How bonding and structure are related to the properties of substances: Practice Questions

Ammonia (\(NH_{3}\)) has a boiling point of \(-33 \text{ } ^{\circ}\text{C}\). Why is the boiling point of ammonia much lower than that of sodium chloride (\(801 \text{ } ^{\circ}\text{C}\))?

Some plastics, such as poly(ethene), melt when they are heated and can be reshaped. These are called thermosoftening polymers. Why do they melt when heated?

Fullerenes such as \(C_{60}\) have potential uses in nanotechnology and drug delivery. Which statement correctly describes the structure of a \(C_{60}\) molecule?

Magnesium has a melting point of \(650 \text{ } ^{\circ}\text{C}\), while sodium has a melting point of \(98 \text{ } ^{\circ}\text{C}\). Which statement best explains this difference in terms of metallic bonding?

Which of the following explains why magnesium chloride conducts electricity when molten but not when solid?

Substances have different physical properties based on their bonding and structure. Consider the two substances, sodium chloride and methane (\(CH_{4}\)).

a) Describe the bonding and structure of sodium chloride and explain why it has a high melting point.
b) Describe the bonding and structure of methane and explain why it is a gas at room temperature.
c) Explain why sodium chloride conducts electricity when molten, but methane does not.

Substances have different properties based on their bonding and structure. Consider the three substances: sodium chloride, diamond, and methane (\(CH_{4}\)).

a) Explain why sodium chloride has a high melting point, whereas methane is a gas at room temperature. Use ideas about bonding and forces in your answer.

b) Diamond and graphite are both forms of carbon with giant covalent structures. Explain why diamond is very hard while graphite is soft and slippery, referring to their bonding and arrangement of atoms.

c) Explain why sodium chloride conducts electricity when molten but not when solid.