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Research summaries practice
ACT ACT Science · 181 questions in the bank
Research Summaries passages describe two or three related experiments in sequence and ask six or seven questions about them. The reading is not hard. Keeping straight what changed between the experiments is.
Map the variables before you answer anything and most of the questions become lookups.
How to answer these
- Find the one thing that changed. Read down the table, not across. Whichever column varies from row to row inside a single experiment is what they manipulated.
- Note it in the margin. 'Exp 1 = temperature. Exp 2 = concentration. Exp 3 = time.' Three short notes map the whole passage.
- Know what a control is for. The trial with the treatment left out exists to answer one question: would this have happened anyway?
- Find the shared condition. Questions combining two experiments are only answerable because the experiments overlap somewhere. That repeated trial is the hinge.
What the wrong answers look like
- Confusing manipulated with measured. The variable they set and the variable they recorded are different columns, and questions exploit the mix-up.
- Comparing across experiments with nothing in common. If there is no shared condition, the honest answer is often that it cannot be determined.
- Reading a purpose question as a data question. 'Why was this trial included' wants the word baseline, not a number.
- Extrapolating without bounding. Prediction questions want a direction and a range, not a calculated value.
Practice questions
Four real questions from the CruxStudy bank, with the keyed answer marked and the explanation behind a click so you can try them first.
Example 1Easier
Catalase, an enzyme in potato tissue, breaks hydrogen peroxide down into water and oxygen gas. In every trial, students sealed 5 mL of 3% hydrogen peroxide in a tube with potato tissue and measured the volume of oxygen gas collected in 60 s.
Experiment 1: One 1 cm potato cube was used at pH 7, and the tube was held at each of six temperatures.
Experiment 2: One 1 cm potato cube was used at 40 °C, and the peroxide solution was buffered to each of five pH values.
Experiment 3: The tube was held at 40 °C and pH 7, and the number of 1 cm potato cubes was varied.
| Experiment | Condition | O2 collected in 60 s (mL) |
|---|
| 1 | 10 °C | 2.1 |
| 1 | 20 °C | 4.0 |
| 1 | 30 °C | 6.8 |
| 1 | 40 °C | 9.5 |
| 1 | 50 °C | 5.2 |
| 1 | 60 °C | 0.4 |
| 2 | pH 3 | 1.0 |
| 2 | pH 5 | 4.4 |
| 2 | pH 7 | 9.4 |
| 2 | pH 9 | 5.1 |
| 2 | pH 11 | 0.6 |
| 3 | 1 cube | 9.5 |
| 3 | 2 cubes | 18.6 |
| 3 | 3 cubes | 27.4 |
| 3 | 4 cubes | 36.0 |
In Experiment 1, as the temperature was raised from 10 °C to 40 °C, the volume of O2 collected in 60 s:
- increased only correct
- decreased only
- increased, then decreased
- stayed the same
Show the explanation
Over that range the Experiment 1 values climb steadily: 2.1, 4.0, 6.8, and 9.5 mL. The drop to 5.2 mL and 0.4 mL happens only above 40 °C, outside the range the question asks about.
Example 2Medium
Catalase, an enzyme in potato tissue, breaks hydrogen peroxide down into water and oxygen gas. In every trial, students sealed 5 mL of 3% hydrogen peroxide in a tube with potato tissue and measured the volume of oxygen gas collected in 60 s.
Experiment 1: One 1 cm potato cube was used at pH 7, and the tube was held at each of six temperatures.
Experiment 2: One 1 cm potato cube was used at 40 °C, and the peroxide solution was buffered to each of five pH values.
Experiment 3: The tube was held at 40 °C and pH 7, and the number of 1 cm potato cubes was varied.
| Experiment | Condition | O2 collected in 60 s (mL) |
|---|
| 1 | 10 °C | 2.1 |
| 1 | 20 °C | 4.0 |
| 1 | 30 °C | 6.8 |
| 1 | 40 °C | 9.5 |
| 1 | 50 °C | 5.2 |
| 1 | 60 °C | 0.4 |
| 2 | pH 3 | 1.0 |
| 2 | pH 5 | 4.4 |
| 2 | pH 7 | 9.4 |
| 2 | pH 9 | 5.1 |
| 2 | pH 11 | 0.6 |
| 3 | 1 cube | 9.5 |
| 3 | 2 cubes | 18.6 |
| 3 | 3 cubes | 27.4 |
| 3 | 4 cubes | 36.0 |
Suppose the pH 7 trial of Experiment 2 were repeated with the tube held at 60 °C instead of 40 °C. Based on Experiments 1 and 2, the volume of O2 collected in 60 s would most likely be closest to:
- 0.4 mL correct
- 5.1 mL
- 9.4 mL
- 18.6 mL
Show the explanation
Experiment 1 was run at pH 7, and its 60 °C trial produced only 0.4 mL, so a pH 7 trial at 60 °C should give about that much. The values near 9 mL come from 40 °C trials, and 18.6 mL required two cubes rather than one.
