Chapter 12, Problem 91A

Interpretation Introduction

(a)

Interpretation:

The type of crystalline solid which can be melted and reformed at low temperature needs to be determined.

Concept introduction:

Crystalline solids have repeating, 3 D patterns of molecules, atoms or ions. The particles tend to maximize the spaces occupied by them, resulting in a solid form that is incompressible. The three main types of crystalline solids are molecular, ionic and atomic (network and metallic)

Answer to Problem 91A

Molecular solid.

Explanation of Solution

Molecular crystalline solids are made up of molecules. These molecules have dispersion, dipole-dipole and hydrogen bonding. All these intermolecular forces are weaker than ionic bonding. Thus, molecular solids are soft and they are poor conductors of heat and electricity.

Thus, they can be melted and reformed at a low temperature.

Interpretation Introduction

(b)

Interpretation:

The type of crystalline solid which can be drawn into long and thin wires needs to be determined.

Concept introduction:

Crystalline solids have repeating, 3 D patterns of molecules, atoms or ions. The particles tend to maximize the spaces occupied by them, resulting in a solid form that is incompressible. The three main types of crystalline solids are molecular, ionic and atomic (network and metallic)

Answer to Problem 91A

Metallic solid

Explanation of Solution

The metallic crystalline solids have atoms held together by metallic bonds. They are strong conductors of heat and electricity.

Since metals are malleable and ductile thus, they can be drawn into long and thin wires.

Interpretation Introduction

(c)

Interpretation:

The type of crystalline solid which can conduct electricity when molten needs to be determined.

Concept introduction:

Crystalline solids have repeating, 3 D patterns of molecules, atoms or ions. The particles tend to maximize the spaces occupied by them, resulting in a solid form that is incompressible. The three main types of crystalline solids are molecular, ionic and atomic (network and metallic)

Answer to Problem 91A

Ionic solid.

Explanation of Solution

Ionic crystalline solids have positive and negative ions. These ions have ion-ion attraction which is stronger than other intermolecular interactions. Thus, they are a good conductor of heat and electricity.

Thus, ionic solids can conduct electricity when present in molten form.

Interpretation Introduction

(d)

Interpretation:

The type of crystalline solid which is extremely hard and non-conductive needs to be determined.

Concept introduction:

Crystalline solids have repeating, 3 D patterns of molecules, atoms or ions. The particles tend to maximize the spaces occupied by them, resulting in a solid form that is incompressible. The three main types of crystalline solids are molecular, ionic and atomic (network and metallic).

Answer to Problem 91A

The covalent network is solid.

Explanation of Solution

In network crystalline solids, atoms have covalent bonds. They are hard and have a high melting point and they are poor conductors of heat and electricity.

Thus, covalent network solids are extremely hard and non-conductive in nature.