TOEFL IBT Reading Practice Test 15 Solution & Explanation

Reading 5 “Physical and Chemical Properties and Changes”

53. C “They [characteristic properties] are subdivided into two categories: physical properties and

chemical properties.” Choice A is not correct because they are used to identify or characterize a substance, not to create a substance. Choice B is not correct because sugar and water are substances, but the physical and chemical properties of them are not identified in the paragraph. Choice D is not correct because the properties do not depend on the quantity of the substance.

54. B In this passage, relate is a synonym for “pertain.” Context comes from the word “relate” in the

previous sentence.

55. C “. . . some intensive physical properties include the tendency to dissolve in water, electrical

conductivity, and density, which [density] is the ratio of mass to volume.” The pronoun “which” does not refer to Choices A, B, or D.

56. C “… to act as a poison or carcinogen (cancer-causing agent).” An explanation of a word or phrase often appears immediately after it in parentheses. Choices A, B, and D are not correct because they are intensive chemical properties that are mentioned before the reference to a “carcinogen.”

57. B The quantity of a substance paraphrases “the amount present” in reference to extensive properties and the characteristics of the substance paraphrases “characterize a particular kind of matter” in reference to intensive properties.

58. D “When a candle is burned, there are both physical and chemical changes.” Choice A is not correct because only the example of the candle is mentioned. Choice B is not correct because the meaning is explained by example, not by definition. Choice C is not correct because the common characteristics were mentioned in previous paragraphs.

59. D In this passage, left is a synonym for “remaining.” Context comes from the word “still.”

60. B “This is a phase change (liquid to gas) which is a physical change.” Because this example of a

physical change is provided, it must be concluded that phase changes are sometimes physical changes. Choice A is not correct because the example is a physical change, not a chemical change. Choice C is not correct because the quantity of a substance (extensive properties) is not mentioned in the discussion on phase changes. Choice D is not correct because in a physical change the fundamental composition of a substance has not changed.

61. B In this passage, important is a synonym for “critical.”

62. A “Has the fundamental composition of the substance changed? In a chemical change… it has,

but in a physical change, it has not.” Choice B is not correct because the quantity refers to extensive properties, not to the difference between physical or chemical properties. Choice C is not correct because both physical and chemical properties are intensive properties. Choice D is not correct because the apparent disappearance of a substance is not necessarily a sign that we are observing a chemical change.

63. D “The following questions pertain to the chemical properties of a substance: ‘… Does it decompose … when heated?’” Choices A and B are mentioned as characteristic physical properties in paragraph 4. Choice C is mentioned as a characteristic physical property in paragraph 2 in the discussion of “viscosity.”

64. B Pronoun reference is a transitional device that connects the insert sentence with the previous sentence. The pronoun “If in the insert sentence refers to “aluminum” in the previous sentence. The description of aluminum as “ductile” and “malleable” in the previous sentence means that this metal can be made into wire or shaped into flexible sheets as stated in the insert sentence.

65. Physical properties: A, D, E Chemical properties: B, C, F, H Not used: G, I