# 6.2.1: The Solid State of Matter (Problems)

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PROBLEM $$\PageIndex{1}$$

At very low temperatures oxygen, O2, freezes and forms a crystalline solid. Which best describes these crystals?

1. ionic
2. covalent network
3. metallic
4. amorphous
5. molecular crystals

(e) molecular crystals

PROBLEM $$\PageIndex{2}$$

As it cools, olive oil slowly solidifies and forms a solid over a range of temperatures. Which best describes the solid?

1. ionic
2. covalent network
3. metallic
4. amorphous
5. molecular crystals

(d) amorphous

PROBLEM $$\PageIndex{3}$$

Explain why ice, which is a crystalline solid, has a melting temperature of 0 °C, whereas butter, which is an amorphous solid, softens over a range of temperatures.

Ice has a crystalline structure stabilized by hydrogen bonding. These intermolecular forces are of comparable strength and thus require the same amount of energy to overcome. As a result, ice melts at a single temperature and not over a range of temperatures. The various, very large molecules that compose butter experience varied van der Waals attractions of various strengths that are overcome at various temperatures, and so the melting process occurs over a wide temperature range.

PROBLEM $$\PageIndex{4}$$

Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances:

1. SiO2
2. KCl
3. Cu
4. CO2
5. C (diamond)
6. BaSO4
7. NH3
8. NH4F
9. C2H5OH

covalent network

ionic

metallic

molecular

covalent network

ionic

molecular

ionic

molecular

PROBLEM $$\PageIndex{5}$$

Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances:

1. CaCl2
2. SiC
3. N2
4. Fe
5. C (graphite)
6. CH3CH2CH2CH3
7. HCl
8. NH4NO3
9. K3PO4

ionic

Covalent network

molecular

metallic

covalent network

molecular

molecular

ionic

ionic

PROBLEM $$\PageIndex{6}$$

Classify each substance in the table as either a metallic, ionic, molecular, or covalent network solid:

Substance Appearance Melting Point Electrical Conductivity Solubility in Water
X lustrous, malleable 1500 °C high insoluble
Y soft, yellow 113 °C none insoluble
Z hard, white 800 °C only if melted/dissolved soluble

X = metallic; Y = covalent network; Z = ionic

PROBLEM $$\PageIndex{7}$$

Classify each substance in the table as either a metallic, ionic, molecular, or covalent network solid:

Substance Appearance Melting Point Electrical Conductivity Solubility in Water
X brittle, white 800 °C only if melted/dissolved soluble
Y shiny, malleable 1100 °C high insoluble
Z hard, colorless 3550 °C none insoluble

X = ionic; Y = metallic; Z = covalent network

PROBLEM $$\PageIndex{8}$$

Substance A is shiny, conducts electricity well, and melts at 975 °C. Substance A is likely a(n):

1. ionic solid
2. metallic solid
3. molecular solid
4. covalent network solid

(b) metallic solid

PROBLEM $$\PageIndex{9}$$

Substance B is hard, does not conduct electricity, and melts at 1200 °C. Substance B is likely a(n):

1. ionic solid
2. metallic solid
3. molecular solid
4. covalent network solid

(d) covalent network solid