Example 3Harder
Bean seedlings of one variety were grown in identical pots of sterilized sand in a greenhouse. After 21 days each seedling was dried and weighed, and the mean dry mass per seedling was recorded.
Study 1: Seedlings received 12 h of light per day. Nitrogen fertilizer was supplied at five concentrations.
Study 2: Seedlings received nitrogen fertilizer at 50 mg/L. Daily light was varied from 4 h to 20 h.
Study 3: Seedlings received 100 mg/L nitrogen and 12 h of light per day. Half the pots were inoculated with a soil fungus that grows on bean roots; the rest were left uninoculated.
| Study | Condition | Mean dry mass (g) |
|---|
| 1 | 0 mg/L N | 0.8 |
| 1 | 25 mg/L N | 1.6 |
| 1 | 50 mg/L N | 2.5 |
| 1 | 100 mg/L N | 3.1 |
| 1 | 200 mg/L N | 2.9 |
| 2 | 4 h light | 0.9 |
| 2 | 8 h light | 1.8 |
| 2 | 12 h light | 2.5 |
| 2 | 16 h light | 3.0 |
| 2 | 20 h light | 3.0 |
| 3 | 100 mg/L N, no fungus | 3.1 |
| 3 | 100 mg/L N, with fungus | 4.4 |
Suppose seedlings were grown with 100 mg/L nitrogen, 20 h of light per day, and the soil fungus added. Based on all three studies, their mean dry mass would most likely be:
- less than 0.8 g
- between 0.8 g and 2.5 g
- between 2.5 g and 3.1 g
- greater than 4.4 g correct
Show the explanation
Seedlings at 100 mg/L with 12 h of light and the fungus already reached 4.4 g, and Study 2 shows that going from 12 h to 20 h of light raises mass by about 0.5 g. Both changes push the result upward, so it should exceed 4.4 g rather than fall back toward the fungus-free values.
Example 4Medium
Catalase, an enzyme in potato tissue, breaks hydrogen peroxide down into water and oxygen gas. In every trial, students sealed 5 mL of 3% hydrogen peroxide in a tube with potato tissue and measured the volume of oxygen gas collected in 60 s.
Experiment 1: One 1 cm potato cube was used at pH 7, and the tube was held at each of six temperatures.
Experiment 2: One 1 cm potato cube was used at 40 °C, and the peroxide solution was buffered to each of five pH values.
Experiment 3: The tube was held at 40 °C and pH 7, and the number of 1 cm potato cubes was varied.
| Experiment | Condition | O2 collected in 60 s (mL) |
|---|
| 1 | 10 °C | 2.1 |
| 1 | 20 °C | 4.0 |
| 1 | 30 °C | 6.8 |
| 1 | 40 °C | 9.5 |
| 1 | 50 °C | 5.2 |
| 1 | 60 °C | 0.4 |
| 2 | pH 3 | 1.0 |
| 2 | pH 5 | 4.4 |
| 2 | pH 7 | 9.4 |
| 2 | pH 9 | 5.1 |
| 2 | pH 11 | 0.6 |
| 3 | 1 cube | 9.5 |
| 3 | 2 cubes | 18.6 |
| 3 | 3 cubes | 27.4 |
| 3 | 4 cubes | 36.0 |
Which statement best describes how each added potato cube changed the total O2 collected in Experiment 3?
- Each added cube raised the total by slightly less than the cube before it did correct
- Each added cube raised the total by slightly more than the cube before it did
- Each added cube doubled the total collected
- Adding cubes had no measurable effect on the total collected
Show the explanation
The step sizes are 9.1 mL (1 to 2 cubes), 8.8 mL (2 to 3), and 8.6 mL (3 to 4), a slowly shrinking gain. Doubling would require 38.0 mL at 4 cubes rather than the 36.0 mL recorded, and the totals plainly change as cubes are added.
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Common questions
What is the difference between the independent and dependent variable?
The independent variable is the one deliberately changed between trials; the dependent variable is what gets measured as a result. On ACT Science, the independent variable is whichever column varies inside a single experiment.
Why do experiments include a control?
To show what happens without the treatment, so you can tell whether the treatment did anything. If a question asks what a study is missing, look for the comparison nobody ran.
How do I answer questions that combine two experiments?
Find the condition that appears in both. That shared trial links the two tables and lets you carry a value from one into the other.