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OFFICIAL ACT Form 2176CPRE · Annual 2024

Science

23 questions ~9 min recommended
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In a particular playa (relatively flat, dry desert basin) evidence shows that some large rocks have moved along the surface, leaving shallow trails in the clay sediment, some up to several hundred meters long. Three scientists provided explanations for how these rocks moved. Scientist 1: In the spring, snowmelt from surrounding mountains runs downhill and collects in the playa. At night, cold temperatures cause this water to freeze around the rocks. When temperatures rise again, the ice begins to melt, leaving a layer of mud on the surface and ice "rafts" around the rocks. The buoyancy of the ice rafts floats the rocks on top of the mud such that even light winds can then push the rocks along the surface. Evidence of this lifting is seen in that the trails left by rocks are both shallow and only about 2/3 as wide as the rocks themselves. Due to the combination of ice, mud, and light winds, the rocks are able to move several hundred meters in a few days. Scientist 2: Snowmelt from surrounding mountains does collect in the playa during the spring. However, the temperature in the playa does not get cold enough for ice to form. When the playa's surface gets wet, the top layer of clay transforms into a slick, muddy film. In addition, dormant algae present in the dry clay begin to grow rapidly when the clay becomes wet. The presence of mud and algae1 reduces friction between the rocks and the clay. Even so, relatively strong winds are required to push the rocks along the wet surface, forming trails. Due to the combination of mud, algae, and strong winds, the rocks are able to move several hundred meters in a few hours. Scientist 3: Water does collect in the playa, producing mud and ice. However, neither mud nor ice is responsible for the rocks' movements. The playa is located along a fault line between tectonic plates. Minor vertical shifts in the plates cause the rocks to move downhill, leaving trails. Due to the combination of tectonic plate movement and strong winds, the rocks are able to move only a few meters over several years.

Consider two sound waves—150 Hz and 1,100 Hz—simultaneously emitted from a speaker into air at 20°C and 45% relative humidity. The intensity level of which wave will more likely decrease at a greater rate due to attenuation?

Three studies compared the effects of five sweeteners on food consumption by rats and on the concentrations of leptin and ghrelin. Sweeteners differ only in the percent by mass of fructose and glucose.

1. According to Scientist 2, friction between the rocks and the clay is reduced by which of the following?

2. Suppose a researcher observed that wind speeds greater than 80 miles per hour are needed to move the rocks in the playa. This observation is consistent with which of the scientists’ explanations?

3. Suppose that no seismic activity was recorded in the playa where the trails left by the rocks are found. This finding would weaken which of the scientists’ explanations?

4. Suppose it were discovered that a particular rock formed a 200m long trail in 72hr. Would this discovery support Scientist 1’s explanation?

5. Suppose that during one year there was no measurable movement of any rocks in the playa during the spring. Scientists 1 and 2 would most likely both agree that this was due to the absence of which of the following factors?

6. Suppose that air temperature in the playa varies between 4°C and 47°C. Would this information support the explanation of Scientist 2?

7. How many grams of fructose would be present in 200 g of a sweetener composed of 46% fructose?

8. If another trial had been performed in Experiment 2 and 450mL of liquid had been measured in the cylinder, the temperature of the diet cola in this trial would most likely have been:

9. Suppose Trial 6 had been repeated, but the bottle of diet cola had been opened and then left undisturbed at 25°C for 12 hours before it was attached to the apparatus. Would the mass of CO produced in this trial likely be greater than 0.969 g or less than 0.969 g?

10. One millimole (mmol) of CO has a mass of 0.044g. How many trials resulted in the production of at least 1 mmol of CO?

11. According to Figure 1, which of Tube A and Tube B, if either, had at least one end submerged in a liquid before the clamp was removed?

12. Assume that room temperature is 25°C. In how many trials was the diet cola tested at a temperature lower than room temperature?

13. According to Figure 1, as the nickel concentration in the nutrient solutions increased, the average iron content of Species M plants:

14. According to Table 1, the Species U plants that were fed the solution that had a pH of 6 and a nickel concentration of 10μM had an average dry mass of:

15. According to Table 1, Species M plants that were fed a nutrient solution with which of the following combinations of pH and nickel concentration had the greatest average dry mass?

16. According to Table 1 and Figure 1, the Species M plants that were fed Solution 3 had an average zinc content of:

17. According to the results of Experiment 1, for any given catalyst, as the temperature was increased, the number of cycles needed to complete the reaction:

18. In Experiment 1, 26 cycles were needed to complete the reaction at 450°C when which catalyst was used?

19. The movement of H and N through the apparatus as Steps 1−4 occurred is best represented by which of the following expressions?

20. Consider the results of Experiment 1 for 375°C. All H and N were consumed in less than 20 cycles when which catalysts were used?

21. If a trial had been performed in Experiment 2 at 425°C and 225atm, the amount of NH produced would most likely have been:

22. At 1 atm of pressure, the melting point of NH is −77°C and the boiling point of NH is −33°C. Based on this information and the description of the apparatus, when the NH exited the condenser, was it more likely a solid or a liquid?

23. Consider the trial in Experiment 2 that produced 550 kg of NH. Based on Figure 1, the number of cycles that were needed to complete the reaction in this trial was most likely:

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