ACT science practice test 19

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.


Despite a global campaign since 1988 to eradicate poliomyelitis (polio), the virus that causes this disease continues to be endemic in four countries. This polio virus, which can exist as Type 1, Type 2, or Type 3, is most often transmitted through water that is contaminated by human waste. People can be immunized from this virus with a highly effective vaccine, which can be administered orally or by injection. Recent analyses of polio virus transmission have focused on the four polio-endemic countries India, Pakistan, Afghanistan, and Nigeria.

Study 1

In 2004, a temporary ban on polio vaccines was instituted in Nigeria in response to concerns that they were contaminated. Researchers reviewed World Health Organization (WHO) records to determine the number of Type 1 polio virus infections that were reported in Nigeria in 2004 and tallied their findings by month (see Figure 1). The World Health Organization has noted that in polio-endemic countries, official records underestimate the number of people actually infected, because numerous infected individuals do not report their symptoms to clinics or rely on local therapists who are not surveyed. In a polio-endemic country, for every person who has reported an infection, as many as ten people may actually be infected in the local population.

Figure 1

Study 2

Although polio eradication efforts have been most consistent in the urban areas of polio-endemic countries, these areas also have a high risk for a reemergence of polio, especially when the large urban populations are exposed to water contaminated with wastes that harbor the polio virus. In 2007, researchers analyzed the number of people who reported infections with Type 3 polio virus in the five largest cities in India. These cities were Mumbai in western India, New Delhi and Kolkata in northern India, and Chennai and Hyderabad in southern India. The analysis was undertaken in the months of June and August. June 2007 was chosen as a representative month for the dry summer season in India, during which there was minimal rainfall. August 2007 was chosen as a representative month for the wet monsoon season in India, during which there was daily rainfall. The results of the findings are shown in Figure 2.

Figure 2

1. According to Figure 1, the greatest increase in the number of reported polio infections in Nigeria occurred between which two months?

A. January and February
B. February and March
C. April and May
D. November and December

2. It is estimated that for every person infected with the polio virus in an endemic country, there are 200 people at risk for contracting the virus. Given the results of Study 1, how many people would have been at risk for becoming infected with the polio virus in Nigeria in June 2004?

F. 80
G. 200
H. 800
J. 16,000

3. Given the information in Figure 2, which of the following might explain the difference in reported cases of polio in major Indian cities between June and August of 2007?

A. Water is more likely to become contaminated with polio-infected human waste in periods of high rainfall.
B. Water is less likely to become contaminated with polio-infected human waste in periods of high rainfall.
C. The polio virus infects more people in India during the summer and monsoon seasons than during the autumn and winter seasons.
D. Those diagnosed with the polio virus in June are able to recover by August.

4. Which of the following hypotheses was most likely tested in Study 2?

F. The number of reported cases of polio infections varies significantly between Nigeria and India.
G. Most cases of polio infections are not reported to medical authorities in India.
H. Poliomyelitis infections affect more people in certain regions in India than in other regions.
J. The number of reported cases of polio infections in India is greatest during the summer and least during the winter.

5. Polio-endemic countries are located in warm climates that harbor many mosquitoes. Would the presence of mosquitoes directly affect the transmission of the polio virus?

A. Yes, because the polio virus is primarily transmitted through mosquitoes.
B. Yes, because the polio virus is primarily transmitted through human waste.
C. No, because the polio virus is primarily transmitted through mosquitoes.
D. No, because the polio virus is primarily transmitted through human waste.

6. The comparison of reported polio infections in India in 2007, as shown in Figure 2, indicates that relative to the number of people in Kolkata infected with polio in June, the number of people infected with polio in Kolkata in August was approximately:

F. half as much.
G. the same.
H. twice as much.
J. ten times as much.

Osmotic pressure (Π) is the amount of pressure, in atm, required to maintain equilibrium of a solvent across a semipermeable membrane. At a constant temperature, osmotic pressure is dependent only on a solute’s ability to dissociate or ionize in the solvent (van ’t Hoff factor, i) and the concentration of solute particles. The osmotic pressure is determined by the equation:

M represents the concentration (in molarity, M), R is the ideal gas constant (0.0821 L atm mol?1 K?1), and T (300 K) is the temperature in Kelvin (K). The value of R is assumed to be a constant for all osmotic pressure calculations.

The dissociation of a solute depends on its unique chemical properties. The van ’t Hoff factors for some common substances are displayed in Table 1. Higher van ’t Hoff factors correlate with greater dissociation or ionization. The effect of the van ’t Hoff factor on the osmotic pressure may be seen in Figure 1.

Table 1
Substancevan ’t Hoff factor *
sucrose1.0
NaCl1.9
MgCl22.7
FeCl33.4
*Values at 300 K

Figure 1

7. According to Figure 1, which of the following solutions would exhibit the least osmotic pressure?

A. 1.0 M FeCl3 solution
B. 1.0 M MgCl2 solution
C. 2.0 M NaCl solution
D. 2.0 M sucrose solution

8. If 1.0 M solutions of various solutes were prepared, which of the following solutions would have the highest level of ionization?

F. Sucrose
G. NaCl
H. MgCl2
J. FeCl3

9. Which of the following solutions would exhibit the closest osmotic pressure to that of a 1.5 M NaCl solution at 300 K, if the gas constant is 0.0821 L atm/ mol-1 K-1?

A. 1.0 M NaCl solution (i = 1.9)
B. 2.0 M NaCl solution (i = 1.9)
C. 2.9 M Sucrose solution (i = 1.0)
D. 3.5 M Sucrose solution (i = 1.0)

10. Based on Figure 1, as the concentration of solute decreases, the pressure required to hold solvent concentration across a membrane at equilibrium will:

F. increase only.
G. decrease only.
H. remain constant.
J. increase, then remain constant.

11. A scientist recently discovered a compound that ionizes readily in solution (i = 3.8) and results in low osmotic pressures. Are the findings of this scientist consistent with Figure 1?

A. Yes, because FeCl3 causes higher osmotic pressure than sucrose.
B. No, because sucrose causes higher osmotic pressure than FeCl3.
C. Yes, because FeCl3 causes lower osmotic pressure than sucrose.
D. No, because sucrose causes lower osmotic pressure than FeCl3.