CHEM 219 Module 1 2026/2027 | Portage Learning Principles of Organic
Chemistry Module 1 Exam Prep, Study Guide, Practice Questions with
Answers & Rationales, Atomic Structure, Valence Electrons, Lewis
Structures, Chemical Bonding, Electronegativity, Formal Charge,
Resonance, Molecular Structure & Functional Groups
Question 1: Which of the following best defines chemistry as a scientific
discipline?
A. The study of living organisms and their interactions with the environment
B. The study of the composition, structure, properties, and changes of matter
C. The study of energy transformations in mechanical systems
D. The study of celestial bodies and their motions
CORRECT ANSWER: B. The study of the composition, structure, properties, and
changes of matter
Rationale: Chemistry is fundamentally concerned with matter, including its
composition, structure, properties, and the changes it undergoes during chemical
reactions. The other options describe biology, physics, and astronomy,
respectively.
Question 2: According to the law of conservation of mass, what happens to the
total mass of substances during a chemical reaction in a closed system?
A. It always decreases because some matter is converted to energy
B. It always increases because new products are formed
C. It remains constant because matter is neither created nor destroyed
D. It fluctuates depending on the temperature of the reaction
CORRECT ANSWER: C. It remains constant because matter is neither created nor
destroyed
Rationale: The law of conservation of mass states that in a closed system, the
total mass of the reactants equals the total mass of the products. Matter is
neither created nor destroyed in ordinary chemical reactions.
Question 3: Which of the following is classified as a homogeneous mixture?
A. A suspension of sand in water
B. A mixture of oil and vinegar
C. A solution of salt dissolved in water
D. A mixture of iron filings and sulfur powder
,CORRECT ANSWER: C. A solution of salt dissolved in water
Rationale: A homogeneous mixture has a uniform composition throughout, and a
saltwater solution is uniform at the molecular level. Sand in water and oil and
vinegar are heterogeneous, and iron filings with sulfur is also heterogeneous.
Question 4: Which of the following represents a chemical change rather than a
physical change?
A. Melting of ice into liquid water
B. Dissolving sugar in warm water
C. Rusting of iron in the presence of oxygen and moisture
D. Breaking a glass rod into smaller pieces
CORRECT ANSWER: C. Rusting of iron in the presence of oxygen and moisture
Rationale: Rusting is a chemical change because it produces a new substance,
iron(III) oxide, with different properties. Melting, dissolving, and breaking are
physical changes that do not alter chemical identity.
Question 5: Which of the following is a pure substance?
A. Air
B. Brass
C. Distilled water
D. Seawater
CORRECT ANSWER: C. Distilled water
Rationale: A pure substance has a fixed composition and cannot be separated into
simpler substances by physical means. Distilled water consists only of H₂O
molecules. Air, brass, and seawater are mixtures.
Question 6: Which of the following statements about elements and compounds
is correct?
A. Elements can be broken down into simpler substances by chemical means
B. Compounds consist of two or more elements chemically combined in fixed
proportions
C. Compounds are always homogeneous mixtures
D. Elements are always found in nature as single atoms
,CORRECT ANSWER: B. Compounds consist of two or more elements chemically
combined in fixed proportions
Rationale: Compounds are formed when two or more elements chemically
combine in definite ratios, such as H₂O. Elements cannot be decomposed by
chemical means, compounds are not mixtures, and many elements exist as
diatomic or polyatomic species.
Question 7: Which of the following is a physical property of a substance?
A. Reactivity with acid
B. Flammability
C. Density
D. Toxicity
CORRECT ANSWER: C. Density
Rationale: Density is a physical property because it can be observed or measured
without changing the chemical identity of the substance. Reactivity, flammability,
and toxicity are chemical properties.
Question 8: How many significant figures are present in the measured value
0.004560?
A. 3
B. 4
C. 5
D. 7
CORRECT ANSWER: B. 4
Rationale: Leading zeros are not significant. The digits 4, 5, 6, and the trailing zero
after the decimal are significant, giving four significant figures.
Question 9: What is the result of the following calculation to the correct number
of significant figures: 12.34 + 1.2 + 0.005?
A. 13.545
B. 13.54
C. 13.5
D. 14
, CORRECT ANSWER: C. 13.5
Rationale: For addition, the result is limited by the least precise decimal place,
which is tenths in 1.2. Therefore, 13.545 rounds to 13.5.
Question 10: Which of the following conversion factors correctly converts 25.0
inches to centimeters, given that 1 inch = 2.54 cm?
A. 25.0 in × (1 in / 2.54 cm)
B. 25.0 in × (2.54 cm / 1 in)
C. 25.0 in × (2.54 in / 1 cm)
D. 25.0 in × (1 cm / 2.54 in)
CORRECT ANSWER: B. 25.0 in × (2.54 cm / 1 in)
Rationale: To convert inches to centimeters, multiply by the conversion factor
with centimeters in the numerator and inches in the denominator so that inches
cancel, yielding centimeters.
Question 11: Which of the following is the SI base unit for amount of substance?
A. Gram
B. Mole
C. Liter
D. Kelvin
CORRECT ANSWER: B. Mole
Rationale: The mole is the SI base unit for amount of substance. Gram is a unit of
mass, liter is a unit of volume, and kelvin is the SI unit of thermodynamic
temperature.
Question 12: Which of the following represents an intensive property?
