Domanda del libro di testo
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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TOC.tableOfContents
- Ch.1 - Introduction: Matter, Energy, and Measurement177
- Ch.2 - Atoms, Molecules, and Ions231
- Ch.3 - Chemical Reactions and Reaction Stoichiometry216
- Ch.4 - Reactions in Aqueous Solution189
- Ch.5 - Thermochemistry175
- Ch.6 - Electronic Structure of Atoms168
- Ch.7 - Periodic Properties of the Elements150
- Ch.8 - Basic Concepts of Chemical Bonding177
- Ch.9 - Molecular Geometry and Bonding Theories200
- Ch.10 - Gases179
- Ch.11 - Liquids and Intermolecular Forces113
- Ch.12 - Solids and Modern Materials154
- Ch.13 - Properties of Solutions157
- Ch.14 - Chemical Kinetics199
- Ch.15 - Chemical Equilibrium128
- Ch.16 - Acid-Base Equilibria164
- Ch.17 - Additional Aspects of Aqueous Equilibria163
- Ch.18 - Chemistry of the Environment105
- Ch.19 - Chemical Thermodynamics164
- Ch.20 - Electrochemistry171
- Ch.21 - Nuclear Chemistry122
- Ch.22 - Chemistry of the Nonmetals82
- Ch.23 - Transition Metals and Coordination Chemistry79
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry16
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Capitolo 12, Problema 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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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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01:42
Resonance Structures
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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01:59Intermolecular vs Intramolecular Forces
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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01:31Crystalline Solids Structure
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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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Domanda del libro di testo
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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Domanda del libro di testo
The electronic structure of a doped semiconductor is shown here. (c) Which region of the diagram represents the band gap?
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Domanda del libro di testo
Which arrangement of cations (yellow) and anions (blue) in a lattice is the more stable? Explain your reasoning. (a)
(b)
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