Rucete ✏ AP Chemistry In a Nutshell
7. Liquids and Solids — Practice Questions 3
This chapter introduces intermolecular forces, vapor pressure, heating curves, and the structure and properties of liquids and solids.
(Multiple Choice — Click to Reveal Answer)
1. Which of the following molecules has only London dispersion forces as its intermolecular attraction?
(A) NH₃
(B) H₂O
(C) CCl₄
(D) CH₃OH
Answer
(C) — CCl₄ is nonpolar and only exhibits London dispersion forces.
2. What type of crystalline solid is formed by potassium bromide (KBr)?
(A) Molecular
(B) Ionic
(C) Covalent Network
(D) Metallic
Answer
(B) — KBr is an ionic compound and forms an ionic crystal lattice.
3. What best describes a property of metallic solids?
(A) Brittle and nonconductive
(B) Good conductors and malleable
(C) Low melting point and soft
(D) Dissolve easily in water
Answer
(B) — Metallic solids conduct electricity and are malleable due to delocalized electrons.
4. Which of the following would have the highest boiling point?
(A) CH₄
(B) CO₂
(C) H₂O
(D) O₂
Answer
(C) — Water exhibits hydrogen bonding, resulting in a higher boiling point.
5. What causes the meniscus of water to curve upward in a glass tube?
(A) Cohesive forces only
(B) Adhesive forces only
(C) Adhesive > Cohesive forces
(D) Surface tension is zero
Answer
(C) — Water sticks to glass (adhesion) more than to itself (cohesion), curving the meniscus upward.
6. Which of the following will have the greatest surface tension?
(A) C₂H₆
(B) CH₃CH₂OH
(C) CO₂
(D) CCl₄
Answer
(B) — Ethanol (CH₃CH₂OH) has hydrogen bonding, resulting in high surface tension.
7. What describes the process of sublimation?
(A) Solid → Liquid → Gas
(B) Gas → Liquid
(C) Solid → Gas
(D) Liquid → Solid
Answer
(C) — Sublimation is the direct phase change from solid to gas without becoming liquid.
8. Which condition increases the rate of evaporation?
(A) Low temperature
(B) High surface area
(C) Low kinetic energy
(D) Decreased molecular motion
Answer
(B) — A greater surface area allows more molecules to escape, increasing evaporation rate.
9. Which of the following is true about amorphous solids?
(A) They have well-defined melting points
(B) They conduct electricity well
(C) Their particles are in random arrangement
(D) They are crystalline in structure
Answer
(C) — Amorphous solids lack a regular repeating structure and have no definite melting point.
10. Which solid has the highest melting point?
(A) CO₂
(B) NaCl
(C) CH₄
(D) I₂
Answer
(B) — NaCl is an ionic compound with strong electrostatic forces, resulting in a high melting point.
11. What happens at the plateau of a heating curve?
(A) Temperature increases
(B) Kinetic energy increases
(C) Phase change occurs
(D) No energy is absorbed
Answer
(C) — During the plateau, energy goes into breaking intermolecular forces, not raising temperature.
12. Which of the following is a property of liquids but not solids?
(A) Fixed volume
(B) Fixed shape
(C) Incompressibility
(D) Ability to flow
Answer
(D) — Liquids flow because particles are not in fixed positions, unlike in solids.
13. Which type of bond is present in covalent network solids?
(A) Ionic
(B) Hydrogen
(C) Covalent
(D) Metallic
Answer
(C) — Covalent network solids consist of atoms held together by covalent bonds in a continuous structure.
14. Why is ice less dense than liquid water?
(A) Hydrogen bonds pull molecules closer in liquid
(B) Molecules vibrate more in solid
(C) Ice has metallic bonding
(D) Ice is amorphous
Answer
(A) — In liquid water, hydrogen bonds allow molecules to be closer, while ice has an open lattice structure.
15. What causes capillary action in narrow tubes?
(A) Surface tension only
(B) Adhesion only
(C) Adhesion and cohesion
(D) Sublimation
Answer
(C) — Adhesion pulls water up the tube, cohesion pulls other molecules along.
