ACT science practice test 17

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.


Metals differ in their relative abilities to conduct electricity. Resistance is a measurement in ohms (Ω) of how much a metal opposes electric current at a particular voltage.

A scientist performed 3 experiments using the circuit shown in Figure 1.

Figure 1

The metal resistor consisted of a coil of metallic wire with a known cross-sectional area and length (see Figure 2).

Figure 2

At the outset, the switch was open and no current flowed through the circuit. A 9-volt battery was used, and the black and red test leads of the circuit were attached to a metal resistor. When the switch was closed, electrons (negatively charged) flowed away from the negative battery terminal, through the circuit, and back to the positive battery terminal. The magnitude of current (charge per unit time) from this electron flow was measured by an ammeter, and was 1.0 × 10-3 coulombs/second for the first trial of each experiment. The resistance (R) of the metal resistor was calculated in ohms (?) from the resulting values for voltage (V) and current (I).

Experiment 1

Three nickel resistor coils, each with a cross-sectional area of 7.61×× 10-10 m2 but with different lengths, were attached separately to the circuit. Results were recorded in Table 1.

Experiment 2

Three gold resistor coils of varying cross-sectional areas were tested. Each resistor coil had a measured length of 100 m. The results were recorded in Table 2.

Experiment 3

Three coils made of different metals were tested. Each resistor had a cross-sectional area of 2.67 × 10-10 m2 and a length of 100 m. The value ρ is related to each metal's inherent resistivity to current flow. Results were recorded in Table 3.

1. In Experiment 2, the scientist varied which of the following aspects of the metal resistor?

A. Identity of the metal coil
B. Cross-sectional area of the coil
C. Length of the coil
D. Value ρ of the metal composing the coil

2. Assume that as ρ increases, a metal's ability to conduct current decreases. Based on the results of Experiment 3, which of the following correctly lists gold, nickel, and tin in order of increasing ability to conduct electrons when shaped as a wire coil?

F. Gold, nickel, tin
G. Gold, tin, nickel
H. Tin, nickel, gold
J. Tin, gold, nickel

3. In the first trial of Experiments 1-3, once the resistor was attached and the switch closed, what charge returned to the positive battery terminal each second?

A. -1.0×× 10-3 coulombs
B. -2.0 ××10-3 coulombs
C. -3.0×× 10-3 coulombs
D. -4.0×× 10-3 coulombs

4. Based on the results of the 3 experiments, the resistor with which of the following values of length, cross-sectional area, and metal type will have the highest current at a given voltage?

Length (m)

F. 100
G. 50
H. 50
J. 50

5. In Experiment 1, the current across the circuit increased and the resistance of the resistor decreased as the:

A. value ρ of the metal resistor increased.
B. cross-sectional area of the metal resistor decreased.
C. length of the metal resistor increased.
D. length of the metal resistor decreased.

6. When the switch is closed in the circuit described in the passage, the battery caused electrons to flow in the direction(s) shown by which of the following diagrams?

F.
G.
H.
J.

Pressure, temperature, volume, and amount of reactant are four variables that affect the rate at which a reaction in the gas phase occurs. A change in any of these variables changes the likelihood of particles running into each other and reacting: Increasing any one increases reaction rate; decreasing any one decreases reaction rate.

Pressure is measured in atmospheres, atm, where 1 atm is the sea level pressure of earth's atmosphere. Volume is measured in liters, L. The amount of reactant is measured in moles, where 1 mole is 6.02 × 1023 molecules.

Figure 1 shows how temperature and pressure affect the gaseous reactants in an experiment. Figures 2 and 3 show how the rate of Reaction A is affected by pressure and temperature, respectively.

Figure 1

Figure 2

Figure 3

7. A scientist claimed that increasing temperature increases the rate at which Reaction A occurs and increasing pressure increases the rate at which Reaction A occurs. Is the scientist's claim supported by the passage and Figures 1-3?

A. Yes; the rate at which Reaction A occurred increased as temperature increased and increased as pressure increased.
B. Yes; the rate at which Reaction A occurred increased as pressure decreased.
C. No; the rate at which Reaction A occurred increased as temperature increased, but decreased as pressure increased.
D. No; the rate at which Reaction A occurred decreased as pressure increased.

8. According to Figures 2 and 3, the reactions occur at the same rate at what pressure and temperature?

F. 20°C and 2.0 atm
G. 40°C and 1.5 atm
H. 50°C and 1.0 atm
J. 70°C and 1.5 atm

9. The amounts of reactants in Reaction A are 1 mole/L of Compound Y and 2 mole/L of Compound Z. According to the passage, the number of molecules of Compound Y is:

A. one quarter of the number of molecules of Compound Z in the reactants.
B. one half the number of molecules of Compound Z in the reactants.
C. equal to the number of molecules of Compound Z in the reactants.
D. twice the number of molecules of Compound Z in the reactants.

10. A scientist tests a new Reaction B. This reaction is conducted with the same gas phase reactants, volume, pressure, and temperature as Reaction A, but the amounts (moles) of reactants are doubled. Based only on the information in the passage and Figures 1-3, how will the rate of Reaction B compare with the rate of Reaction A?

F. Reaction B will be slower than Reaction A because temperature will be lower.
G. Reaction B will be faster than Reaction A because temperature will be lower.
H. Reaction B will be faster than Reaction A because the concentration of reactants is greater, so the likelihood of reactant molecules colliding and reacting is greater.
J. Reaction B will be slower than Reaction A because the concentration of reactants is greater, so the likelihood of reactant molecules colliding and reacting is greater.

11. A chemist wanted to measure Reaction A at the greatest possible reaction rate. She had the ability to change either the temperature or the pressure of the gaseous reactants. Based on the data in Figures 2 and 3, which property did she most likely alter to increase the rate of Reaction A?

A. Pressure, which she decreased from 1 atm to 0.5 atm
B. Pressure, which she increased from 1 atm to 3 atm
C. Temperature, which she decreased from 50°C to 20°C
D. Temperature, which she increased from 50°C to 100°C