ACT science practice test 73

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.

Students crystallized an impure, solid compound. First, they added just enough hot solvent to dissolve the compound. They then allowed the hot solution to cool, whereupon crystals began to form. Finally, the solution was placed in an ice bath to complete the crystallization process (see Figures 1 and 2). Figure 3 illustrates the progression of crystallization.



1 Solution added, undersaturated

2 Solution cools to saturation

3 Concentration decreases with crystal growth

4 Crystal growth during main cooling cycle

5 Supersaturated

Figure 3

Solubility (the amount of solute that will dissolve in a specific solvent) and crystallization are directly related. Since crystallization cannot begin until the solution becomes saturated, the faster a compound dissolves, the more quickly it can begin to form into crystals.

Study 1

Students tested the solubility of four different substances. The temperature was measured in °C, and water was used as the solvent. The results of the study are displayed in Figure 4.


Figure 4

1. In a solution of 60°C water, which sample from Study 1 would begin the crystallization process first?

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

2. A fifth sample was tested for solubility under the same conditions as in Study 1. The solubility at 30°C was 20%. How did the solubility of Sample 5 compare with that of Samples 1–4?

A. It was lower than Samples 1–4.
B. It was higher than Samples 1–4.
C. It was lower than Samples 3 and 4 but higher than Samples 1 and 2.
D. It was lower than Samples 1–3 but higher than Sample 4.

3. According to Figure 4, the solubility of Sample 1 at a water temperature of 30°C was closest to which of the following?

F. 20%
G. 60%
H. 80%
J. 95%

4. Based on the information in the passage and Figure 3, the solution was most likely placed in an ice bath at which of the following points?

A. 1
B. 2
C. 4
D. 5

5. Based on Figure 3, which of the following best explains the relationship between temperature and crystallization?

F. As temperature decreases, crystallization increases.
G. As temperature increases, crystallization increases.
H. As temperature decreases, crystallization decreases.
J. Temperature and crystallization do not affect one another.

Blood type is a hereditary trait. The type is established by the genes inherited from the mother and father. The ABO system is widely accepted as the best blood classification system. In the ABO system, there are four types of blood: A, B, AB, and O. The combination of inherited genes is known as the genotype and the actual blood type is known as the phenotype. The genes ensure that only the blood cells of the proper blood type remain in the body.

Table 1


The Rh (+/–) factor is inherited separately from the blood type. It is possible to have the Rh+ phenotype yet still carry the recessive gene for Rh–. The Rh+ (R) is the dominant gene and Rh– (r) is recessive. Table 2 shows the Rh phenotypes resulting from the various genotypes inherited from parents.

Table 2


The surface of every red blood cell is covered with proteins. Rh factor and blood type determine the proteins and the compatibility of donated blood as shown in Table 3.

Table 3


6. According to Table 1, parents with blood types O and B can only produce offspring with which blood types?

A. B or O
B. A or B
C. A or O
D. A

7. Parents with which blood types could produce offspring with AB+ blood?

F. O+ and A–
G. A– and B+
H. AB– and AB–
J. B+ and B+

8. A person who can donate blood to anyone could have parents with which of the following blood types?

A. A+ and AB–
B. AB– and AB–
C. B– and B–
D. AB+ and AB+

9. List all of the blood types possible for the offspring of parents of blood types A+ and O+.

F. A+ or O+
G. A+, A–, O–, or O+
H. O– or O+
J. AB+, A–, or O–

10. The genes that determine blood type are also responsible for:

A. Rh factor.
B. controlling the types of cells in the blood.
C. controlling blood volume.
D. creating proteins on white blood cells.