Properties of Solids, Liquids & Gases (College Board AP® Chemistry): Exam Questions

Covalent network solids exhibit different mechanical and thermal properties compared to other types of solids.

Explain why diamond is extremely hard, whereas graphite is soft.

Explain why graphite is able to conduct electricity but diamond is not.

Silicon dioxide (SiO₂) has a very high melting point. Explain why in terms of bonding and structure.

A materials scientist compares the structures and properties of three different solids:

• NaCl (s) – an ionic compound

• SiO₂ (s) – a covalent network solid

• Cu (s) – a metallic solid

Explain why copper conducts electricity as a solid, but NaCl does not.

Despite both being solids with strong interactions, SiO₂ is significantly harder than NaCl. Explain this difference in terms of their bonding and structure.

The scientist heats equal masses of NaCl (s) and Cu (s). Explain which solid will melt first in terms of particle motion and structure.

Draw a particulate-level representation of the structure of NaCl (s).
Use labeled circles to represent Na⁺ and Cl⁻ ions. Show an appropriate arrangement in the lattice and indicate any interactions clearly.

A polymer material shows similar conductivity to SiO₂ and is flexible like a soft metal. Suggest a structural explanation for these observed properties.

Acetonitrile (CH₃CN) and acetone (CH₃COCH₃) are both organic liquids with similar molar masses. However, acetonitrile has a significantly higher boiling point than acetone. Explain why.

The normal boiling point of acetonitrile is 81.6°C at 1 atm. If the external pressure is reduced to 0.50 atm, predict whether acetonitrile will boil at a higher or lower temperature. Justify your answer.

Acetone is placed in a sealed container at room temperature, where it begins to evaporate.

i) Explain how the rate of evaporation of acetone changes over time as the system approaches equilibrium.

ii) Using Le Chatelier’s Principle, predict and explain what happens to the equilibrium between liquid acetone and acetone vapor if the volume of the container is suddenly increased.

The physical properties of solids depend on the arrangement of their particles and the forces that hold them together.

Compare the hardness of brass and high-carbon steel. Refer to how alloy type and structure contribute to their mechanical properties.

Compare crystalline and amorphous solids in terms of particle arrangement and structural properties, explaining how interparticle interactions influence their ability to pack together.

Compare the structure and melting points of molecular solids and covalent network solids, explaining how interparticle interactions influence their physical properties.

Iodine (I₂) and carbon dioxide (CO₂) are both molecular solids under certain conditions but have different melting points. Explain the difference in melting point.

A sample of CO₂ gas is trapped in a sealed container at constant temperature. Explain what happens to the pressure inside the container if the volume is halved,