Rucete ✏ AP Chemistry In a Nutshell
7. Liquids and Solids — Practice Questions 2
This chapter introduces the properties of liquids and solids, including intermolecular forces, crystal structures, heating curves, and physical characteristics such as boiling point, vapor pressure, and surface tension.
(Multiple Choice — Click to Reveal Answer)
1. Which type of intermolecular force is present in all molecular substances?
(A) Hydrogen bonding
(B) Dipole-dipole forces
(C) London dispersion forces
(D) Ionic bonding
Answer
(C) — London dispersion forces are present in all molecules, including nonpolar ones.
2. Which of the following is a characteristic of liquids but not gases?
(A) Indefinite volume
(B) High compressibility
(C) Strong intermolecular forces
(D) Fast-moving particles
Answer
(C) — Liquids have stronger intermolecular forces than gases, leading to definite volume.
3. Which phase of matter has a fixed shape and volume?
(A) Solid
(B) Liquid
(C) Gas
(D) Plasma
Answer
(A) — Solids have a fixed shape and volume due to tightly packed particles.
4. What type of solid is NaCl classified as?
(A) Molecular
(B) Metallic
(C) Ionic
(D) Covalent network
Answer
(C) — NaCl is made of positive and negative ions in a crystal lattice.
5. What property of a liquid is defined as the resistance to flow?
(A) Surface tension
(B) Viscosity
(C) Vapor pressure
(D) Adhesion
Answer
(B) — Viscosity describes how easily a liquid flows; high viscosity = more resistance.
6. Which of the following substances is most likely to exhibit hydrogen bonding?
(A) CH₄
(B) H₂
(C) NH₃
(D) CO₂
Answer
(C) — NH₃ has hydrogen bonding due to the presence of hydrogen attached to nitrogen.
7. Which unit is commonly used to express vapor pressure?
(A) Joules
(B) Liters
(C) atm
(D) Moles
Answer
(C) — Vapor pressure is typically measured in units of pressure, such as atmospheres (atm).
8. Which property decreases when intermolecular forces increase?
(A) Surface tension
(B) Boiling point
(C) Viscosity
(D) Vapor pressure
Answer
(D) — Stronger intermolecular forces make it harder for molecules to escape into the gas phase, lowering vapor pressure.
9. Which of the following solids is an example of a covalent network solid?
(A) Ice
(B) Diamond
(C) NaCl
(D) Fe
Answer
(B) — Diamond is a covalent network solid with each carbon bonded to four others in a rigid structure.
10. What happens to the vapor pressure of a liquid as temperature increases?
(A) It decreases
(B) It remains constant
(C) It increases
(D) It drops to zero
Answer
(C) — Higher temperature increases kinetic energy, allowing more molecules to escape into the vapor phase.
11. Which of the following liquids has the highest surface tension?
(A) Water
(B) Ethanol
(C) Benzene
(D) Acetone
Answer
(A) — Water forms strong hydrogen bonds, resulting in high surface tension.
12. What term describes the amount of energy required to change a substance from liquid to gas at its boiling point?
(A) Heat of fusion
(B) Heat of vaporization
(C) Specific heat
(D) Latent heat of condensation
Answer
(B) — Heat of vaporization is the energy required to overcome intermolecular forces and turn liquid into vapor.
13. What does a flat line on a heating curve represent?
(A) Constant temperature
(B) Phase change
(C) Increasing kinetic energy
(D) Increase in pressure
Answer
(B) — A flat line indicates a phase change where temperature remains constant while energy breaks intermolecular forces.
14. Which of the following solids conducts electricity in the molten state but not in the solid state?
(A) Molecular solid
(B) Metallic solid
(C) Covalent network solid
(D) Ionic solid
Answer
(D) — Ionic solids conduct electricity only when ions are free to move in the liquid state.
15. What type of bonding is primarily responsible for the high melting point of metallic solids?
(A) Hydrogen bonding
(B) Metallic bonding
(C) Dipole-dipole interaction
(D) Covalent bonding
Answer
(B) — Metallic bonding involves delocalized electrons, leading to strong attractions and high melting points.
16. What is the term for the curved surface of a liquid in a container due to adhesive and cohesive forces?
(A) Capillary rise
(B) Surface tension
(C) Meniscus
(D) Viscosity
Answer
(C) — The meniscus is the curved surface formed by a liquid at the top of its container due to intermolecular forces.
17. Which condition increases the rate of evaporation of a liquid?
(A) Decrease in surface area
(B) Decrease in temperature
(C) Decrease in humidity
(D) Increase in atmospheric pressure
Answer
(C) — Lower humidity allows more molecules to escape from the liquid to the air.
18. Which property is most directly influenced by intermolecular forces?
(A) Atomic number
(B) Electronegativity
(C) Melting point
(D) Molar mass
Answer
(C) — Melting point is directly related to the strength of intermolecular forces in a substance.
19. What is the shape of the crystal lattice of a sodium chloride crystal?
(A) Hexagonal
(B) Face-centered cubic
(C) Body-centered cubic
(D) Amorphous
Answer
(B) — NaCl has a face-centered cubic lattice structure.
20. Why does ice float on liquid water?
(A) Ice has stronger hydrogen bonds
(B) Ice is denser than water
(C) Ice has a lower molecular weight
(D) Ice is less dense due to open hexagonal structure
Answer
(D) — Ice forms an open hexagonal structure that makes it less dense than liquid water.
21. Which phase change is exothermic?
(A) Melting
(B) Vaporization
(C) Condensation
(D) Sublimation
Answer
(C) — Condensation releases energy as gas becomes liquid.
22. What type of solid is soft, has low melting points, and does not conduct electricity?
(A) Ionic solid
(B) Metallic solid
(C) Covalent network solid
(D) Molecular solid
Answer
(D) — Molecular solids are held together by weak forces, making them soft and nonconductive.
23. Which of the following best describes capillary action?
(A) Liquids form spherical drops
(B) Liquids move up a narrow tube against gravity
(C) Liquids evaporate faster under low pressure
(D) Liquids form bubbles at boiling point
Answer
(B) — Capillary action is caused by adhesive forces pulling liquid into a narrow space.
24. What happens to the melting point of ice under high pressure?
(A) It increases
(B) It decreases
(C) It remains unchanged
(D) It becomes infinite
Answer
(B) — Ice melts at a lower temperature under high pressure due to its open crystalline structure.
25. Which property explains why mercury forms a convex meniscus in glass?
(A) Strong cohesive forces
(B) Weak adhesive forces
(C) High vapor pressure
(D) Both A and B
Answer
(D) — Mercury’s cohesive forces are stronger than its adhesion to glass, causing a convex meniscus.
26. Which of the following correctly explains the high boiling point of H₂O compared to H₂S?
(A) Larger molar mass
(B) Stronger dispersion forces
(C) Hydrogen bonding in H₂O
(D) Ionic character in H₂O
Answer
(C) — H₂O exhibits hydrogen bonding, which is much stronger than the dipole forces in H₂S.
27. Why does iodine (I₂) sublimate at room temperature?
(A) It is highly polar
(B) It has strong hydrogen bonds
(C) It has weak London dispersion forces between molecules
(D) It forms an ionic solid
Answer
(C) — Iodine is nonpolar, and the weak London dispersion forces allow it to transition directly from solid to gas.
28. Which of the following is true regarding metallic solids?
(A) They have low electrical conductivity
(B) Their melting points are always low
(C) They have delocalized electrons
(D) They dissolve easily in water
Answer
(C) — Metallic solids have delocalized electrons, which allow them to conduct electricity and heat.
29. What causes the relatively low melting point of molecular solids?
(A) Ionic interactions
(B) Hydrogen bonding
(C) Weak intermolecular forces
(D) Strong covalent bonds
Answer
(C) — Molecular solids are held together by weak van der Waals forces or dipole interactions, resulting in low melting points.
30. Which of the following has the strongest intermolecular forces?
(A) CH₄
(B) NH₃
(C) CO₂
(D) H₂
Answer
(B) — NH₃ has hydrogen bonding, which is stronger than the dispersion forces in the others.
31. The normal boiling point of a liquid is defined as:
(A) The temperature at which it boils under any condition
(B) The temperature at which vapor pressure equals 1 atm
(C) The point where solid and liquid coexist
(D) The pressure when vaporization equals melting
Answer
(B) — The normal boiling point is when a liquid’s vapor pressure equals standard atmospheric pressure (1 atm).
32. Which type of solid is quartz (SiO₂)?
(A) Ionic
(B) Metallic
(C) Molecular
(D) Covalent network
Answer
(D) — Quartz is a covalent network solid with an extended array of covalently bonded silicon and oxygen atoms.
33. What property allows liquids like water to be drawn upward through narrow tubes against gravity?
(A) Surface tension
(B) Capillary action
(C) Viscosity
(D) Freezing point depression
Answer
(B) — Capillary action arises from adhesion to the tube and cohesion within the liquid.
34. Which condition favors the formation of a crystalline solid over an amorphous solid?
(A) Rapid cooling
(B) Impure materials
(C) Slow, orderly cooling
(D) High vapor pressure
Answer
(C) — Slow, orderly cooling allows particles to arrange into a repeating pattern, forming a crystalline solid.
35. Which of the following statements about amorphous solids is correct?
(A) They have sharp melting points
(B) They have long-range order
(C) Their particles are randomly arranged
(D) They conduct electricity well
Answer
(C) — Amorphous solids lack a regular structure and exhibit short-range order only.
36. Explain why vapor pressure increases with temperature.
Answer
Answer: As temperature increases, more molecules have enough kinetic energy to escape the liquid phase and enter the gas phase, increasing vapor pressure.
37. Describe the molecular structure and bonding in metallic solids.
Answer
Answer: Metallic solids consist of a lattice of positive metal ions surrounded by a "sea" of delocalized electrons, allowing conductivity and malleability.
38. Why does a liquid’s boiling point increase under higher atmospheric pressure?
Answer
Answer: The boiling point increases because the liquid needs more kinetic energy (higher temperature) for its vapor pressure to match the higher external pressure.
39. Compare the structures of crystalline and amorphous solids.
Answer
Answer: Crystalline solids have a repeating, ordered arrangement of particles, while amorphous solids lack long-range order and have random structures.
40. Explain why ionic solids are brittle and break along planes.
Answer
Answer: When force is applied, like charges may be forced closer together, causing repulsion and breaking the solid along cleavage planes.
41. How does hydrogen bonding affect the physical properties of water?
Answer
Answer: Hydrogen bonding leads to water's high boiling point, surface tension, specific heat, and causes ice to be less dense than liquid water.
42. Why is diamond hard, while graphite is soft?
Answer
Answer: Diamond has a 3D tetrahedral covalent network, making it extremely rigid. Graphite has 2D layers with weak forces between them, allowing them to slide.
43. Describe how capillary action works in narrow tubes.
Answer
Answer: Adhesion between the liquid and the tube walls pulls the liquid up, while cohesion among liquid molecules maintains continuity of the column.
44. Explain why molecular solids generally have low melting points.
Answer
Answer: Molecular solids are held together by weak intermolecular forces (e.g., van der Waals, dipole), which require less energy to overcome during melting.
45. What is surface tension and what causes it?
Answer
Answer: Surface tension is the energy required to increase a liquid's surface area, caused by cohesive forces pulling molecules inward at the surface.
46. How does the structure of water cause ice to float?
Answer
Answer: Ice forms a hexagonal open lattice due to hydrogen bonding, making it less dense than liquid water and allowing it to float.
47. What distinguishes a volatile liquid from a non-volatile liquid?
Answer
Answer: Volatile liquids have high vapor pressures and evaporate easily, while non-volatile liquids have strong intermolecular forces and low vapor pressures.
48. Describe how intermolecular forces influence viscosity.
Answer
Answer: Strong intermolecular forces resist flow, increasing viscosity. Weaker forces allow molecules to move past each other more easily, reducing viscosity.
49. Explain why ionic compounds conduct electricity in molten state but not in solid state.
Answer
Answer: In the solid state, ions are fixed in a lattice. In the molten state, ions are free to move and carry electric current.
50. Why do polar substances tend to dissolve in polar solvents?
Answer
Answer: "Like dissolves like" — polar solvents interact with polar solutes via dipole interactions or hydrogen bonding, overcoming solute-solute attractions.