Rucete ✏ AP Chemistry In a Nutshell
7. Liquids and Solids — Practice Questions
This chapter introduces the condensed phases—liquids and solids—exploring how intermolecular forces influence properties such as boiling point, melting point, surface tension, and vapor pressure.
(Multiple Choice — Click to Reveal Answer)
1. Which of the following is the strongest intermolecular force?
(A) Dipole-dipole
(B) Hydrogen bond
(C) London dispersion
(D) Covalent bond
Answer
(B) — Hydrogen bonds are the strongest intermolecular forces, especially between H and N, O, or F.
2. Which phase of matter is characterized by particles that are close together but can slide past each other?
(A) Gas
(B) Solid
(C) Liquid
(D) Plasma
Answer
(C) — Liquids have particles that are close together but not in fixed positions.
3. Which of the following compounds would exhibit hydrogen bonding?
(A) CH4
(B) CH3CH2OH
(C) CO2
(D) CH3CH3
Answer
(B) — CH3CH2OH contains an O–H bond, allowing for hydrogen bonding.
4. What is responsible for water’s unusually high boiling point?
(A) London dispersion forces
(B) Hydrogen bonding
(C) Dipole-dipole interactions
(D) Ionic bonding
Answer
(B) — Strong hydrogen bonding between water molecules elevates its boiling point.
5. Which of the following has the weakest intermolecular forces?
(A) H2O
(B) CO2
(C) NH3
(D) HF
Answer
(B) — CO2 is nonpolar and only exhibits London dispersion forces.
6. Which property decreases as the strength of intermolecular forces increases?
(A) Surface tension
(B) Boiling point
(C) Vapor pressure
(D) Melting point
Answer
(C) — Stronger intermolecular forces reduce vapor pressure.
7. What type of solid is NaCl?
(A) Molecular
(B) Metallic
(C) Ionic
(D) Covalent network
Answer
(C) — NaCl is composed of a regular lattice of ions.
8. Which type of crystal has delocalized electrons that conduct electricity?
(A) Ionic
(B) Molecular
(C) Metallic
(D) Covalent network
Answer
(C) — Metallic solids contain delocalized electrons that allow electrical conduction.
9. What explains the low boiling point of CH4?
(A) Strong ionic bonding
(B) Weak hydrogen bonding
(C) Weak London dispersion forces
(D) Strong dipole-dipole interactions
Answer
(C) — CH4 is nonpolar and only exhibits weak London dispersion forces.
10. Which of the following will have the highest surface tension?
(A) CCl4
(B) CH3CH2OH
(C) H2
(D) CH3CH3
Answer
(B) — CH3CH2OH forms hydrogen bonds, resulting in higher surface tension.
11. Which phase has a definite volume but not a definite shape?
(A) Solid
(B) Liquid
(C) Gas
(D) Plasma
Answer
(B) — Liquids have definite volume but take the shape of their container.
12. What happens to the boiling point of a liquid as external pressure increases?
(A) It decreases
(B) It increases
(C) It remains constant
(D) It becomes zero
Answer
(B) — Higher external pressure makes it harder for molecules to escape, raising the boiling point.
13. Which of the following would most likely be a molecular solid?
(A) Diamond
(B) NaCl
(C) CO2 (solid)
(D) Fe
Answer
(C) — Solid CO2 (dry ice) is composed of discrete molecules held together by weak forces.
14. What is the main force present in noble gases like argon?
(A) Ionic bonding
(B) Dipole-dipole interactions
(C) London dispersion forces
(D) Hydrogen bonding
Answer
(C) — London dispersion forces are the only type of intermolecular force in nonpolar atoms like Ar.
15. Which type of solid generally has the highest melting point?
(A) Molecular
(B) Covalent network
(C) Ionic
(D) Metallic
Answer
(B) — Covalent network solids (e.g., diamond, SiO2) have extremely strong bonds and high melting points.
16. What term describes the process where a liquid becomes a gas below its boiling point?
(A) Condensation
(B) Sublimation
(C) Evaporation
(D) Freezing
Answer
(C) — Evaporation is vaporization at the surface of a liquid below boiling temperature.
17. What is true about the particles in a solid?
(A) They move freely
(B) They are tightly packed and vibrate
(C) They are widely spaced
(D) They expand to fill the container
Answer
(B) — Solid particles are closely packed and vibrate in place.
18. Which of the following liquids has the highest vapor pressure at room temperature?
(A) Water
(B) Ethanol
(C) Acetone
(D) Glycerol
Answer
(C) — Acetone has weaker intermolecular forces, resulting in high vapor pressure.
19. What intermolecular force exists between molecules of iodine (I2)?
(A) Ionic bonding
(B) Dipole-dipole interaction
(C) Hydrogen bonding
(D) London dispersion forces
Answer
(D) — I2 is nonpolar and interacts through London dispersion forces.
20. What is true about substances with high boiling points?
(A) They have low intermolecular forces
(B) They are always polar
(C) They require more energy to vaporize
(D) They are nonvolatile
Answer
(C) — High boiling point means strong intermolecular forces and more energy needed for vaporization.
