WGU D425 — INTRODUCTION TO CHEMISTRY
ORIGINAL PREMIUM OBJECTIVE-ASSESSMENT STUDY
GUIDE
Exam-Style Questions • Answers • Rationales • Memory Cues • Calculation Practice
The supplied Stuvia listing presents a D425 Introduction to Chemistry Objective Assessment resource for 2025/2026. Its public preview
includes atomic structure, ionic compounds, molar mass, moles, oxidation states, polarity, valence electrons, and electron
configurations; related D425 listings describe broader coverage including bonding, reactions, stoichiometry, states of matter, and
laboratory concepts. This guide uses those public topic signals to create independent practice material.
■cite■turn0search0■turn0search7■
ORIGINAL-MATERIAL NOTICE: This guide does not reproduce the paid Stuvia document, actual WGU assessment questions, answer
key, or locked/premium content. It is independently authored practice material.
WGU D425 Introduction to Chemistry • Original Premium Study Guide Page 1
, HIGH-YIELD D425 MASTER MAP
Foundation: matter • properties • physical vs chemical change • measurement • units • significant figures.
Atomic structure: protons • neutrons • electrons • isotopes • ions • electron configurations.
Periodic behavior: groups • periods • valence electrons • atomic radius • electronegativity.
Bonding: ionic/covalent bonds • polarity • Lewis concepts • molecular geometry.
Quantitative chemistry: molar mass • moles • Avogadro's number • stoichiometry • empirical formulas • limiting reactants.
Reactions: balancing • oxidation/reduction • oxidation states.
States & energy: gases • solutions • acids/bases • thermochemistry • kinetics • equilibrium.
Laboratory: safe handling • experimental design • evidence and error checking.
RAPID FORMULA & MEMORY GRID
Skill Fast recall
Neutrons mass number − atomic number
Moles mass ÷ molar mass
Particles moles × 6.022×10²³
Molarity mol solute ÷ L solution
Dilution M■V■ = M■V■
Stoichiometry grams → moles → ratio → moles → grams
Oxidation loss of electrons
Reduction gain of electrons
pH lower pH = higher [H■]
Boyle P↑ when V↓ at constant T
Gas laws use Kelvin
Sig figs ×/÷ fewest significant figures
Sig figs +/− fewest decimal places
WGU D425 Introduction to Chemistry • Original Premium Study Guide Page 2
, MATTER & MEASUREMENT
1. Which statement best defines chemistry?
A. Study of organisms only
B. Study of matter, its properties, and the changes it undergoes
C. Study of planetary motion only
D. Study of weather only
ANSWER: B.
Rationale: Chemistry examines composition, structure, properties, and transformations of matter.
Memory cue / exam trap: Matter + change = chemistry.
2. Which is an example of a chemical property?
A. Density
B. Melting point
C. Flammability
D. Color
ANSWER: C.
Rationale: Flammability describes a substance's ability to undergo a chemical change.
Memory cue / exam trap: Chemical property = ability to react.
3. Which is a physical change?
A. Iron rusting
B. Water freezing
C. Gasoline burning
D. Silver tarnishing
ANSWER: B.
Rationale: Freezing changes physical state without creating a new substance.
Memory cue / exam trap: State change ≠ new substance.
4. How many significant figures are in 0.00450?
A. 2
B. 3
C. 4
D. 5
ANSWER: B.
Rationale: Leading zeros are not significant; the 4, 5, and trailing zero are significant.
Memory cue / exam trap: Leading zeros don't count.
5. A measured value is 12.40 g. What does the final zero communicate?
A. It is meaningless
B. It indicates measurement precision
C. It changes the substance
D. It is always an exact value
ANSWER: B.
Rationale: A trailing zero after a decimal is significant and communicates the precision of the measurement.
Memory cue / exam trap: Sig figs communicate precision.
WGU D425 Introduction to Chemistry • Original Premium Study Guide Page 3
ORIGINAL PREMIUM OBJECTIVE-ASSESSMENT STUDY
GUIDE
Exam-Style Questions • Answers • Rationales • Memory Cues • Calculation Practice
The supplied Stuvia listing presents a D425 Introduction to Chemistry Objective Assessment resource for 2025/2026. Its public preview
includes atomic structure, ionic compounds, molar mass, moles, oxidation states, polarity, valence electrons, and electron
configurations; related D425 listings describe broader coverage including bonding, reactions, stoichiometry, states of matter, and
laboratory concepts. This guide uses those public topic signals to create independent practice material.
■cite■turn0search0■turn0search7■
ORIGINAL-MATERIAL NOTICE: This guide does not reproduce the paid Stuvia document, actual WGU assessment questions, answer
key, or locked/premium content. It is independently authored practice material.
WGU D425 Introduction to Chemistry • Original Premium Study Guide Page 1
, HIGH-YIELD D425 MASTER MAP
Foundation: matter • properties • physical vs chemical change • measurement • units • significant figures.
Atomic structure: protons • neutrons • electrons • isotopes • ions • electron configurations.
Periodic behavior: groups • periods • valence electrons • atomic radius • electronegativity.
Bonding: ionic/covalent bonds • polarity • Lewis concepts • molecular geometry.
Quantitative chemistry: molar mass • moles • Avogadro's number • stoichiometry • empirical formulas • limiting reactants.
Reactions: balancing • oxidation/reduction • oxidation states.
States & energy: gases • solutions • acids/bases • thermochemistry • kinetics • equilibrium.
Laboratory: safe handling • experimental design • evidence and error checking.
RAPID FORMULA & MEMORY GRID
Skill Fast recall
Neutrons mass number − atomic number
Moles mass ÷ molar mass
Particles moles × 6.022×10²³
Molarity mol solute ÷ L solution
Dilution M■V■ = M■V■
Stoichiometry grams → moles → ratio → moles → grams
Oxidation loss of electrons
Reduction gain of electrons
pH lower pH = higher [H■]
Boyle P↑ when V↓ at constant T
Gas laws use Kelvin
Sig figs ×/÷ fewest significant figures
Sig figs +/− fewest decimal places
WGU D425 Introduction to Chemistry • Original Premium Study Guide Page 2
, MATTER & MEASUREMENT
1. Which statement best defines chemistry?
A. Study of organisms only
B. Study of matter, its properties, and the changes it undergoes
C. Study of planetary motion only
D. Study of weather only
ANSWER: B.
Rationale: Chemistry examines composition, structure, properties, and transformations of matter.
Memory cue / exam trap: Matter + change = chemistry.
2. Which is an example of a chemical property?
A. Density
B. Melting point
C. Flammability
D. Color
ANSWER: C.
Rationale: Flammability describes a substance's ability to undergo a chemical change.
Memory cue / exam trap: Chemical property = ability to react.
3. Which is a physical change?
A. Iron rusting
B. Water freezing
C. Gasoline burning
D. Silver tarnishing
ANSWER: B.
Rationale: Freezing changes physical state without creating a new substance.
Memory cue / exam trap: State change ≠ new substance.
4. How many significant figures are in 0.00450?
A. 2
B. 3
C. 4
D. 5
ANSWER: B.
Rationale: Leading zeros are not significant; the 4, 5, and trailing zero are significant.
Memory cue / exam trap: Leading zeros don't count.
5. A measured value is 12.40 g. What does the final zero communicate?
A. It is meaningless
B. It indicates measurement precision
C. It changes the substance
D. It is always an exact value
ANSWER: B.
Rationale: A trailing zero after a decimal is significant and communicates the precision of the measurement.
Memory cue / exam trap: Sig figs communicate precision.
WGU D425 Introduction to Chemistry • Original Premium Study Guide Page 3
