Question 4. Based on the data in Tables 1 and 2, if a potato cylinder were soaked in a 0.2 M sucrose solution for 60 minutes at 25°C, the most likely result would be:
-
A) a mass loss of approximately 5–6%
-
B) no change in mass
-
C) a mass gain of approximately 6% ✓
-
D) a mass gain of approximately 12%
Explanation: Table 1 shows that at 0.2 M sucrose after 60 minutes, the mass change was +6.1%, a gain, because 0.2 M is below the isotonic point of 0.4 M (the solution is hypotonic relative to the potato, so water moves in). The proposed experiment uses the same concentration (0.2 M), same time (60 min), and same temperature (25°C) as Table 1's 0.2 M row. The result should therefore be approximately +6%, matching Table 1 directly. A mass loss would only occur above the isotonic point (above 0.4 M).
Experiments 1–3
Students investigated osmosis, the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. They placed standardized cylinders of raw potato (initial mass 5.0 g each) into sucrose solutions of varying concentration and measured the percent change in mass after soaking. A positive percent change indicates the cylinder gained mass (water entered the potato); a negative value indicates mass loss (water left the potato).
Experiment 1; Effect of Sucrose Concentration
Potato cylinders were soaked for 60 minutes at 25°C.
Experiment 2; Effect of Soaking Time
Potato cylinders were soaked in a 0.6 M sucrose solution at 25°C.
Experiment 3; Effect of Temperature
Potato cylinders were soaked in a 0.6 M sucrose solution for 30 minutes.
Question 5. The students used potato cylinders with the same initial mass (5.0 g) in all three experiments. What was the most likely reason for this design choice?
-
A) To ensure that differences in mass change were due to osmosis and not to differences in starting mass ✓
-
B) To maximize the rate of osmosis in all experiments
-
C) To prevent the potato from absorbing any sucrose molecules
-
D) To make the results of all three experiments identical
Explanation: Standardizing the initial mass at 5.0 g is a controlled variable designed to eliminate a potential confounding factor. A heavier cylinder has more total water to gain or lose, which could produce a larger absolute mass change even at the same osmotic conditions. By keeping initial mass constant, the students ensured that differences in mass change percentage between trials reflected the effect of the variable being tested, not differences in starting size. This is the same logic behind any controlled variable: hold it constant so it cannot confound the results.