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?

ionic
covalent network
metallic
amorphous
molecular crystals

Answer: (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?

ionic
covalent network
metallic
amorphous
molecular crystals

Answer: (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.

Answer: 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:

SiO₂
KCl
Cu
CO₂
C (diamond)
BaSO₄
NH₃
NH₄F
C₂H₅OH

Answer a: covalent network

Answer b: ionic

Answer c: metallic

Answer d: molecular

Answer e: covalent network

Answer f: ionic

Answer g: molecular

Answer h: ionic

Answer i: molecular

PROBLEM \(\PageIndex{5}\)

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

CaCl₂
SiC
N₂
Fe
C (graphite)
CH₃CH₂CH₂CH₃
HCl
NH₄NO₃
K₃PO₄

Answer a: ionic
Answer b: Covalent network

Answer c: molecular

Answer d: metallic

Answer e: covalent network

Answer f: molecular

Answer g: molecular

Answer h: ionic

Answer i: 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

Answer: 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

Answer: 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):

ionic solid
metallic solid
molecular solid
covalent network solid

Answer: (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):

ionic solid
metallic solid
molecular solid
covalent network solid

Answer: (d) covalent network solid

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Contributors

Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).
Adelaide Clark, Oregon Institute of Technology

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