Practice Test 1 - ACT Science

20 questions. Answer them in any order, then submit to see your score and every explanation.

Engineers test why some lithium-ion phone batteries lose capacity faster than others after many charge cycles. Three engineers propose different primary causes. Scientist 1: Scientist 1 hypothesizes that high charging voltage accelerates electrolyte oxidation and structural changes in the cathode. Charging to 100% (higher voltage) stresses the cathode more than stopping at 80%. Scientist 1 predicts that batteries repeatedly charged only to 80% will retain more capacity than those charged to 100%, even at the same temperature. Scientist 2: Scientist 2 argues that high temperature is the dominant factor because it speeds up unwanted side reactions, including growth of the solid-electrolyte interphase (SEI) on the anode. Scientist 2 predicts that batteries cycled at $35\,^{\circ}\mathrm{C}$ will degrade faster than those at $20\,^{\circ}\mathrm{C}$ , regardless of whether they charge to 80% or 100%. Scientist 3: Scientist 3 suggests that high charge/discharge current (fast charging and heavy use) causes lithium plating and mechanical stress. Scientist 3 predicts that batteries charged slowly will last longer than those fast-charged, even if both reach the same final voltage and temperature. How do the hypotheses of Scientist 1 and Scientist 2 differ?
Which model tracks the young trees closely and then departs the most from the measurements as the trees age?
Student A believes the primary reason for ice melting at the poles is global warming. Student B suggests it is due to natural climate variability. Which statement is consistent with Student B's viewpoint but not Student A's?
In a study testing whether temperature affects bacterial growth, cultures are grown at varying temperatures. Which hypothesis is being tested?
In an experiment testing the effect of sugar concentration on yeast fermentation rate, the sugar concentration serves as:
Based on Table 1, which planet has the greatest average density?
Based on Figure 1, at which labeled point is the ground steepest?
A school notices that some classrooms have higher carbon dioxide (CO $_2$ ) levels by afternoon. Building scientists debate why. Scientist 1: Scientist 1 claims the main cause is insufficient ventilation. With many students exhaling CO $_2$ , levels rise unless fresh air exchange is high. Scientist 1 predicts CO $_2$ will correlate strongly with measured air exchange rate and that increasing ventilation will lower CO $_2$ even with the same class size. Scientist 2: Scientist 2 argues occupancy is the main driver. Even with adequate ventilation, more students produce more CO $_2$ . Scientist 2 predicts CO $_2$ levels will scale with the number of occupants and time spent in the room, and that reducing class size will lower CO $_2$ without changing the HVAC system. Scientist 3: Scientist 3 proposes that classroom CO $_2$ sensors drift over time, creating apparent differences that are partly measurement error. Scientist 3 predicts recalibration will reduce differences among rooms. On which point would Scientist 1 and Scientist 2 most likely disagree?
A student tested the hypothesis that increasing salt concentration slows yeast fermentation. She prepared 4 sugar-yeast solutions, each with 10.0 g sugar, 1.0 g dry yeast, and 100 mL water in identical 250 mL flasks. She added table salt to reach salt concentrations of 0%, 1%, 2%, or 3% (mass/volume). Each flask was kept in a 35°C water bath for 20 minutes. After sealing each flask with a balloon, she measured the circumference of the balloon (in cm) as an indicator of CO $_2$ produced. All flasks used the same yeast brand, same sugar mass, same water volume, and the same incubation time. Which of the following is the independent variable?
According to Figure 1, the image forms at what distance from the lens?
According to Table 1, running at 1.0 km/hr causes the metabolic rate of the Lizard to increase by approximately what factor compared to its resting rate?
A student examined whether paint color affects drying time. Four identical wooden boards were painted with the same brand of paint in different colors: white, red, blue, and black. The independent variable was color. The dependent variable was time to "dry," defined as when the surface no longer felt sticky to the student's finger. Boards were placed outdoors in sunlight. Results: white 55 min, red 60 min, blue 58 min, black 40 min. The student concluded black paint dries fastest because it absorbs more heat. Which change would most improve measurement validity?
A biology club tested whether a sugar solution increases yeast fermentation rate. They prepared two flasks: Flask S contained 100 mL of 10% sugar solution and yeast; Flask W contained 100 mL of water and yeast. The dependent variable was CO $_2$ produced after 15 minutes, measured by the volume of gas in a balloon attached to each flask. Results: Flask S balloon circumference 28 cm; Flask W circumference 8 cm. The club concluded sugar increases fermentation. However, Flask S was placed on a warm lab bench near a heater, while Flask W was on a cooler table. Which variable was NOT controlled in this study?
A student tested how the type of metal affects corrosion rate in saltwater. Equal-sized strips of iron, copper, aluminum, and zinc were cleaned the same way and then placed into separate beakers containing 200 mL of 3.5% saltwater. All beakers were kept at the same temperature and left undisturbed for 7 days. Corrosion was measured by the mass lost (g) from each strip after drying. Which of the following is the independent variable?
Student A argues that climate change is primarily driven by carbon emissions. Student B suggests it's due to natural climate cycles. On which point would Student A and Student B most likely disagree?
A student measured how the boiling point of water changes with altitude. Figure 1 shows boiling point versus altitude. Based on Figure 1, the boiling point at 1,500 m altitude is closest to:
Based on Figure 1, the count of which group increased by the greatest factor after restoration?
To determine the effect of soil pH on plant growth, researchers grew plants in soils with different pH levels and measured plant biomass after 8 weeks. Sunlight and water were kept constant. Which of the following was measured?
According to Table 1, how much more runoff did the paved watershed produce than the forested watershed after 30 mm of rainfall?
A lab group investigated whether a caffeine solution increases heart rate in Daphnia (water fleas). Hypothesis: higher caffeine concentration increases Daphnia heart rate. Procedure: (1) Prepare caffeine solutions at 0.0% (control), 0.1%, and 0.5% (mass/volume) in pond water. (2) Place one Daphnia in a depression slide with 1 mL of solution and allow 2 minutes to acclimate. (3) Under a microscope, count heartbeats for 15 seconds and multiply by 4 to estimate beats/min. (4) Repeat for 10 Daphnia per concentration. (5) The same student performed all counts to reduce observer variation. The group compared mean beats/min among concentrations. A flaw in the experimental design is that:

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