21. Which type of solid is most likely to shatter when struck?
(A) Metallic
(B) Ionic
(C) Covalent network
(D) Molecular
Answer
(B) — Ionic solids are brittle and tend to shatter due to repulsion when ions of like charge are forced close together.
22. Which of the following is not a property of liquids?
(A) Indefinite shape
(B) Definite volume
(C) Ability to flow
(D) Fixed positions of particles
Answer
(D) — Fixed particle positions describe solids, not liquids.
23. The boiling point of a substance is the temperature at which:
(A) The substance freezes
(B) Vapor pressure equals atmospheric pressure
(C) Intermolecular forces disappear
(D) The density becomes zero
Answer
(B) — Boiling occurs when the vapor pressure equals the external pressure.
24. What phase change occurs when a substance changes directly from a solid to a gas?
(A) Deposition
(B) Condensation
(C) Sublimation
(D) Evaporation
Answer
(C) — Sublimation is the direct transition from solid to gas.
25. Which of the following would most likely be classified as a covalent network solid?
(A) SiO2
(B) NaCl
(C) CH4
(D) Fe
Answer
(A) — SiO2 forms a giant covalent network structure with high melting point and hardness.
26. What is the Clausius-Clapeyron equation used to calculate?
Answer
Answer: It relates vapor pressure and temperature, allowing calculation of enthalpy of vaporization.
27. Explain why ionic solids do not conduct electricity in solid state.
Answer
Answer: In solid state, ions are locked in a lattice and cannot move freely, which prevents conductivity.
28. What causes surface tension in liquids?
Answer
Answer: Surface tension results from cohesive intermolecular forces pulling molecules inward at the surface.
29. Why does glycerol have a higher boiling point than ethanol?
Answer
Answer: Glycerol has more sites for hydrogen bonding, increasing the strength of intermolecular forces.
30. How does the strength of intermolecular forces affect volatility?
Answer
Answer: Stronger intermolecular forces decrease volatility, making it harder for molecules to escape into gas phase.
31. What is a crystal lattice?
Answer
Answer: A crystal lattice is a repeating, orderly three-dimensional arrangement of particles in a solid.
32. Describe how vapor pressure is related to temperature.
Answer
Answer: As temperature increases, vapor pressure increases due to more molecules having enough energy to escape the liquid.
33. How does a pressure cooker reduce cooking time?
Answer
Answer: It increases external pressure, which raises the boiling point of water, allowing food to cook faster at higher temperature.
34. What distinguishes metallic solids from other types of solids?
Answer
Answer: Metallic solids have delocalized electrons that can move freely, enabling conductivity and malleability.
35. What phase change is exothermic and involves a gas turning into a liquid?
Answer
Answer: Condensation — it releases heat as gas molecules slow down and form intermolecular bonds.
36. Explain why molecular solids are typically soft with low melting points.
Answer
Answer: Molecular solids are held together by weak intermolecular forces, not strong covalent or ionic bonds.
37. What effect does increasing atmospheric pressure have on the boiling point of a liquid?
Answer
Answer: It increases the boiling point since more energy is required to match the higher external pressure.
38. Describe the structure and bonding in diamond.
Answer
Answer: Diamond has a covalent network structure where each carbon atom forms four strong covalent bonds in a tetrahedral arrangement.
39. Why do substances with hydrogen bonds have higher boiling points than those without?
Answer
Answer: Hydrogen bonds are strong intermolecular forces that require more energy to break, elevating the boiling point.
40. What property of a substance is measured by viscosity?
Answer
Answer: Viscosity measures a fluid’s resistance to flow; higher viscosity means slower flow due to stronger intermolecular forces.
41. Why do molecular solids not conduct electricity?
Answer
Answer: They lack mobile charged particles such as ions or free electrons.
42. What is meant by “amorphous solid”?
Answer
Answer: Amorphous solids lack a regular repeating crystal structure, unlike crystalline solids.
43. Which property is most affected by hydrogen bonding in water?
Answer
Answer: Surface tension — hydrogen bonds create a strong cohesive force at the surface of water.
44. Explain why NaCl has a high melting point.
Answer
Answer: The strong electrostatic attraction between oppositely charged ions in an ionic lattice requires a lot of energy to break.
45. Why is ice less dense than liquid water?
Answer
Answer: Hydrogen bonding in ice forms an open hexagonal structure that occupies more volume than liquid water.
46. What is the heat of fusion?
Answer
Answer: It is the energy required to convert a substance from solid to liquid at its melting point.
47. How does a surfactant reduce surface tension?
Answer
Answer: Surfactants disrupt cohesive intermolecular forces at the surface, reducing the tension.
48. What is deposition in terms of phase change?
Answer
Answer: Deposition is the direct transition from gas to solid without becoming liquid.
49. Describe the role of kinetic energy in evaporation.
Answer
Answer: Only molecules with sufficient kinetic energy escape the liquid phase and become vapor.
50. What is the relationship between intermolecular forces and vapor pressure?
Answer
Answer: Stronger intermolecular forces result in lower vapor pressure because fewer molecules can escape into the gas phase.