Practice Test 4 - ACT Science
20 questions. Answer them in any order, then submit to see your score and every explanation.
- A study was conducted to examine the effect of light wavelength on photosynthesis rate. Light wavelength was varied while keeping carbon dioxide concentration and water supply constant. The oxygen production was measured. Which variable was held constant?
- Which step in Figure 1 introduces a difference that could be mistaken for an effect of wing shape?
- A student measures 10.0 mL of a solution using a 10 mL graduated cylinder with 0.2 mL markings. The meniscus is shown at 9.8 mL. Which value is recorded with appropriate precision?
- Based on Table 1, above which catalyst mass does adding more catalyst produce almost no further gain in yield?
- Based on Table 1, which star has a lower surface temperature but a greater luminosity than Star W?
- To evaluate the effect of caffeine on alertness, participants consumed either a regular coffee or a decaf coffee. Their alertness was tested using a reaction time task. Which hypothesis is being tested?
- Researchers tested the effect of different study techniques on memory retention by using flashcards, summaries, and practice tests. What additional trial would most improve the experiment?
- A scientist investigates the effect of salt concentration on the boiling point of water. The independent variable is the salt concentration, and the dependent variable is the boiling point. Which of the following is the best criticism of this experiment?
- Based on the results of Studies 1, 2, and 3, which of the following pendulums would have the longest period?
- Some coastal marshes show sudden die-offs of cordgrass, leaving bare mud patches that may later recover. Ecologists are debating the main cause. Scientist 1: Scientist 1 proposes that die-offs are driven primarily by prolonged saltwater flooding during unusually high tides. Flooding reduces oxygen in the soil, stressing roots and increasing sulfide buildup. Scientist 1 predicts die-offs will correlate most strongly with the number of hours per week the soil remains waterlogged, even when herbivores are excluded. If flooding is reduced (for example, by improving drainage), Scientist 1 expects cordgrass survival to improve without changing predator or grazer populations. Scientist 2: Scientist 2 argues that overgrazing by marsh crabs is the main driver. In this view, cordgrass can tolerate flooding, but intense grazing removes shoots faster than plants can regrow, especially along creek edges where crabs concentrate. Scientist 2 predicts die-offs will be prevented by crab exclusion cages even if flooding remains high. Scientist 2 expects die-off patches to show clipped stems and higher crab burrow density than nearby healthy areas. Scientist 3: Scientist 3 claims both factors matter, but only together: flooding weakens plants, and crabs then finish them off. Scientist 3 predicts that either factor alone will cause little die-off, but the combination of high flooding and high crab density will cause severe die-off. Scientist 3 expects the strongest die-offs where waterlogging and burrow density are both high. On which point would Scientist 1 and Scientist 2 most likely disagree?
- A study aimed to determine the effect of diet on energy levels by comparing high protein and high carbohydrate diets. Which factor introduces a confounding variable?
- In a drug trial, the researcher measuring symptoms knows which patients got the drug. The design is most prone to:
- Based on Figure 1, the "Stratopause" separates which two atmospheric layers?
- Based on the results of Study 3, if the student used a block with a mass of 5.0 kg on the smooth wood surface at 30°, the force required would be closest to:
- In an experiment to determine the speed of sound, students measure the time taken for an echo to return after a clap. If they do not account for temperature variations, the speed of sound calculated would most likely:
- An experiment tests the effect of water temperature on dissolving sugar. The independent variable is water temperature, and the dependent variable is time taken for sugar to dissolve. What additional trial would most improve the experiment?
- A student investigated how the period of a pendulum depends on pendulum length. Figure 1 shows period versus length. According to Figure 1, the period at a length of 0.80 m is closest to:
- Two hypotheses are proposed to explain the increase in atmospheric CO2. Hypothesis 1 states that fossil fuel combustion is the main cause. Hypothesis 2 suggests that deforestation is the primary factor. Data shows a strong link between fossil fuel use and CO2 levels. Which hypothesis is better supported?
- A student tested how fertilizer affects plant growth. Procedure: (1) Fill 12 pots with the same brand of potting soil. (2) Plant one bean seed per pot at 2 cm depth. (3) Assign 3 pots each to 0 g, 1 g, 2 g, or 3 g fertilizer mixed into the top layer. (4) Water each pot with "about 50 mL" daily using a cup without volume markings. (5) Measure plant height after 14 days using a ruler. The pots were placed on a windowsill; some received direct sunlight longer than others. Expected pattern: moderate fertilizer increases height, but too much may reduce growth. Which procedural error would have the greatest effect on the results?
- Suppose the students performed an additional trial in Study 1 with the light source placed at 25 cm. Based on the trend in Table 1, the number of bubbles produced would most likely be: