Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 19: Problem 21

For each of the following pairs of materials, decide which has the larger thermal conductivity. Justify your choices. (a) Pure silver; sterling silver \((92.5 \mathrm{wt} \% \mathrm{Ag}-\) \(7.5 \mathrm{wt} \% \mathrm{Cu})\). (b) Fused silica; polycrystalline silica. (c) Linear and syndiotactic poly(vinyl chloride \()(D P=1000) ;\) linear and syndiotactic polystyrene \((D P=1000)\). (d) Atactic polypropylene \(\left(\bar{M}_{w}=10^{6}\right.\) \(\mathrm{g} / \mathrm{mol}\) ); isotactic polypropylene \(\left(\bar{M}_{w}=\right.\) \(5 \times 10^{5} \mathrm{g} / \mathrm{mol}\) ).

Short Answer

Expert verified
Answer: (a) Pure silver, (b) Fused silica, (c) Linear and syndiotactic polystyrene, (d) Isotactic polypropylene.

Step by step solution

01

Pair (a): Pure silver vs Sterling silver

Pure silver is a highly thermally conductive material due to its metallic nature and crystal structure. Sterling silver is an alloy, made by adding copper (7.5 wt%) to pure silver (92.5 wt%). The addition of copper reduces thermal conductivity compared to pure silver. Hence, the thermal conductivity of pure silver is larger than that of sterling silver.
02

Pair (b): Fused silica vs polycrystalline silica

Fused silica consists of a very homogeneous glass structure with no grain boundaries. This imparts higher thermal conductivity to the material. Polycrystalline silica, on the other hand, has a crystalline structure with grain boundaries. The presence of grain boundaries can cause the phonons to scatter, which reduces the thermal conductivity. Thus, fused silica has a larger thermal conductivity than polycrystalline silica.
03

Pair (c): Linear and syndiotactic poly(vinyl chloride) vs linear and syndiotactic polystyrene

Both poly(vinyl chloride) (PVC) and polystyrene (PS) are polymers, and their thermal conductivities depend on their molecular structure and the arrangement of monomers. Poly(vinyl chloride) has a larger number of irregular, halogen-containing monomers, while polystyrene has a more regular arrangement of monomers. As a result, phonon vibrations propagate more efficiently through polystyrene, which leads to a higher thermal conductivity compared to poly(vinyl chloride).
04

Pair (d): Atactic polypropylene vs isotactic polypropylene

Atactic and isotactic polypropylene are both polymers composed of propylene monomers but differ in their molecular structure. Atactic polypropylene has a random arrangement of monomers, while isotactic polypropylene has a regular arrangement of monomers. The regular structure of isotactic polypropylene allows for more efficient phonon vibrations, resulting in higher thermal conductivity compared to the random structure of atactic polypropylene.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Briefly explain why the thermal conductivities are higher for crystalline than noncrystalline ceramics.

(a) Briefly explain why porosity decreases the thermal conductivity of ceramic and polymeric materials, rendering them more thermally insulative. (b) Briefly explain how the degree of crystallinity affects the thermal conductivity of polymeric materials and why.

(a) Briefly explain why \(C_{v}\) rises with increasing temperature at temperatures near \(0 \mathrm{K}\) (b) Briefly explain why \(C_{v}\) becomes virtually independent of temperature at temperatures far removed from \(0 \mathrm{K}\).

What measures may be taken to reduce the likelihood of thermal shock of a ceramic piece?

A steel wire is stretched with a stress of \(70 \mathrm{MPa}(10,000 \mathrm{psi})\) at \(20^{\circ} \mathrm{C}\left(68^{\circ} \mathrm{F}\right) .\) If the length is held constant, to what temperature must the wire be heated to reduce the stress to \(17 \mathrm{MPa}(2500 \mathrm{psi}) ?\) v
See all solutions

Recommended explanations on Physics Textbooks

Electric Charge Field and Potential

Read Explanation

Magnetism

Read Explanation

Engineering Physics

Read Explanation

Fields in Physics

Read Explanation

Further Mechanics and Thermal Physics

Read Explanation

Scientific Method Physics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free