A. Mass
B. Volume
C. Temperature
D. Length
CORRECT ANSWER: C. Temperature
Chemistry Module 1 Exam Prep, Study Guide, Practice Questions with
Answers & Rationales, Atomic Structure, Valence Electrons, Lewis
Structures, Chemical Bonding, Electronegativity, Formal Charge,
Resonance, Molecular Structure & Functional Groups
Question 1: Which of the following best defines chemistry as a scientific
discipline?
A. The study of living organisms and their interactions with the environment
B. The study of the composition, structure, properties, and changes of matter
C. The study of energy transformations in mechanical systems
D. The study of celestial bodies and their motions
CORRECT ANSWER: B. The study of the composition, structure, properties, and
changes of matter
Rationale: Chemistry is fundamentally concerned with matter, including its
composition, structure, properties, and the changes it undergoes during chemical
reactions. The other options describe biology, physics, and astronomy,
respectively.
Question 2: According to the law of conservation of mass, what happens to the
total mass of substances during a chemical reaction in a closed system?
A. It always decreases because some matter is converted to energy
B. It always increases because new products are formed
C. It remains constant because matter is neither created nor destroyed
D. It fluctuates depending on the temperature of the reaction
CORRECT ANSWER: C. It remains constant because matter is neither created nor
destroyed
Rationale: The law of conservation of mass states that in a closed system, the
total mass of the reactants equals the total mass of the products. Matter is
neither created nor destroyed in ordinary chemical reactions.
Question 3: Which of the following is classified as a homogeneous mixture?
A. A suspension of sand in water
B. A mixture of oil and vinegar
C. A solution of salt dissolved in water
D. A mixture of iron filings and sulfur powder
,CORRECT ANSWER: C. A solution of salt dissolved in water
Rationale: A homogeneous mixture has a uniform composition throughout, and a
saltwater solution is uniform at the molecular level. Sand in water and oil and
vinegar are heterogeneous, and iron filings with sulfur is also heterogeneous.
Question 4: Which of the following represents a chemical change rather than a
physical change?
A. Melting of ice into liquid water
B. Dissolving sugar in warm water
C. Rusting of iron in the presence of oxygen and moisture
D. Breaking a glass rod into smaller pieces
CORRECT ANSWER: C. Rusting of iron in the presence of oxygen and moisture
Rationale: Rusting is a chemical change because it produces a new substance,
iron(III) oxide, with different properties. Melting, dissolving, and breaking are
physical changes that do not alter chemical identity.
Question 5: Which of the following is a pure substance?
A. Air
B. Brass
C. Distilled water
D. Seawater
CORRECT ANSWER: C. Distilled water
Rationale: A pure substance has a fixed composition and cannot be separated into
simpler substances by physical means. Distilled water consists only of H₂O
molecules. Air, brass, and seawater are mixtures.
Question 6: Which of the following statements about elements and compounds
is correct?
A. Elements can be broken down into simpler substances by chemical means
B. Compounds consist of two or more elements chemically combined in fixed
proportions
C. Compounds are always homogeneous mixtures
D. Elements are always found in nature as single atoms
,CORRECT ANSWER: B. Compounds consist of two or more elements chemically
combined in fixed proportions
Rationale: Compounds are formed when two or more elements chemically
combine in definite ratios, such as H₂O. Elements cannot be decomposed by
chemical means, compounds are not mixtures, and many elements exist as
diatomic or polyatomic species.
Question 7: Which of the following is a physical property of a substance?
A. Reactivity with acid
B. Flammability
C. Density
D. Toxicity
CORRECT ANSWER: C. Density
Rationale: Density is a physical property because it can be observed or measured
without changing the chemical identity of the substance. Reactivity, flammability,
and toxicity are chemical properties.
Question 8: How many significant figures are present in the measured value
0.004560?
A. 3
B. 4
C. 5
D. 7
CORRECT ANSWER: B. 4
Rationale: Leading zeros are not significant. The digits 4, 5, 6, and the trailing zero
after the decimal are significant, giving four significant figures.
Question 9: What is the result of the following calculation to the correct number
of significant figures: 12.34 + 1.2 + 0.005?
A. 13.545
B. 13.54
C. 13.5
D. 14
, CORRECT ANSWER: C. 13.5
Rationale: For addition, the result is limited by the least precise decimal place,
which is tenths in 1.2. Therefore, 13.545 rounds to 13.5.
Question 10: Which of the following conversion factors correctly converts 25.0
inches to centimeters, given that 1 inch = 2.54 cm?
A. 25.0 in × (1 in / 2.54 cm)
B. 25.0 in × (2.54 cm / 1 in)
C. 25.0 in × (2.54 in / 1 cm)
D. 25.0 in × (1 cm / 2.54 in)
CORRECT ANSWER: B. 25.0 in × (2.54 cm / 1 in)
Rationale: To convert inches to centimeters, multiply by the conversion factor
with centimeters in the numerator and inches in the denominator so that inches
cancel, yielding centimeters.
Question 11: Which of the following is the SI base unit for amount of substance?
A. Gram
B. Mole
C. Liter
D. Kelvin
CORRECT ANSWER: B. Mole
Rationale: The mole is the SI base unit for amount of substance. Gram is a unit of
mass, liter is a unit of volume, and kelvin is the SI unit of thermodynamic
temperature.
Question 12: Which of the following represents an intensive property?
A. Mass
B. Volume
C. Temperature
D. Length
CORRECT ANSWER: C. Temperature
