• 68 questions

AP Chem Unit 3 Practice Test

Unofficial AP Chemistry Unit 3 practice questions: intermolecular forces and the properties of solids, liquids, gases and solutions.

What causes London dispersion forces?

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Unofficial practice questions, not affiliated with the College Board. Bank checked October 14, 2026.

Next step Next unit: AP Chemistry Unit 4Unit 2: AP Chemistry bonding

All 68 questions

Topic 3.1: Intermolecular and interparticle forces 9

  • A chloride ion, Cl⁻, sits in liquid water. How do the nearest water molecules point? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.3
  • A large nonpolar molecule can have stronger intermolecular attractions than a small polar one. Why? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.1
  • A protein chain folds back on itself and holds its shape. What mainly holds one region of the chain against another? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.5
  • At room temperature fluorine and chlorine are gases, bromine is a liquid and iodine is a solid. All four are nonpolar. What explains the trend? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.1; fact read in Wikipedia, "London dispersion force"
  • Sodium chloride dissolves in water. What kind of attraction holds water molecules around each sodium ion? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.2
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Topic 3.1: Intermolecular and interparticle forces, continued

  • Two molecular substances have molecules of about the same size. One is polar and one is nonpolar. Which has the stronger attractions between its molecules, and why? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.2
  • Water is a small, light molecule, yet its boiling point is unusually high. Which attraction between its molecules explains this? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.4; fact read in Wikipedia, "Hydrogen bond"
  • What causes London dispersion forces? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.1
  • Which of these substances forms hydrogen bonds between its own molecules? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.4

Topic 3.2: Properties of solids 10

  • A white solid melts well below the boiling point of water and does not conduct electricity as a solid or as a liquid. What type of solid is it most likely to be? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.5
  • An unknown solid shatters when hit, melts only at a very high temperature, and carries a current once molten but not before. What type of solid is it? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.3
  • Graphite and diamond are both pure carbon. Why is graphite soft? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.4
  • Liquid A has stronger intermolecular forces than liquid B. How do their vapor pressures and boiling points compare? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.1
  • Small atoms are added to a metal and sit in the spaces between the metal atoms. How does this interstitial alloy compare with the pure metal? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.6
  • When liquid water boils, what is overcome? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.1
  • Which feature do metallic solids have that ionic and molecular solids lack? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.6
  • Which solid is one continuous network of covalently bonded atoms, with no separate molecules? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.4
  • Why does a crystal of an ionic solid shatter when it is struck? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.3
  • Why is diamond so hard and so hard to melt? College Board, AP Chemistry Course and Exam Description, topic 3.2, essential knowledge 3.2.A.4

Topic 3.3: Solids, liquids and gases 4

  • A particle diagram shows particles touching one another with no regular pattern, sliding past each other and colliding. Which state of matter is drawn? College Board, AP Chemistry Course and Exam Description, topic 3.3, essential knowledge 3.3.A.2
  • A substance melts. Why does its molar volume change so little? College Board, AP Chemistry Course and Exam Description, topic 3.3, essential knowledge 3.3.A.3
  • How does a crystalline solid differ from an amorphous solid? College Board, AP Chemistry Course and Exam Description, topic 3.3, essential knowledge 3.3.A.1
  • Why does a gas take the shape and the volume of whatever container holds it? College Board, AP Chemistry Course and Exam Description, topic 3.3, essential knowledge 3.3.A.4

Topic 3.4: Ideal gas law 4

  • A 10.0 L tank holds 0.500 mol of an ideal gas at 1.50 atm. What is the temperature of the gas? (R = 0.08206 L atm/(mol K)) College Board, AP Chemistry Course and Exam Description, topic 3.4, essential knowledge 3.4.A.1
  • A gas mixture is 30% oxygen by moles, and its total pressure is 2.0 atm. What is the partial pressure of the oxygen? College Board, AP Chemistry Course and Exam Description, topic 3.4, essential knowledge 3.4.A.2
  • A sealed sample of an ideal gas is squeezed to half its volume at constant temperature. What happens to its pressure? College Board, AP Chemistry Course and Exam Description, topic 3.4, essential knowledge 3.4.A.1
  • A sealed, rigid flask of ideal gas is warmed, and its pressure is plotted against its temperature in kelvins. What does the plot show? College Board, AP Chemistry Course and Exam Description, topic 3.4, essential knowledge 3.4.A.3

