ACT science practice test 66

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.

Ohm’s law states that V = I × R and WRC/L where V = voltage, I = current, R = resistance, C = cross-sectional area of the wire, W = resistivity of the wire, and L = length of the wire. Using the circuit pictured in Figure 1, a student performed two experiments.


Figure 1

Experiment 1

A 5 V battery was used and the resistance was varied. Table 1 displays the results.

Table 1


Experiment 2

A battery of 1 volt was used and three different wires, each with the same resistivity and length, were used to complete the circuit. Table 2 shows the results and Figure 2 shows the relationship between the diameter of the wire and the measured resistance of each wire.

Table 2



Figure 2

1. In Table 1, what is true about the relationship between current and resistance?

F. As resistance increased, current increased.
G. As resistance increased, current was unchanged.
H. As resistance increased, current decreased.
J. There is no relationship between current and resistance.

2. Based on Table 2 and Figure 1, it could be determined that a wire with a diameter of .5 mm would have a resistance close to:

A. 2.6 ohms.
B. 1.0 ohms.
C. .5 ohms.
D. .25 ohms.

3. In Experiment 2, which of the following factors was varied?

F. Voltage of the battery
G. Diameter of the wire
H. Length of the wire
J. The material of the wire

4. The following hypothesis was put forth prior to the experiments: Current is inversely related to resistance. An inverse relationship implies that when one quantity increases, the other decreases. Do Tables 1 and 2 support this hypothesis?

A. No. Experiment 1 contradicts the hypothesis and shows a direct relationship between current and resistance. The current increases with the resistance.
B. No. Experiment 2 contradicts the hypothesis and shows a direct relationship between current and resistance. The current increases with resistance.
C. Yes. The results of both experiments show an inverse relationship between current and resistance. When the resistance increases, current decreases.
D. No. Neither experiment shows any relationship between current and resistance.

5. Using the circuit in Figure 1 and the results of both experiments, which of the following conditions would result in the largest current?

F. 5-volt battery, .5-mm wire
G. 5-volt battery, .25-mm wire
H. 2.5-volt battery, .5-mm wire
J. 2-volt battery, .25-mm wire

6. Based on the information in the passage, figures, and tables, which of the following sets of conditions would most likely produce a current of about 5 amperes (assume the wire used is the same wire in Experiment 2)?

A. Voltage: 5 volts; wire diameter: .7 mm
B. Voltage: 10 volts; wire diameter: 1 mm
C. Voltage: 1 volt; wire diameter: .2 mm
D. None of the above conditions would produce a current near 5 amperes.

Scientists tested a new method of titration, called atomic absorption inhibition titration (AAIT). They ran a series of experiments to determine if AAIT could be used successfully to determine the presence of phosphate, silicate, and sulfate in river and waste water. AAIT involves continually adding magnesium to a stirred sample solution while monitoring the solution for magnesium absorption.

Experiment 1

The scientists conducted an experiment to determine the effect of sulfate on titration of phosphate. Four trials were conducted, varying the concentration of both the sulfate and the magnesium used for the titration. Table 1 displays the results of the AAIT for solutions containing phosphate and sulfate and varying concentrations of magnesium.

Table 1


Experiment 2

Analysis of water from the Milwaukee River was performed. Solutions containing phosphate and sulfate were analyzed using AAIT. Titrations were performed on river water, river water plus the addition of phosphate, and standardized phosphate solution. The endpoint was noted for each trial when the titration reached the conditions under which only silicate would be detected. Table 2 shows the data collected, in ml.

Table 2


Experiment 3

Scientists created artificial waste water by adding phosphate, silicate, and sulfate to water and then conducting AAIT to simultaneously determine how much of each substance was in the water. Four titrations were conducted. Table 3 displays the results.

Table 3


7. According to the data in Table 2, which trial resulted in the most silicate being detected in river water?

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

8. Based on the information presented in Table 3, which trial resulted in less PO4 being found than was initially added?

A. Trial 1
B. Trial 2
C. Trial 3
D. Trial 4

9. Before conducting Experiment 1, the scientists hypothesized that the higher the concentration of Mg used, the more Mg that would be absorbed. Do the results of the experiment support the hypothesis?

F. Yes. For each trial as the concentration of Mg used increased from 2.5 to 4.5 ppm, more Mg was absorbed.
G. Yes. Table 1 shows that the most Mg absorbed was during Trial 1 and with an Mg concentration of 2.5 ppm.
H. No. The opposite has been shown to be the case. For each trial as the Mg concentration increased, the amount of Mg absorbed decreased.
J. No. There is not a clear relationship between the Mg concentration and the amount of Mg absorbed.

10. Based on the results of Experiment 2, what type of solution was found to reach the endpoint with the least amount of solution?

A. Phosphate and sulfate
B. Standardized phosphate solution
C. River water
D. River water plus phosphate

11. The data in Table 1 supports which of the following statements?

F. The titrations done using Mg with a concentration of 4.0 ppm resulted in the most Mg being absorbed.
G. The titrations done using Mg with a concentration of 2.5 ppm resulted in the least Mg being absorbed.
H. With a Mg concentration of 4.5 ppm, as the titrations included more concentrated SO4, less Mg was absorbed.
J. With a Mg concentration of 4.5 ppm, as the titrations included more concentrated SO4, more Mg was absorbed.