200+ QUESTIONS & ANSWERS WITH
RATIONALES
, WGU D425 INTRO TO CHEMISTRY MIDTERM EXAM 2026-2027 | PRACTICE QUESTIONS &
ANSWERS WITH RATIONALES
Section 1: Scientific Method, Measurement & Units (1–10)
Question 1
What is the SI base unit for mass?
A. Pound
B. Gram
C. Kilogram
D. Ounce
Answer: C — Kilogram
Rationale: The kilogram is the SI base unit for mass; the gram is a derived, smaller unit (1/1000
kg).
Question 2
Convert 25°C to Kelvin.
A. 25 K
B. 248 K
C. 298 K
D. 373 K
Answer: C — 298 K
Rationale: K = °C + 273. 25 + 273 = 298 K.
Question 3
How many significant figures are in 0.00420?
A. 2
B. 3
,C. 5
D. 6
Answer: B — 3
Rationale: Leading zeros are never significant; the digits 4, 2, and the trailing 0 (after a decimal
point) are significant, giving 3 sig figs.
Question 4
Which measurement shows the best precision but not necessarily accuracy?
A. Values that are all close to the true value but scattered
B. Values tightly clustered together, regardless of the true value
C. A single measurement taken once
D. Values that vary widely and average to the true value
Answer: B
Rationale: Precision refers to reproducibility/consistency of measurements, while accuracy
refers to closeness to the true value — they are independent qualities.
Question 5
Density is calculated using which formula?
A. D = mass × volume
B. D = mass/volume
C. D = volume/mass
D. D = mass + volume
Answer: B — D = mass/volume
Rationale: Density is defined as mass per unit volume (g/mL or g/cm³ typically).
Question 6
A block has a mass of 15 g and a volume of 5 cm³. What is its density?
, A. 3 g/cm³
B. 5 g/cm³
C. 15 g/cm³
D. 75 g/cm³
Answer: A — 3 g/cm³
Rationale: D = 15 g ÷ 5 cm³ = 3 g/cm³.
Question 7
Which of these is an example of a chemical property?
A. Boiling point
B. Color
C. Flammability
D. Density
Answer: C — Flammability
Rationale: Chemical properties describe how a substance reacts/transforms into a new
substance (like burning); the others are physical properties observed without changing
composition.
Question 8
Which of the following represents a physical change?
A. Rusting iron
B. Burning wood
C. Melting ice
D. Digesting food
Answer: C — Melting ice
Rationale: Melting changes the state of water without altering its chemical composition (still
H₂O); the other options involve chemical reactions forming new substances.
RATIONALES
, WGU D425 INTRO TO CHEMISTRY MIDTERM EXAM 2026-2027 | PRACTICE QUESTIONS &
ANSWERS WITH RATIONALES
Section 1: Scientific Method, Measurement & Units (1–10)
Question 1
What is the SI base unit for mass?
A. Pound
B. Gram
C. Kilogram
D. Ounce
Answer: C — Kilogram
Rationale: The kilogram is the SI base unit for mass; the gram is a derived, smaller unit (1/1000
kg).
Question 2
Convert 25°C to Kelvin.
A. 25 K
B. 248 K
C. 298 K
D. 373 K
Answer: C — 298 K
Rationale: K = °C + 273. 25 + 273 = 298 K.
Question 3
How many significant figures are in 0.00420?
A. 2
B. 3
,C. 5
D. 6
Answer: B — 3
Rationale: Leading zeros are never significant; the digits 4, 2, and the trailing 0 (after a decimal
point) are significant, giving 3 sig figs.
Question 4
Which measurement shows the best precision but not necessarily accuracy?
A. Values that are all close to the true value but scattered
B. Values tightly clustered together, regardless of the true value
C. A single measurement taken once
D. Values that vary widely and average to the true value
Answer: B
Rationale: Precision refers to reproducibility/consistency of measurements, while accuracy
refers to closeness to the true value — they are independent qualities.
Question 5
Density is calculated using which formula?
A. D = mass × volume
B. D = mass/volume
C. D = volume/mass
D. D = mass + volume
Answer: B — D = mass/volume
Rationale: Density is defined as mass per unit volume (g/mL or g/cm³ typically).
Question 6
A block has a mass of 15 g and a volume of 5 cm³. What is its density?
, A. 3 g/cm³
B. 5 g/cm³
C. 15 g/cm³
D. 75 g/cm³
Answer: A — 3 g/cm³
Rationale: D = 15 g ÷ 5 cm³ = 3 g/cm³.
Question 7
Which of these is an example of a chemical property?
A. Boiling point
B. Color
C. Flammability
D. Density
Answer: C — Flammability
Rationale: Chemical properties describe how a substance reacts/transforms into a new
substance (like burning); the others are physical properties observed without changing
composition.
Question 8
Which of the following represents a physical change?
A. Rusting iron
B. Burning wood
C. Melting ice
D. Digesting food
Answer: C — Melting ice
Rationale: Melting changes the state of water without altering its chemical composition (still
H₂O); the other options involve chemical reactions forming new substances.