Topic 3.5: Kinetic molecular theory 3

  • Hydrogen, H₂, and oxygen, O₂, are mixed in one flask at one temperature. Which molecules move faster on average, and why? College Board, AP Chemistry Course and Exam Description, topic 3.5, essential knowledge 3.5.A.2
  • Sample A of neon is at 200 K and sample B of neon is at 400 K. How do the average kinetic energies of their atoms compare? College Board, AP Chemistry Course and Exam Description, topic 3.5, essential knowledge 3.5.A.3
  • What does a Maxwell-Boltzmann distribution show? College Board, AP Chemistry Course and Exam Description, topic 3.5, essential knowledge 3.5.A.4

Topic 3.6: Deviation from ideal gas law 3

  • A gas is compressed until its particles are almost touching. Which assumption behind the ideal gas law breaks down? College Board, AP Chemistry Course and Exam Description, topic 3.6, essential knowledge 3.6.A.1
  • Ammonia, a polar molecule that forms hydrogen bonds, and helium are each cooled toward the temperature at which they condense. Which departs more from ideal behavior at a given temperature and pressure, and why? College Board, AP Chemistry Course and Exam Description, topic 3.6, essential knowledge 3.6.A.1
  • Under which conditions does a real gas depart most from the ideal gas law? College Board, AP Chemistry Course and Exam Description, topic 3.6, essential knowledge 3.6.A.1

Topic 3.7: Solutions and mixtures 8

  • A 4.0 L batch of solution contains 1.0 mol of dissolved solute. What is its molarity? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.2
  • A student dissolves 5.844 g of NaCl (molar mass 58.44 g/mol) and adds water to make 500. mL of solution. What is the molarity? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.2
  • A student pipets 25.0 mL of 0.80 M solution into a flask and adds water up to the 200. mL mark. What is the molarity in the flask? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.2
  • Calcium chloride, CaCl₂, dissolves completely into its ions. What is the concentration of chloride ions in 0.20 M CaCl₂? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.2
  • How many moles of solute are in 250. mL of a 0.40 M solution? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.2
  • How much 12 M stock solution must be measured out to make 600. mL of 0.50 M solution? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.2
  • In which states of matter can a solution exist? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.1
  • What makes a mixture a solution? College Board, AP Chemistry Course and Exam Description, topic 3.7, essential knowledge 3.7.A.1

Topic 3.8: Representations of solutions 3

  • A particle drawing shows a solution before and after water is added. What should change between the two drawings? College Board, AP Chemistry Course and Exam Description, topic 3.8, essential knowledge 3.8.A.1
  • A student draws a sodium ion, Na⁺, in water. Which drawing shows the interaction correctly? College Board, AP Chemistry Course and Exam Description, topic 3.8, essential knowledge 3.8.A.1
  • Drawing A shows 4 solute particles in 100 mL of solution. Drawing B shows 8 of the same particles in 400 mL. Which solution is more concentrated? College Board, AP Chemistry Course and Exam Description, topic 3.8, essential knowledge 3.8.A.1

Topic 3.9: Separation of solutions and mixtures 4

  • A mixture of dyes is spotted on polar chromatography paper and a nonpolar solvent moves up the paper. Which dye travels the shortest distance? College Board, AP Chemistry Course and Exam Description, topic 3.9, essential knowledge 3.9.A.1
  • A student pours salt water through filter paper. What collects in the flask below? College Board, AP Chemistry Course and Exam Description, topic 3.9, essential knowledge 3.9.A.1
  • On a paper chromatogram the solvent front moved 7.5 cm from the starting line and a spot moved 3.0 cm. What is the R_f value of the spot? College Board, AP Chemistry Course and Exam Description, topic 3.9, essential knowledge 3.9.A.1; fact read in Wikipedia, "Retardation factor"
  • What does chromatography rely on to separate the components of a mixture? College Board, AP Chemistry Course and Exam Description, topic 3.9, essential knowledge 3.9.A.1