16. What is the phase change from liquid to solid called?
(A) Condensation
(B) Vaporization
(C) Fusion
(D) Freezing
Answer
(D) — Freezing is the process of turning a liquid into a solid.
17. Which of the following liquids would have the lowest viscosity?
(A) Glycerol
(B) Honey
(C) Water
(D) Motor oil
Answer
(C) — Water has lower intermolecular forces than the others and flows easily.
18. Which of the following is most likely to be a volatile liquid?
(A) Water
(B) Acetone
(C) Mercury
(D) Ethylene glycol
Answer
(B) — Acetone has weaker intermolecular forces and evaporates quickly.
19. Which of the following exhibits metallic bonding?
(A) NaCl
(B) Fe
(C) H₂O
(D) CO₂
Answer
(B) — Iron (Fe) is a metal with delocalized electrons, characteristic of metallic bonding.
20. Which phase change is exothermic?
(A) Sublimation
(B) Vaporization
(C) Condensation
(D) Melting
Answer
(C) — Condensation releases heat as gas turns into liquid.
21. What is vapor pressure?
(A) The pressure of a gas pushing down on a liquid
(B) The pressure exerted by a vapor in equilibrium with its liquid
(C) The boiling point of a liquid
(D) The surface tension of a liquid
Answer
(B) — Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature.
22. Which statement is true about intermolecular forces?
(A) They exist only in solids
(B) They are stronger than covalent bonds
(C) They determine boiling and melting points
(D) They are absent in gases
Answer
(C) — Intermolecular forces influence the energy needed to change phases, affecting boiling and melting points.
23. Which has the weakest intermolecular forces?
(A) HF
(B) H₂O
(C) CH₄
(D) NH₃
Answer
(C) — CH₄ is nonpolar and has only weak London dispersion forces.
24. What property allows certain liquids to form droplets on surfaces?
(A) Viscosity
(B) Vapor pressure
(C) Surface tension
(D) Boiling point
Answer
(C) — Surface tension minimizes surface area, causing liquid droplets to form.
25. Which type of crystalline solid is formed by diamond?
(A) Molecular
(B) Metallic
(C) Ionic
(D) Covalent network
Answer
(D) — Diamond is a covalent network solid made of carbon atoms bonded in a tetrahedral structure.
26. Which of the following statements best explains why water has an unusually high boiling point for its molar mass?
(A) It has strong dispersion forces
(B) It exhibits hydrogen bonding
(C) It is a polar molecule
(D) It has high vapor pressure
Answer
(B) — Hydrogen bonding between water molecules requires more energy to overcome, raising its boiling point.
27. A solid has a high melting point, is hard, and does not conduct electricity in the solid state, but conducts when molten. What type of solid is it?
(A) Molecular
(B) Metallic
(C) Ionic
(D) Covalent network
Answer
(C) — These are all properties of ionic solids: high melting point, nonconductive solid, conductive molten state.
28. Why is the vapor pressure of acetone higher than that of water at room temperature?
(A) Acetone has stronger hydrogen bonding
(B) Water is nonpolar
(C) Acetone has weaker intermolecular forces
(D) Water has a lower molecular weight
Answer
(C) — Weaker intermolecular forces in acetone mean its molecules escape more easily into vapor phase.
29. Which of the following explains why NaCl does not conduct electricity in solid form but does in aqueous solution?
(A) It forms covalent bonds in solution
(B) Water provides free electrons
(C) Ions are mobile in solution but fixed in solid
(D) NaCl decomposes in solution
Answer
(C) — In solution, Na⁺ and Cl⁻ ions are free to move and carry electric current; in the solid, they are locked in a crystal lattice.
30. Which factor most directly affects the viscosity of a liquid?
(A) Atmospheric pressure
(B) Intermolecular forces
(C) Molar mass
(D) Volume of liquid
Answer
(B) — Stronger intermolecular forces increase resistance to flow, resulting in higher viscosity.
