ACT science practice test 74

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.

In a study of the effects of Ritalin and Adderall on children with ADHD, subjects were given one of four possible doses of medication. Their behavior in social and academic settings was then monitored and rated. The four possible doses were placebo (P), Ritalin given once in the morning (R1), Ritalin given twice daily (R2), or Adderall given once in the morning (A1).

The results for each group were averaged. Figure 1 shows the average behavioral rating (on a scale of 0–15, with 0 meaning no undesirable behavior) at various time periods throughout the day. Figure 2 shows the percentage of children who demonstrated side effects at a moderate or severe level on at least one day.


Figure 1


Figure 2

1. Based on Figure 1, during which of the following time periods was the average behavior rating most similar for the four groups of children?

F. 8:15–9:25
G. 9:25–10:35
H. 10:35–11:45
J. 3:35–4:45

2. A scientist claimed that children given one dose of Adderall daily would exhibit fewer behavior problems than children given either one or two doses of Ritalin daily. During which of the following time periods shown in Figure 1 are the results inconsistent with this claim?

A. 9:25–10:35
B. 10:35–11:45
C. 2:35–3:35
D. 3:35–4:45

3. According to Figure 2, for the group given Ritalin twice daily, the percentage of children who experienced an adverse side effect was greatest for which side effect?

F. Dull
G. Headache
H. Withdrawn
J. Appetite loss

4. According to Figure 1, which dose of medication was the least successful in controlling children’s behavior problems from 3:35–4:45?

A. P
B. R1
C. R2
D. A1

5. Suppose four groups of children were given one of the four possible medication regimens. Between 12:15 and 1:25, one group had a behavior rating of 5. Which medication regimen was most likely given to them?

F. P
G. R1
H. R2
J. A1

6. Assume that an ideal medication is one that has the fewest side effects, yet is most effective. Based on the data provided, which dose of medication is the most ideal?

A. P
B. R1
C. R2
D. A1

A solution consists of a solute dissolved in a solvent. For example, in a saltwater solution, the salt is the solute and the water is the solvent. Osmosis is the movement of solvent molecules across a barrier in order to equalize solution concentrations. When a saltwater solution is placed in a u-shaped tube with a selectively permeable barrier or semipermeable membrane, the phenomenon of osmotic pressure can be observed. Osmotic pressure is the pressure required to prevent the flow of a solvent across a barrier. In Figure 1, saltwater was poured in the right half of the tube and pure water was poured in the left half of the tube. As water passes from left to right in the figure below due to osmosis, the level of solution on the right rises. Eventually, the weight of the solution due to gravity becomes sufficient to prevent the further flow of water from right to left.


Figure 1

The following experiments were carried out to study how varying the molecular weight percentage of solvents and the temperature of solutions affects osmotic pressure. Table 1 shows the molecular weight percentages of the different solvents studied and Table 2 displays the temperatures of the various solutions used.

Table 1


Table 2


Experiment 1

A 1000 ml u-shaped tube was fitted with a semipermeable membrane and 300 ml of solution was added on the right half and 300 ml of water was added on the left half. Table 1 shows the four solutions used in four separate trials of Experiment 1. The percent weight was measured by computing the ratio of the weight of the solute (salt) to the weight of the solution after dissolution. Every 5 seconds, the height of the solution on the right side of the tube was measured and recorded. Figure 2 shows the results of Experiment 1 recorded at 20°C.


Figure 2

Experiment 2

Four more trials were performed but only the 10% solution was used. For each trial, the temperature was varied as shown in Table 2 and the results were graphed in Figure 3. In each trial, the height was measured 5 minutes after the water and solution were poured.


Figure 3

7. Based on Figure 2 and Table 2, which solution resulted in the greatest osmotic pressure after 30 seconds?

F. Solution 1
G. Solution 2
H. Solution 3
J. Solution 4

8. Based on the results of Experiment 2, what is the relationship between osmotic pressure and temperature?

A. Osmotic pressure increases with an increase in temperature.
B. Temperature and osmotic pressure are unrelated.
C. Osmotic pressure decreases with an increase in temperature.
D. Five minutes was insufficient time to allow the effects of osmotic pressure to be observed.

9. Based on Experiment 1, how does solution concentration affect osmotic pressure?

F. Osmotic pressure increases with concentration.
G. Osmotic pressure decreases with concentration.
H. There is no relationship between osmotic pressure and concentration.
J. The results were inconclusive because all solution heights were still fluctuating after 30 seconds.

10. Was Experiment 1 successful in determining the relative osmotic pressure of the four solutions tested?

A. Yes. There is a clear difference in osmotic pressure between the four solutions with Solution 1 having the greatest osmotic pressure.
B. Yes. There is a clear difference in osmotic pressure between the four solutions with Solution 4 having the greatest osmotic pressure.
C. No. All osmotic pressures were too similar to make any determination.
D. No. All solution heights were still fluctuating after 30 seconds.

11. Reverse osmosis occurs when the solvent flows from a solution of higher concentration to a solution of lower concentration. In Experiments 1 and 2, reverse osmosis can be observed by pouring more solution in the right side of the tube. Assuming the pressure required for reverse osmosis occurs at twice the osmotic pressure, approximately what volume of the 30% solution in Experiment 1 would have to be added for reverse osmosis to occur?

F. 0.7 atm
G. 1.2 atm
H. 2.8 atm
J. 3.2 atm

12. Data in Figure 2 is consistent with which of the following trials?

A. Trial 1 and Trial 3
B. Trial 1 only
C. Trial 2 only
D. Trial 2, Trial 3, and Trial 4