Topic 3.10: Solubility 4

  • Ethanol mixes with water, but hexane, a nonpolar hydrocarbon, does not. What explains the difference? College Board, AP Chemistry Course and Exam Description, topic 3.10, essential knowledge 3.10.A.1
  • Iodine, I₂, is a nonpolar molecule. In which solvent does it dissolve better: water or hexane? College Board, AP Chemistry Course and Exam Description, topic 3.10, essential knowledge 3.10.A.1
  • What general rule predicts whether two substances will mix? College Board, AP Chemistry Course and Exam Description, topic 3.10, essential knowledge 3.10.A.1
  • Why do many ionic compounds dissolve in water but not in a nonpolar solvent? College Board, AP Chemistry Course and Exam Description, topic 3.1, essential knowledge 3.1.A.2

Topic 3.11: Spectroscopy and the electromagnetic spectrum 4

  • A molecule absorbs a photon of infrared radiation. What kind of change does it undergo? College Board, AP Chemistry Course and Exam Description, topic 3.11, essential knowledge 3.11.A.1
  • Rank photons of microwave, infrared and ultraviolet radiation by energy, lowest first. College Board, AP Chemistry Course and Exam Description, topic 3.11, essential knowledge 3.11.A.1; fact read in Wikipedia, "Electromagnetic spectrum"
  • Which kind of radiation moves an electron in a molecule to a higher electronic energy level? College Board, AP Chemistry Course and Exam Description, topic 3.11, essential knowledge 3.11.A.1
  • Which region of the electromagnetic spectrum is tied to transitions between molecular rotational levels? College Board, AP Chemistry Course and Exam Description, topic 3.11, essential knowledge 3.11.A.1

Topic 3.12: Properties of photons 5

  • An atom in an excited state emits a photon. What happens to the energy of the atom? College Board, AP Chemistry Course and Exam Description, topic 3.12, essential knowledge 3.12.A.1
  • How do the frequency and photon energy of red light compare with those of violet light, which has a shorter wavelength? College Board, AP Chemistry Course and Exam Description, topic 3.12, essential knowledge 3.12.A.2
  • How does the energy of a photon of 400 nm light compare with that of a photon of 800 nm light? College Board, AP Chemistry Course and Exam Description, topic 3.12, essential knowledge 3.12.A.2
  • One photon carries 3.98 × 10⁻¹⁹ J. What is the frequency of the light? (h = 6.626 × 10⁻³⁴ J s) College Board, AP Chemistry Course and Exam Description, topic 3.12, essential knowledge 3.12.A.2
  • What is the frequency of light with a wavelength of 600. nm? (c = 2.998 × 10⁸ m/s) College Board, AP Chemistry Course and Exam Description, topic 3.12, essential knowledge 3.12.A.2

