Textbook Question
Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond. (a) Is Si a molecular, metallic, ionic, or covalent-network solid?
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Ch.12 - Solids and Modern Materials
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232
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Table of contents
- Ch.1 - Introduction: Matter, Energy, and Measurement140
- Ch.2 - Atoms, Molecules, and Ions192
- Ch.3 - Chemical Reactions and Reaction Stoichiometry172
- Ch.4 - Reactions in Aqueous Solution156
- Ch.5 - Thermochemistry151
- Ch.6 - Electronic Structure of Atoms137
- Ch.7 - Periodic Properties of the Elements127
- Ch.8 - Basic Concepts of Chemical Bonding143
- Ch.9 - Molecular Geometry and Bonding Theories167
- Ch.10 - Gases147
- Ch.11 - Liquids and Intermolecular Forces97
- Ch.12 - Solids and Modern Materials129
- Ch.13 - Properties of Solutions126
- Ch.14 - Chemical Kinetics175
- Ch.15 - Chemical Equilibrium107
- Ch.16 - Acid-Base Equilibria127
- Ch.17 - Additional Aspects of Aqueous Equilibria133
- Ch.18 - Chemistry of the Environment88
- Ch.19 - Chemical Thermodynamics140
- Ch.20 - Electrochemistry137
- Ch.21 - Nuclear Chemistry99
- Ch.22 - Chemistry of the Nonmetals66
- Ch.23 - Transition Metals and Coordination Chemistry69
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry11
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
Chapter 12, Problem 9b
Shown here are cartoons of two different polymers. Which one would have the higher melting point?
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Identify the two types of polymer structures shown in the image: Polymer I has linear chains, and Polymer II has branched chains.
Recall that the melting point of a polymer is influenced by the strength of intermolecular forces and the degree of packing of the polymer chains.
Understand that linear polymers (Polymer I) can pack more closely together, leading to stronger intermolecular forces (e.g., van der Waals forces) and higher crystallinity.
Recognize that branched polymers (Polymer II) have irregular structures that prevent close packing, resulting in weaker intermolecular forces and lower crystallinity.
Conclude that Polymer I, with its linear chains, would have a higher melting point compared to Polymer II, which has branched chains.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Polymer Structure
Polymers are large molecules made up of repeating structural units called monomers. The arrangement of these monomers can significantly affect the properties of the polymer, including its melting point. Linear polymers, like those depicted in the left image, have a more organized structure, allowing for stronger intermolecular forces compared to branched polymers, which are more irregular and can lead to weaker interactions.
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Intermolecular Forces
The melting point of a substance is largely determined by the strength of the intermolecular forces acting between its molecules. In polymers, stronger intermolecular forces, such as hydrogen bonding or van der Waals forces, result in higher melting points. Linear polymers typically exhibit stronger intermolecular forces due to their ability to pack closely together, while branched polymers have more space between chains, reducing these forces.
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Crystallinity
Crystallinity refers to the degree to which a polymer's molecular chains are ordered. Higher crystallinity usually leads to higher melting points because the ordered structure allows for stronger intermolecular interactions. Linear polymers tend to be more crystalline than branched ones, which are often amorphous, resulting in lower melting points due to less efficient packing and weaker interactions.
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Related Practice
Textbook Question
The accompanying image shows photoluminescence from four different samples of CdTe nanocrystals, each embedded in a polymer matrix. The photoluminescence occurs because the samples are being irradiated by a UV light source. The nanocrystals in each vial have different average sizes. The sizes are 4.0, 3.5, 3.2, and 2.8 nm. (a) Which vial contains the 4.0-nm nanocrystals?
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Textbook Question
Which of these molecular fragments would you expect to be more likely to give rise to electrical conductivity? Explain your reasoning. (a)
(b)
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Textbook Question
Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond. (b) Silicon readily reacts to form silicon dioxide, SiO2, which is quite hard and is insoluble in water. Is SiO2 most likely a molecular, metallic, ionic, or covalent-network solid?
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Textbook Question
The electronic structure of a doped semiconductor is shown here. (c) Which region of the diagram represents the band gap?
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Textbook Question
Which arrangement of cations (yellow) and anions (blue) in a lattice is the more stable? Explain your reasoning. (a)
(b)
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