31. A heating curve shows a flat horizontal line. What is occurring during this phase?
(A) Temperature is increasing rapidly
(B) All particles are freezing
(C) A phase change is occurring at constant temperature
(D) The system is cooling
Answer
(C) — During a phase change (melting/boiling), temperature remains constant as energy is used to overcome intermolecular forces.
32. Which liquid would likely have the greatest capillary rise in a thin tube?
(A) Liquid mercury
(B) Water
(C) Oil
(D) Carbon tetrachloride
Answer
(B) — Water exhibits strong adhesion to glass and cohesion within itself, resulting in high capillary action.
33. Why does dry ice sublimate at atmospheric pressure instead of melting?
(A) It has no melting point
(B) It forms ionic crystals
(C) Its triple point is above 1 atm
(D) CO₂ is polar
Answer
(C) — CO₂’s triple point occurs above 1 atm, so it bypasses the liquid state at atmospheric pressure and sublimates directly from solid to gas.
34. Which solid has the most delocalized electrons?
(A) Ice
(B) Sodium
(C) Sulfur
(D) Quartz
Answer
(B) — Metals like sodium have delocalized electrons, allowing them to conduct electricity and heat.
35. Which statement about crystalline solids is FALSE?
(A) They have definite melting points
(B) Their particles are randomly arranged
(C) They form well-defined geometric shapes
(D) They have repeating units in a lattice structure
Answer
(B) — Crystalline solids have ordered, repeating arrangements, unlike amorphous solids which are randomly arranged.
36. Explain why hydrogen bonding causes water to have a high specific heat capacity.
Answer
Answer: Hydrogen bonds between water molecules require more energy to break before increasing kinetic energy, thus increasing the specific heat capacity.
37. Describe how intermolecular forces influence the boiling point of a liquid.
Answer
Answer: Stronger intermolecular forces require more energy to overcome, resulting in a higher boiling point.
38. What distinguishes a covalent network solid from a molecular solid?
Answer
Answer: Covalent network solids consist of atoms bonded by covalent bonds in a continuous lattice, while molecular solids are held together by weaker intermolecular forces.
39. Why is mercury’s meniscus convex rather than concave in a glass tube?
Answer
Answer: Mercury’s cohesive forces are stronger than its adhesive forces to glass, so it curves downward.
40. Explain why substances with low vapor pressure evaporate slowly.
Answer
Answer: Low vapor pressure indicates strong intermolecular forces, so fewer molecules can escape into the gas phase at a given temperature.
41. How does increasing atmospheric pressure affect the boiling point of a liquid?
Answer
Answer: It increases the boiling point, because more energy is required for the vapor pressure to match the higher external pressure.
42. What structural feature of ice causes it to float on liquid water?
Answer
Answer: Ice has an open hexagonal structure due to hydrogen bonding, making it less dense than liquid water.
43. Define volatility in terms of intermolecular forces.
Answer
Answer: Volatility is the tendency of a substance to vaporize. Substances with weaker intermolecular forces are more volatile.
44. Why are covalent network solids generally poor conductors of electricity?
Answer
Answer: Their electrons are localized in bonds and not free to move, so they do not conduct electricity well.
45. What physical property is most affected by surface tension?
Answer
Answer: The shape of liquid droplets — surface tension causes them to form spherical shapes to minimize surface area.
46. Explain how dipole-dipole interactions differ from hydrogen bonds.
Answer
Answer: Dipole-dipole interactions occur between polar molecules, but hydrogen bonds are a stronger type of dipole interaction involving H and N, O, or F.
47. Describe one reason molecular solids have low melting points.
Answer
Answer: They are held together by weak intermolecular forces, such as van der Waals or dipole-dipole interactions, which require little energy to overcome.
48. Why are metallic solids malleable and ductile?
Answer
Answer: Their delocalized electrons allow metal ions to slide past each other without breaking the metallic bond.
49. What happens to particle motion during a phase change like melting?
Answer
Answer: The particles gain energy and overcome intermolecular forces, allowing them to move more freely but without increasing temperature.
50. How can you determine the strength of intermolecular forces from boiling point data?
Answer
Answer: A higher boiling point generally indicates stronger intermolecular forces, as more energy is needed to convert liquid to vapor.