Topic 3.13: Beer-Lambert law 7

  • A 0.10 M standard solution has an absorbance of 0.25. A sample of the same solute, in the same cuvette at the same wavelength, reads 0.40. What is its concentration? College Board, AP Chemistry Course and Exam Description, topic 3.13, essential knowledge 3.13.A.2
  • A cuvette is rinsed with water and not dried, and the sample is poured in on top of the drops. How does this error affect the concentration found from the absorbance? College Board, AP Chemistry Course and Exam Description, topic 3.13, essential knowledge 3.13.A.2
  • A dye has a molar absorptivity of 2.0 × 10⁴ L/(mol cm) at the wavelength chosen. What absorbance does a 3.0 × 10⁻⁵ M solution of it give in a 1.00 cm cuvette? College Board, AP Chemistry Course and Exam Description, topic 3.13, essential knowledge 3.13.A.1
  • The concentration of a colored solution is doubled, with the same cuvette and wavelength. What happens to its absorbance? College Board, AP Chemistry Course and Exam Description, topic 3.13, essential knowledge 3.13.A.1
  • In the Beer-Lambert law, what does the molar absorptivity, ε, describe? College Board, AP Chemistry Course and Exam Description, topic 3.13, essential knowledge 3.13.A.1
  • The same solution is measured in a 1.00 cm cuvette and then in a 2.00 cm cuvette. How do the two absorbance readings compare? College Board, AP Chemistry Course and Exam Description, topic 3.13, essential knowledge 3.13.A.1
  • Why is a spectrophotometer usually set to the wavelength at which the sample absorbs most strongly? College Board, AP Chemistry Course and Exam Description, topic 3.13, essential knowledge 3.13.A.2

How this list was compiled: Our own questions, written to Unit 3 (Properties of Substances and Mixtures) of the College Board's AP Chemistry Course and Exam Description, effective fall 2024, https://apcentral.collegeboard.org/media/pdf/ap-chemistry-course-and-exam-description.pdf, read 2026-10-14: topics 3.1 to 3.13. The rule behind each answer was read on 2026-10-14 in the essential knowledge statement of the course description named under the question; four facts about named substances and regions of the spectrum were read in the Wikipedia articles named. The constants and atomic masses the questions print are those of the description's own equation sheet and periodic table. Every calculated answer is worked from the numbers the question prints and was worked out a second time. Licence: Own work. Short quotations from the public documents named under each question.

How it works

This AP Chem Unit 3 practice test has 68 practice questions of our own on Properties of Substances and Mixtures, from intermolecular forces to the Beer-Lambert law. It is unofficial and not affiliated with or endorsed by the College Board, which owns AP.

Read the full guide

What Unit 3 covers

Unit 3 has thirteen topics in the College Board's course description, read October 14, 2026, and no weights among them, so the spread is ours: intermolecular forces (9 questions), properties of solids (10), states of matter (4), gases (10), solutions and molarity (8), particle drawings of solutions (3), separation (4), solubility (4), spectroscopy (4), photons (5) and the Beer-Lambert law (7).

What the exam leaves out

The description says phase diagrams, colligative properties and calculations of molality, percent by mass and percent by volume are not assessed, so none is asked here. Each constant is printed in its question, since the exam supplies an equation sheet.

  • Name the force, such as hydrogen bonding or London dispersion, and compare it with the others present. "Strong" and "weak" alone explain nothing.
  • Boiling overcomes attractions between molecules, never the covalent bonds inside them.
  • Convert milliliters to liters before any molarity step, and nanometers to meters before using c = λν.

Questions and answers

What is Unit 3 in AP Chemistry?

Properties of Substances and Mixtures, the third of nine units: intermolecular forces, solids, liquids and gases, solutions, and how light is used to measure them. The course description allows about 14 to 15 class periods for it.

How much of the AP Chemistry exam is Unit 3?

Between 18 and 22% of the multiple-choice section, by the College Board's course page. That is the largest share of the nine units: Unit 8 carries 11 to 15%, and each of the other seven carries 7 to 9%.

Does this AP Chemistry Unit 3 practice test cover intermolecular forces and properties?

Yes. Topic 3.1 is intermolecular and interparticle forces, and topics 3.2 to 3.10 are the properties those forces explain: melting and boiling points, vapor pressure, gas behavior and solubility. The current description names the unit Properties of Substances and Mixtures.

What should an AP Chemistry Unit 3 study guide cover?

The intermolecular forces and how to rank them; the four types of solid; PV = nRT and partial pressures; kinetic molecular theory; molarity and dilution; chromatography; why similar substances mix; the three spectral regions; and E = hν, c = λν and A = εbc.

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